Dies for "flow molding" Process

[Brian Richard]

Ok, I am tasked with running/processing an extrusion machine that processes any manner of garbage-plastic we get our hands on and we pump it via extruder into 12-foot dies, and when everything goes right we get lumber.

However!

We seem to be having probelms with our home-made dies. For no reason I can process around the machine "pancakes" at the end of the die that is supposed to fit against the melt-pipe/machine face. I've tried adjusting the clamp, I've tried running a stable recipe that gave us good lumber in the past, hell I even tried praying to Jesus but He's busy with other things and can't take a look at the machine right now.

Who, if anyone, has experience with building these kinds of dies?

[Skip]

Brian,

A naive question from an old PVC extrusion fart-----what would happen if, at the end of your 12 foot die, you had several exit ports for (assume very stiff) melt?? You should be able to pack the 12 feet, and allow a couple of pounds to exit the die----which can be recycled again??

As I understand it, a "die" is a CONTINUOUS shaping tool, while a "mold" is a FINITE shaping tool. If your 12 foot "die" is indeed a die and not a mold, then allowing for excess flow could insure that the "die" is fully filled.

That's my opinion, and you're welcome to it!! :D

[Brian Richard]

That is indeed what we do, good catch.

Problem is what happens when I try to fill the die. The problem is at the filling end.

[Al Hall]

Brian,

To relieve the pressure build up we had to pull a substantial vacuum on the other end. Also gave us more consistent parts.

[PDF]

Just a thought, and a little off topic, but has anyone ever tried to make a mold for plastic lumber that fills vertically? It'd be a monster to handle, but easy to pack the die at the far end.

[Brian Richard]

Brian,

To relieve the pressure build up we had to pull a substantial vacuum on the other end. Also gave us more consistent parts.

I assume this helped prevent the cold-slug from stalling.... I was thinking along these lines. By substantial vacuum, what are we looking at here?

[Louis]

I am guessing inches of Mercury, not water.

We used liquid ring pumps to generate over 20" of mercury.

[Al Hall]

We hooked up the pump from our vacuum forming machine and timed it's start with the injection timer. Don't know the units of measuement. Injection needs to be as fast as possible or we got porous and/or laminated parts.

[Brian Richard]

Ok...

I managed to salvage my notebook.    In my notes I have ten-fifteen pages of notes on die construction, flaws, obesrvations, corrective actions, and overall shortcommings of the design we used with drawings.

So, if anyone needs help assembling flowmolding dies in the future contact me.  I can tell you what won't work at least.    :lol:

[solinc]

We hooked up the pump from our vacuum forming machine and timed it's start with the injection timer. Don't know the units of measuement. Injection needs to be as fast as possible or we got porous and/or laminated parts.

Now that's interesting!

I like hearing about how ya'll on this forum come up with ways to solve problems.
Makes me wish I worked in the shop.
(actually, I'll be doing that next year as we're opening a new office and factory, so I'll be here a lot to bone up on everything....)