| GETTING STARTED First determine what the exact shape and dimensions of the part are, along with the tolerances allowed. Be sure and answer the “4 F’s” questions, Form (of part), Fit (where the part joins other parts), Function (how does the part function) and Field Testing (if the parts will be used for field testing). Now you know exactly what it is you want, how it works and what it is to be used for. Tip: A lack of correct information contributes to inadequate parts. |
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 USING A DIGITAL IMAGE
The manufacturing world today revolves around digital images. A 3D CAD Image of the part, like the one to the left, is a handy way to transfer exact information concerning your part or model to the Spin Casting firm. Some prototyping companies can even use a 3D Cad file to produce CNC machined models of your part, if that is what you require. Tip: Good digital images can save you money for poor and/or useless parts. |
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 PREPARING the SPIN CASTING MOLD
The mold starts out as a disc of uncured silicone rubber. Parts or models are laid out on the disc to determine proper part placement. Since the mold consists of two pieces, an upper and a lower, parting lines on the parts must be determined so the parts can be removed from the mold. To prevent the two halves from adhering to each other during Spin Casting, Mold Parting Compound is sprayed on the adjoining surfaces of the two halves of the mold.
Tip: The better the model, the better the part. |
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 VULCANIZING the SPIN CASTING MOLD
Following preparation of the mold, it is placed in a round Vulcanizing Frame. The frame is then placed in a heated vulcanizing press, where it will remain under pressure until the silicone rubber has cured. Tip: Improper Vulcanizing procedures produces inferior molds. |
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 PLACING GATES and AIR VENTS
Using a sharp scalpel, the technician cuts the gates, runner system and air vents into the cured silicone rubber Spin Casting Mold. The placing of gates, runners and air vents is as much an art as it is a science. Polyurethane plastic Spin Casting Molds may be used interchangeably with molds used to produce metal or wax castings and vise-versa. Tip: Although seldom used, this flexibility in mold usage can prove to be a real money saver for the customer. |
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 USING the SPIN CASTING MACHINE
After cutting the gates, runners and air vents, the mold is assembled, placed in the Spin Casting Machine and centered under the material inlet. The act of closing the door, activates the pneumatic clamp, thereby holding the mold in the proper position until the end of the spin casting cycle. The technician has controls that set clamping pressure, cycle time and the speed the mold will spin. After the technician has set all the controls for the current cycle, he engages the start switch to begin the spin cycle. Tip: Proper settings at this stage of the process requires a very experienced technician to obtain optimum results. |
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 USING the SPIN CASTING MELTING FURNACE
When Spin Casting metals like Lead, Pewter and Zinc, a special Melting Furnace is used to melt the metal prior to pouring. The temperature of the metal is thermostatically controlled at a pre-set level by the technician. The hot metal is poured into the spinning mold where it is pushed outward by centrifugal force. The metal follows the path of the runner system through the gates and into the molds, filling each cavity and creating the required parts. SPIN CASTING WAX functions the same as metal casting. Tip: Improper temperature control is reflected in the quality of the parts. |
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 PLASTIC SPIN CASTING
Two Polyurethane Plastics are mixed to produce a part of the desired hardness and/or flexibility, just prior to being poured into the Spin Casting Mold. The rotating mold speeds the liquid plastic through the route designed by the technician and into the cavity made by the model, completely filling the cavity. There, the plastic hardens as a result of the heat produced by the inter-action of the two plastics mixed together to form the part. The picture to the left is to demonstrate what can be done when spin casting plastic.
Tip: Experience is a real plus when spin casting plastic. Few people have it. |
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 POURING the HOT METAL or WAX
Using a ladle, the hot metal is poured into the spinning mold and is pushed out toward the outer edge by centrifugal force. The metal follows the path of the runner system through the gates and into all the cavities. It fills each cavity and creates the required part. SPIN CASTING WAX functions the same as the metal does when poured into the spinning mold. Tip: Improper temperature control is reflected in the quality of the parts. |
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 REMOVING SPIN CASTING PARTS
When the Spin cycle ends, the metal, plastic and wax parts are removed from the mold. Parts created using Spin Casting can hold tolerances of .001” to .005” per inch.
Tip: Skilled technicians are able to produce the best parts with the closest tolerances. |
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 REMOVING the GATES and VENTS
When the Spin Casting parts are removed from the mold, they must have the excess material located at the Gates and Vents removed prior to shipment. Depending on the part, this can be a tedious and time consuming process.
Tip: This is no job for an amateur. |
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 FINISHING the PARTS
After Spin Casting, parts often require special finishing before shipment. Sometimes parts must be painted or have rough spots sanded lightly to remove them. Finishing may also require the exterior of zinc parts to be glass beaded for example.
Tip: A poorly finished part may be rejected by the customer. |
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 Some Plastic Parts require Sand Blasting as part of their preparation prior to shipment. This service, allows the customer to concentrate their attention on the Assembly Process that follows.
Tip: This is not a job to break a new employee in on. Sand can remove plastic faster than you may expect. |
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 Pewter and Zinc are often given an Antique Finish. Sometimes Pewter and Zinc are given a Brass or Bronze Finish. Tip: Inexperienced staff can wreck the whole project at this stage. The last 2 items in this list, might be thought of as the making or the breaking of the entire project. |
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