Changing Machine Y-axis home 0

I did a searching in the manual and didn’t find an answer to my question, sorry if it’s in there.

I’m looking to move the y-axis home forward 3-4 mm or so. As of now, the nozzle dropping on the back part of the coin when aligning, worse it’s dropping on the edge of the housing of the cleaning strip flexing the table significantly before moving forward and landing on the pad. The machine is brand new and it’s been doing this since the first go.

The easiest way to adjust this is to literally loosen the 4 bolts that hold the lower Y bed extrusion rails to the frame mounts, and then slide them forward or back. Use a Square while you do so to maintain 90 degrees, and make sure you get them locked down again when you are done, but that is the easiest, most effective and recommended method of changing that point.

Easy enough. Thanks!

I’ve had the exact same problem with a brand new TAZ 6 I bought last month (December 2016). It seems to have always been off by a few millimeters, which wasn’t a big deal, but it was obviously misaligned, since you could see:

    • The Z-axis homing comes down on the switch noticeably off-center.
  • About 5 mm of the cleaning pad never gets touched.
  • When auto-bed leveling, it hits the front and back washers in noticeably different spots.

This hasn’t really impacted printing or bed leveling, so I mostly have ignored it so far.

However, it actually has gotten gradually worse over the course of moderate daily use for about a month. It has now moved a least a millimeter or two and has just started to nick the cleaning strip housing with the nozzle when cleaning in the last week or so. It makes me wonder if something wasn’t QUITE torqued down enough and it has been slowly moving due to print vibration, etc.

Anyway, I was originally hoping there was a firmware calibration setting for this (Y-home offset or something), but it sounds like I should go ahead and do the adjustment with the physical hardware as described in this thread.

Questions:

  1. Is there an official procedure for this adjustment? I read the OHAI page on Y-axis assembly, but it didn’t seem to say how it gets calibrated in the first place. Baring other info, I’ll do something ad-hoc (but hopefully decent!) with a square & digital calipers. =)

  2. Is there a torque spec for re-tightening the bolts? The OHAI page has torque specs for other bolts (the ones holding the Y rods), but for these bolts just says to “snug these down”. I’ve got torque wrenches, so I can easily torque to spec if there is a spec!

Try here around Step 6:

https://ohai.lulzbot.com/project/Final-mechanical-assembly/taz-6/

Maybe this is what you might be looking for.

Yes, this looks like what I was missing!

I was only looking in the Y assembly section, not the final assembly of the whole thing.

Thank you.

Just to follow up for posterity, here is what I did, and the results:

    1. Z-homed the machine.
  1. Lifted the Z-axis a few millimeters (enough for step 3).
  2. Measured with the thin plunge end of digital calipers the distance from the center of the Z-homing button to where the nozzle actually hit. (I measured a little less than 4 mm).
  3. Turned off the machine.
  4. Slowly moved the bed forward to expose the bolts holding the Y-axis.
  5. Ensured the thumbscrews were tight.
  6. Measured the distance from between the back of the Y-axis to the bolt carrier (I measured about 109.81 mm on one side, 109.85 mm on the other – your measurements might be different depending on where you measure to and from).
  7. Loosened the bolts – one set of bolts was noticeably easier to undo – maybe that is the smoking gun.
  8. Slowly moved the bed back to expose the other set of bolts and loosened them as well.
  9. Slowly moved the bed to the front again.
  10. Carefully pushed the Y-axis aluminum chassis rods forward together.
  11. Measured one side and repeated step 11 until it was where I wanted it (in this case 113.5 mm).
  12. Screwed the bolts on that side in hand tight.
  13. Measured the other side and adjusted very slightly as necessary to match the other side.
  14. Screwed the bolts on that side in hand tight.
  15. Re-measured both sides (I ended up with 113.52 mm and 113.51 mm).
  16. Torqued the bolts down to 10 inch-pounds per the spec on the OHAI page.
  17. Slowly moved the bed to the back one last time.
  18. Tightened & torqued these bolts the same way, ensuring that the measurement on each side stayed the same (since it was only to ensure squareness the number just had to match – I didn’t write down the number).
  19. Turned it all back on.
  20. Ran a Z-homing.

Result: SUCCESS!

    • The Z-axis homing comes down as perfectly centered in the Y-axis as I can detect visually.
  • The cleaning pad now gets touched everywhere except a reasonable ~2 mm on each end.
  • When auto-bed leveling, it hits the front and back washers in what looks like exactly the same spots.
  • It doesn’t nick the wiper holder at all any more.

Aha! Same here! I love it when I find the solution to a problem I was not even looking for yet!

FWIW: this weekend I ran through the steps outlined above and re-centered on the button and stopped it from nicking the edge of the cleaning pad holder.

When I went to loosen the screws about 1/3 of them were loose.

After adjusting and re-torqueing all the screws and on my subsequent runs I really noticed for the first time how hard the bed the hits the cut off switch every time you initialize. I mean it moves forward at a pretty good clip then BANG against the stops every time. with 20/20 hindsight It is easy to see how that could loosen up and slip over time.