CNC style printer, noob alert, help needed

I fitted a pile of bits together today and mounted a 3d head on my CNC table but the results were less than useful.

I can't seem to get any material extruded, well practically none anyway.

It's just slipping in the feed rollers, even with a very hefty push by hand on the filament while the motor is jogging produces nothing more than a tiny blip of material every minute or so, you can feel the motor trying to feed.

I was expecting to see a thin thread extrude but not so it seems.

I have tried raising the hot-end temperature all the way to 250c but no change really.

The head is a 0.3mm eBay one and i have uprated the motor as my drivers only go as low as 1.5A and the supplied motor was only 0.84A.

I calibrated the A axis by removing the hot end and feeding filament then measuring it etc that seemed the right way to set it?

I have speed in Mach3 set to 100 and acceleration to 20 i think.

The G-code seems to run fine at least.

Have I started out with a bad head or too small a nozzle for PLA??

I'm a complete nooby at this as the machine was built for a plasma torch but while I am awaiting delivery of said torch I thought I'd mess around with plastics

Any suggestions?

This is the head BTW....
[www.ebay.co.uk]

Edited 1 time(s). Last edit at 02/25/2014 11:01AM by Davek0974.

To measure the extrusion accurately you need to check it from the top of the the extruder, not the nozzle i.e.-Mark the filament,say 50mm above the entry point of the extruder and set your host software to extrude 50mm. The mark should stop at the entry point. If not, you need to re-calibrate.

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Waitaki 3D Printer

Those cheap eBay hot ends are often useless for PLA. In fact, the listing only mentions being compatible with ABS. If you want to print PLA you will need a hot end that is compatible with PLA, such as a genuine J-Head (NOT from eBay) or E3D all-metal hot end, among others.

If you release the idler tension, you should be able to easily feed the filament through the heated hot end by hand.

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waitaki
To measure the extrusion accurately you need to check it from the top of the the extruder, not the nozzle i.e.-Mark the filament,say 50mm above the entry point of the extruder and set your host software to extrude 50mm. The mark should stop at the entry point. If not, you need to re-calibrate.

That is exactly what I did.

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NewPerfection
Those cheap eBay hot ends are often useless for PLA. In fact, the listing only mentions being compatible with ABS. If you want to print PLA you will need a hot end that is compatible with PLA, such as a genuine J-Head (NOT from eBay) or E3D all-metal hot end, among others.

If you release the idler tension, you should be able to easily feed the filament through the heated hot end by hand.

But why, surely it's just a bolt with a hole drilled through it?

Where can I order a proper PLA head?

Now you mention it, when I bought the head some time ago, I was going to use abs but later found out it needed a heated bed and smells so I bought a reel of PLA without thinking.

What are the differences in head?

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Davek0974
I can't seem to get any material extruded, well practically none anyway.

It's just slipping in the feed rollers, even with a very hefty push by hand on the filament while the motor is jogging produces nothing more than a tiny blip of material every minute or so, you can feel the motor trying to feed.

Probably the heat has soften a great length of the filament up into the barrel, due to the poor design of the hot end, or missing thermal break.
Enough length of the filament has warmed up, and expanded (coefficient of thermal expansion) to grip (hoop stress) with great force the side walls of the barrel that it is now considered jammed. Any pause or inactivity of the hot end will probably repeat this event, i.e. jam. I have read that for some hot end designs it only takes 10 seconds for this to occur.

Pull the filament out of the barrel, maybe around the glass transition temperature, and inspect it for swelling, post a pic of it, and of your hot end.

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Davek0974
Where can I order a proper PLA head?

Reread this,and use google, it's a thing:

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NewPerfection
Those cheap eBay hot ends are often useless for PLA. In fact, the listing only mentions being compatible with ABS. If you want to print PLA you will need a hot end that is compatible with PLA, such as a genuine J-Head (NOT from eBay) or E3D all-metal hot end, among others.

If you release the idler tension, you should be able to easily feed the filament through the heated hot end by hand.

Edited 1 time(s). Last edit at 02/26/2014 05:01AM by A2.

Thanks A2, you were right on all counts.

I warmed the head slowly towards melt point and pulled most of the filament out, it was indeed jammed solid by swelling in the head support bolt, it took considerable force to remove it.

The head is now clear but the jet is solid, could not even probe it when hot with 0.3mm hard steel wire, totally blocked. As its buggered I am going to drill it through with a 0.3mm drill and try that. It could possibly be a bit of swarf in it?

I can see how the heat spread up the support bolt and melted the filament before it reached the hot-end, but what i cant see is how this head could ever work the way it is built. I have seen the same unit on eBay listed as PLA/ABS suitable but they are all 0.4mm, that seems to be the only difference?

Will need to find a way of thremally isolating the support tube i guess or at least a way of bleeding more heat off of it???

Interesting stuff.

It managed to run for most of one print and made the nut attached. Its not pretty as the bottom 4 layers are missing while i was messing about trying to get it to feed material.

10 seconds after that print it was blocked solid again so i turned it off and gave up as there is no point trying if it wont reliably feed plastic.

I have also drilled it out to 0.4mm now.

The temperature was 10 degrees hot so I adjusted the offset in my PID controller to compensate, this test was at 190c as labelled on the reel as the lowest temperature.

I am seriously thinking about getting an RS-Ormerod now before throwing more money at this conversion, are they any good or am I just heading for a more expensive world of pain????

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Davek0974
I am seriously thinking about getting an RS-Ormerod now before throwing more money at this conversion, are they any good or am I just heading for a more expensive world of pain????

Most people have good success with them. Check out the sub-forum for the Ormerod: [forums.reprap.org]

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Great, just ordered an ormerod

The CNC table I have been messing with is destined to be a plasma cutter next week, have been messing around while waiting for the new plasma cutter torch to arrive, it will get very messy very quickly when cutting steel, not good for delicate 3d stuff I guess.

Can't wait to get building