Printer makes large curves bumpy

So I recently finished a prusa i2 I started over a year ago. It uses generation 7 electronics and teacup firmware. It mostly prints great so far. However, on large curves I get small blobs of plastic that in the end give me the appearance of bumpy curves. I've attached a picture.



Can someone give me some direction on how to eliminate this? Is it acceleration/look ahead related?

Thanks!

Not all firmware has the same result while printing. I would try 'Sprinter' firmware.
Another possible cause is the slicer but frankly, I doubt it.
If you drew all objects yourself with 3D software, there also is a possible cause. Your software is not exporting your file correctly. If you print objects from other sources with the same result, forget about 3D software errors.

It's no mechanical problem because the bumps appear in both 'Y' and 'X' direction very regularly.

Chris

So far all but a couple things I've printed have just been grabbed off thingiverse (that picture included). I'll give a shot at an alternate firmware tonight, it's easy enough. I liked the philosophies I saw with gen7/teacup but whatever ends up working, I'm okay with. Also just so you/others know, I'm using slic3r. I agree I don't think it's the slicing or mechanical issues, I basically figured it was down to firmware.

Thanks for the advice

Is it possible the print head slows down at each of these bumps? It looks like raising the X_JERK and Y_JERK values would improve the situation. Like always with Teacup, the default values are very conservative.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I was also thinking the head was slowing down at each change in curvature Traumflug - Although it's not something exaggerated that I can see just by watching it print. That's why I was thinking accel or look ahead. Currently I have 1500 m/s^2mm/s^2 acceleration and 100 mm/min for X/Y jerk. I was working on bumping up acceleration yesterday but then I had some problems that started slowing me down (I crashed through my x endstop).

Maybe the first thing I'll do is start bumping up XY jerk. Also just to throw more info out there, I'm printing at something like 60-70mm/s.

Thanks!

Edited 2 time(s). Last edit at 05/15/2014 01:17PM by Glow.

Throwing an update out there for anyone who may end up having a similar issue in the future. Increasing the max_jerk for XY solved my problem. Attached is a side-by-side picture of an object printed with 100 for max XY jerk (left) and 400 max XY jerk (right).

Thanks again, Traumflug

Thanks for the follow up! I was able to fix a similar problem thanks to your thread!

Hi Glow !

Where can i find max_XY jerk option in firmware ? I'm use a Marlin.

It's in Configuration.h

But if you have eeprom settings enabled, you can change it with M205 without having to recompile the firmware.