Beginner to injection moulding

[Curious and confused]

Hello
I find this forum very informative and helpful..
Whenever I get time I go through the messages and other information on the site

I am about to start manufacturing in a way that I have bought a couple of moulds by myself and planning to get my products manufactured by factories who have moulding machines of different sizes.

I am confused over the size of the machine ... Size of the mould is 1600*700*800... One of the moulding factory I visited which had 650ton machine with tie bar distance 950mm claimed they could manage this work. They also claimed that if the mould is bigger than the platten from one side it is no problem... Production is going to be about 5000 pcs per annum.
Another question is if we run our mould on this machine wil it affect the life of the mould

[Suhas]

Hello,

The mold can be put in between the platen and then rotated to fit between the platens - OR - slide it from the side, which in your case may be difficult because of the size of the mold. But this is possible. Just make sure the whole molding area (ie your part) is supported by the platen.

-Suhas

[Curious and confused]

Dear suhas
Thank you very much

[JayDub]

Ideally, the mold should fit within the platen, but as long as the cavity doesn’t extend outside the platen you may be fine (if it does, you won’t be exerting any clamp pressure on the edges and you will get flash). However, platen size is only one concern:

1) What is the projected area of the cavity? You need (rough estimate) 3 to 5 tons (tonnes) per square inch of area to keep the mold closed enough to prevent flash. So if your projected area is more than about 1000 cm squared, you may need a bigger machine.

2) Shot size – what does your part weigh and what is the shot capacity of the machine? You want to use somewhere in the range of 20 to 80% of shot capacity. But keep in mind, even if you meet this – if the barrel is over-sized for the machine, it may not generate enough injection pressure to mold your part successfully.

3) Plasticating capacity – I once had a 2 Kg part that ran in a press with a 3 Kg barrel. Should have been ideal, except yield was poor unless we extended the cycle by 30 seconds and ran the screw slower. On a faster cycle, the machine couldn’t melt plastic fast enough without starting to degrade it. The part ran much more efficiently (faster cycle, less scrap) on a machine with a 4.5 Kg barrel.

4) Daylight – How deep (thick) is your mold, and how far does it need to open to eject the part without damage? Does the machine platen have enough travel to achieve this?