Preloading support pillars.
Preloading support pillars.
(OP)
Hello forum members,
How much preload do you recommend for support pillars in a mold?
Jerzy
How much preload do you recommend for support pillars in a mold?
Jerzy
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Preloading support pillars.
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Preloading support pillars.Preloading support pillars.(OP)
Hello forum members,
How much preload do you recommend for support pillars in a mold? Jerzy Red Flag SubmittedThank you for helping keep Eng-Tips Forums free from inappropriate posts. Reply To This ThreadPosting in the Eng-Tips forums is a member-only feature.Click Here to join Eng-Tips and talk with other members! |
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RE: Preloading support pillars.
Are you having trouble with an existing mold, or planning for a new tool?
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Preloading support pillars.
I have though discussed their bearing area and calculated the tonns load they must bear without distorting enough to allow some parts of the mould to flash.
Yes moulds can and sometimes do bend under injection pressure.
I believe bearing area and steel grade are the answer. Preload is a poor Bandaid.
Regards
Pat
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RE: Preloading support pillars.
The question arose regarding an existing mold that a client was
having some problems with. Their toolmaker claimed to use .008 inch as a standard preload for support pillars. I have always thought that zero to .002 would be commonly used.
While researching the topic, I found that for some severe thin-wall applications a preload of .004 to .005 on the center pillars
might be appropriate, but this would not be normal practice for most molds.
The application in question is not a thin-wall case.
Thanks again for your valuable contribution.
Jerzy
RE: Preloading support pillars.
These are just a few of a hundred variables that come to mind immediately.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Preloading support pillars.
If wear on the tie bars allows the mould to rock, that leaves the flash down one side. If the projected area is not uniformly distributed about the axis of the platen, the flash will always be on the side where the most projected area is located.
If the flash is thick near the gate and thin near the edges, the mould is bending.
Either the platen itself is not true or is bending or the cavity is bending relative to the back plates.
If the cavity is bending it is because there is to much space between pillars or the pillars are compressing or being driven into a back plate that is compressing locally only.
Without seeing examples of the actual problem moulding and the mould and being able to take measurements, I really can't say any more.
Regards
Pat
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RE: Preloading support pillars.
Flashing had not been a problem: the preload question came up because there was some hobbing of the support plate and pillars.
The problem was galling of a moving core on a near-vertical shutoff. We were looking for distortion of plates.
Jerzy
RE: Preloading support pillars.
Getting any rub spots on the leader pins or bushings that would indicate lateral movement?
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Preloading support pillars.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Preloading support pillars.
Besides distortion of plates,there might be a metallurgical problem: the galling surfaces do not seem to differ much in type or hardness.
Thanks for the helpful comments.
Jerzy
RE: Preloading support pillars.
I have uploaded a PDF showing how to do the calculations.
RE: Preloading support pillars.
RE: Preloading support pillars.
Jerzy