Weird bed mesh

[Jan_26]

Hello there, just finished building my 2.4 kit (LDO) and did some prints. I noticed, my bed wasn't flat, did a mesh. (see picture) the result made me check my gantry, I did check squareness that again, to be sure. Checked my extrusions, since I crashed into the bed, while configuring klicky, seems all fine, nothing bent. I loosened all connections, while doing that, including the x/y rails to be sure there's no misalignment or slight bent from heat. My bed is heating at 70% max, well within recommend power.

I can't get my head around the bed "warp" in the corners. Any suggestions anyone? To me, it seems the magnetic sheet is not flat. The corners are 0.25mm high, the middle is dead flat within 0.02

Sorry for the bad Pic, I have nothing else atm,since I'm away from home.

[Dirk]

Your bed mesh looks straight. So the gantry seems leveled.

The highest points are the four corners.

That is what is giving you the somewhat higher range. Which is 0.25, and not very bad for a 300+ bed.

You have a bed probing of 5*5 and Klipper fills in the space in between according to the other settings in your [bed_mesh] section.

You could try increasing the probe count and see if it gets more accurate, but doubt it.

I don't think your plate or bed is warped. 

To test, you could tape some blue tape below your pei sheet .. but in my opinion not worth the trouble.

Beware though of thermal drift, that can also look like this.

[Jan_26]

Yeah, I guess I'm screwed. Got a good straight edge from work. Aaaaand I bent my gantry. It's high in the middle on x and y, the ruler is rocking on all 3 extrusions. Dang. 

Any suggestions? Is it possible to bent it back? 

I mean, the mesh should correct for it, the bed is pretty much flat. So my prints would be accurate when corrected for the bend, if I disable fade out, right? 

[Dirk]

You have a brand new printer. So I would suggest correcting that 'rocking'. I do not know if you bent anything. The chance you connected the gantry extrusions a little off, is bigger. 

If I were you, I would disassemble my gantry, and see one by one, if the extrusions are crooked or not. Honestly, I do not believe an LDO kit will be shipped with a bent extrusion. So check that first.

If you have a bent extrusion, you can try to correct it, but to do it nicely, you would need 'equipment'. It is usually easier to just replace the one bent extrusion. If you contact the LDO reseller, I am sure they will not mind sending you a new one. Else you can get for 5 bucks, not worth the time and effort you put in straightening a bent one on a new kit.

As an emergency, to see if your axis is indeed twisted, you can try running the klipper-axis-twist compensation. It is as simple as setting your z offset with a paper.

Let us know how things go and what you find.

 

[Jan_26]

Dirk, 

 

First, thanks for your suggestions, didn't do that in my last answer. I'm greatful for any help here. 

I don't think the kit was damaged front the start, either. But as I said, I crashed my nozzle, missconfiguring klicky. ( set the offset to z endstop instead of probe.) That's a 2mm difference, i don't know if it would result in a 0.25mm bend. 

I didn't disassemble the whole gantry yet, hoping it's not needed. Now I don't trust the straight edge anymore. Tried it in my Glas stove top, and.... It rocks. 

I did square up my gantry, for the third time now, before posting, to be sure, I did what I could. Maybe I'm doing something wrong. I'm a seasoned mechanic, I'm not new to printers, but questioning my skills here... Nobody's perfect, but that's just so frustrating. 

 

Gonna do twist compensation for a test next. Didn't know thats applicable on a flying gantry core xy. 

 

###

Did the compensation, its minimal, about 0.03mm wich is within tolerance, i suppose?

Quote

AXIS_TWIST_COMPENSATION_CALIBRATE: Calibration complete, offsets: [0.011666666664936542, 0.010416666667554253, -0.02208333333248813], mean z_offset: 7.885417

 

Edited May 10 by Jan_26

[Dirk]

You are welcome. 

Axis twist compensation works on all printers as long as they use klipper. It especially picks up torsion in the x-rail.
The difference of 0.03 is not big indeed. within the error margin of paper testing. But so is the variance in your bed mesh for a big bed. So I wouldn't have bothered with it.

However, a wobbling gantry sounds strange. Since you are the mechanics guy, you should know how to fix that. As I said, I would disassemble and identify the bend. and fix it.

Again, I doubt LDO would mind replacing the bent part. But first identify the bend and show it to them.

And no, a crash of clicky will not bend your extrusion. Klicky will break.

The chance of a loosened screw is much much higher. Especially if you had been printing for a while.. I am sure others will agree with that.

I do not understand exactly where it is wobbling (a picture?) but I would see why it is doing that...

[Jan_26]

Quote

However, a wobbling gantry sounds strange. Since you are the mechanics guy, you should know how to fix that. As I said, I would disassemble and identify the bend. and fix it.

I think I was unclear there, not the gantry is wobbling, the straightedge on the gantry. But checked the  straightedge itself and it seems to be defective, so the result is inconclusive.

 

I'm gonna disassemble the gantry tomorrow and check rails and extrusions. Will take some pictures , too. And i need a known good, straight, flat surface, i guess.

 

Quote

The chance of a loosened screw is much much higher. Especially if you had been printing for a while.. I am sure others will agree with that.

I can pretty much rule that out, rechecked all screws on the whole motion system, but i will do another 100% bolt check, if or when I reassemble the gantry. 

Edited May 10 by Jan_26

[Jan_26]

Hello there. Yep, my assumption was correct, got a bend. The extrusions seem fine. The rails, not so much. Attached some pictures. Will try to contact my seller, or LDO. Hopefully one of them has pity on me. 

[Dirk]

Indeed. Very obvious when you put it like that.

I doubt you can bend it like that with a crash of klicky.

I remember having to cut through one of those rails. Not done easily.

I would contact them indeed and state you received a not so straight rail and ask them to replace it.

It's clearly a fabrication error... And they don't want that in an ldo kit... Especially when you post about it on a big online forum....

 

[Jan_26]

I emailed my seller, will see what's his response. If he won't or can't help, I'm gonna contact LDO. 

 

I'm really not sure if it's my fault or not. All three rails are similarly bent. The x rail is bent in the carriage axis, wich would indicate crash damage, but both y rails are too. Wich would be the "wrong" axis for crash damage. They should be bent along the wider side. 

But I'm just speculating here. 

[Jan_26]

Wohooo. 

New rails, first bed mesh. And look at that! I'm actually a little excited. That's a mesh I can live with. The gantry isn't finally squared up yet, neither heated up once. Just roughly squared and meshed, to see if I get results. No build plate on either. 

 

I'm definitely happy with that. 

 

Thanks again, btw @Dirk