NEED MOLD PRESS HELP

[BAD DOG]

WE ARE LOOKING AT MOLDING OUR OWN PARTS,,, WE OWN THE MOLDS AND WHEN LOOKING AT PRESSES WE WERE TOLD THAT THE LARGER PRESS WE WERE LOOKING AT WOULD NOT WORK BECAUSE OF THE SHOT SIZE OF OUR MOLD IS SMALL,,,,,, IS THAT TRUE THAT PRESSES HAVE TO BE SIZED TO THE SIZE OF THE MOLDED PART.

THANKS,,

BAD DOG

[mactec54]

Hi Bad dog

This can be the case if the machine has to big a shot size for a small part & the machine control can't control the large shot very well (older machines don't have controls) like new machines have which can control the shot a lot better

How big/many Tons shot size is the machine you were looking at & how many
square inches surface area is the part in your small mold that you want to run on it

I have sent you a PM

[plastibob]

You absolutely don't won't an over sized machine. The material will degrade in the barrel. A perfect example of this is a part that was done in China. They had used a 150 ton machine on a Elastomeric part that should have been in a 50 ton machine. Bottom line is the parts were breaking prematurely and it was because the residence time of the material was too long. The parts looked good but failed. So be careful. The machine size is dictated by the projected area, material and shot size.

[SORCHEROR]

that is correct,too large of a machine wont even be able to close enough on small mold,they have a max and min opening,u have to check the specs on the machine your looking at,some larger machines do come with smaller barrels,or shot size capacity
besides a smaller machine is cheaper to run,cost alot to heat the large barrels and the palstice will degrade sitting to long

[dpryor]

B.D.
All of the responses above are correct. For the sake of the material and part, you want to size your press & barrel size for the shot size. You also need to consider the clamp tonnage vs. the size of the molds. If your molds are too small, you can acutally crush the parting lines. If your molds are too big, you may not get enough clamp tonnage to keep the molds closed.

[bakarack]

Bad Dog.....there is a rule of thumb pertaining to the weight of the molded part, verses the shot capacity of a machine.
If your mold size is small {MUD} and your weight is small, consider a small
machine 40-80 ton with a shot size from 1-4 oz.
We have molded 1.5 oz parts made of polycarbonate in a 40 tons machines.
Mold size with also determine the machine size, disregarding the molds shot size....larger the mold, the wider the tie bar spread, hence, general rule...the
larger the machine.
Hope this helps some...Bakarack