Many local businesses are under more pressure to reduce manufacturing costs as a result of the rising worldwide competition. Due to its emphasis on eliminating waste in the broadest sense, just-in-time production has become widely used. Manufacturers work to reduce stock levels and manufacturing flaws.
Traditional tooling, while offering economies of scale in terms of component costs, frequently proves costly for makers of high value, low volume products since it forces them to keep a lot of low value components in stock. Once tooling has started and first stock levels for manufacturing components have been obtained, producers producing new designs may find it expensive to correct production problems. Changes to the design could result in wasted stock and extra expenses for putting up a new tool for the tooling process.
Many manufacturers have resorted to vacuum casting which enables them to acquire low amounts of production components, in an effort to avoid these potentially expensive production issues.
Components for silicone moulds can be made out of plastic or rubber using the vacuum casting process. The parts created using this procedure are exact, dimensionally correct copies of the original pattern, faithfully reproducing all profiles and textures. The steps in the procedure are as follows:
Any of the available Rapid Prototyping procedures, usually SLA due to the high quality part finish that can be obtained using this process, are used to build a master pattern from 3D CAD data. The required part finish is subsequently achieved through post-production finishing.
The master pattern is equipped with a casting gate before being attached to the parting line and suspended in a frame for casting moulds. In order for silicone rubber to flow around the master pattern, it must first be blended, de-aerated, and then poured into the mould casting frame.
The mould is then heated in a chamber to cure it. Once set, the master pattern is removed and the silicone mould is cut along the parting line.
After measuring the urethane resin, a dye is injected where a certain colour is required. The mould is sealed shut after a casting funnel has been added.
To prevent any air pockets or cavities, the resin is then combined and poured using computer-controlled machinery while under vacuum.
The mould is placed in the heating chamber once the resin has been cast, where it will stay for two to four hours so that the urethane resin can cure. The casting is taken out of the mould once it has hardened.
To create an identical replica of the master pattern, the gate and risers are taken off, and any necessary post-production painting or plating is finished. 15–30 castings can be produced using each mould.
When Brandon Medical, a high value, low volume maker of medical lighting equipment, wanted to cut back on stock holdings for low value parts of their HD LED Quasar lighting system, they turned to vacuum casting. Although Brandon Medical wanted to reduce their inventory levels, they were mindful of the lead times and quality standards of its customers. Vacuum Casting offered the best answer.
Brandon Medical was able to find cost-effective, high-quality production parts within days by using a nearby Rapid Prototyping bureau, doing away with the need to keep vast quantities of stock and incurring hefty tooling costs.
