I have designed a new model that is massive on the 2.0S Printer. It measures 9"x7" on the model, and 9.5"x7.5" on the glass bed with the raft. I started the print on Friday so it would be done by the time we got back on Tuesday. The print was 64 hours and around 541m of material. I am using a 5lb spool of PETG from Toner Plastics. So that is roughly 2.25kg of material. I have it on a shaft and bearing design to severely reduce friction and drag. Also, the shift was away from the reel. So I don't see the weight of the spool being the culprit. It glides smoothly with little effort.
That being said, I started researching through our forums about any topics related to my error. I searched "Shift", "Failed", and "Layer Shift". I found some posts regarding these issues. I will provide their links below along with their (OP) and Replying Posters (RP):
3D Printing vertical step. Print Failure - @Jesus_Corbacho_Redon (OP), @AL3DConcept (RP)
Layer shifted sideways. X axis stuttering? - @Rejutka (OP), @Gueni (RP)
For reference, here is a picture showing the issue:
The Problem:
The print begins smoothly for several layers, and then suddenly, the printer starts a new layer and it is shifted along the X and Y axes apparently for no reason. So, what happened?
The Process:
I downloaded a few gcode viewers and tried to load it into the web-based viewers to no avail. The file is 200MB so it kills them almost immediately. So the next option, the only option, is to have a downloaded and installed program to verify them. I tried several to no avail as well. I found one that runs the file, though the bed wasn't calibrated to show the correct dimensions for the ZMorph, so it overhangs the virtual bed. This was fine because I only wanted to verify the shape of the code and to verify that the shift wasn't inside the code itself. The program is called Repetier Host. So, let's take a look at that!
As you can see, the file is verifiable and it is square. No shifts or anything. So the code is clean. So what does this mean? It has to be a mechanical problem.
The underlying issue as I currently see it:
The acceleration of the stepper motors could be, and I think it likely is, the culprit. How fast is my Travel Speed inside the General Tab in the Project Settings window under Advanced Options? It was set to 120mm/s for this print. If the torque of the motor was overcome due to an electrical glitch (ie. the hotbed heater turned on during a long travel run), then the printer could have skipped a few steps in the motor itself. I hope this is making since. Basically, a stepper motor's strength is key to having its accuracy maintained. If you don't drive it with enough power to maintain strength, any slight power that is given to another motor, heater, etc, can drain the power and, in turn, lower the strength of the motor. You can see what I'm talking about by tightening the tensioner plate and extruding some filament. You will see that the extruder motor stutters and doesn't extrude filament as you want it to. That is the kind of issue I think we are experiencing. Does that make sense?
Possible Solution:
Let's run the same gcodes, BUT! Let's lower the speed on the printer itself to be an overall, 80% of 100%. What this will do, essentially, is to take the Travel Speed, as well as other speeds down by 20%. For the test, we want the Travel Speed to come down to around 100mm/s. Ideally, for the actual print, we want the Travel Speed reduced for larger prints, not all speeds. But for the sake of SCIENCE, this will have to suffice.
Hypothesis:
This should lower the speed of the motor across longer travel stretches giving the motor more torque/strength. Thereby maintaining the accuracy of the print dimensions. This should lower the chances of a print failing.
I will keep this post updated until the problem is solved. Stay tuned!
EDIT: I need to run an additional print ahead of this test. So I will start this test after the current one finishes tomorrow. So expect the results of my test by Thursday, mid to late afternoon US Eastern time.
