Injection molding forum?


--Doesn't seem to be one on usenet (!!) Can someone suggest a place
to discuss this topic? I'm taking a whack at making a small injection
molding die for a small, but fairly odd piece..
Reply to
steamer
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I could probably help out a little Ed. I've done a lot of things but one of them was 30 years designing and building injection molds.
Reply to
John R. Carroll
I have a post-grad certificate in plastic injection mold design, but John would probably be a better bet.
Reply to
Spehro Pefhany
I would also like to know some small-scale feasibility. I'm paying $25/each for injection-molded camera hot-shoe connectors for which I have found exactly one supplier in the universe.
Reply to
Richard J Kinch
That's not a bad price if the contacts are inmolded.
Reply to
John R. Carroll
I've got a few years under my belt running injection mold presses. Only complete hydraulic, no toggles. Mostly on HPM and Cincinnati. My focus was on running them faster, adding pickers, going to runnerless molds, etc. Not much prototype work.
Karl
Reply to
Karl Townsend
--Aha! Looks like RCM is da place after all. Well I'm trying to make a die to make these:
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--I dreamed this up more than a decade ago and I've given up on trying to get a die made that costs less than any potential worldwide sales of the widget in question. Sooo I've managed to carve out the fin part of the cavity with a Bridgeport and my little Sherline rotary table (total depth of fins not right due to short endmill; longer ones back ordered). But making the 3 inserts (and the plate that will hold them accurately) is getting a bit tricky. Will try to post some photos to my blog in a day or two. --I'm thinking of pouring in an epoxy of some kind as I really don't want to injection mold them until I get the geometry of the die just right. Gotta figure out what's available that has the correct durometer; something like nylon would be ideal. --I've got one of those 1/3 oz injection molding machines that a now-gone supplier of same for trade schools sold many moons ago but it needs to be thoroughly gone thru as it's been sitting idle under the workbench forever; that's another can of worms I'll need to open eventually..
Reply to
steamer
You are aware of the widely available and very inexpensive quick stop clamp nuts:
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(Currently a whopping $4.25)
Or the slightly fancier and more difficult to install version:
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Reply to
Pete C.
Cool.
Steel or aluminum? You planning on unscrewing a threaded bit to get it out?
Have you looked at cast urethane (you probably have a vacuum pump for degassing)?
For a test run you could also consider doing rapid protyping, but it will be a few hundred dollars cost most likely.
Is 1/3-oz enough?
Reply to
Spehro Pefhany
Cute, but the this threaded feature on the Bridgeport is an obsolete analog item. Replace it with a flatted rod and thumbscrew clamp, and measure with a DRO, better/faster/cheaper.
Reply to
Richard J Kinch
Lordy Ed, I remember when this first appeared in Machine Design! Hope you finally get it off the ground and make some $$ with it!
Jon
Reply to
Jon Anderson
--Yeah, yeah, been there, done that. Ever have one slip on you and go .05" too deep? ;-)
Reply to
steamer
--Aluminum. Threading occurs after molding, when two parts are snapped together; makes the making of the mold much easier.
--Yes; have vac pump but want to avoid the step if possible.
--Heh. For my next project I'm going to build a Mendel
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so's I can make 'em that way but I really don't think the resolution is good enough yet..
--Oh yeah; plenty big enough.
Reply to
steamer
--Different strokes for different folks; I've used the prototype for over a decade: no complaints..
Reply to
steamer
--Heh. Yah, sometimes it takes me a while to get around to something but the time has finally come for this one!
Reply to
steamer
In that case, forget injection molding and think extrusion. You've got something that's basically like a big T05 heatsink, so you should be able to extrude as a complete part (no snap together) and then slice into the appropriate lengths.
You could also just lathe and mill it with a 4th axis, taking a solid plastic rod, bore the center hole on the lathe, then put in 4th axis on the mill and mill the fins. A 24" rod should yield like 45 parts.
Reply to
Pete C.
> =A0 =A0 =A0 =A0 --Doesn't seem to be one on usenet (!!) =A0Can someone su= ggest a place > to discuss this topic? I'm taking a whack at making a small injection > molding die for a small, but fairly odd piece.. > > -- > =A0 =A0 =A0 =A0 "Steamboat Ed" Haas =A0 =A0 =A0 =A0 : =A0Blue Cross socks= us =A0 > =A0 =A0 =A0 =A0 Hacking the Trailing Edge! =A0: =A0$23,000/yr!! ... > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0www.nmpproducts.com > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0---Decks a-wash in a sea of words-=
Reply to
Denis G.
--The thought has crossed my mind but again it becomes a part best made by experts and the price goes up accordingly. I want to do it all 'in house' so's it becomes more cost effective. Die's almost done now; hope to get some epoxy parts out of it soon.
--Not set up to do this either. Sigh..
Reply to
steamer
Instead of epoxy, do a search for "casting resin" on Ebay. A half-gallon kit is $30 (plus shipping), a two-gallon kit is $80. Much thinner than any epoxy I've used so degassing may not be necessary, hardens in about five minutes, no significant exotherm in small parts, nice off-white color, tough product.
Just a satisfied customer.
Best -- Terry
Reply to
Terry

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