Auto_Bed_Leveling with positive Z_PROBE_OFFSET_FROM_EXTRUDER

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Originally Posted by Roxy

I do not think this is very difficult to do. There would be a couple of approaches. Probably the simplest and most straight forward method would be to modify the run_z_probe() function to return values that were compensated. These values would bubble up to the G29 code that is collecting them and the Bed_Level_Correction_Matrix that is needed for the rest of the moves would have this factor built into it.

It would not be difficult to make it selectable on either of two basis. It could be made so it was optional for a machine and gets built into the firmware with a #define in the configuration.h file. It would also be very straight forward to add a parameter to the G29 command to build the Bed_Level_Correction_Matrix with this factored in.

Assuming the firmware existed, the process of setting up a printer to use this would not be hard. It would involve taking a measurement on one side and comparing it to when you manually adjusted the nozzle to just barely touch the bed. And then repeating it on the other side of the bed.



Hey! I have an idea... Would it make sense to get one machine all the way working before you ramp production? :)

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I have shared the Marlin that we are working on with a few guys that also have a very similar machine on the SmartRap forum.
They are testing it too. Their machines are also the same configuration of the hardware.
One of the guys is having a few issues, but I think the problem could be that he has an open z probe caused by the Bowden weight holding the probing mechanism to one side. I had that happen to me once and recognized the same problems that he is having.

http://forums.reprap.org/read.php?34...614#msg-356614

Hi All, Nice to see you working on this. I just got a printrbot metal simple. It's using an induction sensor for autoleveling. It's never extended or retracted as i just sits about 1 mm above the nozzle all the time. The sensor detects the metal bed about 2-3 mm above it and acts as the sole z-endstop. It was really simple to measure the offset and enter it into the firmware using M212. I'm really impressed with this little printer. I've since purchased another probe to install it on my bigger printer. I'll let you know how it goes when I get it installed.

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Originally Posted by KDog

Hi All, Nice to see you working on this. I just got a printrbot metal simple. It's using an induction sensor for autoleveling. It's never extended or retracted as i just sits about 1 mm above the nozzle all the time. The sensor detects the metal bed about 2-3 mm above it and acts as the sole z-endstop. It was really simple to measure the offset and enter it into the firmware using M212. I'm really impressed with this little printer. I've since purchased another probe to install it on my bigger printer. I'll let you know how it goes when I get it installed.

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Great stuff, can you tell me more about the probe you are using, I would like to try it out too.

Here is the sensor: http://www.amazon.com/Cylindrical-In...J12A3-4-Z%2FBY

And here is a link where Brook Drumm explains how to set the offset: http://www.youtube.com/watch?v=lgVmN...hl2F_bmR01sjaA

Autoleveling is fun stuff.

Thanks for that, very interesting.

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Originally Posted by KDog

Hi All, Nice to see you working on this. I just got a printrbot metal simple. It's using an induction sensor for autoleveling. It's never extended or retracted as i just sits about 1 mm above the nozzle all the time. The sensor detects the metal bed about 2-3 mm above it and acts as the sole z-endstop. It was really simple to measure the offset and enter it into the firmware using M212. I'm really impressed with this little printer. I've since purchased another probe to install it on my bigger printer. I'll let you know how it goes when I get it installed.

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It would be interesting to see how repeatable it is. Can you be talked into loading the M48 code and running the test?

Please check out: http://3dprintboard.com/showthread.p...atability-code

I could be talked into it but my nozzle clogged last night so am out of business until then. Brook stated somewhere that repeatability was 0.1 - 0.2mm and this sounds right from what I've seen on the prints I've made so far.

BTW, Brook is a really nice guy and very accessible. I'm sure he would be very interested in your repeatability measurements and may even contribute to the cause. If you don't know the Printrbot story take a look. He did a 25K kickstarter a few years ago that turned into over 800K. He has done nothing but design newer and better printers since then and still sticks to the open source philosophy. It looks like he is selling over 50 of the printrbot metal simples a day now.

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Originally Posted by KDog

I could be talked into it but my nozzle clogged last night so am out of business until then. Brook stated somewhere that repeatability was 0.1 - 0.2mm and this sounds right from what I've seen on the prints I've made so far.

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Your printer doesn't have to be able to print to install and/or run the M48 test. .2mm sounds too high to get reliable prints. If you are getting good results, my guess is you have better repeatability than that.

lol...maybe it said 0.01 to 0.02...doh!