z_thermal_adjust

[therm_virtual0y]

I’m curious if anyone has Z_Thermal_Adjust in use?

More specifically, I’m wondering where you take your adjustment temp measurement from.  
also, there is an article that talks about moving your bed mesh zero point reference to a more stable corner too.  Just seeing if anyone has any experience implementing it or is it worth the hassle. 

[Dirk]

The only z thermal adjust I know of, is the one mentioned in Ellis' tuning guide in the thermal drift article.

It references a GitHub resource

- https://github.com/alchemyEngine/measure_thermal_behavior

And a few klipper documentation references about thermal measurement and adjustment.

 

Funny thing is that it looks like nobody really trusts this method. Not even the author of the github page.

I think mainly because there are easier and more reliable and less complex solutions( like buying a set of 80€ titanium backers) 

But if you genuinely want more information, I suggest the github reference and it's author alch3my 

Edited February 15 by Dirk

[Dirk]

I realise I did not answer your questions.

I do not use it. I have not seen it mentioned previously.

A more stable /reliable reference point would be close to the corner of two rails. So positions (0,0) or (350,350)(and the other two corners). The bed movements during heating is most extreme at the center of the bed. The corners move least. Take a look at the thermal graphs from the initial research 

Something different where thermal adjustment scripts were also mentioned, is the cartographer3d probe. On their discord I saw the author mention developing scripts for thermal adjustment, a-work-in-progress. 

[therm_virtual0y]

This is what I have seen also.  Thanks for the confirmation that thermal adjustments based on frame temperature is really not mainstream enough for me to mess with at this point.  
as far the zero point reference, are you using a corner or the center?  If I do 0,0 then all calculations for z end stop, Probe z offset and auto Z will be in the corner.  This seems like something I might try this weekend.  

[Dirk]

I don't use those scripts

I bought two linear 400mm rails (for both sides) and a titanium backer for the center. (Total cost +-40€)

But it you look at those pictures I linked and the story from whoppingpochard, then your bed becomes a 'taco' when heated compared to an unheated bed.

When heated the side rails move becoming a C. With the highest point in the center.

https://github.com/VoronDesign/VoronUsers/blob/master/printer_mods/whoppingpochard/extrusion_backers/images/no_backer.png

This means your bed becomes like a turned down taco. The corner points of your bed are relatively fixated.

And the center moves up... On a 300mm bed, 0.4mm in 1-1.5 hours. The more you go to the edges, the less the moving up is.

So if you are going to try it out, the corners would be the best place. I think you need to adjust 0,0 to a number that can be measured by your probe. 

I'll be interested in your tests I think many others as well

[Dirk]

oh... and just saw this post: 

 

pointing to another effort in thermal correction: https://github.com/JiMcNulty/FDC

 

[therm_virtual0y]

I finally read through this white-page ( https://github.com/VoronDesign/VoronUsers/blob/master/printer_mods/whoppingpochard/extrusion_backers/images/no_backer.png), and decided to buy new Y rails for my Voron 300.  I spent a little extra on the HoneBadger Mgn9 and used the old ones as backers.  I had to cut the z belt holders on top so the old rails would fit but that wasn't too bad.  I'll just reprint later.  Anyway, the results actually surprised me.  Attached is a before and after of my bed mesh and the results speak for themselves.  Let me first say that I had a regular bed taco that I thought was the problem.  I still had pretty good prints despite the 0.1 to .15mm height difference from front to middle of the bed.  Doing this was because I have my Voron totally finished, and this was the last mod (for now) LOL.  

[mvdveer]

Well done - just fitted titanium backers to all my "big printers".  Similar results.

[therm_virtual0y]

I thought about the titanium backers too, but also wanted better linear rails. Figured I would try and see if it would work.  It seems to have done well, so I’m happy with it.  I also am using Cartographer probe with my BTT SB2209/2240.  Still trying to dial in the z-offset though.  It seems too squished on the first layer but when I put z to .1mm and use my .1 feeler gauge, I barely feel the nozzle.  It’s new so I will figure it out.