It's new to me

[ddmckee54]

Today was spent putting the Y axis leadnut assembly together. I started with your standard 3D printer anti-backlash leadnut, looks like this when assembled on the leadscrew.


This is just 2 modified leadnuts assembled back to back with a spring between them.. The spring keeps the 2 halves of the nut separated, removing the backlash, and a tab/slot arrangement keeps them in sync. This works fine for the minimal tool pressure of a 3D printer. BUT, and there's always a big butt, any tool pressure that opposes the travel will overpower that wimpy little spring and your backlash is back - don't think that'll do the surface finish any favors.

I remembered that Awesome CNC Freak had modified his 1310 machine to deal with backlash, so I did some digging - and then quite happily swiped his idea. This was the test rig I built.


It proved the concept. By using the nut to squeeze the 2 halves together you eliminate the thread backlash, and it's much more rigid. It does take careful adjustment though, you go from free falling to totally locked up in 1/4 turn of the nut. The bolts I used on the test rig weren't long enough though, the nylocks wouldn't lock - going from M3x35mm to M3x40mm bolts solved that problem. The bolts also keep the 2 halves in cync. This is what the business end of the Y axis anti-backlash leadnut assembly looks like.

That part will be buried between the Y axis bearing blocks though. This is all you'll see.


OK, OK, if you ignore the bit in the lower LH corner - THAT's what you'll see. Really shoulda cropped that picture.

[vtsteam]

Thanks greatly for pics! 

[ddmckee54]

Thanks greatly for pics! 

I had my old Blueberry flip-phone for so long, I keep forgetting that my new flip-phone has a camera.  It doesn't have the anti-blur capability of my camera so sometimes it takes several attempts to get a decent shot.

[ddmckee54]

I had a couple of 3D printing milestones recently, I started printing with something other than PLA and the P1S glitched on me.  Although in all honesty I probably made it worse than it should have been. 

I decided to try PETG, and I wanted to get the scaling dialed in to correct for shrinkage.  I decided that I might as well be printing something useful to do this testing.  My new spindle uses an ER11 collet, so I found an STL for a chip fan that presses onto the collet nut.  The friendly Google AI said the scaling factor should be 100.3-100.8%, so I scaled the fan to 100.5% and gave it a shot, way too tight.  I scaled it to 100.8% and printed it again. It takes less than 1/2 hour to print the fan - including the 7+ minutes the P1S uses for setup on every print.  It was still too tight, but I could force it on the nut.  I printed it again, this time scaled to 101.5%.  It presses onto the nut, not all the way, but since I didn't design the fan I can only guess the designers intentions.  I WAS going to print a fan scaled to 102%, but that's when the glitch occurred.  I started the print and left to do something else.  When I came back about 15 minutes later I had a bird's nest on the print bed.  It happens, so I did what I do when the D6 screws up late at night - I shut off the power and went to bed.

When I got up the next day and fired up the printer it was not happy with me, the AMS was making very unhappy noises.  I realized that I SHOULD have aborted the print, then shut off the power and gone to bed.  Ain't 20/20 hindsight just wondermus though?  I realized that the filament had frozen in the extruder and that I needed to get it out of the hot end so the AMS could retract it and be happy again.  But, I needed to do that before the AMS was powered up.  I decided to try unplugging the AMS, heat up the hot end, and see if I could pull the filament back by hand - to see if that would work.  I did, and it did - so I decided to try printing again.  All seemed to go well, until it tried starting to print about 50mm above the print bed.  All I could do was abort the print and hang my head in shame wondering "What the Hell did I do to this poor machine?"  Before I contacted Bambu Labs and confessed my sins, I wanted to run the initial calibration cycle again.  I wanted to see if that would let the printer find its' lost marbles. 

I'm proud to report that it worked and the plastic pooping robot is now about 7 hours into an 8 hour print.  That print will give me the Z axis rail holder, and the bearing block that will slide on those rails.

Don