Strange behavior after recalibration

[noahcoleman]

Hey all, this is my first post. We just bought two stock Rostock Max v2's for the college I work for. I've assembled one of them and did some test prints that came out lovely. I tried a larger diameter print and realized that the nozzle pulled up a little at the front and pushed down a little at the back. No worries, I thought, I'll just do a little recalibration. So I tried recalibrating and the Z tower's screw is now half as tall as the other two and even though I have the nozzle gripping the paper at all three towers and in the center, the vertical travel from front to back is even worse. I tried printing a single-layer test (image below) and you can really see how bad it is. I'm really wishing for a ctrl-z on life right now so I could at least go back to where I could print smaller stuff without a problem. Any help will be greatly appreciated. Thanks!

[ZakRabbit]

How exactly did you recalibrate? It doesn't make sense that one adjustment screw is half the height as the others. That adjuster screw being half the height of the others bothers me. It tells me either something's loose or has slipped. I'd go through everything from the pinions on the stepper motors to the joints on the arms then run the calibration as if it's just been built.

[mhackney]

Make sure the set screws on the pulleys on all 3 stepper motors (bottom of towers) are tight. It could be that your Z pulley is loose.

[noahcoleman]

ZakRabbit- I rezeroed the z height and went through the calibration sequence on p. 240 of the build manual.
mhackney- It seems like the all the pulleys on the steppers are tight.

Also, when I run the "Bed Center" macro the nozzle is a few mm toward the z tower of the center of the platform. I suspect this is related to the adjustment screw issue.

[KAS]

Check the endstop switches and make sure they're not loose.

[mhackney]

+KAS - I wager you have some sort of mechanical issue.

Noah, yes, the off center issue is likely due to the wicked Z adjustment screw. Maybe post some photos of the tops of the towers and the carriages and platform. You have to have some issue somewhere.

[noahcoleman]

No problems with the endstop switches. They are solid and they return H/L values as expected. I returned the set screws to their starting length and re-zeroed the Z axis. When I run the tower calibration macros, the x and y are about 4-5 mm above the platform while the z pinches hard. Here's a photo of the nozzle when I run the Y tower macro.

I just realized I mislabeled that as Y axis instead of Y tower...

[mhackney]

Does the machine look "normal"? Is it possible that the top plate or base slid along the towers slightly? Perhaps by lifting by the top? This is perplexing to say the least.

You should measure with a tape measure the length from the Rostock top plate (the white/black melamine near the tower) to the switch on all 3 towers. Report those back here.

[noahcoleman]

Here are pictures of the tower tops and carriages. Measurements of towers are:
X-26 13/16"
Y-26 13/16"
Z-26 3/4"

[noahcoleman]

The z tower belt is a little off-center and might be rubbing a bit. Could that be the cause of all this?

[mhackney]

Ok, tower lengths are all good and close together. Is your build surface perpendicular to the towers?

See that belt end that protrudes above carriage in the X photo? Any chance that one or more of those are hitting the endstops and throwing things off?

[mhackney]

Probably not, a little off center in the tower groove is not going to be a big contributor.

[noahcoleman]

The x and y towers are a hair out of true with the bed. I can just barely see daylight at the bottom of my square with it flat on the bed and the top of the square on the tower. I am super stumped where this coming from. The belt ends don't really interact with the switches at all, even though they are kinda long.

[mhackney]

Interesting problem. Where are you located? You might be down the street and this would be easy!

[mhackney]

A skype session where you can show the printer might help uncover something too. Things are just odd.

[noahcoleman]

I'm in Chicago. I'm open to a Skype session at some point. Is there any chance this could be a firmware issue? The thing that is so weird is that it worked perfectly before.

[mhackney]

not likely a firmware issue but you never know.

When you recalibrated, what did you change? Did you muck with the delta radius? or any other firmware values? Did you change these in the firmware and recompile and upload or in the eeprom?

Or did you simply adjust the carriage screws?

[noahcoleman]

In an effort to get back to square one, I reset the carriage screws and changed the delta radius back to 126.85 through the eeprom. I haven't changed any other firmware settings.

[mhackney]

Ok, so please verify -

From a firmware perspective all settings now are the same as they were before you started re-calibrating, correct?

From the carriage screw perspective, you've eye balled them and they are about where they were before as well, correct?

[noahcoleman]

Correct.

[mhackney]

And how does it have now?

[geneb]

Change your horizontal radius to 130 and then start calibrating. [edit: reset Z, etc.]

g.

[cyber.shifter]

I'm interested in this thread as I am seeing a similar problem but a different axis. My Y axis screw is half as tall as my other two easily. Also, I am getting print anomalies in that tower arc sometimes. I've checked a bunch of mechanical stuff as well, like the OP.

[geneb]

cyber.shifter, make sure that the top section on the Y axis is resting on the top stop-screw. (Also check the other axes to see if they're the off ones and Z is ok.)

g.

[cyber.shifter]

I checked that last night after reading the other posts. I've got exactly 29 3/16" all the way around. The measurement couldn't get more exact, actually. I was kinda proud... lol