Extrusion Issues
July 26, 2015 02:59PM
I am still trying to get my homebuilt delta up and running. I am running a duet board and dc42 firmware. The firmware seems to be doing ok. I an home...level the bed...etc. I am using pronterface and slic3r. The machine will read the temps and move to position as it should.. however I have tried 2 different J-head hot ends with a wade extruder and it will not extrude as its supposed to.

In fact...it will start...then no mater what i set the extruder motor current to it will just grind a groove into the filament. ive tried uping the temp of the hot end and it doesnt seem to help. I have tried 3 different filaments with no difference...

im tempted to try and purchase a whole different setup and redesign the effector...

any thoughts?
Re: Extrusion Issues
July 26, 2015 04:11PM
Hello,

Can you post a picture of your entire printer and a photo closeup of the effector / hotend

And inform the following:

Type of filament (PLA or ABS), size of filament (1.75 or 3), temperature you run with and if you can push material through manually (with the bowden disconnected)
Re: Extrusion Issues
July 26, 2015 04:40PM
Start with PLA filament, it's easier to print with than ABS. Make sure you have configured the correct B value in the M305 P1 command in config.g to match the thermistor in your hot end, and that the hot end temperature reading is roughly correct at room temperature. Heat the hot end to 200C, then as Larsk suggests in the previous post, with the hot end well above the bed try to push filament through by hand. If you can't push filament through, then neither can the extruder.

Edited 1 time(s). Last edit at 07/26/2015 04:41PM by dc42.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extrusion Issues
July 26, 2015 04:45PM







ABS 1.75mm filament... 230c nozzle temp... i can push material through but it doesnt seem like its coming out like it should. Ive taken the hot end apart and cleaned it but manually and by soaking it in acetone with no change. its a .4mm nozzle.
Re: Extrusion Issues
July 26, 2015 05:00PM
230C is quite low for ABS, you may get better results with 240C or 245C. Also check the thermistor parameters in config.g as I suggested earlier.

Your extruder has a high gear ratio (I estimate about 5:1) and also a long motor, so I suspect you need to run the motor at only 25 to 30% of its rated current and not set the extruder acceleration too high. The idea is to keep the extruder motor current low enough so that the motor skips steps before it grinds the filament. If it's not gripping the filament, it may be that the clamping pressure is too low, or the hobbed insert is not gripping. Do you use a good-quality hobbed insert in the extruder drive?

I have recently changed the extruder on my delta from a RepRapPro Mini Geared Extruder with a long motor and gear ratio 5:1, to an Ormerod extruder with a shorter motor and gear ratio 3:1. This seems to me to be better balanced.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extrusion Issues
July 26, 2015 05:08PM
i bought the extruder as a complete setup. i only had to supply the motor. i even tried running it at 250-275c with the same result. is i run the current down to 350 it wont push the filament but if i run it to to 400 it will push till it grinds. the hobbed bolt is well done and grabs almost too well. you can hear when it loads up and strips
Re: Extrusion Issues
July 26, 2015 05:23PM
I don't claim to be an expert on extruder drives, but here are my suggestions:

1. Try running the extruder with the output Bowden tube disconnected, and see how much force it can push the filament out at before it skips steps or grinds filament. Then compare that with the force you need to push filament through the hot end by hand at 5 to 10 mm/sec.

2. I'm still wondering whether the clamping force you are using in the extruder is too low. With the correct amount of force, there should be distinct teeth marks on the filament emerging from the extruder.

3. Also check that the bearing that supports the back of the filament against the pressure of the hobbed insert is rotating freely.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extrusion Issues
July 26, 2015 05:35PM
Your printer looks very nice.

It seems you have access to a machine shop so I recommend you consider drilling up your nozzle to 0.5 or 0.6 mm. It makes a big difference for the force required to push material through and you can buy a new nozzle very cheap for later replacement. Also already now set your retraction length to 0.5 mm and speed 20.


Now, lets talk about your hotend.

Is it with the teflon pipe inside or is it all steel? Here shown with PTFE (teflon):



Also a little more information:

Does it ever extrude? Reading your post it is unclear to me if it works for a very short time after cleaning the nozzle - Or if it just NEVER works, as in, no plastic has ever been extruded by your extruder (?)
Re: Extrusion Issues
July 26, 2015 06:18PM
no machine shop... actually ive built most of it with a dremel...a cordless drill and a hacksaw....i am working away from home though so most of it has been built as a project to keep me busy.

the motor/pulley mounts i did build in my garage. i have a CNC plasma cutter in my garage


i have both...all steel and one with a ptfe liner...

right now its the all steel end. it will extrude for a short time. then as soon as it gets a bit of pressure it grinds away... ill mess with the clamping pressure on the extruder.
Re: Extrusion Issues
July 26, 2015 07:40PM
Ok, be sure to try and change retraction length to 0.5 or even just 0.

How does your cooling block on your hotend feel? Down at the part closest to the heating block it should be warm to the touch but you should still be able to rest your index finger on it without it being "very" uncomfortable.

In conjunction to what DC says you can try to take away the nozzle and let it extrude just through the heatbreak and see if that works. Especially pay attention to what DC said about your filament post extruder needs to have distinct white teeth marks.

If no luck I suggest you change back to the PTFE lined heatbreak. First verify that the PTFE liner is lying flush with the end of the heatbreak. It cannot be allowed to protrude or reveal any bare steel in the heatbreak- Also test that the PTFE liner is firmly fixed and that it cannot be pushed up into the heatbreak by the counter pressure of the molten plastic (some chines PTFE liner is cut in wrong length and this will be a problem then).

Then install the nozzle so it has full contact to the heating block, then screw in the heatbreak - when installing the heatbreak wrap it at the heating block side with PTFE tape (like you would seal a pipe). When screwing it in pay attention that it is very important that your nozzle and heatbreak end up meeting each other.


Now try printing at 225 deg. Retraction 0.5mm . Print speed 30 mm / s.
Re: Extrusion Issues
July 27, 2015 02:08AM
Quote
LarsK

Then install the nozzle so it has full contact to the heating block, then screw in the heatbreak - when installing the heatbreak wrap it at the heating block side with PTFE tape (like you would seal a pipe). When screwing it in pay attention that it is very important that your nozzle and heatbreak end up meeting each other.

Sorry for the hijack.

Does that wrapping in PTFE-tape give some heat-insulation?

I can recommend that you don't screw the nozzle all the way in, or rather all the way in and then back 1/2 - 3/4 turn and then screw in the heatbreak making sure they meet, heat it up to ~230C and then tighten it, to prevent leakage of plastic.
Re: Extrusion Issues
July 27, 2015 02:21AM
Can you confirm that you have a fan cooling the hot end heatsink, permanently connected to 12V so that it runs all the time? Most hot end designs need this in order to keep the top end of the heat break cool.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extrusion Issues
July 27, 2015 08:32AM
i had (2) - 40mm fans bolted to the end effector but ive reduced it to one...neither seemed effective since its not ducted around it like the clip on 30mm fans.i plan on changing my design to allow for this now that im seeing the issues. and yes...I have it set in slic3r in the custom code that it turns the fan on full throttle before it turns on the heaters.

ive had these nozzles apart a few times.. i am making sure the nozzle and heatbreak are meeting in the middle. i read that on another post here and the reason makes sense. the liner is short but it is pushed all the way to the end.

i might have some time later today to mess with it again. i will post back the results when i get them. thanks guys for all your help.
Re: Extrusion Issues
July 27, 2015 09:02AM
Quote
Freebird01
i had (2) - 40mm fans bolted to the end effector but ive reduced it to one...neither seemed effective since its not ducted around it like the clip on 30mm fans.i plan on changing my design to allow for this now that im seeing the issues. and yes...I have it set in slic3r in the custom code that it turns the fan on full throttle before it turns on the heaters.

If your hot end is the sort that requires a hot end fan blowing on the heatsink (as most hot ends are), then you should not connect this to the cooling fan output of the Duet - that is for a print cooling fan, and is what slic3r generates commands to control. Instead, connect it to permanent 12V, as here:



Otherwise, when slic3r commands the print cooling fan off or you try to extrude manually, heat will creep up the heat break and soften filament too high up in it, resulting in a blockage.

Edited 2 time(s). Last edit at 07/27/2015 09:03AM by dc42.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Re: Extrusion Issues
July 27, 2015 09:18AM
i created a button in pronterface to turn the fan on full while im messing with it manually and it hasnt been an issue. it stays on when commanded
Re: Extrusion Issues
August 20, 2015 05:45PM
ok im back at this again...

what parameter do i need to adjust for my z probe offset? I run the bed homing and it works just fine, but i believe i am slightly off on my offset because when it comes down to lay down the first layer its too close to the bed. im thinking this is the bulk of my issues as its essentially stopping off the nozzle and not allowing the plastic to come out.
Re: Extrusion Issues
August 20, 2015 05:53PM
It's the Z parameter in the G31 command.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extrusion Issues
August 20, 2015 05:55PM
ok...so if im too close to the bed i should increase that number correct?
Re: Extrusion Issues
August 20, 2015 05:58PM
No, reduce it. It's the nozzle height above the bed at which the probe triggers when the probe is descending.



Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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