My Elephant has Pimples

Hello Reprappers!

I have been trying to print the LSF elephant from thingiverse, and no matter what i do, it gets theese small pimples that you see on the pictures in the end of this post.
I have been fine tuning and calibrating for a couple of days, and the belts are tight, the steps per mm. on the extruder is correct, and i have also measured my filament and used an average of that as the filament diameter.

I am printing at 100mm/s with an outline underspeed of 60%. and an infill at 80%.

The print is done at 0.2mm Layer height, 210 degrees celsius (PLA) with 30% infill on a PRUSA I3

What can cause this?
Too fast outline speeds?

I tryed enabling the wipe nozzle function in simplify3d, which did not help at all....

I tried printing something else (Gears) which came out absolutely perfect.




Edited 2 time(s). Last edit at 09/16/2015 03:37AM by Kafledelius.

Are you using a RAMPS/Arduino board with an LCD? Are straight walls just fine, but curves are problematic?

If so then you're experiencing blobbing due to micro-pauses because the controller can't keep up. I'm having the same problem. I think the only solution is to go 32-bit...

Yes i am actually
Straight walls are perfect !

How do you upgrade to 32 bit? a new controller board?

Yes, a new controller like a Smoothie. Works very well.

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My printer: Raptosaur - Large Format Delta - [www.paulwanamaker.wordpress.com]
Can you answer questions about Calibration, Printing issues, Mechanics? Write it up and improve the Wiki!

I see.
I'll definitely look into it!

I am also printing with Octoprint - Could this have an effect on the print as well?

I have noticed that all of the prints take quite a lot longer than it used to, when printing directly from SD and not via octoprint.

Would it help to upgrade to the raspberry pi 2?

Edited 1 time(s). Last edit at 09/16/2015 01:41PM by Kafledelius.

Is the printer actually stuttering on curves though? If so, then yes, the printer should probably have an electronics upgrade, but this is unlikely since the RAMPS should work well with standard cartesian printers (it even works well on my CoreXY machine, though I've heard it has problems with delta printers).
However, if it looks like it's moving smoothly then the cause is probably filament related; try turning the temperature down a little and see if it helps.

I have never noticed any stuttering

But as i mentioned, when using octoprint, the print does take alot more time.. Which might be due to micro pauses? Or am i wrong?

Are you absolutely certain that printing takes longer using Octoprint than it does from SD card? Have you tried printing the elephant from SD card, and comparing the time it takes and the pimples (or lack of) with the version printed from Octoprint?

IMO, printing via USB to an Arduino/RAMPS setup is never a good idea. The reason is that the Arduino Mega doesn't have a true USB port. Instead it converts the USB data stream to a serial stream without any flow control. This means that the sending program can't just send data to USB. Instead it has to wait for the "OK" after sending each command so as to know that there is enough buffer space. This is much less efficient than flow control implemented in the hardware and device driver. No professional engineer would design a system this way.

The Linux die-hards on this forum claim this is only a problem when running a host program under Windows, however the same considerations apply in theory to Linux. So this could be the problem you are seeing. The extent of the problem will depend on what else you have running on the host computer (in your case, on the RPi). I have always assumed that it is possible to set up Octoprint on an RPi to have very little else running and so avoid the problem, but perhaps it's not that easy.

If this is the cause, then potential solutions include:

1. Change your electronics to a board with a native USB port (e.g. Duet or Smoothieboard) instead of USB-over serial, and configure Octoprint not to wait for "OK" after each command (if that's possible).

2. Don't use Octoprint, instead print from SD card. If you want a web interface without Octoprint, use Duet electronics.

Edited 1 time(s). Last edit at 09/17/2015 03:41AM by dc42.

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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].

Yes i actually perfomed the test, and the result was better (lesser pimples) and the print took 1 hour 34 minutes (even though i halfed the speed like 75% in to the print), and a print from octopi took 2 hours 22 minutes AND the x-axis skipped (i checked the current of the steppers which were exactly as they used to be) And this is not the first time i experience this skipping. while printing from octopi. It has never occured when printing from SD

My raspberry pi is only running Octopi, nothing else. However, i do have a webcam attatched.
Is there a chance that the raspberry pi b+ model is simply too slow? Maybe upgrading to a raspberry pi 2 would solve the issue?
Or is there no way around changing the electronics?

Does nobody have any thoughts about upgrading the raspberry pi 2? - It is stated to be up to 6 times faster, maybe that will help a bit?

or this one with the option to upgrade to 6 extruders

T3P3D Duet 0.8.5

I have a RPi2 running in a robot, I can't say how much better it might be or not, its my first RPi, but it seems quick enough for now

Edited 1 time(s). Last edit at 09/21/2015 05:24PM by deaconfrost.

It seems that you are not the only person who finds that RPi + Octoprint can't feed the printer with data fast enough. See [forums.reprap.org].

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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].

I just tried printing from SD Card...
This also has the same pimples, not as many, but still has them

Does this narrow the issue down a bit?

Are you performing retraction on the same spot ?, if no, try to change it to that.

No i use the random point selection.

I will try a print with the same position.

If this helps, how can i avoid it in the future? i'd hate to see a seem all the way through my prints.
Plus, this only happends on round spots.

Well.. the thing is, if it turns out to be that particular issue, i just stuck with an alligned seam around the object - you can fiddle around with the retraction parameters in order to optimise the seam.

Things to check:
-Loose nozzle
-Loose bed
-Overextrusion

Also, do you have a layer fan/part cooling fan?
It is a slim chance but the layer could be warping causing the ledges. A video of the printer printing would also help us think of solutions.

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Master Tinkerer