Successful injection molding depends on the machine's […]
Successful injection molding depends on the machine's ability to operate the molded parts and the materials used under the correct pressure, temperature and operating speed conditions. It also depends on the ability to keep operating conditions close to limits for a long time, and the ability to accurately repeat the operating cycle thousands or even millions of times.
These requirements can first be considered from the perspective of whether the machine is basically suitable for work, and then whether it can be controlled to the required limits.
Determining whether a machine can meet its requirements may be a matter of trial and error, but if some fairly simple calculations are carried out, the feasibility of a job can usually be determined without going further.
Some assumptions need to be made and accepted, because a comprehensive mathematical analysis of the injection molding process is extremely complex and not the kind of exercise that the average actual mold maker is willing to perform. If these assumptions are accepted, a simple mathematical approximation can be derived, which will give a result close enough to the desired purpose. The type of information required is:
(a) What injection speed is required for satisfactory mold filling? In other words, how long is the injection time?
(b) Assuming the injection rate in (a), what is the pressure requirement?
(c) According to the pressure requirement in (b) and the injection rate in (a), how much hydraulic oil is needed to drive the machine, and how large is the pump motor to be able to require pressure?
After deciding on these issues, the question of whether the machine can be accurately controlled at the required number of cycles and at the required rate becomes a question of machine mechanics.