REFINING CUSTOMERS - Due to the current influx of precious metal pricing, our standard lead time has increased by 3 business days. Please allow 6 business days for refining clean scrap and 13 business days for stone removal and/or sweeps.
About Molds
We select the mold material that best suits your piece unless otherwise requested. Generally, there is 1% to 6% total shrinkage from master to finished piece. Shrinkage occurs during molding, injection, casting, and finishing. Shrinkage has been calculated from in-house tests and manufacturer specifications and may be different depending on model geometry. (Example: Marquise dimensions change differently than squares and outside dimensions change differently than inside dimensions.)
It is your responsibility to plan for the dimensional change in your parts based on your needs. Consider your model’s sprue location, mold material, finishing process and final part requirements. Please call or e-mail with any dimensional change (shrinkage) questions, concerns or for further assistance.
Sometimes, the pieces we receive, while esthetically beautiful, do not account for the natural laws of precious metal flow dynamics. These technical design issues often cause porosity, non-fills, and other casting defects. Based on our experience and testing capability we can compensate for these issues by changing sprues, adding risers, adjusting flask and metal temperatures or recommending a change in the model.
PLEASE NOTE: Bracelets and/or complex-cut molds will require a quote.
Mold Recommendations
If you want us to work from your mold or metal model, we may recommend modifications to ensure quality. Most commonly we need to replace, modify, move, or completely alter the feed sprue system of your metal model to get the best casting results. Alterations to molds or sprue changes on models are done for a fee. Sprue changes on models will also require making a new mold for a minimal fee. We will contact you in advance regarding any recommended changes.
IF YOU CHOOSE NOT TO HAVE MODIFICATIONS TO YOUR MOLDS OR MODELS, we reserve the right to reject a model mold, or waxes if we feel that the labor required to produce the order exceeds our costs, or that the results will produce poor quality pieces due to pre-existing uncorrected defects.
If you have spent a lot of time or money making a hand carved wax or rapid prototype, it is always in your best interest to make an RTV mold of your valuable design. The small $30+ investment in a mold is far cheaper than re-carving or rebuilding your design again in the event of a less than satisfactory casting. Back up molds from waxes, are always made in RTV. The casting and mold department will make individual decisions on what type of mold is needed based on the model sent.
Copyrights and Trademarks: Hoover & Strong will not copy or infringe on a customer’s copyright and is not liable for copyright infringements by others. It is the customer’s responsibility to maintain ownership of the submitted design. Hoover & Strong will not cast designs that have trademarks other than those owned by the customer.
Design and spruing are two of the most fundamental aspects of lost wax casting. They can be the source of a quality casting, or dreaded porosity. The challenge is that not all custom designs can be treated the same. Moreover, a good design or sprue placement for wax injection does not necessarily translate to a good casting. The general guideline is to allow the molten metal to flow from thicker areas to thinner areas; the sprue should be placed at the thickest area to facilitate this flow and metal freeze, as allowed by the detail of the piece. Otherwise, shrinkage occurs and porosity appears.
This principle holds true for design as well. For instance, a piece that holds several geometry variations (i.e., thick areas to thin and back to thick, etc.) will require more creative spruing in order to prevent porosity from forming. Occasionally, creative spruing is not enough, and a design must be reworked.
Other key design recommendations involve minimum thickness of 1mm throughout and metal flow pertaining to negative space and wax-engraving. If a piece has sections that are too thin, the molten metal may be unable to reach that area, causing a non-fill area. Smaller widths can sometimes cast successfully, but are dependent on how pervasive the small area is. The further the molten metal has to travel through these narrow gaps, the less likely it is to fill completely.
This same principle applies to metal flow and negative space in design (engravings, thin ridges, small settings, pinholes). We recommend a minimum draft angle of 7°, a maximum depth of 0.5mm, and a minimum width of 0.75mm for all CAD/wax engraving.
Hoover & Strong is happy to evaluate your design for spruing and castability. For new customer designs, or custom contract casting, some pieces will be evaluated at a higher success rate. This is not common, but may be due to design complexity, size, thickness (whether very thin or very thick), elaborate engravings, etc. Some examples would be large cuff bracelets, belt buckles, or highly custom rings.
Please Ensure Your Design Can Be Successfully Cast!
• sprue at thickest areas so that metal freezes from thick to thin or you will get shrinkage porosity • 1mm thickness recommended throughout (if smaller than 1mm, it is subject to evaluation and possible rejection) • engravings (in wax or CAD) must include a 7° draft angle • depth maximum = 0.5mm • width minimum = 0.75mm
If your part does not clearly meet these requirements, we are happy to evaluate it and provide design suggestions if needed. We can cast it regardless, but labor is non-refundable if the casting fails and we recommended against it.
What do you cast in? We can cast in most of the grains we keep in stock. The most commonly used is 14W, 14Y, 14P, 18R and STR.
What is the price per gram for casting? We don’t have a set price per gram. The cost is based on the labor rate, final weight of the piece and the finishing level. The more work done to the piece the more it will cost.
How long will this take? The average lead time for clip & ship is 5 production days, mass finish 5 days, hand polished 10 days, with stone setting 15 days. Lead times are subject to change based on the time of year and current business volume.
What finishing levels do you offer? Many of our customers choose to finish themselves. We offer clip & ship (no finishing), mass finish (grind, desprue and magnetic tumble) and hand polishing. Please note that for silver castings, we offer clip & ship, burnish and mass finishing. We do not offer additional finishing services for silver.
Do you set stones? Yes, we offer stone setting for gold and platinum alloys only. We can set diamonds and all major gemstones. Opals are extremely soft, therefore are subject to rejection. The customer will need to send in the Stone Submission Form with the stones.
