Bed levelling hardware mod?

[Captain Starfish]

One thing that's always annoyed me about the max is the whole endstop screw and measure cycle.

MatterControl allows us to do the same thing for quicker fine tuning in software, but only if you're using MatterControl. When it spits the chewie, as happens occasionally, and I decide to print that model with Cura or something else, I'm back to square one with bed levelling.

At work we now have a Creatbot cartesian jobbie. Its heated bed has four spring loaded adjustable feet which allow bed alignment. It's pretty quick and easy - drive the Z to zero, drive the X-Y to the four corners, doing the paper trick and adjust the bed height at each spot, and you're done.

It has one dubious advantage - if (as occasionally happens) you get halfway across a big bottom part of the bed and you want to adjust the bed height, you can.

I'm wondering, has anyone tried something similar with the Max? Has anyone tried to make the base plate adjustable at three points?

[Jimustanguitar]

I don't understand the advantage vs just moving the existing endstop screws... (I'm pleading ignorance, not refuting your statement)

In theory, the bed should be "true" and parallel with the geometry of the frame so that the endstops are just an adjustment to account for differences in the length of the aluminum extrusions and the endstops themself... The bed would tend to stay put while the aluminum and top/bottom would be what shifts over time and with transport, so I think that adjusting the endstop screws is the way to go after you're sure that your bed is right the very first time.

I guess that regardless of which way you adjust things, it's supposed to be a 1 time thing that "sticks", right?

[Captain Starfish]

It's a one-time thing that should stick.

But it doesn't. A bit of crap stuck between the Onyx and the glass. Too much glue or juice on the glass from old prints. The glass might not be completely flat and gets shifted in its clips. All sorts of minor things.

I don't religiously check the bed alignment on either printer. But, with the Creatbot's configuration, as the bottom layer is playing out I can glance at it and go "Hey, that's too stringy or too squished out" and adjust it on the fly to good effect. With the Max, I see it's a little far one way or the other and generally can't be bothered aborting the print, so I put up with it with the intention of doing the calibration later. Which I inevitably forget to do until the next time I go to print, etc, etc, etc.

Not a biggy and yes, I appreciate the irony of being able to calibrate properly again in less time than it took to start and continue this thread

[geneb]

Keep in mind that "bed level" isn't the same as "bed calibration". MatterControl does bed leveling. (well!)

The whole ring-around-the-rostock nonsense is to calibrate or trammel the machine to ensure that it's moving perfectly (or as close as) parallel with the build surface. When you've got it to that point, running MC's level wizard can help, but isn't needed.

While the bed glass is flat, there's still enough variance in it to cause problems sometimes, especially if you're removing it for cleaning, etc.
In the 2nd Ed. manual, I recommend marking the edge of the glass so you can return it to the exact same place when you remove it - this will help eliminate issues caused by variations in the thickness or surface of the glass.

Using MC's bed level wizard with cartesians is awesome, but does require that the printer have anti-backlash nuts on the Z axis drive or it won't work well.

g.

[Nylocke]

Keep in mind that "bed level" isn't the same as "bed calibration". MatterControl does bed leveling. (well!)

The whole ring-around-the-rostock nonsense is to calibrate or trammel the machine to ensure that it's moving perfectly (or as close as) parallel with the build surface. When you've got it to that point, running MC's level wizard can help, but isn't needed.

While the bed glass is flat, there's still enough variance in it to cause problems sometimes, especially if you're removing it for cleaning, etc.
In the 2nd Ed. manual, I recommend marking the edge of the glass so you can return it to the exact same place when you remove it - this will help eliminate issues caused by variations in the thickness or surface of the glass.

Using MC's bed level wizard with cartesians is awesome, but does require that the printer have anti-backlash nuts on the Z axis drive or it won't work well.

g.

That coming from your TAZ experience?

[geneb]

Yep. I'm hoping to get the poor girl back on her feet this week. I completely destroyed the hot end (don't ask...) and I just got in the wire I needed to add a PEEK fan for the hotends.com J-Head I'm going to be installing on it. For those that like printing in PLA, the VERY BEST hot end for printing PLA is the hotends.com J-Head. I've run probably close to 10 kilograms through the .4 one installed on Orange Menace and it's never jammed once, even with piles of retracts.

g.

[dtgriscom]

I don't understand the advantage vs just moving the existing endstop screws... (I'm pleading ignorance, not refuting your statement)

The problem with adjusting the end stops is that they only take effect when you home. So, if you find that one position is a little high, you have to adjust the end stop, re-home, and then go back to the position.

If you were able to adjust the bed, then you'd move to the desired position and no further motion of the effector would be needed; just adjust the bed to the right location. (This is assuming that the different bed height adjusters wouldn't interact, which they would, but that's a secondary problem.)


Dan

[theverant]

The problem with adjusting the end stops is that they only take effect when you home. So, if you find that one position is a little high, you have to adjust the end stop, re-home, and then go back to the position.

If you were able to adjust the bed, then you'd move to the desired position and no further motion of the effector would be needed; just adjust the bed to the right location. (This is assuming that the different bed height adjusters wouldn't interact, which they would, but that's a secondary problem.)


Dan

Seems to me you could solve that problem with a three way leveler? They are pretty common in the film industry for leveling camera heads, jibs, cranes, on tripod legs. One can be seen on this page:

http://www.porta-jib.com/standard.htm#lpl" onclick="window.open(this.href);return false;

But, I'm not sure how that would play into squareness of towers, etc. It could get weird.

[Captain Starfish]

That's kinda the way I was headed but more along the lines of springs under the bed pushing up against clamps that screwed down onto the glass with some release mechanism that allowed the glass to be removed without losing the 'setting'.

I started the thread to see if anyone else had been down this road already, I'm a firm believer in learning from others' mistakes where possible

[bot]

The home built Rostock I played with had a three point spring based bed leveling thing. I never used it. I just put it wherever and had to level the end stop way regardless.

[626Pilot]

When your printer homes, it does the usual G28 move, and then it makes the following assumption: "X=0 and Y=0."

Endstops are purely for that purpose - telling it that if it just does this mechanical move, the effector will be perfectly centered. If you turn the Z screw, it will adjust the machine's notion of "center" toward or away from where it was before along the line from the Z axis to the center. Every single move it makes after that will be influenced by that change.

The printer also assumes that the bed's surface normal is {0, 0, 1} - in other words, the print surface is at a perfect 90-degree angle relative to the towers, and Z points perfectly up and down. Adjusting the endstop screws isn't the same thing as telling it the surface normal!

One of the upgrades I'm working on for the Smoothie firmware is the ability to change the surface normal. That code actually works right now on my machine, but it hasn't been uploaded.

[Nylocke]

Pilot, the things you've done with this code are amazing. Really good work, the community appreciates it.