Trigger height

[Puppet172]

when i'm going through checking my trigger height throughout my print bed it is not the same throughout the bed. It can be off as much as 1 mm sometimes. I know this isn't right and how can i fix this because i think this is also leading to my problems when im printing.
Thanks

[JoergS5]

@puppet172 If you give some more information like a few pictures of your printer and print bed, someone can give you hints how to improve your bed. You can correct it through firmware also, but it's good to calibrate your printer first.

[Puppet172]

@joergs5
my printer is a big custom printer i built with my brother. it has Four z axis motors and 2 Y axis motors with one x axis motor. The boards are a duet wifi and a deux 5 extender. The bed is ig metal plate that the taped down to the frame to there is not adjusting the bed.

Thanks

[JoergS5]

@puppet172

Your print bed is thin, so it will bend from his own weight. (it could bend to top also, if the frame outside squeezes it together a bit). You can support it at the underside. If this is not possible because there is the heating, I would connect the left and right frame by a strut, so the bed is pressed apart and levels the bed this way by the tractive force. But be aware that if you heat the bed, it expands by the heat at bit. So you could construct the strut so it expands itself, like with two struts connected with a spring.

The 1 mm deviation: is it at different places or just at one end? If it is at one end/side, you can set that side higher. For easier calibration, you can use a three point approach, described in
https://drmrehorst.blogspot.com/2017/07/3-point-print-bed-leveling-vs-4-point.html
So fixing at at two corners and the third support at the opposite side in the middle, e. g.
BUT three points instead of four makes the bending worse, so you should support the bed from the underside here as well.

[Puppet172]

@joergs5
So do you think it would be worth while getting a thicker print bed, so that we can do the 3 three point approach because right now it would just bend. what thickness would be good Like 1/4 In? Also what the point cause if the bending is worse with 3 point then just use another point so that its not as bad right? whats bad about the 4th point?

"The 1 mm deviation: is it at different places or just at one end? If it is at one end/side, you can set that side higher.
the way i look at it is the left side is just a little low and the right side is a high. but this could then be fixed with a thicker peice of metal and then some 3 point leveling like you said.

But if im not able to get a peice of metal right now how would i set the one side higher/lower?

[JoergS5]

@puppet172

I use 8 mm casted Aluminium, routed flat. Good is Ecocast = MIC6 = ALCA5. I have AW5083 however.

With 4 points it's difficult to calibrate. This is explained well in the blog I mentioned.

Before you buy a new bed, an overall review of the printer makes sense. I am not sure whether you have other issues also like the stability of your frame which you can improve cheaper.

[JoergS5]

@puppet172

But if im not able to get a peice of metal right now how would i set the one side higher/lower?

You can try to place aluminium foil between the bed and your frame, optionally multiple layers. (Loose the screws first)

[dc42]

Inductive sensors don't work especially well on aluminum targets. The trigger height may be varying because of the proximity of other metal parts at certain XY positions.