SoliForum - 3D Printing Community — Drillbit stabilizer ?

Re: Drillbit stabilizer ?

null@example.com (IanJohnson) — Wed, 06 Aug 2014 14:55:29 +0000

If you don't want to use a melt filter, at the very least you should wash and dry the pellets. I started doing that before Tim sold the melt filter because I would see debris left behind on the sides of what had been a clean hopper after a load of pellets had been through. Also sometimes plastic gets caught in threads, or a corner, and sits there and burns. Later bits of that burned plastic can find its way into the filament. When you see black specks in the filament, there are several things it could be other than shavings, so just preventing wear inside the barrel won't keep contaminants out of your filament.

Re: Drillbit stabilizer ?

null@example.com (elmoret) — Wed, 06 Aug 2014 14:42:49 +0000

To elaborate on the above now that I'm at a computer...

Here's a list of ways debris/contaminants get in your filament:

- From the barrel/auger wearing against each other
- From the pellets themselves
- From dust in the air
- From dirt on the cup/bag used to put the pellets in the hopper
- From corrosion on the barrel/auger

Here is a list of causes that are taken care of by perfect centering and radial constraint of the screw in the auger:

- From the barrel/auger wearing against each other (note: the auger experiences several hundred pounds of axial load, and the barrel/auger clearance is half a millimeter. It is very likely that the auger will deflect 0.5mm as a result of this loading, nullifying any attempt at stabilization.

However, centering/constraining the auger in the barrel would require at minimum a bearing or a bushing at both ends, meaning one end is in the path of the polymer. In addition to making things much more complicated to machine, and obstructing the flow path for a very viscous polymer, you have one of two problems:

1.) Bushings wear. These wear particles would be dumped right back into the polymer, negating the whole point.
2.) Bearings are typically not designed to withstand 200C operating temperatures, most normal lubricants can't handle this (so add $$$)

On the other hand, here's a list of causes that are solved with a melt filter:

- From the barrel/auger wearing against each other
- From the pellets themselves
- From dust in the air
- From dirt on the cup/bag used to put the pellets in the hopper
- From corrosion on the barrel/auger

A melt filter is also much easier to machine, and is optional (does not increase cost if the user does not need it, which is the case if they're using nozzles bigger than 0.6mm).

You tell me which approach is better.

Re: Drillbit stabilizer ?

null@example.com (wardjr) — Wed, 06 Aug 2014 13:06:28 +0000

elmoret wrote:

Again, you will never keep it perfectly centered and even if you did, the pellets themselves have debris in/on them. The correct solution is a melt filter.

Are you sure that's the correct solution? How can one be certain you know what your talking about

Re: Drillbit stabilizer ?

null@example.com (elmoret) — Wed, 06 Aug 2014 12:06:54 +0000

Again, you will never keep it perfectly centered and even if you did, the pellets themselves have debris in/on them. The correct solution is a melt filter.

Have you looked at how industrial extruders work? There is a lot to be said about learning from experts.

Drillbit stabilizer ?

null@example.com (tonycstech) — Wed, 06 Aug 2014 06:48:07 +0000

What does stabilize the drillbit, the white spacer and the bearing ?
If so, they why does it grind the tube inside making the front end move slightly ?
Thats what produces shavings inside.

How to keep it centered.

Thanks !