Grid bed compensation

[Jackal]

Which movement speed setting should I change for the grid bed compensation probe? Does the M558 F and T parameters contribute to it?

[dc42]

Yes, they do.

[darookee]

I have a problem using the bed compensation. It does not seem to compensate, the print is too close to the bed on the back left and 'okish' on the front right, the bed is oviously not levelled, but neither the G30 compensation nor the G29 compensation has any effect on this, or is the effect just too minor to see a difference?

Here is a picture of it, the left was on the front right of the bed, it is a bit stringy, the right side was on the back left and is realy flat:

[dc42]

Two Three suggestions:

1. Check that the trigger height of whatever Z probe you are using is the same at back left, centre, and front right.

2. To check that the grid compensation is working:

(a ) On a Cartesian printer you should be able to see the Z drive moving as you move the head in the XY plane

(b) Position the nozzle 1mm above bed centre. Check the height using feeler gauges. Then move the head to back left and check the height using feeler gauges again. Repeat for back right. Do this with and without bed compensation.

3. Make sure that you have entered the XY offset of your Z probe from your tool reference point (normally the nozzle in a single-nozzle machine) in your G31 command in config.g.

[Adamfilip]

That's correct. I should get time to implement loading the height map from file later this week.

Any news?

[darookee]

@dc42:

The probe is setup in config.g with this:

G31 P500 X45 Y-25 Z0.30

But in bed.g I just found this:

G31 X0 Y0

I bet this is the problem…

[Rommie]

I have only started to use this feature and have done my G29 run this is my results

RepRapFirmware height map file v1 mean error -0.54 deviation 1.21
xmin xmax ymin ymax radius spacing xnum ynum
-140 140.1 -140 140.1 150 20 15 15
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 -0.191 -0.328 -0.26 -0.152 -0.3 -0.169 -0.066 0 0 0 0
0 0 0 -0.197 -0.287 -0.25 -0.2 -0.153 -0.029 0.09 -0.154 -0.137 0 0 0
0 0 -0.008 -0.109 -0.325 -0.084 -0.11 -0.208 -0.019 -0.16 -0.16 -0.219 0.158 0 0
0 -0.3 -0.281 -0.075 -0.149 -0.216 -0.269 -0.148 -0.13 0.271 0.145 -0.005 0.145 0.243 0
0 -0.116 -0.191 -0.054 -0.139 -0.224 -0.134 -0.084 -0.055 -0.111 0.035 -0.079 -0.13 -0.009 0
0 -0.009 -0.188 -0.05 -0.155 -0.254 -0.175 -0.025 0 -0.196 0.004 -0.12 -0.076 -0.006 0
0 -0.075 0.01 -0.069 -0.13 -0.016 -0.006 -0.031 0.004 -0.301 0.126 -0.08 -0.05 -0.047 0
0 -0.022 -0.076 0.034 -0.17 0.019 0.01 0.055 -0.09 -0.091 -0.112 -0.009 0.003 -0.087 0
0 0.027 0.055 0.028 0.06 0.031 0.007 0.061 -0.133 -0.058 -0.076 -0.102 -0.124 -0.365 0
0 0.65 0.431 0.157 -0.255 -0.779 -1.455 -2.056 -2.79 -3.523 -4.16 -4.71 -5.471 -5.511 0
0 0 0.674 0.46 0.026 -0.577 -1.119 -1.67 -2.318 -2.956 -3.624 -4.385 -4.835 0 0
0 0 0 0.496 0.22 -0.201 -0.738 -1.281 -1.888 -2.495 -3.14 -3.17 0 0 0
0 0 0 0 0.39 -0.076 -0.361 -1.148 -1.526 -2.091 -3.021 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

could someone tell me if its good or not as I'm not too sure on what it all means, sorry for being stupid but this is all new to me

thanks

just ran another grid and reduced my bed radius from 150 to 120 and I have got this now

RepRapFirmware height map file v1, mean error -0.09, deviation 0.10
xmin,xmax,ymin,ymax,radius,spacing,xnum,ynum
-100.00,100.10,-100.00,100.10,120.00,20.00,11,11
0, 0, -0.196, -0.315, -0.176, -0.160, -0.045, 0.090, -0.139, 0, 0
0, -0.053, -0.321, -0.076, -0.081, -0.172, -0.027, -0.180, -0.171, -0.227, 0
-0.154, -0.110, -0.230, -0.230, -0.257, -0.160, -0.116, 0.259, 0.104, 0.007, 0.160
-0.209, -0.080, -0.116, -0.214, -0.115, -0.061, -0.085, -0.100, 0.036, -0.116, -0.134
-0.176, -0.061, -0.164, -0.255, -0.191, -0.030, -0.002, -0.214, 0.006, -0.191, -0.109
-0.011, -0.082, -0.181, -0.064, -0.037, -0.061, 0.000, -0.339, 0.059, -0.110, -0.073
-0.069, -0.075, -0.186, -0.010, -0.002, -0.025, -0.107, -0.141, -0.081, -0.030, -0.006
0.013, -0.005, 0.041, 0.013, 0.012, -0.009, -0.129, -0.101, -0.085, -0.121, -0.116
-0.110, -0.065, 0.016, -0.086, -0.038, 0.016, -0.059, -0.111, -0.064, -0.121, -0.140
0, -0.056, -0.059, -0.014, -0.045, -0.116, -0.109, -0.143, -0.134, -0.464, 0
0, 0, -0.130, 0.011, -0.056, -0.155, -0.096, -0.139, -0.189, 0, 0

that's the best mean error I have ever had and lowest deviation I have ever had also I'm hoping that is pretty good lol

[Qdeathstar]

Guys, I'm trying to understand the process here.

is it

1. Set z-probe trigger height & Figure out H value to put in the bed.g file for effector tilt
2. run autocalc
3. define the bed via M557 R85 S15
4. run grid leveling via G29
5. put G29 S1 at the end of bed.g to load the height map
6. put G32 in your starting print script to activate auto-cal before prints

Is that correct?

RepRapFirmware height map file v1 generated at 2016-11-12 19:58, mean error -1.66, deviation 0.22
xmin,xmax,ymin,ymax,radius,spacing,xnum,ynum
-75.00,75.10,-75.00,75.10,85.00,15.00,11,11
      0,      0,      0, -1.640, -1.512, -1.474, -1.399, -1.340,      0,      0,      0
      0, -1.497, -1.471, -1.486, -1.445, -1.539, -1.507, -1.448, -1.384, -1.259,      0
      0, -1.663, -1.641, -1.696, -1.512, -1.516, -1.449, -1.359, -1.379, -1.288,      0
 -1.572, -1.628, -1.666, -1.614, -1.615, -1.551, -1.540, -1.526, -1.403, -1.291, -1.172
 -1.851, -1.815, -1.735, -1.775, -1.686, -1.685, -1.574, -1.550, -1.460, -1.365, -1.301
 -1.899, -1.829, -1.798, -1.750, -1.749, -1.647, -1.561, -1.600, -1.536, -1.442, -1.324
 -1.952, -1.951, -1.879, -1.979, -1.799, -1.747, -1.699, -1.604, -1.592, -1.463, -1.352
 -2.037, -1.970, -1.973, -1.915, -1.866, -1.792, -1.791, -1.677, -1.623, -1.532, -1.449
      0, -2.027, -1.987, -1.825, -1.899, -1.862, -1.824, -1.587, -1.612, -1.515,      0
      0, -2.089, -2.052, -1.950, -1.984, -1.872, -1.821, -1.800, -1.677, -1.627,      0
      0,      0,      0, -2.026, -2.065, -1.986, -1.765, -1.901,      0,      0,      0

my values seem a little crazy.

[Qdeathstar]

The reason they were all off by about 1.6 mm was because my z-height was too high. I have my z-height configured like this:

G31 X0 Y-8 Z0.84 P500 ; Set the zprobe height and threshold (put your own values here)

and i've doubled checked to make sure that is correct, which it is, so i'm not sure why after auto-cal it would make the z-value so off?

//// == was loading the previous grid compensation file that was way off, i still don't know why z went to high to begin with, though.
***derp
I've ran the autocal again, and now it seems like its a bit over 1mm to low this time ??

Also, out of curiosity, after i ran the auto calibration and noticed it was too low, i ran G30-S1, the web interface shows z-height is 2.52, but the G-code console says stopped at height 0.834 mm
derp***

[dc42]

@darookee:

@dc42:

The probe is setup in config.g with this:

G31 P500 X45 Y-25 Z0.30

But in bed.g I just found this:

G31 X0 Y0

I bet this is the problem…

For 1.17rc1 you should remove the G31 command from bed.g, then change the XY coordinates of your probe points to account for the firmware applying the offset.

[dc42]

@Qdeathstar:

Also, out of curiosity, after i ran the auto calibration and noticed it was too low, i ran G30-S1, the web interface shows z-height is 2.52, but the G-code console says stopped at height 0.834 mm
derp***

The value reported by G30 S-1 is the Z value without inverse bed compensation applied. So if bed compensation is active, the Z value reported by the web interface will be different. Perhaps I should have G30 S-1 report both figures.

[Qdeathstar]

Maybe, but is my process correct for doing the bed compensation? And why so I need to change my trigger height from what it reports after G31 S-1

That is very consistent at .84, but in order to print I have to add about .5mm to the trigger height. I am using glass with an aluminum heat spreader….

[dc42]

Yes your process is correct; but bear in mind that there are no H corrections for G29, so if you need to use a lot of H correction in bed.g then you will not get good G29 results.

I don't understand why you have that 0.5mm offset, assuming you have defined the G31 trigger height to be correct at/near the centre of the bed (so the H correction on the centre probe point is zero).

[Qdeathstar]

My largest h value was .64mm, most are under .2mm. Is that a "poor"? I'm not sure what would be causing the effector tilt.

The thing is it is consistantly high accords the entire bed…. it's almost like it looses track of z=0 after reset.

One more question is, does it matter what I set my maximum z-height to? I calibrate before every print, so that sets z=0, so if I made z-max a larger number would it matter? Right now I have it set to what one of my calibrations said was (387.569) but would it matter if I set it to say 500?

EDIT: In another moment of derp, it turns out that the reason that the print was too high was because it wasn't positioned correctly in my slicer.... i was trying o figure out why my cooling fan was comming on during the first layer, and it was because i was trying to bridge the entire first layer. whoops.

[Jackal]

If you never home the printer after calibration then setting Z max should not change anything since the printer will be moving relatively.
But if you change the max height to be higher than what it really is, then you z=0 will be below your build surface, i.e. print head crash

[Russ Gries]

ok, finally got things worked out where I'm able to test this better.

a few notes / questions.

Notes first:
I have the auto cal set to probe at a ratios of 130, if i set the bed comp at lest say R80, everything out side that R80 is now xxmm lower than the places where i set it.

let me give an example where I'm using this.

I have been making PCB's , There 6"x6". I run a auto cal that is just the bed to set end stop heights. (R130) I then run a G29 where the PCB is. (R80) in this case it works ok, but if it ever goes out side that window ( even when running manual controls) it will drop. some time up to 5mm if i probe the G29 from a new Z height…

so any how just something I think I should bring up. it might be good to set the rest of the bed out side that window to the average height of the spots probed? this may just be a one time problem for me. most will not use this like i am. however, i know i will be using smaller sections of bed types that are smaller than my full bed. ( like when testing new bed surface's)

Q. what is the max probe spots for G29? i see some where it might be 100?? could be more??

ok, here are some photos for fun, i will post a video of the CNC on the CNC thread.

~Russ

This is ALL temporary for testing... a work in progress. oh and yeah, the spindle, Vac, and printer are all powered by that one PS. 90A 12v ( 24V boost converters )

[Qdeathstar]

neat, a delta with a drill. It combines two of my favorite things. Do you use the delta for printing too or just for pcbs?

[dc42]

Hi Russ,

Can you post your heightmap.csv file? The height correction for points outside the probed radius should be zero, so if you are getting a 5mm difference that suggests that you have about 5mm correction within the probed radius, unless there is a bug that I haven't seen yet.

[StephenRC]

To make the first layer thinner, increase the z offset.

[deckingman]

@CaLviNx:

Just a question to get it clear in my head.

If I want to reduce layer height i.e. Squish the layers down a bit.

Is that done by increasing or reducing the Z trigger height number?

I find it helps to think of it like this:- The trigger height is the distance from when the probe triggers to the point where the nozzle will just touch the bed. So, say for example it is 2.0mm. What are "telling" the machine is that to just touch the bed, it needs to move a further 2.0mm from the point where the probe triggers. So if your first layer needs to be 0.3mm then the machine will move in Z by 1.7mm (2.0-0.3). If you want the first layer to be squashed a bit then you have "tell" the machine that the trigger height is greater i.e 2.1 mm then it'll "think" that it has to move 1.8mm (2.1-0.3) in Z from the point where the probe triggered. Conversely if the first layer is squashed too much, then you have to "tell" the machine not to move so far after the trigger point so reduce it.

Well that works for me. Otherwise just think that less is more:)