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Compression Molding Pros and Cons

I have been working with both processes and in my humble opinion. To make Beverage closures for water, soft drinks and similar with 28 to 38 mm diameter the best process in compression molding using rotary machinery. This process is most versatile on the following aspects:

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.

Cons:
Manufacturers: There is no many compression molding machines manufacturers in the world. Sacmy, Imola, Italy is the bench mark manufacturer and leader on R&D on this process and their products. Also Alcoa has this own technology but only for their own use on their customers locations (on my best understanding not for sale). There are some manufacturers in China and India but it's not easy to get them.
Investment: A Compression molding line has a high investment costs (Between 1.5 and 2.0 MM Euros) compared with a high speed Injection molding machine which can be around 800 K USD.

I hope to be helpful with this humble information. My final recommendation is to go with compression molding machines, and just call Sacmi, they will give you the technical assistance that you deserve.
Hi

this website really helped me in my research for college studies.


many thanks

Nour
- - - -> by: Nour Aly

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