Z-axis not locked

[scott216]

I have a Makerbot Replicator 2 and just started using Simplify 3D. My first print came out great, but I had a strange problem with my second. The first layer wasn't sticking to the build plate. So I cancelled the print and ran it again, but this time I tried adjusting the bed height as the first layer was going down. I noticed when I grabbed the leveling screws I could easily move the z-axis; it's as if the z-stepper motor wasn't holding the bed in place. So I cancelled the print and just ran the print with ReplicatorG, which worked fine. Any idea what the problem is?

I attached a zip file with the G-code from ReplicatorG, my .factory file and .stl file. I wanted to inlcude gcode from Simplify 3D, but I can't figure out how to get it.

[JoeJ]

Try removing the following 2 lines from your starting script

G130 X20 Y20 Z20 A20 B20 ; lower stepper Vrefs while heating
G130 X127 Y127 Z40 A127 B127 ; default stepper Vrefs

To be fair, even when including those lines it still works fine on my machine, but that's the only thing I could think of that might cause this. Maybe your machine requires more current to the Z-axis motor..

[Scottbee]

There is also a bug in the Makerbot firmware associated with "Z hold". This bug will only get you when you print over USB (not off of the SD), and will "go away" if you cancel the print and then start again.

This bug was clearly identified and rectified by the Sailfish firmware team, but to the best of my knowledge it still exists in even the latest release of MBI firmware.

Folks with heavy build platforms (glass, auto-levelers, etc..) have actually seen their Z stage run to the bottom of the bot.....

[scott216]

I think the z-axis not locking was a fluke. I tried again and it didn't move. I still have the problem where replicatorG slicing did a great job printing my object but Simplify 3D had trouble with the first layer. I looked at the gcode for both and for replicatorG the z height for the first layer is 0.1 and for Simplify 3D it's 0.18. I'm not sure why there is such a big difference, but I think this is my problem.

[JoeJ]

There is a first layer height setting in S3D, so it's very easy to adjust if you want something finer

[scott216]

I think I figured out the root cause of my problem. I found out there is a bug in the Replicator 2 where the z-axis doesn't always lock. This was fixed in Sailfish 7.7 - although apparently it's not a Sailfish bug, but Sailfish was able to to a fix. I've upgraded from Sailfish 7.6 to 7.7 and that seems to have fixed this issue.

See this post of more info:
https://groups.google.com/d/msg/makerbo ... gMZo92fRUJ

[Scottbee]

I think I figured out the root cause of my problem. I found out there is a bug in the Replicator 2 where the z-axis doesn't always lock. This was fixed in Sailfish 7.7 - although apparently it's not a Sailfish bug, but Sailfish was able to to a fix. I've upgraded from Sailfish 7.6 to 7.7 and that seems to have fixed this issue.

See this post of more info:
https://groups.google.com/d/msg/makerbo ... gMZo92fRUJ

Ummmm... isn't that what I said on the 4th??

[Scottbee]

I think the z-axis not locking was a fluke. I tried again and it didn't move. I still have the problem where replicatorG slicing did a great job printing my object but Simplify 3D had trouble with the first layer. I looked at the gcode for both and for replicatorG the z height for the first layer is 0.1 and for Simplify 3D it's 0.18. I'm not sure why there is such a big difference, but I think this is my problem.

This most likely has to do with the way that the slicers anticipate your Z=0 nozzle gap.

If memory serves me correctly, S3D expects Z=0 to actually be 0. In other words, the nozzle would be touching the build surface. RepG assumes that you did your tramming/leveling with a feeler gauge or business card... so at Z=0 there is actually a gap.

[scott216]

I think I figured out the root cause of my problem. I found out there is a bug in the Replicator 2 where the z-axis doesn't always lock. This was fixed in Sailfish 7.7 - although apparently it's not a Sailfish bug, but Sailfish was able to to a fix. I've upgraded from Sailfish 7.6 to 7.7 and that seems to have fixed this issue.

See this post of more info:
https://groups.google.com/d/msg/makerbo ... gMZo92fRUJ

Ummmm... isn't that what I said on the 4th??

Yup, you were right.