Cavity blocking
Cavity blocking
(OP)
Hey all,
Just a little survey, what do you use to block cavities??
Just a little survey, what do you use to block cavities??
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: Cavity blocking
A different sprue bush.
By rotating the sprue bush to align to with different runners.
Regards
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RE: Cavity blocking
RE: Cavity blocking
Scrapping parts is easy compared to having to fix a parting line that got hosed up because something got smashed in it.
RE: Cavity blocking
Cyanoacrylate to glue a runner section in - works best with styrenics.
For small tools, part design permitting, do one shot, take out moving half before ejection stage (leaving part in cavity) and remove ejector pins from that cavity.
Cyano part into fixed half ( a bugger to get CA off but can be done with hardwood pointy stick without damage to even aluminium tools).
dgowans:
set the mould protection correctly and no damage will be caused....
Cheers
Harry (with stuck together fingers)
RE: Cavity blocking
Thanks for blowing the dust off my brain. It's been a while since I worked for a molder, and even then I wasn't involved in processing. I'd forgotten all about mold protection....
RE: Cavity blocking
dgowans,
Ah! that explains it! Modern kit has very, very accurate mould protection - 1-2KN closing force - 0.1mm before clamp9ng comes on. Should be able to put a small piece of cigarette carton between the clamping faces and it will not clamp up... All achieved at over 100mm/s speed. Clever stuff.
Cheers
Harry
RE: Cavity blocking
"What do you mean you can't hold +/- .005" on the overall length of an 8" long polypropylene part?!?!?!?!!?"
RE: Cavity blocking
Simply run semi auto so you can confirm it is safely in place between shots.
A rough house way to quickly disable ejection is to cut a hole in the part where the ejection pushes against it.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Cavity blocking
When they get in a hurry and DON'T have this capability...Then they fashion a brass tapered little "pin" that they tap into the tunnel gate..
PS: They're *always* in a hurry..
RE: Cavity blocking
Smokehouse:
Other trick: small piece of electrical solder in tunnel gate (called submarine or sub gates here in UK), suitable size rounded end ejector pin utilised as a punch to tap into gate opening. Easy to get out with (another suitably sized) self-tapping screw!
Cheers
Harry