Build plate height differences

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airscapes
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Joined: Wed Jan 31, 2018 11:36 pm

Build plate height differences

Post by airscapes » Sat Jul 14, 2018 7:05 pm

So I just spent the morning with some nice long feeler gauges trying to make sure my M2 bed is level. The bed is as level as I can get it, however the center of the plate is about .08mm higher than the corners. If I loosen the hold downs that number is slightly less, but the the glass slides around and screws up my larger prints with shifted layers. Some folks have suggested that the gantry may be bowed and it well may be, however the center of the clearance at the ends of the bed in the center of the gantry are close to that of the corners so not sure the gantry is the complete story.
Which do you think is a better compromise, center .08mm too close to bed and most of bed correct, or center .04mm too close and most of bed .04 too far away. Or am I over thinking this way too much?



Test was to print 5 single walled squares that a 2mm tall and measure them..

Final test was done with this gcode, .factory file can't be attached and I don't seem to have winzip on this pc. This gcode was for eSun PETG at 245C 1.72 diameter and a .35 nozzle if anyone would like to print it.
Level check 5 26x26x.4x2.gcode
(90.17 KiB) Downloaded 19 times

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ednisley
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Re: Build plate height differences

Post by ednisley » Sat Jul 14, 2018 9:45 pm

airscapes wrote:
Sat Jul 14, 2018 7:05 pm
center .04mm too close and most of bed .04 too far away
Absolutely: split the difference!

If you're printing 0.20 mm layers, then the first-layer variation is a survivable 0.16 to 0.24 mm.

However, if you're trying for 0.10 mm layers, then the variation is 0.06 to 0.14 mm and you may have trouble.

After the first layer goes down and soaks up the height error, the remainder should be dead on whatever you set. So, for example, you should set a 0.20 mm (for example) first-layer height, even if you're doing crazy 50 micron layers for the rest.

IMO, painstaking measurement and adjustment like this separates routine "just works" printer operation from trial-and-error fumbling ... [grin]

airscapes
Posts: 261
Joined: Wed Jan 31, 2018 11:36 pm

Re: Build plate height differences

Post by airscapes » Sat Jul 14, 2018 11:08 pm

Yes, I agree and thank you as you were very instrumental in my training and still are!
Now I know exactly what the difference is, I can alter the starting height to be correct for printing miniatures in the center of the plate, then do an M206 Z10.xx (adding .04) if printing something larger of even .08 and let the center get squished as it will not show..
Can you use the M206 on all printers or is it specific the way the M2 is laid out?

I read other forums with people talking about prints not sticking to the bed.. and I have to wonder.. is your starting height correct? I was at the RepRap festival a couple of weeks ago talking to a guy who was saying how he has trouble with this or that sticking (nothing exotic) and I asked if his starting height was correct.. he says "yes my machine sets that automatically".. but did you check it.. the answer was no I don't have too.. :) Ah Ok, good talking to you, have a nice afternoon!.. :lol:


Thanks Ed!!

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ednisley
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Re: Build plate height differences

Post by ednisley » Sun Jul 15, 2018 12:13 am

airscapes wrote:
Sat Jul 14, 2018 11:08 pm
use the M206 on all printers
Haven't a clue.

I measured the height of a cube a long time ago, tweaked the initial Z offset with M206 to make the answer come out right, and it's been working fine ever since. The platform in my M2 is fixed in place and Nothing Changes from print to print, so maybe I'm an outlier.

Vandal968
Posts: 212
Joined: Mon Jul 13, 2015 4:30 am

Re: Build plate height differences

Post by Vandal968 » Wed Jul 25, 2018 7:08 pm

Switching to a mic6 build plate is one of the best mods that I've done. Not only is the bed perfectly flat all across the surface, but the superior heat-conduction of aluminum means that my prints stick nearly as well in the corners as they do in the center (unlike glass). I've even got some thermal images that prove it.

cheers,
c

Gwhite
Posts: 212
Joined: Tue Jul 11, 2017 3:38 pm

Re: Build plate height differences

Post by Gwhite » Wed Jul 25, 2018 9:44 pm

Is anyone making MIC6 plates available for the M2 these days? I know there have been a couple limited runs in the past. I know I can buy some & cut it down myself, but I already have a backlog of other projects.

Also, how thick is your plate?

Vandal968
Posts: 212
Joined: Mon Jul 13, 2015 4:30 am

Re: Build plate height differences

Post by Vandal968 » Sat Jul 28, 2018 10:18 pm

Mine is 1/4" thick, which I believe is what everyone else is using. I think they were being sold for ~$100 pre-made. I bought a pair of mic6 plates on eBay for something like $25 delivered and then shaved down 2 edges on my mill for a perfect fit (and I've got a spare). Not everyone's got a mill, so the premade ones with the PEI are not a bad deal if you can't DIY. Likewise PEI is available inexpensively on Amazon.

cheers,
c

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