Bltouch giving me bogus height map

fcwilt

I think I mentioned that what you are trying to do is get the bed to be perpendicular to the Z axis and parallel to the XY axes plane.

This is actually called tramming. Making the bed level using a actual level may not give the desired results.

Imagine tilting the entire printer, say, 45 degrees to the right. Then using an actual level on the bed is clearly going to say the bed is way out of level - but it can still be perpendicular to the Z axis.

On a printer with easily accessible "thumb screws" that adjust the bed there is a fairly simple procedure you can run on the printer itself which probes the bed near the thumb screws and reports how much adjustment is needed for each.

But that is not going to work for you.

It seems you are going to have the tram the bed as best you can and create a height map to see how it turned out. You may have to repeat the process several times.

Perhaps someone with a machine like yours will chime in.

Frederick

ageis

@fcwilt
I am beginning to think perhaps I should of got it built by Prusa.
I have learnt the hard way that building a 3d printer isn't just bolting it together.

fcwilt

@ageis said in Bltouch giving me bogus height map:

@fcwilt
I am beginning to think perhaps I should of got it built by Prusa.
I have learnt the hard way that building a 3d printer isn't just bolting it together.

I did not know Prusa sold kits.

Building a printer needs a lot of attention to detail to get first rate results.

If, like me, you tend to have a slight case of OCD it actually helps.

Frederick

droftarts

@ageis said in Bltouch giving me bogus height map:

Looking at your bed heightmap, it isn't that bad; it's only -1.84mm to +0.58mm at the extremes. This quite possibly looks okay with a level, which is really not the best way of levelling a bed.

I'm not sure what version Prusa i3 you have (Mk2?), but Prusa i3 printers usually have a built-in calibration routine. But as you've removed the Prusa electronics and added a Duet, you don't have access to this. However, you can still do the same thing manually, and later add a macro to do it automatically on the Duet. For the Prusa instructions, see https://help.prusa3d.com/article/xyz-calibration-mk2-s_112396

This starts with moving the X axis to the top, so it hits the top of the Z axis on both sides. You can do this manually, by jogging the Z axis until the X axis is just at the top. Then send M18 to disable the motors. Then you can turn each leadscrew by hand (slowly, you don't want to destroy the stepper motor driver by spinning the motor fast) individually until the X axis is touching the top of the Z axis on both sides. This should square the X axis to the Z axis.

With the X axis square, you now need to square the bed to the X axis. Jog the X axis down (ie move down in Z) until the nozzle is a little above the bed. Move the nozzle to the four corners of the bed making sure you don't actually hit the bed with the nozzle. The idea here is to adjust the bed so it is the same distance from the nozzle at the four corners, or as close as it can be.

Then run bed mesh and see what kind of mesh you get.

However, before that, your acceleration settings look a bit odd:

M201 X500.00 Y20.00 Z400.00 E250.00

Y is set very low, and is probably causing the bed to move slowly, while Z is quite high for a leadscrew axis, and might possibly cause it to miss steps. The RRF config tool usually suggests these quite conservative numbers:

M201 X500.00 Y500.00 Z20.00 E250.00

My bedslinger has higher acceleration on X and Y, but Z is the same. They are just not designed to move very fast in Z!

Ian

ageis

@droftarts
I don'tknow about the acceleration settings. Maybe i edited themby accident at some point.

I have a problem with squaring the bed to the x axis. The upper right hand corner appears to be higher than the lower right hand corner.

So I squared up the x axis with z then went down till the nozzle was 0.4mm above the bed. IT didn't hit the bed when the nozzle was in the lower left or lower right corner. But the gap disappeared when I moved to the top right hand corner.

HOw is this possible? I haven't built it correctly then lol.

The direction of the slope also keeps changing. It's really weird. If you look at the last height map it slopes right to left. However the latest height map slopes from left to right.

Why is this

ageis

@ageis #banging his head against the wall

ageis

@droftarts

Do you have any bright ideas why the back of the print can be higher than the front of the printer? driving me insane. I won't be recommending Prusa printers to anyone.

droftarts

@ageis I asked before; what version of Prusa i3 do you have? It says on the bed, usually. I think you have a Mk1 or Mk2 of some sort, rather than a Mk3.

Generally, Prusa i3 printers don't have adjustable beds. The heated bed bolts onto a frame, the frame sits on the Y axis linear rods, and the Y axis bolts to the big square Z axis. If you assemble it carefully, on a flat table, it should end up pretty square. The X axis is set square by running it to the top of the Z axis, and any variation, which should be only a few tenths of a mm, can be fixed using mesh bed levelling.

If your bed is a long way out (ie more than 1mm), something has gone wrong in the assembly; possibly the bed carrier is bent/warped, or something else is not straight. It's also possible that your printed parts (some of which don't look that great) are throwing it off. Go back and check through the instructions of Y axis assembly, and connecting the Z to the Y axis.

Post your current bed mesh, either a picture (make sure we can see the min/max/rms data on the right side) or the heightmap.csv, so we can see how it's changed. (By the way, no need to use Google Drive to store pictures, you can upload them in your post on the forum.)

Ian

ageis

@droftarts
Sorry I forgot to tell you it's a Prusa MK2S
I ave tried the tramming process using my feeler gauage as reference. However I still get a bogus height map. Now it's has a little mountain in the top right corner.

So I have home all axis then used dwc to move to each of the four corner. the back two corners are now lower than the front two.

I have order some springs from Amazon. I will try with the springs tomorrow.
heightmap