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heidelberg-makerspace / dai-makerspace-do-something

Issue tracker for tasks you could do in the DAI Makerspace
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Prusa B Z-offset or bed calibration is off again #103

Closed ragflyer closed 7 years ago

ragflyer commented 7 years ago

In the front left corner it prints into air while in the back right corner the nozzle touches the bed.

Also the flow does not seem to work as in Prusa A, sometimes it does not print anything, sometimes it flows into areas that should be empty. I tried different filament and temperatures today which did not improve the behaviour.

LukasFreeze commented 7 years ago

we should check whether the bed is bent, it's weird that it doesn't work so shortly after the last calibration!

beanobeano commented 7 years ago

I'm at the makerspace now and had a quick look. The cable for the Y-Stepper was looped under the back left corner of the acrylic frame. This might of caused the printer to twist slightly and possibly caused the issue. I'll tie up the cable so it can't slip under the frame again.

beanobeano commented 7 years ago

... and both nuts at the back on the M8 threaded rods were loose.

LukasFreeze commented 7 years ago

phew, that's bad! Good thing you noticed, otherwise we would go mad over calibrating over and over again... I think André mentioned he mounted his i3 to a wooden board for transport, maybe we should find a good way to do that and then calibrate?

beanobeano commented 7 years ago

I was just thinking a similar thing, as there was a lot of crap on the table under the printer including some partial prints and some filament clippings from changing filament. Any of these under one of the corners could have also caused it to twist (especially with the loose nuts). Fixing the printer to a stable flat board would address this permanently or relatively permanently :-) or at least improve the situation. I'll check for warping of the bed too... just in case that is also an issue. Hopefully not.

beanobeano commented 7 years ago

Bad news. There is quite a substantial warping across the bed in the X direction. Raised in the middle compared to the left and right sides - by over 1mm. It's not so bad in the Y direction.

LukasFreeze commented 7 years ago

Do you think loosening a screw or two might help? I think we had a similar problem with Prusa A once and ended up exchanging the springs between the bed and its carriage for weaker ones. Otherwise I guess we'd have to bend it back carefully :-P

beanobeano commented 7 years ago

It's quite warped. We can try loosen the screws but I think it's already permanently warped.

Andi-Heidelberg commented 7 years ago

I dismounted the bed, and it is warped in x and y-direction. Sorry for the bad news...

Pakue95 commented 7 years ago

I bend the bed back as good as I could. Also the printer is now secured on a piece of wood with some brackets which should prevent further miscalibration in the future.

To Do

  1. mount the bed again
    • otherwise the Z sensor won't work
  2. Recalibrate the printer
Ianmcmill commented 7 years ago

Hello! I visited your makerspace yesterday as a guest and looked around a bit. I also have a very slightly bend bed. 2mm MK3 ALU-Heatbed Dual Power. I directly print onto it's surface with blue painters tape. I got the bed for 15€ with minor scratches from ebay. I am using cheap and low tension springs from my local hardware shop. They work nicely.

If you already use an (permanently attached) inductive probe like LJ12A3-4-Z/BX the you could enable ABL (auto bed leveling) in Marlin/Repetierfirmware (as of Marlin 1.1.0 RC7 quite stable) and still print on a bend bed without hassles. There are several bed leveling methods of which the bilinear method should work best with an uneven i.e. bend bed * - BILINEAR * Probe several points in a grid. * You specify the rectangle and the density of sample points. * The result is a mesh, best for large or uneven beds.

Also current UBL fork of Marlin (experimental) has some new mesh bed leveling methods up for testing. Though I could not try them because this fork is currently under heavy testing and it's hardcoded for use with an attached LCD to the printer which I don't happen to have.

LukasFreeze commented 7 years ago

We do have bed leveling, but I think the firmware just calculates a plane and with a bent bed parts of that virtual plane end up under or too far over the actual bed. Not sure if this "bilinear" method is included in our firmware, but if it works with bent beds it's yet another reason for an upgrade, thanks!

To whoever will mount the bed: please make it as square as possible using the leadscrews (slide x and y with the power off to check) and maybe replace the springs with softer ones (found in the workshop material cabinets, but maybe not four of a kind) to reduce further stress on the plate :-)

ragflyer commented 7 years ago

Bed is leveled and taped now, I adjusted the firmware on the slicing laptop and did some test prints in each corner and center. Could somebody with more experience check those prints and let me know if I should put the firmware on github? It looks like the bed is marginally higher in the center but current setting seems to work in every location on the bed.

LukasFreeze commented 7 years ago

A while ago I set the first layer thickness to 0.3 mm regardless of any other settings, so it might be okay if it is just slightly higher in the middle - would be interested to see your prints sometime!

On Sat, Feb 4, 2017 at 11:06 AM, ragflyer notifications@github.com wrote:

Closed #103 https://github.com/heidelberg-makerspace/do-something/issues/103.

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Andi-Heidelberg commented 7 years ago

Great job! Thumbs up!

Am 04.02.2017 um 11:06 schrieb ragflyer:

Bed is leveled and taped now, I adjusted the firmware on the slicing laptop and did some test prints in each corner and center. Could somebody with more experience check those prints and let me know if I should put the firmware on github? It looks like the bed is marginally higher in the center but current setting seems to work in every location on the bed.

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/heidelberg-makerspace/do-something/issues/103#issuecomment-277433143, or mute the thread https://github.com/notifications/unsubscribe-auth/AVCfpUt_BiMJaIJtodYG4ZCZBSpZRyYZks5rZE2YgaJpZM4LKuQQ.

LukasFreeze commented 7 years ago

looking at @ragflyer 's test prints I would say the nozzle gap is good on the left, slightly too small in the center and slightly too big on the right. This may not be fixable without replacing the aluminum plate, but it's no problem for printing! Just print in the center for a very flat bottom and on the right if you're afraid your print won't come off ;-) I printed a large piece across the majority of the bed area and it looks perfect!