investment plastic stool moulding
investment plastic stool molding, frequently referred to as precision molding, have a number of favorable characteristics which can be summarized by saying that they offer dimensional tolerances superior to the rougher shapes too complex for powder metal parts and of materials with melting points too high for die molding.
The stool parts to be made are poured in plastic stool mould which have themselves been cast in master molds. The plastic stool mould molding material is plastics .
Patterns for individual parts are made by forming wax, frozen mercury or plastics (usually polystyrene) in a master die. The patterns material which is allowed to harden. When the ceramic shell has set, the investment material (wax, mercury or plastics) is melted out to leave the cavity for pouring the casting.
Each of the investment materials has some advantage.
- Wax permits the greatest flexibility of design and is the least costly.
- Plastics permit a more rapid production of patterns and also allows a surplus of patterns to be made and stored for future use.
- The frozen mercury allows larger sizes to be cast and requires only a thin ceramic shell which in turn result in better metal quality.
plastic stool mould features
The mechanical properties of alloys cast in shell molds are high and in some cases equal to wrought metal properties. Stool Parts to be made as investment molding can be quite complex. The chief restrictions to complexity are the need to remove the pattern from the master die. With the investment materials used, small elements of a pattern can be formed separately and then joined before covering with the refractory material to attain the highest degree
Dimensional tolerances possible with investment molding vary widely from foundry to foundry. Too, exceptionally close dimensional tolerances can be held if the customer is willing to pay for the extra work involved. The usual commercial tolerances are in the range of ±0.003 to 0.005 in. per in. of casting length, with closer dimensional control being possible on specific sections and very small parts.
Extremely small stool are well suited to production by investment plastic stool mould making. Production of such parts is speeded by molding larger clusters of parts at one pouring. Most investment molding are in the weight range of a few ounces up to a max of 26 lb. Some shops using frozen mercury patterns are making much larger molding, however. By far the greatest number of investment molding is in the smaller sizes, weighing from 1 oz up to 3 or 4 lb.
Massive metal areas are not desirable in investment molding. Good design limits sections to 1 in. thick or less. Extremely thin sections, too, are to be avoided where possible.