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Knickohr
(@knickohr)
Member Moderator
Y distance from min

What does this mean ?

Thomas

Posted : 18/12/2017 7:16 pm
Knickohr
(@knickohr)
Member Moderator
Topic starter answered:
Re: Y distance from min

Found the description in the MK3 handbook :

8.3 View XYZ calibration (detaisl)

But what does this mean ? What I have to to to optimize it. They says, it should be 10mm ore more.

Thomas

Posted : 20/12/2017 10:06 am
william.g19
(@william-g19)
Eminent Member
Re: Y distance from min

In my book for the MK2S there is a picture below describing what the values correspond to, the distance from the axis start to the front calibration point. For the MK2S the minimum is 0.5mm and ideally between 2 and 3 mm.

The second screen outlines the skew and how it will compensate.

Posted : 20/12/2017 6:52 pm
Knickohr
(@knickohr)
Member Moderator
Topic starter answered:
Re: Y distance from min

n my book for the MK2S there is a picture below describing what the values correspond to, the distance from the axis start to the front calibration point. For the MK2S the minimum is 0.5mm and ideally between 2 and 3 mm.

Yes correct, I've found this in the MK3 handbook too, but what does this mean ? Any explanations ?

Thomas

Posted : 21/12/2017 9:29 am
kevin.r5
(@kevin-r5)
Estimable Member
Re: Y distance from min

From MK2S manual:
Pict. 20 - Distance of the front calibration point from the axis start. Ideal value is between 2 and 3 mm but everything larger than 0.5 mm is good enough.
Pict. 21 - Example in the picture - moving the frame forward on the Y axis (increasing the 100 mm distance from the build manual) will increase the Y distance from min.

I believe they are measuring the distance from the y-axis endstop to the calibration points in the build plate. As it says, you could adjust this by moving the z-frame on the y-axis (100mm distance as described in the build manual). They are using these measurements to calculate the skew of your X/Y axes.

A little farther down in the manual where it talks about skew compensation:
Up to 0.25° = Severe skew compensating for offset of 1.1 mm on 250 mm length
Up to 0.12° = Slight skew compensating for offset of 0.5 mm on 250 mm length

The "offset" here is the difference between the left and right measurements.

arctangent(1.1 / 250) = 0.252°
arctangent(0.5 / 250) = 0.115°

My printer shows Left: 0.81, Center: 0.76, Right: 0.71
The next screen shows Measured skew: 0.02°
arctangent(0.1 / 250) = 0.023°

Bottom Line: if you want to optimize your printer, try to get all three measurements to be equal (no skew).

-Kevin

Posted : 22/12/2017 2:04 am
Knickohr
(@knickohr)
Member Moderator
Topic starter answered:
Re: Y distance from min

I believe they are measuring the distance from the y-axis endstop to the calibration points in the build plate. As it says, you could adjust this by moving the z-frame on the y-axis (100mm distance as described in the build manual). They are using these measurements to calculate the skew of your X/Y axes.

Ahhh, OK. So I have to move the z-frame a little backward 😉

THomas

Posted : 22/12/2017 10:04 am
william.g19
(@william-g19)
Eminent Member
Re: Y distance from min

You have to push it backward on the right side (at least how I read it). I was fortunate that I didn't have to adjust mine.

I would suggest moving one of the sides and running the calibration again. If it gets worse then you know you went the wrong way. 😀

Posted : 22/12/2017 5:17 pm
kevin.r5
(@kevin-r5)
Estimable Member
Re: Y distance from min


Ahhh, OK. So I have to move the z-frame a little backward ;

According to your first picture, the difference between your left and right measurements is only 0.05mm (0.011° skew). Perhaps not perfect but difficult to improve (the firmware considers skew of less than 0.12° to be perpendicular).

MK3 manual says:
Ideally, all of these are positive and at least 10 mm or more.

MK2S manual says:
Ideal value is between 2 and 3 mm but everything larger than 0.5 mm is good enough.

I don't know if you have an MK3 or MK2S, but the actual numbers aren't as important as the difference between left and right (skew). As long as you're able to print to the entire build plate, what difference does it make whether the distance is 4.62mm, 0.62mm, or 10.62mm?

-Kevin

Posted : 23/12/2017 3:13 am
Knickohr
(@knickohr)
Member Moderator
Topic starter answered:
Re: Y distance from min

what difference does it make whether the distance is 4.62mm, 0.62mm, or 10.62mm ?

Yes, that's the really question I ask for !

Thomas

Posted : 23/12/2017 10:42 am
Intrudermax
(@intrudermax)
Eminent Member
Re: Y distance from min

Interesting. When I look at mine (mk2s) it shows Y DISTANCE FROM MIN: LEFT: 1.80 CENTER: 1.80 RIGHT: 1.80. It also shows a skew of 0.12. But by the explanation above, shouldn't the skew be zero?

Posted : 24/03/2018 2:50 pm
john.f14
(@john-f14)
Active Member
Re: Y distance from min

Seems this could really use some follow up. I'm fighting with inconsistent prints on my kit (and have had this problem from the start). Sometimes my prints are fine, sometimes they're a disaster - sometimes using the same gcode. It seems like the layers are inconsistent or the extruder is, but I'm not sure.

I decided to disassemble most of the kit and start over. Previously I had a 0.16 skew after XYZ calibration - indicated as OK. This time I went through and adjusted the unit carefully and repeated the XYZ calibration until I got it more in line. My measurements are within 0.02 now in Y-mins, yet my skew is still 0.12? Is this a bug, or does this actually not mean what is indicated above with the arctan?

Interestingly, while I was calibrating, my skew went as low as 0.02 - however my measurements were over 1mm off at the time that it measured that. Also, if I repeat the xyz calibration multiple times, I get different results each time.

Does xyz calibration actually work/is it consistent for everyone else, or are these just random numbers to keep us happy?

Posted : 01/05/2018 3:12 pm
john.f14
(@john-f14)
Active Member
Re: Y distance from min

So I've reset/rerun the calibration 3 times now without any physical changes to the printer, results being

2.56 2.57 2.59 skew 0.09
2.52 2.54 2.55 skew 0.12
2.54 2.58 2.61 skew 0.04

I don't see the sanity here, but also not sure why they keep changing or what the expected accuracy is.

Posted : 02/05/2018 1:19 am
BillC
(@billc)
Reputable Member
Re: Y distance from min

I believe PINDA plus heat is the answer to that question. Since the point being compared to the end stop is the "best" reading from the PINDA and we all know PINDA readings vary with temperature.

I am about to adjust skew on one of my printers once I am happy with hyperfine on the second. I will preheat before running xyz as an experiment to see how much difference I can get from cold readings.

Bill
Tagaytay City, Philippines
Founder member of Philippines Prusa Printer Owners FB Group
Sponsor Pillars of God Academy in Bacoor

Posted : 02/05/2018 7:14 pm
john.f14
(@john-f14)
Active Member
Re: Y distance from min

In this case, all 3 calibrations were done cold at room temperature. I don't think heat would be a consideration here. The XYZ calibration doesn't use heat/preheat.

That would still only account for the variance in the repeat calibrations though, it wouldn't answer why the skew number seems to be unrelated to the values. Especially for the guy who has 3 perfectly matched values and a skew of 0.12

Posted : 02/05/2018 9:42 pm
john.f14
(@john-f14)
Active Member
Re: Y distance from min

Well, I did a live chat with support to try to solve this. Spoke with Martin L there - he looked into it for a bit and asked me to send it in via email to support. Sent it in, and unfortunately, got no answer - instead a suggestion that it's model/g-code issues (didn't even respond to the calibration issue). Unfortunately getting a very strong feeling that despite these units still being pretty new - mine is less than a year old, support is pretty much "gone". The MK2(s) forums have certainly died off in favor of the MK3.

I had an MK3 order that I went ahead and canceled - too afraid I will never be able to get these units printing well and the support just isn't there. Seems to be a lot of complaints in the MK3 forum that people can't get issues resolved either.

Posted : 08/05/2018 4:25 pm
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