English 
Arabic 
French 
Italian 
German 
Russian 
Korean 
Japanese 
Portuguese 
Spanish 
How to do Quality Inspection for Jewelry Stone Setting?
Common Defect Analysis and Cases, Solutions
Introduction
The most dazzling part of inlaid jewelry is the various shapes and colorful gemstones inlaid in it. The quality of the setting process directly affects the jewelry’s appearance and grade, but the Jewelry setting is mainly done by manual operation. The quality of the jewelry set is closely related to the work attitude, skill level, and proficiency of the operator, so it is necessary to strengthen the quality of the inspection of the setting during the production process.
Table of Contents
Section I: Jewelry setting quality inspection content and quality requirements
1. Jewelry Setting quality inspection content
The inspection and control of setting quality mainly focus on the quality of gemstones and setting work.
1.1 Gemstone quality inspection
Jewelry factories generally set gem inspectors and stone keepers in the setting process, aiming to inspect the quality of gems before setting them and to equip gems that meet the requirements of texture, grade, size, color, quantity, etc., according to the order requirements. The well-prepared gems, base mounts (wax or metal), and production orders are sent to the stone-setters by the inspector to prevent problematic gems from entering the production process.
The main tools for gem quality inspection are magnifying glasses, gem tweezers, QC lamps, sponge trays, diamond gauges, vernier calipers, electronic scales, etc.
During inspection, according to the order requirements, the gems provided by customers are weighed, counted, and checked for breakage, flaws, decay, etc., and whether the color and clarity grade of the gems are the same as the order requirements. Stones are strictly selected according to the order requirements, tested with wax or metal mounts, whether the shape, size, and setting of the gems are appropriate, and promptly feedback to the customer if any issues are found.
1.2 Setting work quality inspection
The main tools for setting work quality inspection are magnifying glasses, tweezers, steel needles, oily pens, etc. Inspectors need to be familiar with the setting requirements of the order, check whether the number of stones, positions, and setting methods meet the order requirements, and then inspect the quality of each gem setting, including the integrity of the inlaid gems; the position, direction, stability of the inlaid gems; and the processing status of the metal edges (prongs), etc.
2. Setting Quality Requirements
Standard setting methods mainly include paved setting, prong setting, bezel setting, gypsy setting, channel setting, invisible setting, etc. The type of gemstone setting can be divided into wax and metal settings. Each setting method has its characteristics, but many quality issues are common, generally divided into gemstone issues and setting issues, requiring intact gemstones, firm setting, no loose stones, oblique stones, high and low stones, twisted stones, crooked stones, etc., claws, setting bases, prongs, edges, are smooth, pleasing appearance. The quality requirements for various setting methods are as follows:
2.1 Prong Setting
The prongs should be symmetrical; the prong heads should be round or regular, close to the stone, not deformed; the prongs of the same stone should not have differences in height, diameter, and weak prongs, etc.; the prongs should not cover more than 2/3 of the stone’s side, and the pong heads and bottom mounts should not have metal chips.
2.2 Channel Setting & bezel Setting
The thickness of the metal edge should be consistent; the surface metal should be close to the stone, not covering more than 1/3 of the stone’s side; channels of round diamonds, the spacing of the stones should be consistent; channels of baguette and square-shaped stones, stone gaps should not exist, and stones should not touch each other; the cross of the square-shaped channel should be symmetrical, the edges should be at right angles, and the lengths should be consistent. There should be no metal chips on the stone edges and bottom mounts; the metal edge should retain a 0.3-0.4mm thickness.
2.3 Pave Setting
The prong head should be round, symmetrical, and push the stone closely, without different sizes of prongs; the prong head covering the stone should not exceed 2/3 of the stone’s side; there should be no metal chips on the edge or bottom of the Prong; the edge should not be too thin or cracked.
2.3 Gypsy setting
The prong positions should be uniform, and the direction of the Prong should be consistent; the Prong pushes the stone closely, without different size prongs; the prong length should be controlled at half of the stone’s side, not too long or too short; the edges of the stone setting holes should be uniform and consistent in thickness.
Section II: Common Setting Problems
3. Problems with the Quality of Gemstones
During the production of inlaid jewelry, various problems related to the quality of gemstones are often encountered, mainly including the material, grade, cutting, size, color, and quantity. The gemstones to be set do not match the material requirements of the order.
【Case 8-1】Natural crystals with artificial zircon mixed in.
Analysis:
A jewelry factory produced a batch of jewelry set with natural crystals provided by customers. When inspecting these crystals, it was found that a small amount of artificial zircon, similar in color and easily confused, was mixed in. To avoid such problems, the jewelry factory must have professional gemstone inspectors and the necessary testing equipment to inspect customer-made stones
4. Gemstone Grade Issue
Gemstones are generally graded based on color, clarity, cut or processing characteristics, single crystal size or size of jade blocks, etc. The standards for grading different types of gemstones are different, and other international organizations or large companies may have different standards for grading the same kind of gemstone.
For diamonds, GIA, the Gemological Institute of America, pioneered the diamond grading standards now widely recognized in the industry, including color, clarity, cut, and carat weight, known as the 4C standard.
【Case 8-2】The diamond clarity does not meet the requirements, as shown in Figure 8-1.
Analysis:
There are relatively apparent cracks on the bottom surface of the diamond, which do not meet the customer’s quality requirements. Clarity is one of the standards for measuring the grade of diamonds. Diamonds are natural minerals and may contain some other minerals or natural flaws such as cracks. The fewer inclusions, the higher the value of the diamond, so it is graded based on the flaws’ size, quantity, color, location, and characteristics. In the jewelry processing industry, flaws inside diamonds are commonly referred to as “inclusions,” which can be classified as slight inclusions, small inclusions, severe inclusions, half inclusions, one inclusions, two inclusions, etc.
【Case 8-3】 Diamond has a chipped corner, as Figure 8-2 shows.
Analysis:
Stone chipping refers to defects or missing corners on the surface of a gemstone, which can be classified as edge chipping, facet chipping, table, culet chipping, or corner chipping. In this case, one corner of the diamond has chipped.
【Case 8-4】The number of diamond facets is insufficient; it is a single-cut stone, as shown in the figure 8-2 shows.
Analysis:
The quality of the cut directly affects the diamond’s fire. When a diamond is cut in proper proportions, light can produce total internal reflection inside the diamond, with most of the light refracting out from the crown of the diamond, emitting a dazzling light. A poorly cut diamond will have less sharp edges, and light may flow from the bottom or sides, reducing the brilliance.
In this case, the order calls for full-cut diamonds, but the provided stones include single-cut stones. Single-cut diamonds typically have only 17 facets, with 1 table facet, eight crown facets, and eight pavilion facets, possibly with one culet or none. Full-cut diamonds have at least 57 or 58 facets. Diamonds cut in the brilliant style have 32 aspects on the crown, 24 on the pavilion, and 1 table facet, possibly with one culet or none. The physical brilliance of single-cut diamonds is significantly inferior to that of full-cut diamonds.
【Case 8-5】Diamond Waist is Too Thick, as shown in the figure 8-4.
Analysis:
The quality of the diamond waist directly affects the fire color and visual effect of the diamond. A too-thick waist will make a diamond of the same quality look much smaller in appearance than a thin-waisted diamond, causing light leakage into the diamond, and sometimes the shadow of the waist will refract into the diamond’s interior, creating a gray shadow. A too-thick waist is also not conducive to the setting. Therefore, a waist that is too thick reflects poor diamond cutting. Of course, if the waist is too thin, it is prone to chipping or cracking when impacted or compressed. The thickness of the waist should be sufficient to resist external forces.
5. Inlaid Stone Issues
Matching stones are an important link to ensure the quality of setting and production efficiency. Here are some common Inlaid stone issues.
【Case 8 -6 】The diamond shape does not match the setting, as shown in figure 8-5.
Analysis:
One essential requirement for a gemstone setting is to match the shape; that is, the shape of the gemstone should match the size and shape of the setting, which should be paid attention to from the beginning of the stone selection. In this case, a large acute angle appears in the channel setting of the jewelry. When using the diamond, as shown in the diagram, there will be problems of significant gaps in the middle and excessive metal buried in the two corners, and the wider the diamond, the more pronounced the problem. Therefore, when setting stones, the size of the diamond should be reasonably selected, and if necessary, the diamond should be cut and polished to fit the setting better.
【Case 8-7】Incorrect stone setting angle during stone setting, as shown in Figure 8-6.
Analysis:
In this case, starting from a specific position in the middle of the groove to set the stones, only the left side is taken care of, and it will be challenging to set suitable diamonds on the right side. When requesting a stone setting, consider the arrangement of individual stones and the overall effect.
[Case 8- 8] Diamonds are too long, as shown in Figure 8 -7.
Analysis:
In this case, besides the diamonds at the corner position not fitting the setting, the diamonds on the left side are too long, with one corner extending into the outer tiger prong setting. In this way, when setting the tiger prong stone, it is easy to damage the diamond.
【Case 8-9】The diamond is too short, as shown in Figure 8-8.
Analysis:
In this case, the diamonds at the corners are too short, resulting in obvious gaps between the metal and the stones during setting, affecting the stability and appearance of the diamonds.
【Case 8-10】There is a large difference in gemstone colors, as shown in Figures 8-9.
Analysis:
For colored gemstones, even if they are purchased from the same supplier in the same batch, color variations are inevitable. When setting stones, selecting gemstones with similar colors from the materials for matching is necessary. In this case, there is a significant difference in the color of the gemstones in the left and right earrings, which could be more harmonious and require the purchase of new stones.
Section III. Setting Issues
Setting issues involve the setting effect of gemstones and the handling effect of metal prongs (edges). Setting is one of the essential indicators to measure the grade of jewelry products. Different settingmethods with common setting issues and issues specific to the type of setting method.
6. Common Setting Issues in Prong Setting
Prong setting is usually not used for setting central stones but smaller (diameter less than 3 mm ) side stones or clusters of tiny diamonds. It fully utilizes the excellent flexibility of precious metals, uses special tools to dig out small metal teeth, clamps the gemstone’s girdle, and thus secures the gemstone. Prong setting is widely used for setting small gemstone particles and can be divided into two-prong setting, three-prong setting, four-prong setting, and close-prong setting according to the number of prongs.
The quality of the prong setting should be examined regarding the gemstone’s flatness, fastening condition, intactness, and prong treatment condition. The set gemstone should not have phenomena such as tilted stones, uneven stones, loose stones, or damaged stones; the metal position around the gemstone and the metal edge should not be scratched; the prong head should be round, not flattened, and no metal chips should appear on the prong edge; the Prong should not be too long or too short, and so on. Common prong-setting issues are shown below.
【Case 8-11】The prong-set round diamond has cracked, as shown in Figures 8-10.
Analysis:
Regardless of the setting method, there should be no gemstone cracking issue after setting. The prong-setting process relies on metal prongs to secure the gemstone. Force presses the setting prong against the gemstone edge during the setting process. If the force is misapplied, it may damage the gemstone, causing it to crack.
【Case 8 -12】The Prong does not push the stone closely, as shown in Figure 8-11.
Analysis:
When the setting prong does not adhere to the gemstone edge, the gemstone is unstable and prone to falling off or coming loose.
[Case 8-13] The setting base for the pave setting is too large, and the stone is not flat, as shown in Figure 8-12.
Analysis:
Pave setting is a method of embedding multiple gemstones on the same item using pave setting technology, which requires that the gemstones not have uneven heights. In this case, the setting base is too large, causing the gemstone to sink noticeably after being placed in the setting base. Therefore, when operating, the position of the setting base should be determined based on the workpiece’s shape and the gemstone’s size. To observe the flatness of the gemstone, that should be observed from the overall shape of the workpiece, comparing the gemstone surface with the embedding position, considering the gemstone surface as a straight line, comparing it with the embedding base from four directions, if they are parallel, then the gemstone is flat.
【Case 8-14】The prong head is not round, as shown in Figure 8-13.
Analysis:
The prong setting process requires the prong head to be round and smooth, without flattening or extra edges like covering the hat. Otherwise, it will affect the appearance. In this case, the prong head is not round, and the extra edges have an obvious problem due to improper prong polishing operation.
【Case 8-15】The edge of the prong setting is too narrow, as shown in Figure 8-14.
Analysis:
In this case, the inner and outer circles of dense Prong setting round drills have the problem of the metal edge being too narrow, affecting the appearance.
[Case 8-16] Prong is too long, as Figure 8-15 shows.
Analysis:
In this example of a pave setting with round diamonds, prongs are too long and higher than the surface of the round diamond. This affects the appearance and luster of the diamond. The length of the prongProng should be controlled, neither too long nor too short, and should usually be controlled at half of the waist of the stone surface.
[Case 8-17] Inconsistent prong sizes, as shown in Figure 8-16.
Analysis:
Good pave setting craftsmanship requires consistent prong head sizes and uniform paving. In this example, the pave setting was done manually, resulting in inconsistent sizes, affecting the appearance effect.
[Case 8-18] The pavement’s diamond edge exceeds the stone setting area, as shown in Figure 8-17.
Analysis:
In this case, in the pave setting with multiple stones, two stones’ edges exceed the edge range of the stone setting area, affecting the appearance. This issue is related to the deviation of the stone setting hole position, inappropriate gemstone sizes, and setting displacement.
[Case 8- 19 ] The stones squeeze each other, as Figure 8-18 shows.
Analysis:
In a pave setting, stones should be evenly spaced between each other, and the situation where one stone is stacked on top of another stone, as shown in this example, should be avoided.
7. Common Setting Issues in Prong Setting
The Prong setting is representative of traditional craftsmanship. It tightly holds gemstones with long metal prongs (poles), allowing a large amount of light to enter from all directions without much metal obstruction, revealing its brilliance and making it appear larger and more dazzling. Prong setting is suitable for gemstones of different sizes; even large central stones can be securely fixed, becoming a popular solitaire diamond jewelry setting technique in the market. Prong settings come in various forms, such as round prongs, square prongs, triangular prongs, nail prongs, six prongs, four prongs, three prongs, two prongs, single prongs, and shared prongs.
Good prong setting worker should ensure that the prongs are tightly attached to the gemstones; the gemstones must be flat, without slanted stones, uneven stone position, loose stones, cracked stones, or other phenomena; the length of the prongs should be consistent and symmetrical, not crooked; the prong heads should be regular, not pinched or scratch on the back of the Prong; the gripping position of the prongs should be consistent in depth, shallowness, length. Common prong-setting problems are as follows.
【Case 8-20] Prong setting with cracked stones, as shown in figure 8 -19.
Analysis:
The Prong setting generally uses pointed-nose pliers to clamp the prongs tightly to fix the gemstones. Improper force or direct clamping on the gemstones during operation may cause the gemstones to crack and rot. Therefore, when using pliers to operate the prongs, use pointed-nose pliers to slightly clamp the symmetrical prongs, making the prongs attach to the stones, then clamp the adjacent two prongs straight and tight, careful not to exert excessive force.
【Case 8-21】Prong marks are too deep, as Figure 8-20 shows.
Analysis:
If the edges of the pliers are too sharp or excessive force is used when clamping the prongs, very deep plier marks will be left on the prong setting, which is not easy to remove during filing or weakening the prong setting to remove them.
【Case 8-22】Polishing prongs make stone surface scratches, as shown in Figure 8-21.
Analysis:
After the gem is set tightly, file and repair the prong head, polish it round, and complete it. Choose the appropriate Cup Burr to polish the Prong; Polish evenly from the inside to the outside and on both sides until the prong head is rounded. If the Cup Burr does not rotate smoothly during operation, causing jumping or vibration, it may damage the stone surface.
【Case 8-23】There is a gap between the gem edge and the setting base, and the Prong does not touch the stone, as shown in Figure 8-22.
Analysis:
Prong setting is used to secure gemstones by coordinating with the gemstone girdle, and a setting base should be cut before setting the stones. The cutting method of the setting base directly affects the stability and appearance of the gemstones. In this case, the angles and depths of the setting bases do not match the gemstone girdle, leaving gaps between the gemstone edges and the setting bases. To solve such problems, the position and size of the setting bases should be determined based on the size and thickness of the gemstones, ensuring consistent depth and height of the setting bases. The depth of diamond seat setting bases is generally 1/4-1/3 of the prong depth.
[Case 8-24] Incorrect prong position, as Figure 8-23 shows.
Analysis:
In this case, it is a four-prong setting, requiring four prongs to be symmetrically distributed without any deviation.
【Case 8-25】The Prong is too short, as Figure 8 -24 shows.
Analysis:
In the prong setting process, the gemstone is fixed by the Prong gripping the girdle of the gemstone, which requires the Prong to have a minimum length and enough metal to press against the gemstone girdle otherwise, there is a risk of loosening or dropping the stone.
【Case 8-26】The Prong is too long, as Figure 8-25 shows.
Analysis:
After setting the stone, the optical effect, comfort, and safety of wearing the gemstone should be considered. In this case, the Prong is too long.
[Case 8-27] Broken Prong, as shown in Figure 8-26.
Analysis:
The Prong setting is generally fixed with pointed-nose pliers to secure the gemstone. Due to the relatively thin diameter of the prong setting, the strength is limited. Improper operation may cause prong breakage. The reasons may include defects in the prong setting affecting strength and flexibility, excessively deep seating causing the prong setting to be fragile, multiple bending of the Prong causing the prong setting to become brittle, etc.
[Case 8-28] Prong skew, as Figure 8-27 shows.
Analysis:
In this case, one of the prongs at the bottom of the water drop-shaped gemstone is skewed, with asymmetric prongs on both sides. The reason is that when finishing, the skewed Prong was not corrected, or improper force was applied when setting the stone with the prong clamp, causing the Prong to skew.
[Case 8-29] The claws are not facing the corners of the diamond., as shown in Figure 8-28.
Analysis:
In this case, it is a four-prong corner setting, requiring symmetrical prongs on both sides of each stone corner to surround it, and shifting to one side should not occur.
[Case 8-30] The prong set gemstone does not cover the bottom mounts, as shown in Figure 8-29.
Analysis:
When setting drop-shaped, oval-shaped, heart-shaped gemstones, the position of the gemstone and the bottom frame of the setting must be aligned, and one end must not be offset to expose the bottom frame at the other end, as this will seriously affect the appearance. Therefore, before setting the stone, carefully check it, arrange the position of the gemstone reasonably, and pay attention to not twisting or displacing it when tightening the prongs.
[Case 8-31] The triangular Prong is not aligned, as shown in Figure 8-30.
Analysis:
Each type of Prong has specific requirements for the shape of the prong head. Round prongs require a round prong head, square prongs require a square prong head, and triangle prongs require a prong head in a regular triangle shape. In this example, the triangle prong head has issues such as multiple edges not being straight and angles missing, so further adjustments are necessary.
8. Common Setting Issues in Channel Setting
Channel setting is a setting method where slots are carved on the side of the setting, and gemstones are placed in the slots and firmly pressed. This method is commonly used for setting secondary stones in high-end jewelry. Additionally, some square and trapezoid diamonds are set using channel setting, resulting in a better visual effect.
Standard channel-setting methods include tension setting and channel setting. Tension setting uses the tension of metal to secure the waist or the waist and bottom tip of the gemstone, exposing more of the gemstone to showcase its brilliance. Channel setting involves carving grooves on the precious metal mount first, then placing the gemstones into the grooves. In this method, gemstones are continuously set in a metal channel one after another, utilizing the metal on both sides to support the gemstones, giving the jewelry surface a smoother appearance. The channel setting is suitable for round brilliant-cut gemstones of the same diameter and for varying baguette-cut gemstones.
The gemstone setting should be flat, consistent in height and placement, without loose, swinging, cracked, or slanted stones; reasonable control of the spacing between gemstones based on their shape, quantity, and the length of the setting; the metal edge should be tightly against the gemstone edge; after setting the gemstones, there should be no deformation or unevenness on the metal surface, etc. Common problems with gemstone settings are as follows.
Copywrite @ Sobling.Jewelry — Custom jewelry manufacturer, OEM and ODM jewelry factory
[Case 8-32] The diamond was shattered during the metal edge setting, as shown in Figure 8-31.
Analysis:
When setting gemstones, a setting stick is used to strike the metal edge and press against the gemstone girdle for stability. During the striking process, if the setting stick is not positioned correctly, it may directly impact the gemstone’s edge or surface, causing it to shatter.
【Case 8-33】When setting diamonds, the positioning is displaced, as shown in Figure 8-32.
Analysis:
When setting diamonds, the essential operation is to carve a setting base at the edge of the metal setting, insert the diamond girdle into the setting base, and then tighten it. Due to the gap between the diamond girdle and the setting base, improper pressing may cause the diamond to vibrate and shift. The correct operation should be: based on the thickness of the diamond edge, select a suitable setting bur to carve the setting base, then use the wheel needle to diagonally sweep the bottom metal according to the diamond thickness, aligning both sides of the metal with the gem. Place one side of the diamond into the setting base, press down the other side with appropriate force, arrange the diamond flat, press the diamond setting edge vertically to the metal surface, and tilt inward to push the corner of the setting until the diamond is tight, then press the metal edge vertically to the metal surface, press the metal edge until the diamond is tightly secured.
【Case 8-34】When setting multiple diamonds, uneven stone surfaces may occur, as shown in Figure 8- 33.
Analysis:
When setting multiple diamonds, the arrangement of diamonds should follow the outer shape of the metal setting, keeping it flat and smooth without unevenness. To solve the uneven stone surface issue in this case, besides ensuring the essential consistency of stone thickness during stone selection, the key is to adjust the setting base height appropriately during carving to make the metal base thickness similar.
[Case 8 -35 ] When setting multiple diamonds, the gaps between diamonds and between diamonds and the metal edge are too large, as shown in Figure 8-34.
Analysis:
When setting multiple baguette-cut diamonds, it is required that the diamonds are arranged continuously and the outermost diamonds are closely attached to the metal edge without obvious gaps. Otherwise, it will significantly affect the appearance. To solve the problem of excessive gaps, in this case, a careful comparison of the stones should be made during stone selection. Also, consider the arrangement and order of the stones during setting, taking the first stone as the standard, sequentially placing other diamonds, and requiring the diamonds to be flat and evenly spaced. If the mismatch is found, replace it with suitable gemstones for resetting.
[Case 8 – 36] The gemstones are skewed, as shown in Figure 8 -35.
Analysis:
For the channel setting of multiple rectangular diamonds, it is required that the diamonds are arranged in parallel and in close touch with each other. When operating, please control the depth of the setting reasonably based on both metal edges. After placing the diamond in the setting base, adjust its orientation before forcing it tightly. During the tightening process, the diamond is also prevented from vibrating, and slanted stones are checked. If so, observe which direction the gemstone is slanted towards, and add force on the corresponding symmetrical side until the gemstone is level. If the slanted stone is too severe, consider removing it, resetting the position, and then setting it again.
[Case 8-37] Stone dropping in channel setting, as Figure 8-36 shows.
Analysis:
When setting diamonds, the setting base position should be cut first, paying attention to the thickness of the setting base to the surface metal. The surface metal should maintain a specific thickness, generally about 0.4 ~ 0.5 mm, not too thick, as it can easily cause workpiece deformation, nor too thin, as it can lead to loose stones or stone dropping. The bottom metal should not be cut too hollow, as cutting too hollow can easily cause the stone to be too loose. When setting multiple gemstones over a long distance, a support pole should be set at the bottom to prevent the metal edge from deforming. The support pole should not be cut off during setting.
【Case 8-38】The bottom of the setting base is cut through, as shown in Figure 8-37.
Analysis:
The base of the setting supports the edge of the gem. If cut too much, it is easy to cause the gem to fall off and create an uneven gem-setting surface. Therefore, be cautious when cutting the setting base. If the bottom of the setting base is accidentally cut through, welding repair should be carried out.
【Case 8-39】The metal edge of the channel setting is too thin, as shown in Figure 8-38.
Analysis:
In the process of channel setting technology, the gemstone is fixed by the metal edges on both sides, pressing the waistline of the gemstone. If the metal edge is too thin, there is a risk of falling off during subsequent polishing, cleaning, or wearing. Therefore, it is required to control the thickness of the metal edge to about 0.4 -0.5 mm.
[Case 8-40] The edge is not smooth, as shown in Figure 8-39.
Analysis:
In channel setting technology, the metal surface and the two metal edges on the inner side become uneven after tightening the metal edge. It is necessary to use a flat chisel to make them smooth. When chiseling the edge, use a flat chisel to remove the metal chips left on the stone surface and chisel the metal edge flat to observe whether it is closely attached to the gemstone. The effect of chiseling the edge is related to the quality of the grinding and operation techniques. When grinding the chisel, the wrist and the forearm are in a straight line; the armrest maintains a certain angle and height. Use the wrist to control the angle between the needle and the oilstone; grind the chisel to a 95-degree angle; this angle is ground thinner and sharper, which is conducive to removing metal. When grinding the chisel, pay attention to not swinging the hand left and right; the two faces of the chisel should be the same size, the surface should be smooth and shiny, and should not form an arc and multiple cutting surfaces; the cutting edge of the chisel should be a sharp straight line. When chiseling the edge, the hand should be stable, and the direction of chiseling should follow the shape to prevent chiseling the metal edge into a wavy line or scratching.
[Case 8-41] Corner Not Trimmed Correctly, as shown in Figure 8-40.
Analysis:
In channel setting technology, the metal surface and the two metal edges on the inner side become uneven after tightening the metal edge. It is necessary to use a flat chisel to make them smooth. When chiseling the edge, use a flat chisel to remove the metal chips left on the stone surface and chisel the metal edge flat to observe whether it is closely attached to the gemstone. The effect of chiseling the edge is related to the quality of the grinding and operation techniques. When grinding the chisel, the wrist and the forearm are in a straight line; the armrest maintains a certain angle and height. Use the wrist to control the angle between the needle and the oilstone; grind the chisel to a 95-degree angle; this angle is ground thinner and sharper, which is conducive to removing metal. When grinding the chisel, pay attention to not swinging the hand left and right; the two faces of the chisel should be the same size, the surface should be smooth and shiny, and should not form an arc and multiple cutting surfaces; the cutting edge of the chisel should be a sharp straight line. When chiseling the edge, the hand should be stable, and the direction of chiseling should follow the shape to prevent chiseling the metal edge into a wavy line or scratching.
[Case 8-42] Metal Edge Concave, as shown in Figure 8-41.
Analysis:
In this case, the metal edge becomes uneven after the forced push and needs to be smoothed by edge sanding. The metal edge depression, in this case, is exposed after the edge sanding. The reasons may include poor metal texture, hidden pores, shrinkage, inclusions, sand holes, and other defects; uneven channel during forcing; excessive forcing at that point resulting in deep depression. To solve this problem, corresponding measures should be taken for the above reasons.
[Case 8-43] Uneven width of metal edge (commonly known as large and small edges), as shown in Figure 8-42.
Analysis:
When setting gemstones, it is generally required that the widths of the metal edges on both sides are consistent, there should be no too-large and too-narrow edges, and the edges should be close to the gemstones. The reasons for the occurrence may include: the jewelry master mold already has large and small edges; when holding the mold, the setting mouth edges are sanding into too large and too narrow.
[Case 8-44] Metal residue with metal edges, as shown in Figure 8-43.
Analysis:
When shoveling the edge, the remaining metal chips on the stone surface were not cleaned, covering part of the stone surface.
[Case 8-45] Residual lacquer on metal pieces after setting stones, as shown in Figure 8-44.
Analysis:
Generally, when setting gemstones, lacquer is used to fix the metal pieces for pressing, and then the lacquer is cleaned with turpentine after setting the stones. In this case, the lacquer was not cleaned properly, affecting the subsequent work and needing to be cleaned again.
9. Problems with Invisible setting
Invisible setting is a new type of gemstone setting method, which is highly welcomed in the market for its appealing gemstone appearance. The basic principle is that when setting multiple rows of gemstones, shallow grooves are opened on the bottom side, transferring the fixed metal from the stone surface to the stone bottom groove and using external force to force the metal into the groove to secure the gemstones. Therefore, only the outermost metal of the gemstone is visible, and no metal can be seen between the gemstones, commonly known as “seeing the stone but not the metal.” Invisible setting technology breaks the traditional setting technique, allowing diamonds to have no metal covering above the girdle, ensuring optimal light entry at the crown and girdle, allowing the gemstone’s fire to shine more perfectly, thus ensuring the diamond presents the perfect optical effect, further enhancing the appearance of the entire jewelry piece. Especially for cluster-set diamonds, as there are no metal prongs or edges around the diamonds, the joining and color transition between diamonds are perfect and natural, creating more elegant patterns. Without the traditional metal prong barriers, light propagates more widely between the diamonds, making the diamonds more brilliant and dazzling.
The requirements for the invisible setting are as follows: the gemstones should be flat, tightly set, consistent in height, with no gaps visible to the crossbar, and should not exhibit loose stones, cracked stones, crooked stones, or slanted stones phenomena. The gemstones should align, and the cross position should be correct. However, the invisible setting is a highly skilled manual technique for setting and is prone to setting problems. Typical invisible setting setting problems are as follows.
【Case 8-46】Diamonds are not arranged neatly, resulting in gaps and misalignment, as shown in Figure 8 -45.
Analysis:
At least three steps need to be done well to achieve the effect of an invisible and seamless setting. Firstly, the cutting and grinding of diamonds are crucial. The shape and size of each diamond must be consistent, which requires precise calculation and cutting to ensure. Secondly, when making the metal base, it is necessary to accurately control the shrinkage amount, maintain the original setting position, and avoid deformation of the setting during the inversion and holding molds. Thirdly, the setting operation should be correct, with stones set from the middle to the sides in sequence, diamonds arranged neatly, and correct cross position. Each diamond’s edge should cover half of the crossbar, and after two stones are set, the crossbar should be covered entirely, with no apparent gaps between diamonds.
【Case 8-47】The Invisible setting diamond fell off, as shown in Figure 8 -46.
Analysis:
To achieve the effect of seeing the stone without seeing the metal in the Invisible setting, the metal fixing the gemstone needs to be transferred from the stone surface to the bottom groove of the stone, and the gemstone is securely fixed by forcing the metal into the groove through external force. Compared with other setting methods, in this process, the diamond is fixed by the minor concave groove at the bottom of the diamond, making the operation very difficult and more prone to stone-dropping issues. To solve this problem, several aspects should be considered. First, the metal base support structure should have sufficient strength, especially for large areas or long rows of Invisible settings. In addition to a sufficiently strong crossbar in the jewelry master mold, bottom support should also be added to give the jewelry a specific ability to resist deformation and prevent gemstone loss.
Specific requirements are also placed on the crossbar and bottom support to secure the gemstone without affecting its appearance.
Generally, the thickness of the crossbar metal should be controlled at 0.35 〜0.45 mm, and the height should be lower than the metal surface on both sides by 0.75 〜0.85 mm. The bottom support serves a reinforcing role, and since it affects the brilliance of the gemstone, its dimensions should be set as small as possible to meet mechanical requirements.
Secondly, the height and depth of the diamond bottom groove should be appropriate. The diamond is not easy to fix when it is too high, and excessive pressure can easily cause stone breakage. When it is too low, the groove can be seen from the top of the gemstone, affecting the appearance. Generally, the groove should be milled at a distance of 0.5 ~ 0.6 mm from the gemstone waistline, with an opening width of 0.2 ~ 0.3 mm and a depth of 0.1 〜0.2 mm.
Thirdly, when setting the gemstone, attention should be paid to the grooving, setting, and pressing methods. Suitable grooves should be cut on the metal base support, with the opening size of the middle crossbar groove at 0.2 〜0.3 mm, a depth of 0.1 〜0.2 mm, and a height from the metal top surface of 0.2 〜0.3 mm; the opening size of the two side metal grooves at 0.25 〜0.35 mm, a depth of 0.2 〜0.25 mm, and a height from the metal top surface of 0.4 〜0.5 mm. After setting the grooves properly, use a flat shovel or tweezers to pick up the gemstones, starting with the side that needs pressing, and then gently push the side of the stone with the groove into the groove of the crossbar, fitting them together like gears.
For Invisible settings with three rows or more, it is better to start setting the crossbar and gemstones from the middle because the middle stone does not have metal on the face for pressing. Controlling the loose stones depends on the gemstones on both sides pushing the crossbar towards the middle, so the positioning must be accurate, and the stones must not be loose; otherwise, the middle is easily raised during pressing.
Due to the tiny amount of metal holding the gemstone setting base, loose and dropping stones are prone to occur. To address this issue, some factories adopt a rigorous 40-hour high-temperature and high-frequency vibration test process, using the high-frequency vibration and high-temperature 100℃ water of an ultrasonic machine to test the firmness of the gemstone setting.
【Case 8-48】The Invisible setting stone corner collapsed, as shown in Figure 8-47.
Analysis:
When tightening the diamond, the stone corner broke. To solve this problem, the thickness of the surface metal should be manageable, the force, position, and direction of tightening the stone should be controlled, and a direct hit on the stone surface should be avoided.
[Case 8 -49 ] Excessive metal covering on the stone surface in an invisible setting, as shown in Figure 8-48.
Analysis:
To achieve a good appearance effect, an invisible setting requires controlling the width and thickness of the stone edge; the metal edge should not cover more than 2/3 of the stone side, and excess should be removed. When selecting the stone, attention should be paid to matching the size with the setting.
【Case 8- 50】The metal setting without edges does not stick to the stone, as shown in Figure 8-49.
Analysis:
After setting, there may be a situation where the gemstone and the metal edge cannot be tightly attached, resulting in a gap in the middle, affecting the stability and appearance of the gemstone. The reasons may include the diamond being too small and not matching the setting, the stone setting being biased to one side, improper direction of force during pressing, over-shoveling during edge shoveling, etc.
10. Common Setting Problems in Bezel setting
Bezel setting is a method in which metal is tightly embedded around the gemstone. It can be divided into two categories: edged bezel setting and invisible bezel setting. Edged bezel setting has a metal edge wrapped around the gemstone, technically known as a ‘setting mount,’ which is a common gemstone setting way; invisible bezel setting wraps the metal around the gemstone without a circular edge, mainly used for the setting of small gemstones or side stones. In addition, according to the size of the metal edge surrounding the gemstone, it can be further divided into whole setting, half setting, and tooth setting. Tooth setting is a setting method for cabochon gemstones, only wrapping around the top corner of the gemstone, also known as ‘corner setting.’
The Bezel setting with gemstones is more secure and suitable for the setting of considerable size, expensive, and brightly colored gemstones, such as large diamonds, cabochon, or saddle-shaped jadeite jade ring faces; however, due to the metal wrapping, the light transmission of the gemstone is relatively reduced, and the area of the gemstone seen is also reduced compared to the original stone. Therefore, it is unsuitable for transparent gemstones with fire color highlights and small size settings.
Bezel setting is craftsmanship with specific difficulty, requiring the gemstones to be flat after setting, in the center of the setting, without slanting stones, loose stones, cracked stones, crooked stones, uneven stones, etc.; the workpiece cannot deform after setting, the metal edge should be smooth, the surface metal should retain a specific thickness, not too thick or too thin. Common bezel-setting craftsmanship problems are as follows.
【Case 8-51】Setting mount is broken, as shown in figure 8 – 50.
Analysis:
When the setting mount is broken, the gemstone cannot be wrapped entirely, leading to unstable setting stones and poor appearance. The reasons for the breakage may include incomplete mold and filing too much during setting.
[Case 8-52] Bezel setting edge not attaching stone, as shown in Figure 8-51.
Analysis:
There is a gap between the gem and the metal edge; the metal edge does not cover the stone, leading to the risk of the stone falling off. Possible reasons for this problem include the gem size needing to be bigger and matching the setting mount, the stone setting being biased to one side, the stone needing to be correctly positioned during setting, and improper force and direction when pressing the metal edge.
[Case 8 -53 ] Bezel setting edge is not smooth, as shown in Figure 8-52.
Analysis:
In this case, the round diamond in the bezel setting and the metal edge after the setting present a polygon, seriously affecting the appearance. After tightening the gemstone, edge sanding and setting trimming are necessary for the process of setting. The edge trimming must follow the shape, and the metal edge of the round diamond in the Bezel must be trimmed round and smooth.
[Case 8-54] The bead in the bezel edge is not smooth, as shown in Figure 8-53.
Analysis:
In this case, after the round diamond in the Bezel is set, the metal edge of the bead appears uneven, sometimes present and sometimes absent. The correct technique should be mastered during operation to achieve a good bead effect. The bead chisel should not deviate from the metal edge, and when rolling and pressing the bead back and forth, it should follow the original trajectory without deviation.
11. Common Setting Problems with Gypsy Setting
Gypsy Setting is a technique similar to bezel setting. The gem is deeply set in a circular metal base, with the edges tightly wrapped by metal, and the gem’s periphery has a recessed metal ring. Under light, it looks like a halo, hence the name Gypsy Setting. Depending on whether there is a metal hook inside the metal stone bowl, it can be divided into Gypsy Bezels Setting and Gypsy Prongs Setting. Gypsy prongs Setting, or Italian setting, involves hand-carving several metal teeth on the metal ring to set the gemstone. Gypsy Setting, due to the presence of the metal halo, visually gives the impression that the gemstone has increased significantly in size, and the circular halo also has a specific decorative effect.
For good quality Gypsy Setting craftsmanship, the gemstone should be set flat and tight, without phenomena such as cracked stones, slanted stones, or crooked stones. The edges of the setting should be even, consistent in thickness, and shiny without scratches. The prongs should not be too long or too short; the prong direction should be consistent, and the prongs should be symmetrical and uniform in size. Common problems with Gypsy Setting craftsmanship are as follows.
【Case 8-55】The cross prongs of the prong setting are not positioned correctly, as shown in Figure 8-54.
Analysis:
In this case of a prong setting, the positions of the four prongs are not asymmetrical, affecting the overall appearance.
[Case 8-56] The prongs of the gypsy setting are broken and deformed, as shown in Figure 8-55.
Analysis:
In this case of the gypsy setting, some prong prongs are broken, and some are deformed and curled, affecting the appearance effect.
[Case 8-57] The position of the gypsy setting stones displaced, as shown in Figure 8-56.
Analysis:
The gemstone deviates from the center position after setting, which may be due to the gemstone size being too small and not fitting the setting; the gemstone was not placed correctly during setting; the Prong pressing caused the gemstone to be displaced.
[Case 8-58] The edge of the gypsy setting is incomplete, as shown in Figure 8-57.
Analysis:
The periphery of the gemstone in the gypsy setting has a ring with a bowl-shaped metal edge. Due to the thin top edge, defects such as jewelry casting incomplete and filing too much may occur during production.
12. Setting Problems in Wax Setting Casting
Wax setting is a widely used method in jewelry-making, especially with many inlaid gemstones. The wax setting process has become a meaningful way to reduce production costs, improve production efficiency, and increase product competitiveness. The so-called wax setting is in contrast to the metal setting. It is the process of pre-setting gemstones in wax models before casting. After investment, dewaxing, and burnout, the gemstones are fixed on the plaster wall of the mold cavity. When the molten metal is poured into the mold cavity, the metal encases the gemstones, and after cooling and shrinking, the gemstones are firmly fixed in the metal setting. The wax setting technology is based on the traditional lost wax casting process, but each production process has uniqueness and difficulties. While bringing efficiency to jewelry processing enterprises, it also carries certain risks. Only with a complete understanding and strict operation of the wax setting process as required, can the stability of wax setting quality be ensured and the advantages of wax setting technology be genuinely realized.
Wax setting casting technology is a comprehensive technology that integrates knowledge from various fields such as casting technology, gemology, metallurgy, jewelry-making technology, aesthetics, etc. It has a wide range of expertise and many influencing factors. Any change in factors may affect the wax setting casting effect, leading to quality problems or even scrapping of the final product. Therefore, if this process is not effectively controlled, the cost of wax setting casting may be higher than that of conventional jewelry casting.
As shown below, common problems in wax settings include cloudy stones, cracked stones, black spots, stone loss, uneven or misaligned stone positions, and metal-wrapped stone surfaces.
【Case 8-59】Wax setting diamond shattered, as shown in Figure 8-58.
Analysis:
In wax setting casting, it is common for some gemstones to crack or shatter, mainly occurring in jewelry pieces with multiple stones set closely together. Possible reasons for gemstone breakage in wax settings include:
(1) The quality of the gemstone needs to be improved for wax setting casting. Regardless of the type of gemstone, if it contains defects such as cracks, potential cleavages, or many internal inclusions, it is likely to crack or shatter after being subjected to high temperatures and thermal shock.
(2) The shrinkage rate of the master model is incorrect. If the shrinkage rate of the master model is reserved small but shrinks large, it may cause gemstone-shattering issues.
(3) When setting stones, if the gaps between gemstones are too small or they touch each other, the stones may be squeezed and shattered during casting shrinkage.
(4) If the heating rate during burnout is too fast, there is a risk of cracking when gemstones are subjected to high temperatures, thermal shock, and thermal stress.
(5) When the casting temperature is too high, the gemstones are in direct contact with the molten metal, causing the gemstones to undergo a sudden and significant thermal shock. The higher the casting temperature, the greater the thermal shock, and the more likely the gemstones are to shatter.
(6) The metal alloy itself could be more suitable for wax casting. When the alloy has a high melting point and poor fluidity, producers often need to increase the casting temperature to create a tremendous thermal shock to ensure practical molding.
The corresponding solutions to the above reasons are as follows:
(1) Use gemstones suitable for good-quality wax casting, requiring gemstones to withstand relatively high temperatures and have a certain tolerance for uneven heating and cooling, avoiding gemstones with cracks or sensitivity to temperature and heat shock.
(2) Rubber molds, wax injection, and casting processes all involve a certain amount of shrinkage, significantly impacting gemstone settings. When designing and making the jewelry master molds, the total shrinkage of rubber molds, wax molds, and metals must be comprehensively considered.
(3) Distribute gemstones reasonably, ensuring they have uniform and sufficient gaps, with particular attention to closely arranged gemstones. Calculate the size of reserved gaps according to the shrinkage rate, generally controlling the gemstone gaps at 0.015〜0.04 mm in cases where gemstones are required to be closely arranged and ensuring that the gemstone gaps are uniform and consistent, avoiding problems such as stacked stones, squeezed stones, stone corner contact. Due to the tendency of V-shaped gaps at corners, arranging gemstones at corner positions first should be followed during the setting operation, and individual stones may be inserted upside down if necessary to ensure gemstone gaps.
(4) Control the heating rate during burnout, as the burnout of the mold is a crucial aspect of wax casting. The burnout furnace should be capable of precise temperature control, ensuring that the mold is heated as evenly as possible to reduce the risk of gemstones developing cracks due to thermal shock and heat stress.
(5) Pay attention to controlling the number of jewelry pieces on the casting tree and reduce the temperature of the molten metal as much as possible while ensuring molding. The casting equipment should have precise temperature control to ensure consistent and stable quality of the castings.
(6) Select an alloy suitable for investment casting. The alloy used for investment casting should have a low melting point, good fluidity, and oxidation resistance. During production management, investment casting scrap and conventional casting scrap should be stored separately, and attention should be paid to timely refining.
[Case 8-61] The gemstone becomes cloudy after investment casting, as shown in Figure 8-59.
Analysis:
After investment casting, the diamond loses its original luster and turns milky white. Possible reasons for the cloudiness include:
(1) The quality of gemstones. If there are apparent inclusions inside the gemstone, it may turn milky or frosty during the casting process; secondly, gemstones that cannot withstand high temperatures or change color at high temperatures are not suitable for wax setting; these gemstones include amethyst, blue topaz, citrine, etc., especially some gemstones that have been artificially treated to improve color, the color will change or fade after heating, the emerald has a weak tolerance to heating, especially uneven heating, so it is not suitable for wax setting casting process; furthermore, gemstones that burn at high temperatures are also not ideal for wax setting casting, such as pearls, amber, coral, turquoise, etc., they will burn at high temperatures.
Making the gemstone surface rough and slightly cloudy inside, so the wax setting casting process cannot be used
(2) No protective measures are taken in the investment powder, and general investment powder is used to make the mold. In wax setting casting, gemstones are baked at high temperatures for a long time with the mold in the burnout furnace, and the high-temperature metal liquid during pouring also produces thermal shock on the gemstones, causing problems such as discoloration and loss of luster. In production, a boric acid solution is generally used for protection, and boric acid plays a role in preventing gemstones from discoloration in wax setting casting.
(3) The burnout temperature is too high, or the metal pouring temperature is too high, exceeding the tolerance of the gemstone.
For the above reasons, corresponding solutions should be adopted:
(1) Use good quality gemstones suitable for wax casting.
(2) Use wax-specific casting powder, or add boron acid and other protectants in the general casting powder as required.
(3) Control the burnout temperature so that it does not exceed the specified upper limit, and adjust the mold temperature according to the casting structure during casting.
(4) Choose the appropriate sprue metal composition and try to reduce the pouring temperature of the metal liquid.
【Case 8-62】Diamonds turn black after wax casting, as Figure 8-60 shows.
Analysis:
It is called “displaying black” because when the diamond is removed from the parcel, it is found that it does not turn black. It is often the optical effect caused by the metal covering the bottom of the diamond. Possible reasons for the appearance of black caused by the metal covering the bottom of the diamond include
(1) The pre-drilled setting hole at the bottom is too small, blocking the light from entering, and the delicate gypsum column is prone to cracking, causing the metal covering at the bottom of the diamond, as shown in Figure 8-61.
(2) Careless inspection during wax model-making results in the existing metal covering inside the hole.
(3) When setting stones, no setting bases are opened, and the gemstones are directly heated to embed in wax. After the wax melts, a layer of wax film is covered on the bottom of the stone in a triangular shape, forming a metal film after casting, as shown in Figure 8-62. Since the gemstone is set in a metal setting, the transparency of the bottom of the stone directly affects its brightness. The more the bottom of the stone is covered, the poorer the brightness and the more severe the degree of blackness displayed.
(4) When making wax casting trees, if the wax mold is not oriented correctly on the wax tree, with the stone surface facing up and the bottom setting hole facing down, air bubbles may be trapped at the bottom of the stone during vacuuming, making it difficult to remove, resulting in the formation of metal beads after casting and causing blackness.
(5) When mixing gypsum slurry, if the powder-to-water ratio is appropriate and the water content needs to be higher, the gypsum slurry becomes too dense and cannot quickly fill the bottom setting hole.
(6) After casting, residual gypsum powder remains if the bottom setting hole is not cleaned thoroughly.
For the above reasons, the following solutions should be taken:
(1)Make the end pre-drilled hole as large as possible, with a diameter at least the size of the gemstone diameter 2/3.
(2) Before wax setting, carefully inspect the wax mold, drill through the pre-drilled hole, and remove any internal burrs.
(3) When setting, create setting base sizes on the wax mold that fit the diamond’s waist, positioning the diamond in the setting base. Generally, the setting base should be shaped like ” <, “with an opening size of about 0.25 ~ 0.35 mm and a depth of about 0.2 〜0.25 mm. Avoid directly heating the gemstone to embed it in the wax mold. If necessary, only slightly heat the gemstone to ensure it is not covered by wax.
When dealing with the bottom wax, reduce it as much as possible while providing the stone is secure. Bottom wax is relatively easy to handle for straight rows of multiple gemstones. Still, for curved products, especially at large corner areas, when setting rectangular or baguette gemstones, it is easy for the gemstone to not fit well in the setting, causing two corners of the stone to protrude too much into the wax edge.
In comparison, the other two corners are left hanging. In this case, only directly fill the wax after further processing the stone bottom, as this can lead to wax accumulation at the bottom, causing blackening of the stone after casting. Additionally, due to the gradient of the stone and the curvature of the bend often being uneven, if the placement of the stone is not adjusted correctly during wax setting, triangular gaps can quickly form, affecting the appearance and potentially causing the stone corners to touch, leading to chipped stones after casting.
Therefore, in wax setting operations, the principle of minimizing bottom wax should be followed as much as possible. The step wax pattern should be used in areas with prominent bends, as shown in Figure 8-63. This approach does not affect the appearance of the stone but significantly reduces the bottom wax’s light-blocking and heat-shock effects, ensuring the gemstone’s brightness.
(4) Wax molds are placed on wax trees, with the gemstone facing down and the bottom setting hole facing up so air bubbles are less likely to be trapped at the bottom.
(5) When mixing gypsum slurry, appropriately reduce the powder-to-water ratio to increase the flowability of the slurry.
(6) After casting, carefully rinse the castings, soak them in an acid solution to remove the residual gypsum inside the bottom setting holes, and clean the bottom of the stone during sanding.
【Case 8-63】Gemstone covered with metal film, as shown in Figure 8-64.
Analysis:
After wax setting and casting, a layer of metal foil appears on the surface of the gemstone, or it is partially covered with metal, affecting the luster of the gemstone. Since diamonds are oleophilic, a skinny layer of oil film is easily formed on the stone surface during wax setting operation. In addition, when adjusting the stone clearances and handling the wax position, wax crumbs on the bottom of the stone are sometimes inevitable and must be thoroughly cleaned with alcohol. Otherwise, a metal foil will form after casting, affecting transparency and causing black stones. Therefore, after the wax setting operation, pay attention to the cleanliness of the stone surface and bottom, and use alcohol to remove wax crumbs, dust, and other debris.
【Case 8-64】Poor fixation of stones or gemstones falling off after wax setting and casting, as shown in Figure 8-65.
Analysis:
Wax setting and casting involve directly setting the gemstone on the wax mold, and the metal edge fixes the gemstone after casting. Since wax setting involves multiple process steps, improper process parameters or operations will result in poor fixation of stones or gemstones falling off after wax setting and casting. The possible reasons and solutions for gemstones falling off after wax setting and casting are as follows:
(1) The jewelry master mold setting mount is not suitable. When wax setting, the gemstone should be kept in the plaster mold and ensure that the gemstone is fixed in place. To prevent the gemstone from shifting or loosening during stone investment, burnout, and casting, the gemstone should be supported by the mold in at least two positions.
Therefore, generally, holes are opened at the bottom of the setting mount, and they should be made as large as possible, even larger than half the diameter of the gemstone, to avoid covering the metal on the bottom surface of the gemstone or unstable fixation of the gemstone after casting.
(2) The gemstone is not firmly set in the wax mold. The main reasons include the gemstone not being suitable for setting, needing more support in the wax mold, the bottom wax being too hollow when waxing, and a large gap between the gemstone and the wax edge.
Therefore, careful preparation should be done to inspect stones, stone placement, setting mount, and positioning before setting. Place the stone in the setting mouth to see if it fits. If it is not suitable, it needs to be replaced. Adjust the stone’s height and the wax models’ depth on both sides when setting the stone, and seal the wax edges on both ends to make it stable.
(3) The inappropriate casting process results in defects in the castings, leading to gemstones falling off or being unstable. There are several main aspects:
First, the design of the pouring system is unreasonable, such as the cross-sectional size of the sprue being too small, too few sprues, improper positioning, uneven distribution, etc., causing the metal liquid flow path to be too long, and the passage is blocked before complete filling. The sprue should be determined according to the casting structure. In addition to considering the flow state of the metal liquid under general conditions, the friction of the metal liquid on the mold wall, the cooling situation of the metal liquid, and the fluidity of the metal liquid should also be considered. Ensure sufficient head pressure height and shorten the metal liquid flow path as much as possible to ensure smooth metal liquid flow.
Second, the casting mold temperature is low, accelerating heat absorption from the metal liquid. It may condense before the metal liquid can fill the mold cavity. Therefore, the casting mold temperature can be appropriately increased without affecting the quality of the gemstone.
Third, there are problems with the smelting and casting operation. For example, poor quality of the smelted metal liquid with a lot of gas or inclusions reduces its fluidity; the casting temperature of the metal liquid is too low, the filling capacity is poor, which may easily lead to incomplete cold shuts; the casting speed is too slow, or the casting is not smooth, intermittent; insufficient metal liquid for casting, etc.
Therefore, calculate the amount of metal liquid before smelting, protect the metal liquid during smelting, appropriately increase the casting temperature of the metal liquid, the casting speed should not be too slow, and interruptions in the liquid flow should be avoided during casting.
