Comments on RepRap: Blog: Small Melt Zones Look Good

I wondered if gas jets might also work as nozzles?...

2009-05-17T09:38:00.000+01:00

I wondered if gas jets might also work as nozzles?

Hmm, I need someone to look over my gas stove anyway. One of the jets needs replacing 'cos it's not big enough ... I Might have an opportunity here :)

Vik :v)

i never thought about using mig welding tips befor...

2009-05-17T02:36:00.000+01:00

i never thought about using mig welding tips before. thats not a bad thought.

Once I finish repstrap baby this weekend. I will m...

2009-05-16T00:31:00.000+01:00

Once I finish repstrap baby this weekend.
I will mill the plastic drive block then turn the peek heat barier on the lathe.
Then using the longer 0.5mm copper welding tips from B&Q £3.42 I will wind the insulated nichrome directly on to the welding tip cover it with the DX high temp tape and give it a go.

Yes ABS gets very hard to extrude below 195C. I th...

2009-05-15T17:32:00.000+01:00

Yes ABS gets very hard to extrude below 195C. I think HDPE has a more gradual change with temperature.

"ABS requires far less force than HDPE to extrude,...

2009-05-15T17:26:00.000+01:00

"ABS requires far less force than HDPE to extrude, so if you found it took more then I suspect you were suffering from the effects of the long transistion."

You may well be correct, however, keep in mind that I was operating my extruder barrels at much lower temperatures {~185-190 C} than you subsequently discovered were optimum. That may have made a difference, too. :-)

ABS requires far less force than HDPE to extrude, ...

2009-05-15T17:12:00.000+01:00

ABS requires far less force than HDPE to extrude, so if you found it took more then I suspect you were suffering from the effects of the long transistion.

I don't know if the inside of a copper pipe is any more sliperry than stainless steel.

The other thing that makes a huge difference is having a taper in the transition zone.

"Yes but ABS starts to go soft at 80C" I was usin...

2009-05-15T17:04:00.000+01:00

"Yes but ABS starts to go soft at 80C"

I was using HDPE.

"Did you try any ABS and leave it resting long enough to jam?"

I ran some ABS through it, but my polymer pump at the time was right at the edge of being able to supply the force necessary for ABS and polypropylene.

There may have been a jamming issue, mind. With the much more powerful pump that you've confected with the GKM-17 hack, however, I don't think that is going to be much of an issue in future, hopefully. :-)

"The transition zone has to be only a few millimeters in my experience, or else made from PTFE."

As I mentioned earlier, I'm wondering whether your problem with the transition zone is made better with the rather slick inside surface of the 5/32 inch copper tubing that I'm using for an extruder barrel.

It's certainly going to be rather fun to find out in the next few weeks. :-D

Yes but ABS starts to go soft at 80C, so it would ...

2009-05-15T16:14:00.000+01:00

Yes but ABS starts to go soft at 80C, so it would swell and fill the hole length of your barrel.

Did you try any ABS and leave it resting long enough to jam?

My guess is that it would jam like the soldering iron I tested and like the stainless steel barrel I tried.

The transition zone has to be only a few millimeters in my experience, or else made from PTFE. No other combination has worked reliably for me.

You don't need a heatsink anywhere near that big. ...

2009-05-15T15:45:00.000+01:00

You don't need a heatsink anywhere near that big. I kept the heated zone of my old 60 mm extruder barrel down to 20 mm at the business end. A simple brass mounting plate at the other end of 25x50 mm kept the temperature at that end at 80 C.

A heatsink might make the old granule extruder des...

2009-05-15T15:11:00.000+01:00

A heatsink might make the old granule extruder design viable.

Nice work. I'm going to dig out my old CPU heatsi...

2009-05-15T12:01:00.000+01:00

Nice work.
I'm going to dig out my old CPU heatsink box and build one too.