RepRap Guru issue

I bought a used RepRap Guru a few weeks back knowing it needed to work but having trouble figuring out a print issue. The part on the left in the attached image is from the Guru and on the right is from my Ender 2. I can't get rid of that orange peel like finish and have pretty noticeable ringing in both x and y axis.

At first I thought this was going to be a simple mechanical issue so I tore it down, squared up the x and y, tightened down/checked all the screws and secured it better to the work surface. Improvement was very minor.
I then started to reduce acceleration, speed and jerk values. I have them down to accel:800, jerk:10 and max speed:1000. This is down to half of the default setting and still very minor if ANY difference in print. Slowing down to 60% print speed with these settings still shows ringing and that orange peel surface!

At this point I figured I might have a driver issue. I checked vref on the drivers and bumped them up a bit from the recommended 550mV to 600mV. At this point I realized my motors or drivers aren't even warm to the touch, only 5-10C over ambient. I tried cranking the vref up to about 900mV, just under where the motors would start to jitter, and still no difference in motor or driver temp. Even swapped the PSU to make sure that wasn't an issue.

Any ideas on what I'm overlooking? Shouldn't my motors and drivers be running hot with those voltages I tested?
It's using a RAMPS 1.4, Mega 2560 and A4988 drivers.

Are both object in the pictures printed with the same gcode file? Or at least sliced with the same settings? The part on the left almost looks like you can see the infill in the outer surface as if one has more outer layers.

Yes, same settings for both prints. There is no infill as the part is only 1mm thick.

Edited 1 time(s). Last edit at 10/13/2018 08:55PM by Navin_R_Johnson.

My printers are similar to you RepRap Guru, When I printed my Yard Light Globe. which is also a thin skinned model.

I found that the Connection between the Stepper motor and the Lead Screws, by way of the flexible coupler was not a "True" connection.
Ended up wrapping a single revolution of electricians tape around the bottom of the lead screw before attaching the coupler to true the fittings with the lead screw.

This was what was causing my X Y Lines anyway.

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Computer Programmer / Electronics Technician

Looks like motor current needs to be tuned, it looks like as though microstepping isn't exactly smooth. Try a move at 10mm/min and see if the motion is smooth, if it sounds and/or appears to be irregular, jumping you can try adjusting motor current until smooth.

Edited 1 time(s). Last edit at 10/15/2018 12:01PM by imqqmi.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Thanks for all the input and an update.
I printed some feet and secured the printer to a butcher block along with a few other reinforcements to secure the top of the printer yesterday. I also took a stethoscope to the motors and tuned vref for least noise as recommended. 0.65mV seemed best and was set for all the drivers.


The prints look way better from where I started and ringing is gone but, I still have minor orange peel finish. I think I've come to the conclusion I'm looking at two things contributing to this.
1: The biggest issue might be that this is my fist experience with a direct extruder and I may be expecting too much? I'll need to experiment a bit more with this, maybe a geared setup or just try a Bowden to see the difference.
2: After a lot of reading last night, it seems the A4988 drivers also have some known issues that directly relate to what I'm seeing. Instead of adding external diodes and reworking components on the board to fix decay times, I may just upgrade the drivers to TMC's or some others.

I bought this printer dirt cheap for the parts and I'm checking to see all is in order before I dive in too far. Now that I think I have a handle on things and have this printing good enough to make parts, an extruded frame will be cut from my scraps.