Big thanks to Prusa Research  

Re: Big thanks to Prusa Research

Martin,
When this happens "I could blow the filament away from the sheet with ease. It took -1.950 mm to get the correct first layer" you need to move your PINDA probe.
I'm new myself starting in Feb, but I think you have to move it down. Using their recommended "one ziptie width" you lower the the tip of the nozzle to the heatbed surface and adjust the probe.
I think this is why you're almost at -2mm.

Experts, please verify that the probe needs to come down and not up.

Re: Big thanks to Prusa Research

Experts, please verify that the probe needs to come down and not up.

Not an "expert", but I think you will find that the probe is too low and needs to be raised 😉

The nozzle is too high when the probe triggers, hence the large negative "Live Z" adjustment. Raising the probe will lower the nozzle, so "Live Z" will require a less negative value.

It was possibly the probe knocking things off the build plate.

Peter

Re: Big thanks to Prusa Research

I have a similar issue. I've been asking about it here repeatedly since I built the kit to no avail. I spent the better part of 2 days fiddling with that blanking PINDA; up, down, up, down, up, down...(ad nauseam) in anywhere from 0.50mm down to 0.20mm increments, and I cannot get a decent first layer unless the z adjustment is at -1.250 or lower. It seems to print fine there.

Despite my asking repeatedly, no one can/will give me an answer to what's so magical about "between -0.500mm and -1.000mm, or if there's any risk to the equipment operating at -1.250.
Do I have a wonky PINDA? WHAT? Is it possible some of them have different sensitivity?

Re: Big thanks to Prusa Research

PJR, thanks for the correction. I've got it written down at home and will need it tonight when I calibrate my second MK3.
I've got everything completed up to hooking up the wiring.

Rufus, I had the same problem when I first received my MK3 and again when I had to replace the hotend. I'm going to face it two more times when I finish building my second MK3 tonight and when I upgrade the first one with the new R3 extruder parts.
My first successful calibration had the setting at -0.920mm after alot of work. When I replaced the hotend I chased it up and down again, but gave up. It's currently -0.460mm

I never got an answer either about the recommended distance, but my guess is going to be ACCURACY. I think the probe is more accurate and responds better if the distance is between -0.500mm to -1.00mm.
Depending on the thickness of the wire-tie and how much you press down on the print bed when you press down with the nozzle or PINDA probe on the wire-tie you could be affecting distance.
I'm thinking this is why we end up "Chasing the Rabbit"!

Re: Big thanks to Prusa Research

I never got an answer either about the recommended distance, but my guess is going to be ACCURACY. I think the probe is more accurate and responds better if the distance is between -0.500mm to -1.00mm.
Depending on the thickness of the wire-tie and how much you press down on the print bed when you press down with the nozzle or PINDA probe on the wire-tie you could be affecting distance.
I'm thinking this is why we end up "Chasing the Rabbit"!

Except that I wasn't pressing down. I did for the very first measurement, realized what was happening, and backed off--using various other reference points (bench top, carriage rods, frame, extrusions, etc.) so as not to repeat the error. It was serendipitous that I purchased a digital caliper accurate to ±0.02mm just before the build; it came in handy. All my measurements were within ±0.05mm of each other.

Something's wonky though; I just printed 2 sequential copies (all settings/variables equal) of the same large flat object in the exact same position/orientation on the build plate. One had a small area of "washboard effect" on the bottom--the other didn't. 😕

Re: Big thanks to Prusa Research

@Rufus

Did you let the printer cool down completely between prints? Most failed repeat prints happen because PINDA is too warm from the previous print to get accurate readings.

That said you are on MK3 and have the ability to heat tune your PINDA, have you done this?

Re: Big thanks to Prusa Research

@Rufus

Did you let the printer cool down completely between prints? Most failed repeat prints happen because PINDA is too warm from the previous print to get accurate readings.

Actually, the problem was with the first print; the second didn't have the washboarded area; it was homogenous. I've seen the effect on prints before, and thought I was on to a low spot on the build plate. (This is the largest area print I've done so far.) I was surprised when the second print came out without the effect. Now (as I'm typing this) I'm wondering 💡 about a possible "cool" spot on the heater/build plate that warmed up by the second print. ❓

That said you are on MK3 and have the ability to heat tune your PINDA, have you done this?

I tried to; not sure I did it correctly. If you can describe it or point me someplace, I'll try it again.

This has not been a HUGE issue--more of an annoyance. The affected first layers have always been covered up by the subsequent base layers, leaving only a rough spot on the print bottoms--it doesn't seem to affect print integrity (for what I'm doing)

Re: Big thanks to Prusa Research

Pretty sure the PINDA probe's height relative to the nozzle has no effect on accuracy. It's going to trigger at the same (probe) height from the bed no matter what (unless the nozzle hits the bed before it triggers). The reason you don't want a a Live Z < -1 is that your PINDA probe will be almost even with the tip of the nozzle, so if a print warps up the PINDA probe might collide with the part and get damaged.

Re: Big thanks to Prusa Research

thankyou so much for starting prusa forum its an Awesome Forum Platform for Exchange the Knowlege of Many Fields

Re: Big thanks to Prusa Research

davit.t28 I have it configured with the ziptie

When I chatted with the support they told me that with the powder coated plate you might have to get as low as -2.5 to get a correct first layer (since it thinner than the other plates).

The magical -1.0 maximum is changed in the newest guide they told me.

Re: Big thanks to Prusa Research

Ideally, what you need to achieve is the probe as high as possible with the calibration still passing.

As has been mentioned earlier, the higher the probe is, the less chance there is of it hitting the model during printing.

Most prints have a tendency to curl upwards in some parts (eg the Adalinda front legs before being joined to the body), unless you print slowly, and properly cool the filament as it is being laid down.

It really is well worth the extra hour or so get get the probe adjusted in this way and a set of feeler gauges will also assist with this.

Peter

Re: Big thanks to Prusa Research

Extra hour? I've already spent 8+ hours on the blasted thing until I just kept repeating the same results (and you know what they say about expecting different results after repeating the same thing over and over...) Any adjustment higher than where it is, and the nozzle grabs the paper and drags/rips it across the bed. As it is now (-1.250) the PINDA appears to be 1-2 mm above the nozzle tip.

Believe me, I'd LOVE to have it fall within range!

The magical -1.0 maximum is changed in the newest guide they told me.

Do you know which guide? I just checked the online Assembly Manual and 3D Printing Handbook, but didn't see anything different.

Re: Big thanks to Prusa Research

Extra hour? I've already spent 8+ hours on the blasted thing until I just kept repeating the same results (and you know what they say about expecting different results after repeating the same thing over and over...)

Is that with the steel build plate or without?

I usually do this adjusting with the build plate on the printer. Once the printer has been through initial calibration, it's the 9-point calibration that matters most. I think the steel plate gives a better reading than the copper pads on the heater.

And really, after initial calibration, it should not take too long to tweak the probe. Place steel plate on bed and heat bed only, 9-point calibration, raise probe (use feeler gauge to measure and lift), 9-point calibration, repeat until 9-point calibration fails, then lower probe to last setting.

Then run live z calibration without filament, but with a two-thickness sheet of copy paper (or feeler gauge at 0.175 mm) under the nozzle, until it starts to grab the paper.

Peter

Re: Big thanks to Prusa Research

Is that with the steel build plate or without?

I followed the instructions in 01 Original Prusa i3 MK3 kit assembly v3.05 and New User Guide EXACTLY.
When they said to move the PINDA up, I moved the PINDA up. When they said to move the PINDA down, I moved the PINDA down. Over and over and over, between the nozzle scraping the paper and the filament not squishing/sticking at all. I've done it so many times, the handbook now falls open to page 25 (which is now heavily worn). We spent 3 more days going back and forth with the developers of Octo and the Bed Level Visualizer, finally getting that operating to see if it might indicate some problem. It didn't. Our bed has less than 0.50mm difference between it's highest & lowest points, which I've been told on this forum the PINDA & firmware should be able to compensate for.

I apologize if I come off as a little testy, but... I AM a little testy--about this subject. It's not meant personally.

Re: Big thanks to Prusa Research

The magical -1.0 maximum is changed in the newest guide they told me.

Do you know which guide? I just checked the online Assembly Manual and 3D Printing Handbook, but didn't see anything different.

I chatted with the support that told me that.
I also did the PINDA adjustment (9.Preflight check) several times but as soon as the nozzle didn't touch the paper I could not get a good first layer with a value less than -1.0.
I have now printed two rolls of PLA and 1 roll of ABS and everything is working great with my high value for the first layer setting

Re: Big thanks to Prusa Research

I apologize if I come off as a little testy, but... I AM a little testy--about this subject. It's not meant personally.

Nah, not a problem. I guess it's like going to a driving school, where you learn to pass your test, and then you learn to drive.

I usually follow manuals (when they are available ) for building printers and then I go my own way. Some of my ways have even found their way into the PR manuals. But not that many.

The manual may be OK for most users, but it doesn't work for everyone.

When I first started 3D printing, there really were no manuals parts did not always work as they should and calibration really was tough. That really is the way to learn.

Peter

Re: Big thanks to Prusa Research

I chatted with the support that told me that.
I also did the PINDA adjustment (9.Preflight check) several times but as soon as the nozzle didn't touch the paper I could not get a good first layer with a value less than -1.0.
I have now printed two rolls of PLA and 1 roll of ABS and everything is working great with my high value for the first layer setting

You're a lucky guy who hit the perfect mounting angle. The PINDA thread should have around 1mm distance. So you're bouncing between 0 and 1mm offset (more or less, let's don't be picky here). If you turn your PINDA probe bei 180 degrees, you should get the right value. Happened to me once on my MK2.

Re: Big thanks to Prusa Research

We are very thankul prusa to have this info

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Joan