Auto bed probing and compensation with G29 Development

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1013
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Re: Auto bed probing and compensation with G29 Development

Post by 1013 » Wed Aug 14, 2013 7:56 pm

thanks for the info.... but you might be able to simply adjust the tightness by upping the flowrate to 110% or more during the print. 0.1mm is very little difference. Changes in room temperature, may affect the part more.

Only one nut (the top one) really needs to be tight. The bottom one can be looser in the hex...it just needs to be able to take the spring force and take-up the backlash, so if it is tighter than the spring force can overcome, that would not be good.

Maybe I could just add some small bumps near the top nut area, so it can be pressed in place.


You can also use slightly smaller pins in the alignment holes if you want the nuts closer together....but remember, the nut in the window should be the only thing touching the spring. You do not want that nut up too high, and then the spring is pushing on the plastic. The top of the spring should only push on the nut.

1013
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Re: Auto bed probing and compensation with G29 Development

Post by 1013 » Wed Aug 14, 2013 8:00 pm

BTW,

This may not be clear, but the 1/8" pins in the 4 holes are ONLY used during assembly. Once the threaded rod is in place, and holding the nuts, you should remove the 1/8" pins so that the threaded rod and nuts take up the spring force.

aadamson
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Re: Auto bed probing and compensation with G29 Development

Post by aadamson » Wed Aug 14, 2013 8:32 pm

1013 wrote:thanks for the info.... but you might be able to simply adjust the tightness by upping the flowrate to 110% or more during the print. 0.1mm is very little difference. Changes in room temperature, may affect the part more.

Only one nut (the top one) really needs to be tight. The bottom one can be looser in the hex...it just needs to be able to take the spring force and take-up the backlash, so if it is tighter than the spring force can overcome, that would not be good.

Maybe I could just add some small bumps near the top nut area, so it can be pressed in place.


You can also use slightly smaller pins in the alignment holes if you want the nuts closer together....but remember, the nut in the window should be the only thing touching the spring. You do not want that nut up too high, and then the spring is pushing on the plastic. The top of the spring should only push on the nut.
good feedback and I'll give that a try... the most enclosed nut I can get completely movement free and snug and with just a slightly smaller alignment rod on the other nut I think I can make do.... Yes I knew about those pins for assembly only.

Thanks!
Alan

reef1944
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Joined: Tue Aug 20, 2013 5:17 am

Re: Auto bed probing and compensation with G29 Development

Post by reef1944 » Tue Aug 20, 2013 6:07 am

What about putting a sheet of aluminum foil on the bed, putting a small voltage on the nozzle, and checking for electrical continuity between the nozzle and the bed? That would alleviate any uncertainty in the switch position and would not require additional parts. My only concern would be that the aluminum be dead flat. Maybe a sheet of known thickness the size of the glass bed would do it. It would be even better to have an aluminum sheet the thickness of the first layer. Those values could be used for correction and one could do a multipoint sweep quickly.

1013
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Re: Auto bed probing and compensation with G29 Development

Post by 1013 » Tue Aug 20, 2013 10:24 am

reef1944 wrote:What about putting a sheet of aluminum foil on the bed, putting a small voltage on the nozzle, and checking for electrical continuity between the nozzle and the bed? That would alleviate any uncertainty in the switch position and would not require additional parts. My only concern would be that the aluminum be dead flat. Maybe a sheet of known thickness the size of the glass bed would do it. It would be even better to have an aluminum sheet the thickness of the first layer. Those values could be used for correction and one could do a multipoint sweep quickly.
If any plastic ooze or residue is on the nozzle, the contact will not be made and the machine will continue down, and likely break the glass. Plus it is not automatic, since you have to manually remove the aluminum.

Micro-switches are very reliable and cheap.

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gannon
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Re: Auto bed probing and compensation with G29 Development

Post by gannon » Sat Aug 24, 2013 11:40 pm

Just got my printer up and running, gotta try this auto leveling out :D
Image

jebba
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Re: Auto bed probing and compensation with G29 Development

Post by jebba » Sun Aug 25, 2013 2:34 pm

@gannon, wow that's a nice looking system there, congrats. :)

-Jeff

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gannon
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Re: Auto bed probing and compensation with G29 Development

Post by gannon » Sun Aug 25, 2013 4:09 pm

Had to reprint the bearing holder on one of my other printers due to the lash still in my TAZ (guess it does need a bit of work still :P)
After mounting the bearing holder I noticed that it is near impossible to access the belt screws with it installed. Two zip ties fixed that and gave me an easier way to tension the X belt.
Image
Thinking I will need a longer push rod also, but that shouldn't be too hard.

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gannon
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Re: Auto bed probing and compensation with G29 Development

Post by gannon » Mon Aug 26, 2013 8:58 am

@1013, I tried this out last night with stock X ends / etc and the Z correction was extremely exaggerated. Thinking I might need stiffer parts or that I messed up the code somewhere.
BTW, I merged the auto leveling code into the latest marlin release for my tests. The one thing that I want to add is a way to have a separate Z endstop and probe. I'm thinking I can plug the probe into the Z max endstop port and code it to work from there. The other method is more a hardware fix and would be to just wire the switches in parallel. Once I get it working I can release the code for those that would like.

1013
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Re: Auto bed probing and compensation with G29 Development

Post by 1013 » Mon Aug 26, 2013 10:18 am

I wired the switches in parallel, that way the "stock" switch is a lest resort....in case the other switch gets knocked off, or stuck or something. That way it will never crush the glass.

It did take a while to get the Z offset just right, and it may be very different on your machine. (especially with those solid bushings). Not sure what the latest release of marlin does differently....but what files from the bed-level firmware did you use? I am still not sure where all of the actual bed leveling code is in that mess of files.

I suggest you add the M206 to your start G-code....that way you can easily fine tune the Z offset without having to re-flash the firmware each time

Code: Select all

M206 X0.0 Y0.0 Z0.0; offset home position for fine tuning 
BTW, I just ground down the end of the allen wrench, so I could get to those screws....but a zip tie is not a bad idea.

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