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Join Date: Feb 2009
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# Tonnage Required for Plastic Injection

02/05/2009 2:17 AM

Dear Sir,

Here i want to know any thumb rule or method to calculate m/c tonnage required for plastic injection.

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Associate

Join Date: May 2007
Posts: 45
#1

### Re: Tonnage Required for Plastic Injection

02/05/2009 10:48 PM

Does m/c mean "mechanical cooling" and "tonnage" mean "tons of refrigeration"?

Are you trying to cool injection moulds or finished product? I can help you, if you provide me with the above answers.

Regards

Phil

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#3

### Re: Tonnage Required for Plastic Injection

02/05/2009 11:00 PM

Its not @ "cooling" , its @ calculating the clamping force required for moulding a particular plastic component.

I want to know , given a plastic component how do we arrive at the tonnage/clamping force required for producing the plastic part.

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Join Date: Aug 2008
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#4

### Re: Tonnage Required for Plastic Injection

02/05/2009 11:19 PM

Dear Phil,

As i understood the question, it is related to the locking tonnage required to lock the particular mold, not related to the cooling of the mold. I know that, "tonnage" word is used in refrigeration also but i think this is not related to mold cooling.

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#2

### Re: Tonnage Required for Plastic Injection

02/05/2009 10:56 PM

As far as my information the calculation of tonnage requirement in plastic injection molding is as follows.

Required Tonnage = Projected Area of the article x Injection Pressure.

Now Injection Pressure is Actual pressure applied on the melted plastic material in Injection barrel. Do not considered the gauge pressure shown on the machine.

Data of the required injection pressure will be available with raw material manufacturer.

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#5

### Re: Tonnage Required for Plastic Injection

02/06/2009 12:44 AM

Never use the shortcut thumb rules it will cut you short

follow the link and look for coolingtowers you would get know the basics you are looking for http://www.cheresources.com/exprules.shtml good luck

crm

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#6

### Re: Tonnage Required for Plastic Injection

02/06/2009 1:23 AM

Hello. We use the following rule of thumb for calculating the Molding machine tonnage required to mold a product. Calculate the projected surface area of the part and runner-system in the mold. Choose your material. Find the recommended tonnage per square inch from the plastic material manufacturers specs. For automotive grade PP we use a rule of thumb that uses a 2.25 tons per square inch of molding area. e.g an 18 square inch PP part will need 18 x 2.25 as your minimum tonnage. This rule of thumb is pretty accurate. We calculated tonnage requirements for 145 molds in an automotive project. One mold in that project was slated for a 2,200 ton machine. It has angel hair flash on the whole parting line when used in a 2,000 ton machine but quickly has venting trouble in a 2,500 ton machine.For thermoplastic rubber the manufacturer recommends 4-5 tons per square inch. Using less than 4 ton in the calc will allow parting line flash. I hope this is helpful to you.

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#7

### Re: Tonnage Required for Plastic Injection

02/06/2009 1:40 AM

Great information.

I would like to have more information from you. The constant factor 2.25 tons per sq/inch. for PP material. Pl.also give us constant factors for other plastic material.

Thanks

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#8

### Re: Tonnage Required for Plastic Injection

02/06/2009 2:05 AM
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#9

### Re: Tonnage Required for Plastic Injection

02/06/2009 2:08 AM

Hello Mumbai, The constant factor is given by the plastic material manufacturer. There are some great sites for researching plastic. The more specific you are with plastic type,name ,manufacturer etc, the easier to answer such specific questions as molding tonnage requirement. There is a lot at stake from getting it wrong. Here is a helpful site. www.matweb.com. There are automotive plastic suppliers and medical plastic suppliers that are very helpful as they sell more if you spec their material and are a happy customer.

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#10

### Re: Tonnage Required for Plastic Injection

02/06/2009 1:51 PM

Some other leads for good plastics information are www.ticona.com , Advanced polymers and Bayer materials. Good luck

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