Y-Axis Out of Calibration

Just bought a 4th gen model of the MB Replicator 2 and I'm having a couple problems with it related to the y-axis calibration. I put in a support ticket for the problem, but I'm still waiting to hear back.

Printer: MB Replicator 2, 4th Gen
Firmware: 7.6
Software: MB Desktop, v3.9.1.1143

The issue started when I tried to print the bolt and nut that comes preloaded on the SD card. It printed fine, but it was more oval shaped...longer in X than in Y. Next I tried printing the 20mm cube example that comes on the Makerbot Desktop software. Again, it printed, OK but the cube measures 20mm in the x-direction and only 17.8mm in the y-direction. I have since tried printing several calibration objects and they are all too small in the Y-axis.

Both the Onboard preferences and the .jsom file associated with with software list the steps/mm as 88.573186. I have read online where people modify this value slightly to correct printing accuracy...but the changes are always small like 88.888888. To see if it would fix the problem I changed my steps/mm on the y-axis to 99.520433 (88.573186*20/17.8) in both the onboard preferences and the .jsom file. Printed another cube, but it didn't change anything. To see if these changes were even working I changed the x-axis to 99.520433 and again no change...still a 20mm x 17.8mm cube.

So, I'm at a loss for the moment. I figure the y-axis stepper motor probably has a bad output signal and needs to be replaced, but I don't know why my changes to the steps/mm are having no effect to either axis.

https://lh3.googleusercontent.com/-I...0/IMAG2788.jpg

It took some time, but I got it to print correctly.

I never could get the MakerBot software to update the steps/mm on the bot firmware correctly. The onboard preferences would make it look like it was fixed, but it still wouldn't print correctly. I suspect that there is a bug in the MB software because despite the fact that it initially recognized my printer as a Rep2 as shown in the name beside the USB icon on the monitor, it shows a picture of a Rep2X. It also changed the table size in the prepare window to the size for a 2X.

https://lh3.googleusercontent.com/-4...ktop_Error.bmp

I ended up doing a lot of reading and eventually downloaded Sailfish v7.7 bot firmware and ReplicatorG software. You can download these files through the Thingiverse which is linked on the Sailfish website below. RepG is required because it allows you to select which type of Firmware you want to upload...versus the MB software that will only let you select which version of their software you want to upload. The process was fairly painless if you follow the Sailfish instructions.

http://www.sailfishfirmware.com/

RepG has a better control panel that lets you jog the X,Y,Z axis by specified increments (1mm, 5mm, 10mm, etc.). I was able to use this feature and some calipers to verify that the stock calibration value of 88.573186 was off by about 11.5%. With SF installed, I was able to use RepG to change the steps/mm parameter to my calibrated value of 99.520433 by changing the default profile xml file in the RepG folder. Once the change is made, the next time RepG communicates with the bot it will see the difference in onboard parameters and rewrite them. The nice thing about RepG is there is a script window that displays the program outputs which verified that the update was actually made. I was able to use the jog feature again to verify that I am less than 1.5% error at 50mm.

As a test, I printed a portal companion cube that I found on Thingiverse that is supposed to be 1in square...yes I could have printed another preloaded 20mm cube, but if you saw how many incorrect rectangles I have sitting on my table right now, you would understand why I don't want to see another one of these ever again. The cube is within 0.003in from being a perfect 1in sqaure. Looking back at the changes I made, I probably could have just used RepG and the stock firmware without needing to install SF...but the SF interface on the bot is a lot better than the stock firmware.


https://lh3.googleusercontent.com/-6...0/IMAG2792.jpg

I still don't know why I had to change the calibrated steps/mm value so much...maybe the stepper motor does need to be replaced or maybe there is a different pulley diameter on that axis...but for now, I'm happy.

On a related note, from a pure slicer point of view, I like the MakerBot software better than RepG. The main reasons, are MB uses an infill pattern that is a series of stacked hexagons whereas RepG has some hexagons, but the rest is random. Also, the MB software uses diagonals for the top and bottom solid layers versus RepG which uses vertical and horizontal lines. I'm still new to both versions of software, so there is probably some fine tuning that can be done in RepG.

One of the nice features with the Sailfish firmware is that it will still work with the MB Desktop app. Although, I just use the MB app to create a .x3g file, copy that to an SD card and then print from the SD card so you don't really need it to communicate.

...last comment...I still haven't heard from MakerBot support. The online form states that someone will contact you within the next 24hrs. I'm currently at 48hrs and I highly doubt I will hear from them this weekend. For a relatively expensive printer that only has 60 days of warranty, they are taking their sweet time...