Latest Update and G36

Hi all, I had issues with the last update. I got to a point I can use the machine but I really want to like the Bi-Linear Bed Leveling. So I set my Z offset, went and set the probe offset, entered it M265 Z-.3 then ran the M500. I check on the Eprom and it has the correct values. So when the Bed leveling routine runs It appears the Center 3 on the Y axis are slightly off. If I print everything looks on the outer edges, however the center appears to print much higher. I was dumbfounded for about 5 hrs but I am wondering if the G36 is my issue? It runs G35 which adjusts for Ambient light. The room is darker and in the center I am just wondering if the probe is triggering sooner? Will try later today but think I can replace the G36 with just a G29?

 

Will definitely give the 1.1.8-dev branch a look. I was however talking about simply in my startup Gcode. Remove the G36 and put in a G29. Also Sorry I need more coffee today. I did mean M206, not M265... Not sure where I pulled that out.

 

Try changing the probe points to four instead of three in Marlin. That seems to work well for the people who are having the problem you are describing. It changes up the probe points and defines the bed a little more.

G36 is doing the extra probe on the bed at the beginning of the print. It's setting the M851 offset based upon the trigger distance of the IR sensor. If you want to see what it's actually doing, set a zoffset with M206 then do a G28 G29 and then do a G1 Z0 (or whatever you feel comfortable going to) you'll notice that the printer will air print. Then run G28, G35, and G29 then go to Z0 you'll see the nozzle actually reach the bed. Robo didn't want to set a static M851 because the correct M851 offset can change with the time of day due to the IR sensor being sensitive to the changing light. G35 just automates the M851 offset collection process to set your nozzle to where it was placed during the zoffset wizard.

If you don't want to use G36, you just have to set an M851 offset before each print.

 

@WheresWaldo I disagree. One really cool problem G36 solves is people changing the color of their bed. You mentioned doing 20 or 30 iterations of the probe accuracy test. Try doing the same test with a blue bed, or a white bed. Instead of running M48, run a G30 (http://marlinfw.org/docs/gcode/G030.html) . This command probes the bed at a given point, then outputs the z position the probe triggered at. The accuracy is the same, however the actual trigger distance is not the same between the beds. So if you change your bed color suddenly, your offset does not remain accurate. It may only be off by a little bit, but it is still enough to ruin your new bed or it prevents the nozzle from connecting with the bed. G36 Measures that bed color change by measuring the trigger distance of the probe, then updates the M851 offset and maintains a great first layer.

TL;DR There is nothing wrong with the IR sensors accuracy, but there is a discrepancy with the trigger distance based off of available light and the color of the bed.

 

People change from the black buildtak bed, to painters tape, to offbrand buildtak, to anything an everything. By "New Bed" I did not mean an entirely new bed, just a new surface. It is definitely not an extreme example.

 

You guys are lucky. Mine crashes the bed into the head. Now I have lots of little ding marks on about 4 of the 9 probe points


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I was getting those "Probe Failures" and dings, too. I've discovered that if I whisk off the sensors with a soft paintbrush before every print, I don't get the crashes. I'm guessing something's getting on the sensors from static cling...

I'd like feedback from someone else who tries this brush sensor cleaning idea to report back on success/failure. It sure seems to be necessary and working for me.

 

I have been using compressed air between every print and still had the same problem. I truly believe mine has to do with something related to light intensity and the surface of the Buildtak



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I've only had the printer a couple weeks and have only run 15 print jobs, all PLA. I was having a lot of Probe Failure crashes until I started brushing off the sensors and that seems to have fixed it. I'll need to keep this up a while to be sure. Perhaps my sensors are weak or mis-aimed and therefore more sensitive than normal. Perhaps I should request a new sensor assembly. I'm waiting a bit to be sure this is the problem. I'm near Las Vegas and humidifying the house to around 45% so static doesn't seem to be a real problem, although there's a tendency for black plastic surfaces around here to show a light white frost of some kind of micro-dust. Especially if I dust using a Swiffer cloth (uses static charge) instead of a damp generic cloth.
If you think it's a lighting variation problem, how about starting the prints in a darkened room, at least while the bed probing sequence is running? That would be a good test for a while.

 

I wonder if there is some UV component to the white LEDs I have in my case (kilrah’s mod)? I know that white LEDs are really not white. They are broad spectrum. I think mine are cool white, which are really blue/UV diodes with yellow phosphor...

Maybe there is some component of the LEDs causing issues? Maybe...


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I thought the sensor was IR not UV??