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11 comments
Anonymous Poster

How to calculate injection moulding clamping force?

04/10/2009 12:40 AM

i would like to know how to calculate injection moulding clamping force.is there any calculation?

Let me know?

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Guru

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#1

Re: How to calculate injection moulding clamping force?

04/10/2009 3:30 AM

Injection pressure x active area in the separation plane of mold x safety coefficient( ≥1.5).

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Anonymous Poster
#11
In reply to #1

Re: How to calculate injection moulding clamping force?

11/29/2009 10:56 AM

Hi,

I'm also facing the problem of determine the clamping force.

In my situation, i have to calculate the clamping force then choose a suitable type of injection molding machine which close to allowable clamping force of the machine. Injection pressure is one of the variable (in my situation) then i can't use the formula with injection pressure. So is there any formula to calculate the clamping force without using the injection pressure?

Thanks

Regards,

Low

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#2

Re: How to calculate injection moulding clamping force?

04/10/2009 4:20 AM

Hello,

I will take a stab at a reply.

You really need to supply more info as each Polymer has a different recommended tonnage per square inch value. This is given by the material manufacturer. Sources below.

We use a huge amount of Polypropylene copolymer. So here is the method of calculation specifically for it. It will flash out with a gap of .0008"-.0012" between the faces of the mold.

Calculation square area" x a tonnage factor given by material mfg

Calculate, closely, the projected surface area of the product to be molded.

That is the projected surface of the part sitting perpendicular to the parting-line of the mold.

Subtract any areas where there are throughholes.

Add in for the runner and gate projected area.

Multiply by 2.25 for any PP or PE and you will have the tonnage needed.

Example: part length x width = 2" x 26"= 52"square - (window areas: 0.2" x 10"= 2" sq + (runner and gate 1/4" x 8"= 2"sq) = 52"sq - 2"sq + 2"sq= 52"sq x 2.25 tons per sq inch= 117 tons.

So now you have the tonnage.

Consideration 1.

Your next consideration is. Can you fit that size of mold between the tie bars of a standard 125 Ton machine. If you can, well and good. Physical Mold size.

Consideration 2.

Then the next consideration is whether the Machine that you must use has a barrel that will plasticize the amount of material that you need to fill the part.

This is tricky. If you are pushed to using a large machine to get the Platen size you need, you may end up with a much larger barrel than necessary. Barrel Size (Vol)

Consideration 3.

Whence you have to consider the residence time in the barrel before the material is used as you may cook the ---- out of the material. Based on the weight of the part.

Lastly:

Here is another sample at the other end of the spectrum. The specific calc for Thermoplastic Elastomer (Rubbery material). You need a minimum of 4 tons per square inch and 5 tons per square inch is recommended. Rubber will flash out of a gap of 0.0005" between the faces of the mold.

Engineering materials typically need less tonnage per square inch eg. Ultem or Glass filled nylons etc. It will flash out with a gap of .0015-.002" between the faces.

LCP or Liquid chrystalline Polymers need hot molds, slightly higher tonnage as the cavity is filled with boost and there is no hold time needed as it sets up so fast. This material likes to travel in straight lines and short flowlengths.

Use www.matweb.com or www.ticona.com for material info and find the recommended molding clamping tonnage recommended.

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#7
In reply to #2

Re: How to calculate injection moulding clamping force?

05/05/2009 11:11 AM

Great answer 2tinker,

Now, the square area is for each cavity ?? I'm in the process to calculate the machine tonnage for part made of Zytel 70G33L

Thanks for your help

Ed2009

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#3

Re: How to calculate injection moulding clamping force?

04/13/2009 3:36 PM

HELLO,

OP WHERE ARE YOU?

Houston we've got a problem!

or is it,

Car 54 where are you?

I give up. Op I hope you get the point.

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#4
In reply to #3

Re: How to calculate injection moulding clamping force?

04/13/2009 11:17 PM

Hey 2tinker,

Makes you wonder if the effort you put in to your clear, concise answers is worth it, doesn't it.

The sad thing is, you sometimes never know if the OP ever comes back to read your stuff.

And, surprise, Guests are the worst offenders!!!!!!!!!!!!!!!!!!!!!!!!!!!! This is an elementary question as are most, proving that the dimwit OP doesn't know the subject in the first place.

Most of them have, apparently, never heard of Google or the other primary information sources available. Material suppliers. Mold makers. Machine builders. Consultants.

Never mind.

LL

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#5
In reply to #4

Re: How to calculate injection moulding clamping force?

04/14/2009 12:07 AM

Hello LynLynch,

I probably should have been more patient but it was the second OP question on this page that I cared enough to answer.

I have heard others express this type of frustration and really should have expected that the disappearing OP would visit me sometime.

What a cool site though, to stretch our knowledge and spur continuous learning.

Thank you for your reply.

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#6
In reply to #5

Re: How to calculate injection moulding clamping force?

04/14/2009 12:14 AM

I stumbled across this site with a question about my shiny new aluminum radiator last year.

Never, ever expecting that I would become ADDICTED!

It's a great place to hang out.

LL

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#8

Re: How to calculate injection moulding clamping force?

06/16/2009 10:02 PM

how do I determine tonnage from tie bar stretch on a toggle machine

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#9

Re: How to calculate injection moulding clamping force?

06/30/2009 12:23 AM

Firstly, maybe the OP was after the actual clamp force in a machine rather than the "required" clamp for a particular mould tool. In which case they would need to know their hydraulic pressure and cylinder dimensions if it was an hydraulic machine.

And for the request for tie bar stretch, use the "SEARCH CR4" option using tie bar stretch. There has been a discussion in the last fortnight discussing that including lengthy and knowledgable calculations from many experts.

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Anonymous Poster
#10

Re: How to calculate injection moulding clamping force?

08/14/2009 8:46 AM

http://www.custompartnet.com/calculator/clamp-force

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