Extrusion issues on UM2

[kerry 0]

Sorry if this comes off a bit harsh, as I've been frustrated quite a bit at the hit or miss prints I've been getting on my UM2. I received it last month, and have had some fantastic prints off of it. But I've also had extrusion issues that require me to go through various steps to get it working again. For the past couple of days I've been printing 3-5 part batches at .2mm, 50mm speed, PLA, 20% infill, 210 deg (also 220) for a project I'm working on. I set them up to print at night as they are usually 5-7 hour prints. The first night went flawlessly. The second night, same plastic, temps etc., printed fine until the last 10% then terrible extrusion and ruined prints. Pulled PLA, re-insterted, put fine metal wire in nozzle to clear it, reprint and things look great until ~ 2mm in then extrusion issues again. Repeat cycle of fixes, set up a print for overnight and in the morning that batch looks great. Next print, ruined due to extrusion.

I don't think I need to show photos, as there are many already on this forum that look exactly like what I'm getting.

Can someone from UM tell me what the current plan is to fix the design? And what the status of that fix is? Thanks.

Kerry

 

[illuminarti 17]

Is the filament getting chewed up when the extrusion issues happen, or is the motor simply clicking back because it's unable to move the filament any more?

Can you confirm that the fan on the back of the print head is running?

 

[kerry 0]

The fan is always running when it is on. At least I hear it.

I'm not at home to reproduce it, but I think the filament is getting chewed up.

One thing that may be aggravating it is the layer height. I was printing most things at .1, but for these larger builds I went to 0.2mm layers otherwise they take forever and the resolution increase isn't needed for this type of part. I upped the temps from 210 - 220 for the 0.2mm layers, but it hasn't seemed to fix it (although it may have helped). What is the standard temps for 0.2mm layers?

 

[illuminarti 17]

The temperature you need is a function of the volume per second you are printing - which in turn is dependent on the layer height multiplied by the extrusion width multiplied by the linear speed.

Have you tried printing the http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/?p=33427, to get a sense of what speeds your extruder can happily handle?

I'd certainly try printing at 230º. Also what are you using as the shell thickness setting in Cura? Is it an exact multiple of the 0.4mm nozzle width?

 

[kerry 0]

Yes, the PLA I'm using is silver, and has some transparency to it so I need to set shell width to 1.2mm (a multiple of .4) to get it to look solid. Otherwise I can see the infill pattern.

I have not tried the test piece yet. Once I get it back to functioning I will give it a go.

I've read some postings about Robert's extruder. Is that a known 'fix' for folks? Are they still seeing extrusion issues after installing it?

 

[illuminarti 17]

If it's chewing up the filament you should try increasing the tension a little on the extruder. Do this by turning the tensioning screw anti-clockwise (as viewed from above) in order to lower the white indicator piece slightly.

If you can share a gcode file that causes problems, I'd be happy to take a look at it, and see if I can identify any potential issues.

You should also consider installing the test firmware that I built which contains fixes for filament grinding at the start of prints (among other things):

http://umforum.ultimaker.com/index.php?/topic/5935-z-axis-homing-inconsistent-on-um2-workaround-and-patch/?p=57095

After installing that, I recommend re-leveling the bed.

 

[kerry 0]

Thanks illuminarti, sorry I've been busy and haven't had much time. I increased the tension as suggested, it is now right in the middle of the range (I have a UM2 purchased in May).

I have already installed a version of your firmware that had the filament grinding fix in an earlier build.

Here are some not so great photos of the extrusion test piece.

 

[kerry 0]

Looking at those photos it looks like the only consistently good walls I'm getting are at 3mm.

I watched it print that piece for a bit, and noticed the grinding/skip sound from the feeder about once per revolution once it was above 3mm. It was a short sound, but pretty consistent per layer.

It feels like there is some fundamental design issue with the UM2. My old Thing-O-Matic was a bit long in the tooth after 2 1/2 years, but I never had any issues with extrusion, even at fairly high acceleration rates.

 

[illuminarti 17]

See my PM...

 

[kerry 0]

See my PM...

 

Reply sent. Thanks illuminarti.