General Design Points (click images for larger version)
- Draft angles are not normally required.
- Try to keep casting sections to a uniform thickness.
- Avoid sharp internal corners, a small radius is preferred.
- Most hole can be cast at clearance, reaming or tapping sizes.
- Specify all numbering and lettering required and state embossed or debossed.
- Indicate finish grinding or machining allowance if required.
- Casting feed pads are normally placed at the heaviest section, in a flat area for ease of removal.
- A 0.010" feed witness is usually left on the casting after linishing, but can be removed flush if required.
- When specifying casting material use one of the standards shown in this brochure if possible.
Types of Industries Supplied
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Tooling (click images for larger version) A negative die is required. This is manufactured by our precision toolmakers from aluminium with steel or brass inserts for coring and pattern ejection. |
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The Process (click images for larger version)
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From the die an expendable wax pattern is produced conforming exactly to the shape and size of the desired casting but incorporating contraction allowances for both the wax and the metal to be cast. A given number of wax patterns are assembled onto a wax runner system and necessary feeder head. This constitutes the pattern assembly. |
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The pattern assembly is then dipped into a wet ceramic based slurry and coated with a dry refractory, once this has dried back-up coats are applied to the required thickness. After drying the wax is removed from the ceramic shell by steam autoclaving. This shell is then fired at 1000°C and cast upon removal from the firing oven. After cooling the ceramic shell is vibrated off the castings. |
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Fettling and finishing of investment castings is carried out by various methods, including abrasive slitting, abrasive blasting, linishing and power grinding. The castings are then ready for any heat treatment, non-destructive testing, machining and final inspection before despatch. |
