Sota heat bed problem

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Re: Sota heat bed problem

Postby fulg » Mon Apr 18, 2016 2:34 pm

Looking at your image, your home Z is definitely too high. After leveling you still have to correct for the thickness of the paper, otherwise your home position is not zero. You should lower the printing height slightly by lowering the Z endstop using the adjustment screw. You can also fix this in your start G-code by adding an offset to your prints (putting G92 Z0.2 after G28 homing will move the head 0.2mm closer to the bed while printing). Auto-leveling makes this easier because the offset is always the same regardless of the state of the bed or X gantry leveling, and only changes if you touch the hotend or autolevel sensor.

Cheers,
Ben.
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Re: Sota heat bed problem

Postby geoffs » Mon Apr 18, 2016 10:19 pm

You've talked me into installing auto levelling! What's the best source for info on this?

I'm going to do an accurate measurement of the height of the horizontal Makerslide to make sure that it's level. then I can use it as a reference to measure the level of the bed/glass surface. I did have this properly adjusted but I printed some of the z-axis anti wobble thingies and I may have upset things installing them.
My new roll of PLA should arrive today so the possibility of the old stock I have affecting print quality can be discounted.

I'll get there.

Regards
Geoff
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Re: Sota heat bed problem

Postby fulg » Mon Apr 18, 2016 10:54 pm

Auto-leveling is not hard (though it is annoying to set up), but the exact procedure varies a lot based on your print surface(s) and what kind of fiddling you are willing to tolerate. There is a lot of misinformation out there, especially on the typical industrial proximity sensors... One thing is for sure however, it will completely change the way you use your printer, and it is definitely worth putting effort into getting it working.

Tom's video (http://www.youtube.com/watch?v=EcGFLwj0pnA) is the best source of information out there, but even he does not tell the whole story. The method he suggests to connect the sensor did not work for me, most likely because I am not using a Ramps board. Someone else started a thread on auto-leveling and I replied back when I did not have it working, I will go back and update it for the benefit of others (and you as well!).

I currently use a 18mm capacitive proximity sensor, and my bed is made of a 3mm aluminium block with a 3mm sheet of borosilicate glass on top. Capacitive sensors are supposedly unreliable since they are affected by air humidity and other factors, but in practice it makes no difference for me. I could just be lucky... Inductive sensors are better, but only detect metal surfaces. I have a servo-based solution ready to install (a microswitch at the end of a probe that extends when leveling and retracts once completed), this would make the leveling consistent and work with all printing surfaces with zero adjustment. I'm still debating whether or not I change printing surfaces often enough to warrant the effort.

Cheers,
Ben.
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Re: Sota heat bed problem

Postby geoffs » Wed Apr 20, 2016 12:16 pm

Decided to make sure everything was level and square before trying to lvel the bed.
Before I knew it, it was all in pieces!
Going back together nice and square.

apart.jpg
Hope I haven't lost any bits...


Geoff
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Re: Sota heat bed problem

Postby fulg » Wed Apr 20, 2016 12:53 pm

Since you have everything in pieces, check that the bearings in your v-wheels cannot slide along the rotation axis. In my kit I could move the bearings side to side by holding the wheel with my fingers and pressing the bearing with my thumbs, it did not take much force until they would snap and slide across the inside the wheel. It wasn't much, maybe a millimeter of movement, but it caused me great pains trying to level the bed. Everytime I touched the bed for any reason (even removing a print!) I would have to redo the leveling procedure completely in order to be able to print again. I wasted several weeks of manual leveling before I found this... All of my wheels were broken this way, but its only critical for the Y axis, so these are the only ones I replaced from another source.

See this thread for more info:
https://discuss.inventables.com/t/shoul ... ring/11237

Cheers,
Ben.
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Re: Sota heat bed problem

Postby geoffs » Wed Apr 20, 2016 2:20 pm

Good timing, it's still apart. :(

I can't seem to adjust the X-axis makerslide so that it's parallel with the lower extrusion AND have all 3 wheels in contact on the two Z axis carriages. I can get one or the other, not both. Having to remove the X axis completely to get at the adjusting screws on the back of the Z axis carriages doesn't help.

GEoff
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Re: Sota heat bed problem

Postby fulg » Thu Apr 21, 2016 10:56 am

I am not sure I understand why you need to remove the X axis to adjust the Z v-wheels? Since the eccentric spacer is on the outside wheels (along the Z axis), you should be able to access it easily with a wrench from the side. The screws on the v-wheels don't need to be tightened super hard, otherwise you can compress the nylon spacer and cause binding and misalignment. Some people here have swapped out the nylon spacers for metal ones, probably for this reason...

Don't give up just yet :)

Cheers,
Ben.
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Re: Sota heat bed problem

Postby geoffs » Thu Apr 21, 2016 11:39 am

I'm sure my description of this was a bit confusing.

It's one of the fixed wheels that doesn't make contact with the makeslide and the only way to correct that is to twist the Z axis plate a bit. This is turn causes the X axis makerslide to tilt one way or the other putting one end higher than the other.

Perhaps the approach I should take is to get the wheels on each carriage adjusted correctly and then try to level the makerslide between the two carriages. I've tried just tightening the one accessible screw in each Z axis carriage but I seem to knock things out of alignment when I lift the entire Z axis assembly off to tighten the remaining screws.

Geoff
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Re: Sota heat bed problem

Postby fulg » Thu Apr 21, 2016 11:57 am

Ah, that makes more sense. If the inside wheels can't make simultaneous contact to the Z beams, then either the Z beams are not parallel, or the metal plates on the X axis are crooked. Fixing the X axis is easy (just check it with a flat surface!), but getting the Z beams straight is harder. It will pay off later to get this right, so it is worth taking the time now to fix it.

Cheers,
Ben.
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Re: Sota heat bed problem

Postby geoffs » Thu Apr 21, 2016 12:19 pm

Z axis posts are parallel and perpendicular to the bottom extrusion, checked with a couple of 123 blocks.
It's getting the plates/makerslide level and with the correct spacing for the Z posts that's frustrating me.

Perhaps it's time to read the wiki again to see how I SHOULD he assembling it ...

It doesn't help having spent more than a few hours today getting my X-Carve aligned then having the CNC controller fail. It would be nice to have a win! :D
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