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Labor: A whole line would require only two people (the whole line is compounded by compression molding machine, folding, slitting and lining (EVA) machines).
Maintenance: The compression molding and other lines machines have a different but, in my opinion, easier maintenance. The mold centenarian is also easier due to you deal with every cavity separately, no frame, no plates.
Quality: The compression molding machines has a per unit quality inspection on line, discarding any off specs closure from the production line - That is not possible using injection molding process - Also the closures has minimum stress compared with injection molding.
Raw materials: the common resin is PP, it's better to use a lower melt flow index but the range suitable for this process is wider that the required for injection molding.
Productivity: At the end of the line you will have a bigger and better production with compression molding compared with similar cavitation molds using injection molding. A usual rotary machine may have 64 cavities and its production may be as high as 60 MM caps/month.
Costs: Also at the end of the month your production costs will be lower using compression molding compared with Injection.
Market: Most Soft drinks producers and water bottlers around the world know and trust in compression molded closures.
The critical parts of the question will be (1) "What are you typically going to run on the machine?"; (2) "Why do you want electric?, and, as a subset of (2), (3) would be "What part of the machine do you want to be electric? e.g. clamp, injection, ejection, nozzle contact force. What about hydraulic core pulls--will you need those?"

Different manufacturers take different approaches. Ball screws for major axes are very popular, but they are also limited in both speed and longevity, in part because of the single point of contact of the balls with their races. Planetary gear systems are much stronger, can be much faster and are much longer lasting. Tiebarless platens give great access to the molding area, but continue to have issues with mold alignment. Electric machines may, or may not, be any cleaner than well-maintained hydraulic machines, it depends on the form of the electric drive--direct drive is much cleaner than belt driven. Using hydraulic force for nozzle contact is a much better way to do things--hydraulics are designed to statically "push" on something; a servo motor is designed to move very precisely, pushing on something is not its strong suite. A careful analysis needs to be done on all these questions, unless your customer says, "I want you to do this on an electric machine," then the point is probably moot.
Most of the important facts have already been mentioned earlier of the lifetime of an injection molding machine. Not only maintenance but also preventative service is required to keep the injection molding machines producing good quality. The environment plays a great role in this as well. No dust, no moisture, temperature at normal level (ambient temperature) and no sudden changes in the ambient temperature. Those are the 4 most important environmental elements to ensure quality.

The oil needs to be filtered by a by-pass-filter... it is a suggestion for all injection molding machine's regardless of the manufacturer. Except of course full electrical machines. The newer the machine is, the more sophisticated the hydraulics gets. It is very important to have the oil clean, checked regularly and changed if needed.

The brains of the injection molding machine need clean air as well. The more dust there is the more often you need to change the air filters. And make sure all the fans are working too, the electrical cabinet is clean and sealed.
If you're looking for an average time frame, I would say around 10-15 years life is normal. The injection molding machines will most likely still be functional well past this age. However, due to evolving technology, higher level control requirements, and costs of repairs, many people will consider replacement after the injection molding machine reaches this age.

With that said, these injection molding machines still have a use. Since much of an injection molding machine's cost is tied to the main structure, many times it makes sense to rebuild, refurbish, or reconfigure it for another use. This could be as simple as fixing minor issues all the way through a complete ‘frame off' restoration. Our most common rebuilds consist of control changes, machine options, and replacing worn hydraulic components. Also, since safety standards are always evolving, a rebuild could include updates to safety features on the equipment.
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