Those ebay extruders

IR thermometers don't work on reflective surfaces. You need to paint it black to get a good reading.

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ohioplastics
IR thermometers don't work on reflective surfaces. You need to paint it black to get a good reading.

Yes. I knew that.

I was just being stupid.

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Coherent
You should try putting the thermistor at the nozzle like they do for jheads or makergears. You need to know the temperature at the nozzle not the transition zone and that should give you a more stable temperature.

Agreed.

However with the design of this hot end, I'm not sure how practical it would be to drill into it to insert the termistor.. There isn't much metal (brass) to drill into in the lower part of the hot end.

And as the heater in this hot end is a resistance wire that is wound around the length of the transition area, i.e around 1.5cm, I'm not sure what the differences in temperatures are going to be, between the top and the bottom of the area that is being heated across its entire length.

Just taping my thermocouple probe (of my digital temperature meter), to the side of the nozzle reads lower temperatures than the thermistor is showing (by around 5 degrees), but this is highly dependent on the contact area between the thermocouple and the nozzle.

Ultimately, the best way to use this extruder system, is probably to thow away their hot end, and use a standard hot end bock, with a cartridge style heater etc, but I'd like to see how well the extruder performs before throwing 1/2 of it away.

Another update..

Well. I'm now having other issues with this extruder.. I'm sure no one is surprised ;-)

After finally figuring out the wiring of the motor, as there was no details with the extuder, I got the motor to turn, and push filament into the transition area and into the hot end.

Initially I had issues with filament jamming, but realised that this was caused by a combination of attempting to run the extruder on its side, and also not having the top of the transition zone tube as close to the main heat sink block as possible
Making both of these changes, seems to have fixed the jamming issues.

However, I've now got drive issues, because the cog attached to the motor, is slipping and not biting into the filament.
The cog just looks like a regular cog, i.e not specifically designed for gripping the filament.

Fortunately I some drive cogs from RobotDigg



Which have sharp points on the teeth, so I'm going to try to use one of these instead of the cog that came with the unit.

I also have a "mk8" stepstruder drive cog (more like a hobbed pulley), which I could also try.

Overall, I can't really see how this extruder could work at all. Unless it was designed to extrude a filament which is much softer.
BTW. Currently I'm using PLA, as it doesn't smell bad.

The extruder came with a 0.3mm nozzle, and its very had to push the filemant though by hand, so I'm not surprised that the cog is slipping.

I have some 0.4mm nozzles, so I may also see if they fit and in which case, whether the current cog can push though a 0.4mm

I'll post another update with my results.

Cheers

Roger

Edit. Switched to 0.4mm nozzle and reduce the extrusion speed in pronterface and it works.

Tried 0.3mm nozzle again, at very slow extrusion speeds, but it would only work when the speed was unusably slow e.g. 10mm per minute.

Edited 3 time(s). Last edit at 12/20/2013 02:28AM by rogerclark.

Hi Roger, Ive been a bit busy with other stuff. (New job)
From your pics it looks like I was lucky not to break through the brass while drilling. I drilled in from the top, not the side, and went in about 3mm. It is still working well but it defiantly under-reads in that position. Not a problem you learn what temp works well.
Also that little direct stepper has some real pull. I have trouble hanging on to the filament when its extruding. Currently its pulling through 1mtr of Bowden cable (bike brake outer) without probs.
I still get the nozzle dragging over the work sometimes and cant get to the bottom of it. Ive tried various heights for Z lift and it makes no difference. There is no slop anywhere that I can find. It may just be the nozzle end shape.
I may make my own hot end soon. Like a J-head but with removable nozzle.

Hi Vince,

Drilling though the side wasn't too much of an issue, because its much harder to drill though the stainless steel section in the middle.

Currently I've still got the spiked cog the exruder which I bought from RobotDigg, but I think the original cog may be OK as long as it doesn't need to extrude too quickly.

If I get time I may test the "mk8" extruder cog I bought from eBay, which has a much smaller diameter of cog in contact with the filament and also has a concave circular cross section, which I presume is supposed to increase the surface area in contact with the filament and hence increase friction and stop the slippage.

Looking at the motor, its relatively small really, smaller than the motors on my MendelMax, but doesn't seem to have an issue with torque now that I increased the current from the stepper drivers.


Unfortunately, at the moment I'm not in a position to try my extruder in an actual printer, as I don't want to take my MendelMax apart as its working fine.

But I am building another printer in a cuboid frame design, which is a cross between a number of different designs which have a moving XY carriage.
However its slow going, so I don't think its going to be finished for several weeks (if not months ;-)
So it will be a while before I'll be able to test it.

Cheers

Roger