Marlin vs Repetier: Surface Finish on 3D Printed Parts on Delta printers.

Lets start from the beginning on this one. What does a 3D printer run on? The answer might be “G-code!” – but that is only half the answer. The other half is the firmware that runs on the controller board that translates the motor moves in the G-code into actual physical movements. Most popular controller motherboards at the moment are based on the ATMEGA 8-bit processor line, and are quite limited in their capabilities. I was looking into upgrading to an ARM based board, for reasons I will explain in a moment, but there is a limited range, and they are typically 3-4x more expensive.

For a cartesian 3d printers, the computation required for movement is fairly low, and it is possible to achieve a high enough update rate (khz) to perform 32x microstepping on the stepper drivers to get smooth movement. Delta printers (see image below) are different, as they must translate the x-y-z coordinate system into positions of the vertical blocks, which in turn drive the arms through some complex trigonometry. As a result, they place a much higher load on these already strained 8-bit micros.

I found that the surface quality of my prints on my G2S Pro (review here) was quite poor, and I noticed a distinctive throbbing sound to the motion produced during printing. I read online:

Andrew Lindsey : I noticed a significant increase in smoothness and consistency of printing and movement when I switched to Repetier. (here)

3DRapidClone: Repetier is the better firmware for running Deltas, its more resource efficient and Marlin will bog down if you have a graphic lcd attached and try to go slightly too fast.(here)

On the Repetier GitHub: Fast – 16000 Hz stepper frequency and more is possible with a 16 MHz AVR. (here)

The G2S is supplied running the marlin firmware from the factory. Here is my first successful print:

IMG_0398

A thing of beauty and a joy forever. And I might, just might, need to tweak the retraction settings a little….

Looking at the hull of the boat, we can see that the surface finish is quite poor:

IMG_0399

 

I’ve been making custom builds for this printer for both Repetier and Marlin firmwares. I installed the Repetier firmware next, and printed the exact same gcode file. This is the result:

 

IMG_0415

IMG_0409

The bottom print in both photos was done with Repetier, while the top print is the Marlin print. It is fairly easy to see the different in the surface finish – and the sound of the motion is also noticeably smoother too! Yes, I am aware that the bottom print is only partially printed – no, I was not impatient, the cheap power supply GeeeTech provided failed mid way through!! Both prints were printed at 40mm/s, which is hardly going to break any speed records. I imagine that printing at faster speeds would make the difference even more noticeable.

The design of the Repetier firmware is such that driving the stepper motors smoothly is the highest priority, which is clearly a key advantage over marlin for delta printers.

Conclusion: if you have a delta 3D printer, you probably want to use Repetier.

A good starting configuration for Repetier for the G2S can be found here. You can load the json file provided into the Repetier configurator here. Good luck – feel free to ask a questions if you want some help as it is a a good upgrade for any delta printer!

2 Comments

  1. John

    This is a poor example. Both of those prints look like complete ass. Before this comparison was made, you needed to make sure your printer was printing well (fix the extrusion issue!). The hull of the benchy will never look that bad if your printer is properly calibrated with slicer settings dialed in for the filament you are printing, regardless of firmware.

    • admin

      Well, don’t hold back, tell us what you really think 😄!

      Mate, this printer fits the category of “complete garbage”. And yes, I could have probably improved the print with more tuning, but I think you missed the point: this is a comparison of the same GCode printed on two different firmwares. Care to provide a helpful comment on that aspect? Peace, Sam 😉

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