Fully automatic molds

Where fully automatic molding machines are used, hydraulic ejection with perhaps a joggle facility is necessary, since thermosets have a tendency to stick in the mold. 

Figure 6.21 Parting line injection molding machine for semi-automatic or fully automatic molding of thermosetting plastic parts.

In many insert molding operations, fully automatic molding becomes possible when mechanisms are installed to put the insert into place before each cycle and to remove the insert with the molded part following each cycle. 

BMC formulations can also be processed by injection molding. A typical product made of a BMC formulation is a headlamp reflector produced by a fully automatic injection molding process in very short cycle times. Modem installations produce several thousands of these products per day. 

With extremely high piece counts injection molding is superior in polymer processing to all other manufacturing processes. The advantage of injection molding is the possibility for a fully automatic production of structured bipolar plates in one step. 

In contrast, the pin gate (Figure 4-2) is pulled off at its connecting point on the molded article, when this is removed. The pin gate thus leaves only a small mark on the molded part, requiring little or no finishing. Fully automatic degating is possible. 

As soon as the mold has been opened, the article can be removed at the parting plane. In the simplest cases, this can be performed manually. However, the injection molding process is designed specifically for mass-producing articles at a fast rate and should ideally operate in fully automatic mode. It is therefore obvious, that manual removal takes too much time. Furthermore, the cycle time fluctuates as a result of the operator s intervention in the machine cycle. This can cause variations in the molding s quality. With thermoplastics, manual removal is used only in exceptional cases, where articles are dehcate or of complex shape. 

Degree of automation Measures the change-over of a molding shop to fully automatic production... 

Figure 6.8 Fully automatic compression molding press with material feed to multiple cavities and removal of cured parts each cycle. ( Courtesy Hull Corporation.)...

Figure 6.24 Fully automatic blast-t5fpe deflasher with magazine-to-magazine feed for thermoset molded parts. (Courtesy HulUFinmac Corporation.)...

For fully automatic cycles, molds for such a part may be constructed with cam-actuated or hydraulically actuated side cores which serve the same purpose as the previously described mandrel. In each cycle, after the mold is closed and prior to injection of material, the side core is automatically actuated into place. Following the cycle, the side core is retracted automatically prior to mold opening and part ejection (Fig. 6.26). 

Compression molding presses are generally classified according to method of operation (i.e., hand, manual, semiautomatic, and fully automatic). They may be classified also according to their source of power (i.e., mechanical, hydraulic, and... 

Another problem not yet solved completely is concerned with economic fabrication techniques for mass production. Fully automatic wet winding has been developed but is not yet applied. Pulltrusion and sheet molding will be two of the methods to be used in future for most economic fabrication. 

The equipment used includes discontinuously operated cheesemakers (vats or tanks with stirring and cutting devices) and coagulators for continuous curd formation with subsequent fully automatic whey separation and molding. 

Neither statistical methods, which are able to determine dimensions and weight of a molded part in advance with the help of a design of experiment (DOE), nor control methods, which fully automatically readjust and optimize the process, are able to prevent rejects. This means that a so-called zero-defect production (0 ppm) is desirable but impossible to achieve in practice. The goal is not to produce zero defects but to deliver. For this reason, there is no way around monitoring the process. 

In the case of multi-cavity molds or family molds, intelligent electronics recognize when the first cavity and the last cavity have been filled. Depending on the application, switch over to holding pressure can be done fully automatically in either case. 

Figure 15.20 Fully automatic rotational molding machine. (Courtesy Persico SpA)...

There are three types of compression molds hand molds, semiautomatic, and fully automatic. Hand molds are limited to prototypes, small size parts, and short runs. Semiautomatic molds are self-contained and securely installed in a conventional mold press. The... 

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