ฝังพลอยที่เทียน( wax set)1 กับ คุณสันต์ ภาณุสฤษฏิ์ -1

GENERAL CASTING ADVICE ON STONE IN WAX CASTING We hope that this section is a helpful tool and will help you to begin to cast stone in wax pieces. However much care and testing should precede the manufacture for full production runs, especially when using precious stones. Ensure your equipment is calibrated accurately and that you have taken the appropriate steps to fully educate yourself on the entire stone in place process. WHICH STONES CAN I USE? Many stones can be cast in place but not everything. Stone-in-wax casting always involves risk— stones can break or have their appearances changed by any number of factors during this intricate process.A word of caution when trying to use stones where the colour has been enhanced by heat-treating: the casting process may negatively affect the stones appearance and colour. Always test stones first for colourfastness and heat tolerance during casting before using them in your stone-in-wax designs.If you are not sure whether your stones can be used we have a simple test as follows:We suggest taking two stones of the same kind, imbedding one in a paper or plastic drinking cup with investment and running through the burnout process. Compare the two after the burnout to see if the quality of the stone has changed.Do not use lab-created spinel doublets in stone-in-wax settings.Use good quality stones, which are of a consistent size for stone in wax setting. CLICKSET™ masters are engineered to close tolerances and will not always accept variation in stone sizes. Out of calibration over sized stones can be set in the wax however, heat and pressure from the casting process can crack or break the stones later in the process costing money in lost production and set up time. Choose to use quality-calibrated stones for the best results with stone in wax setting.It is safe to say that most soft stones cannot be used. It does not matter weather the stone is transparent or not the hardness is the key.Larger more expensive stones should not be attempted because there is always a risk of damage to the stone.Highly included or fractured stones should not be cast in place.Stones that have been found to be unsuitable for stone in casting include: amethyst, lapis, pearls, peridot, topaz, tourmaline, turquoise and black colour CZ’s.opal can be cast in place, but care has to be taken to heat and cool these stones very slowly.When using CZ in the stone in wax models keep in mind that small stones (under 2mm) can withstand temperature shock and typically do not tend to crack easily. They however will dull more quickly than larger diameter CZ stones. CZ over 5mm diameter tends to be more susceptive to temperature shock stress cracking. Make temperature transitions as smooth as possible to reduce the opportunity for shock cracking of larger CZ material stones.The shape of the stone to be cast in place should also be considered. Stones with knife edge girdles, inclusions and sharp points are at higher risk for potential damage.Proper point voids should be built into the master to accommodate stone shapes like Marquise, Pear, Trillion, Trilliant or Princess cuts. Voids in the model where the points of the stone rest relieve any stone stress and reduce the opportunity for the tip to break when hot metal is cast around the stone later in the process. MODEL MAKING Master models must be adapted for stone in wax casting. The shrinkages that occur during the rubber moulding, waxing and casting process have a critical impact on the setting of the stone.It is necessary to engineer the master pattern firstly to allow the stone to “click” into the wax easily and securely and secondly to ensure a good setting in spite of all the shrinkages during casting.The master model requires very strict dimensional control to maintain stone integrity and quality results. All shrinkage factors must be accounted for when designing the stone in wax master model: metal shrinkage, moulding shrinkage and injection wax shrinkage. Not accounting for all of the shrinkage factors can cause stone breakage later in the process. Remember that the master is the benchmark for all processes to follow and the quality of the master directly affects the quality of the end result. Stone in wax casting can be a costly process if not thought through and controlled explicitly.It is possible to adapt the master model yourself and many companies already do this. However it is a complicated process and requires precision engineering work and exhaustive testing to ensure the correctly functioning master pattern. SRS propose Clickset™ master settings or their own stone in place master model making service which will allow jewellery companies to bypass this most complicated stage and to start stone in wax setting immediately.Make sure that the master model for stone in wax is finished down to a 4/0 emery finish or polished to a high lustre for rhodium plating if desired.There should not be any tool marks in the master model; it should look like you expect a fine finished jewellery piece to look.When using the Clickset products make sure to file and shape the components as desired, do not hammer or bend them to fit a contour as this will result in severe distortion of the master product and stones will not fit properly in the wax and give poor results. RUBBER MOULDS We recommend standard organic rubber like Castaldo white or Gold label as the preferred rubber for stone in wax setting.Properly designed master models for stone in wax casting will have the built in tolerance for standard organic rubber moulding procedures. When using the CLICKSET master components do not mould the master model using any RTV or 0-1% shrinkage mould materials, the tolerance for organic rubber moulding is built into the master on the front end, using zero percent moulding materials may result in stones being loose in the metal pattern after casting. Please be aware that not all models will shrink by the same amount.When cutting the mould to remove a stone in wax master model be sure to hide the parting lines as much as possible. In the case of the CLICKSET master, place the internal parting line on the seat nibs not where the stone will seat. Parting lines can translate into flash or an edge that could possibly cause a stone to break later in the process. Also, carefully place any external parting lines on edges of the master pattern for ease of clean up and aesthetics. As with all mould making procedures, ensure that the wax model is properly vented to reduce any defects when shooting the wax into the mould. It is extremely critical that the quality of the injected wax pattern for stone in wax setting be of the highest quality without any defects in the wax or on the wax pattern surface. Cut moulds so that wax patterns pull easily without distortion to the overall design.  WAX INJECTION It should be possible to use most types of wax for stone in wax setting. Much is dependent on ambient temperature inside the work shop.It is however necessary for the wax to have a certain elasticity to allow the stones to really “click” into place. SRS recommends the SRS 003 Pink wax.Inspect all wax patterns for signs of defects or blemishes that will translate into the metal in the final product.With the time that is invested into making a master for stone in work it is well worth additional time on the front end of the process to insure that the end cast result is of the highest quality.Clean and smooth all wax patterns in preparation for the stone setting into the wax.As a general practice, all waxes that are injected in a day should be used the same day.Wax patterns that set over night can become brittle and break when the stone is clicked into the stone seat.Freshly injected wax patterns should be allowed to set and normalize for several hours, if a stone is set into a warm newly injected wax this could result in distortion of the wax pattern and a poorly fitting seat for the stone in the wax. * When