Taz 6 Leveling Issues

Greetings hopefully this is the appropriate place to post this, I have a Taz 6 that I cannot seem to dial in properly. Problem is the first layer is "smooshed" from one side of the bed to the other and first layer appearance is important to me. I have tried the following

• Confirmed that frame is square
• Confirmed Y axis frame is secure
• Swapped Beds
• Move the leveling pads to different posistions
• Clean Nozze
• Polish leveling pads with 2000 grit sand paper
• Level z axis - using several methods such as measuring from top X rail to frame, measuring from bottom x rail to leveling pad, using a calibration cube as a feeler gauge and measuring between the nozzle and print surface
• Sanding the bed

Im sure there is something else Im forgetting. This is the second machine, Lulzbot swapped my first one for the same issue. Any suggestions? Im not sure if Im expecting to much out of the machine or if something is wrong with it. I was considering swapping to one of the other Z probe methods that are listed on the wiki and also modifying the bed mounts in a way that they could be adjusted to manually set the beds level position.

What you may be seeing is the limits of the precision of the Z probe. Maybe that's as good as it gets. It doesn't look so bad, but I guess it depends on what you do with the first layer of your prints. If that first layer becomes the top or front of the print, maybe this is unacceptable. OTOH, the bottom layer is never going to look like the other layers (and the top is always going to look different from the sides and bottom), so maybe you're expecting too much.

I had problems leveling a bed on a Taz 3 at the makerspace. It didn't have autoleveling, the bed didn't heat evenly, and it was very difficult to get prints to stick to it. Someone broke the glass bed so I took the opportunity to straighten it out. I replaced the bed with MIC6 aluminum, modified the mount for 3 leveling screws, and put a piece of PEI on the bed plate. Now it's easy to level, stays level, heats evenly, and prints stick (the way it should have been from the beginning...).

There's a write-up on the conversion here.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Lulzbot have their own support forums [forum.lulzbot.com]

You should be able to get specific help there, vs the generic help from here

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Dust
Lulzbot have their own support forums [forum.lulzbot.com]

You should be able to get specific help there, vs the generic help from here

I know thanks, just wanted to get a different perspective. Everyone over there has resolved these issues with the usual loose pad wires, polish pads, dirty nozzle.

I'm not sure sanding the bed and leveling pads would have done anything but hurt. Sanding the bed would create high and low spots, and the 'leveling pads' are precision machined washers from what I've read, so I doubt you could improve them by going at them with sandpaper by hand.

To me, the bottom layer doesn't look like a constant level change across the bed, like you would get with a tilted bed. It looks to me more like a localized minimum. This could be from a slightly bowed bed or from uneven sanding. Things tend to bend and warp a bit when heated, so this isn't too surprising to me.

I personally think that looks fine, if you're fussed just over extrude or squash the first layer and take 30 seconds to clean up the bottom edge when it's done.

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Trakyan
I'm not sure sanding the bed and leveling pads would have done anything but hurt. Sanding the bed would create high and low spots, and the 'leveling pads' are precision machined washers from what I've read, so I doubt you could improve them by going at them with sandpaper by hand.

To me, the bottom layer doesn't look like a constant level change across the bed, like you would get with a tilted bed. It looks to me more like a localized minimum. This could be from a slightly bowed bed or from uneven sanding. Things tend to bend and warp a bit when heated, so this isn't too surprising to me.

I personally think that looks fine, if you're fussed just over extrude or squash the first layer and take 30 seconds to clean up the bottom edge when it's done.

Thanks, what do you mean by clean up the bottom edge?

Also worth noting my sanding is all very conservative and the bed was done wet
The bed was sanded after the pei started to bubble Ive read this is ok to do a couple of times before replacing the actual bed. At one point during the leveling sequence the nozzle would press the corners down thus reporting false z heights and "polishing" them corrected this. If first layer is important to me should I consider swapping to a glass or alum bed? Or just another leveling system?

I've seen other reporting tearing the PEI on a Prusa machine, and now your mention of bubbling under the PEI. Both seem odd to me - I use 30 mil (0.7 mm) thick PEI on my printer and it never bubbles or tears. I put a piece of 60 mil PEI on a printer at the makerspace and it's been on the machine for 2 years and abused daily by many people and no one has managed to damage it. I suggest you use thicker PEI if it will work with the autoleveling system. A piece of 300x300 mm x 30 mil PEI is $21 on amazon these days- the price has gone up from $17 in the last year.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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the_digital_dentist
I've seen other reporting tearing the PEI on a Prusa machine, and now your mention of bubbling under the PEI. Both seem odd to me - I use 30 mil (0.7 mm) thick PEI on my printer and it never bubbles or tears. I put a piece of 60 mil PEI on a printer at the makerspace and it's been on the machine for 2 years and abused daily by many people and no one has managed to damage it. I suggest you use thicker PEI if it will work with the autoleveling system. A piece of 300x300 mm x 30 mil PEI is $21 on amazon these days- the price has gone up from $17 in the last year.

Yes, it does happen with PETG. It sticks like hell and therefore when removing the part you can get bubbles even tear chunks of the Buildtack. Some advise to smear the bed with the glue used for PLA on glass to prevent it.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

When you overextrude or squash the first layer, you end up with a slightly wider bottom edge where it bulges out, basically a burr. By clean up the bottom edge I mean give it a quick pass with a knife, deburring tool or sandpaper. Your bed leveling issues sound like they would have been caused by filament on the nozzle preventing electrical contact, I don't see how the washers would have caused problems solved by polishing.

Overall, I don't think the issues you're having are to do with the bed leveling system so much as they are with the bed flatness, and I don't think they'll get much better. The lulzbot (from what I'm aware) uses a sheet of glass under the PEI and glass is usually quite flat. You could if you really wanted to place another sheet of glass over top to get flatter surface than what your PEI seems to offer, or use something like tooling plate which has been milled flat. The upside of the tooling plate is that you can use it for the probing as well and either get more probe points and mesh bed level to compensate for any bowing or warping of the surface, and you wont have to deal with the offset from the washers. A contact based sensor that uses the nozzle is the best you can get, and that's basically what the lulzbot has just with a precision machined washer so they can use PEI instead of a metal build surface.

Another question is are you doing your bed leveling with the bed at your printing temperature or cold? Try probing when it's at printing temperature if you aren't doing that already. Lastly, is the high/low spot on the bed consistent? I.e. if you print the same part in the same place a couple of times, does the same artifact show up in the same place or no? If the answer is no, the issue could be with your extruder not the bed level.

How about getting rid of this lame unreliable Lulzbot Z homing system and go for a good one ? OK for the Z nozzle contacting the bed, but using a displacement sensor. To rely on the nozzle making an electric contact with some washers on the bed is unreliable ! I looked at it in the past and discarded it.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Most people find it reliable, and if you ask me it is working. What about it makes it unreliable in your opinion and could you explain what you mean by a displacement sensor?