Beer Can mod for Prusa MK3/S/+  

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @antipode

[...] Bed tramming we are discussing is needed to ensure that printed parts have a flat bottom, and square walls.

Sorry, I thought I was pretty clear on the difference. My post was a reaction to the suggestion that introducing springs and adjustment knobs to the Prusa was a good way to do exactly that.

RE: Beer Can mod for Prusa MK3/S/+

@antipode

It is nice and it was a challenge to get them past the magnet.  I doubt my friend would be willing to machine beer can.  

RE: Beer Can mod for Prusa MK3/S/+

Some time ago I tried harvesting the rolled aluminum from drink cans for the purpose of making DIY PCB solder paste templates.  Other people who had the same objective were cutting off the ends of the cans with either a box cutter or snips, but when I tried their methods I found that using knives and/or snips  crinkled the aluminum, whereas what I wanted was nice smooth rolled aluminum.  In the end the technique that worked best for me was  running a Dremel at high RPM  with a rotary metal cutting blade.  No crinkles.  😎 

RE: Beer Can mod for Prusa MK3/S/+

@cwbullet

Your machinist friend is likely to appreciate the beer cans in other ways, meaning full of beer in return for said machinist's help.

RE: Beer Can mod for Prusa MK3/S/+

@dimprov

Beer cans have lots of uses. Back in the days when I drank beer, I always preferred glass bottles, so I often brought a couple of empty beer cans with me from parties. Remember, there were such things as parties? 🙂

RE: Beer Can mod for Prusa MK3/S/+

@antipode

Have you confirmed that with shims there's no subsequent need to relevel the bed?  The reason I ask is that there was a post on the openbuilds forum which claims that by putting on a belt which ties the two z-axis together that he practically never needs to bed level more than just the first time:

https://openbuilds.com/builds/trueup-glide.3938/

In that thread he claims to have also tried it on a Prusa i3 and found it to be true with it as well. 

So, if true, the corollary would be that without it you would still need to abl a lot.

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @dimprov

@antipode

Have you confirmed that with shims there's no subsequent need to relevel the bed?  The reason I ask is that there was a post on the openbuilds forum which claims that by putting on a belt which ties the two z-axis together that he practically never needs to bed level more than just the first time:

https://openbuilds.com/builds/trueup-glide.3938/

In that thread he claims to have also tried it on a Prusa i3 and found it to be true with it as well. 

So, if true, the corollary would be that without it you would still need to abl a lot.

Don't all PRUSAs use ABL anyways? Sounds like a solution trying to find a problem. 

Personally, the shim mod is probably the easiest and most stable way of getting a trammed bed. I don't think there's a need to chase for absolute flatness nor is that any real value, especially for a machine in this price bracket. We can spend all day and night debating which method is best for which temps and such. Due to warping at different temps, your bed will always warp and cause variance in the tramming, and that's just inevitable. I don't see how the single driven Z lead screw really addresses this issue.

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @dimprov

[...] The reason I ask is that there was a post on the openbuilds forum which claims that by putting on a belt which ties the two z-axis together that he practically never needs to bed level more than just the first time

That's an interesting read. If I'm following the progression, he went through:

• Starting with dual Z motors and lead screws.
• Removing one Z motor due to inconsistency .
• Linking the lead screws via a belt driven by a single Z motor.
• Moving the Z motor to the center of the X carriage.

I would be curious to see how the claim of "never need to relevel" holds up against a removable build surface that is regularly flexed. I'd think you'd want MBL to compensate for differences in placement and different types of sheet.

The Artillery Sidewinder 1X boasts dual Z motors with lead screws linked by a belt at the top. After a couple of months of frustration, I finally stumbled on an article explaining that the entire design is over-constrained. I have since removed the belt completely, adjust the Z couplers to allow some play, and even removed the top bearings. This yielded immediate improvement in Z banding. 

RE: Beer Can mod for Prusa MK3/S/+

Another key item in the design is the use of belt gearing such that no microstepping is used on the Z axis. All moves are full steps. Interesting stuff. The article claims they needed to relevel before every print though, which hardly sounds like the Mk3. 

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @dimprov

@antipode

Have you confirmed that with shims there's no subsequent need to relevel the bed?  The reason I ask is that there was a post on the openbuilds forum which claims that by putting on a belt which ties the two z-axis together that he practically never needs to bed level more than just the first time:

I've just measured my bed. It's interesting, the left side of the table (where I had the shims installed) did not move at all, and remains within about 0.05 mm variance. However, on the right side (where I did not need to install any shims originally, because it was flat enough), the far right corner sunk by about 0.07 mm, which pushed the overall adjustment to 0.16 mm variance.

So, the adjustment stuck where I had shims, drifted where I did not.

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @dimprov

What's the repeatability tolerance on the Prusa Pinda probe?  If it's, say, 0.1mm or worse, then were already at the limit.  The BLTouch version 3.1 supposedly is 0.1mm.  On the other hand, my Clockwise Tools digital dial indicator has better repeatability than that.

Thomas Sanladerer measured PINDA to be accurate to about 0.2 micrometers. See here:

https://www.youtube.com/watch?t=559&v=il9bNWn66BY

RE: Beer Can mod for Prusa MK3/S/+

@antipode

I find it hard to believe the BLTouch is +-0.1.  It is a mechanical switch.  

RE: Beer Can mod for Prusa MK3/S/+

@cwbullet

Mechanical switches have a high degree of accuracy and precision in terms of when they trip. Not to mention it's an instantaneous 1 or 0. Of course over many many cycles that accuracy and precision may drift simply due to mechanical wear. 

Inductive sensors have the issue of electronic noise to deal with but have longer durability since there's no moving parts.

I'm just curious if LVDTs will ever be implemented for 3d Printers in some way. 

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @dragon1291

@cwbullet

Mechanical switches have a high degree of accuracy and precision in terms of when they trip. Not to mention it's an instantaneous 1 or 0. Of course over many many cycles that accuracy and precision may drift simply due to mechanical wear. 

From over 2 years of experience, I think I can say that the PINDA is pretty precise for my use.  I have printed some pretty exotic filaments and I have had pretty good results from the PINDA.  In my line of work, military physician, the enemy of good is better and better almost always leads to a worse outcome.   I am interested to just watch.   

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @cwbullet

@antipode

I find it hard to believe the BLTouch is +-0.1.  It is a mechanical switch.  

Where are you getting 0.1 number for BLTouch? And 0.1 what? It looks like it's about +- 3um if operated slowly, or +- 6 um if operated fast (refer to the chart at 7m25s of the video I linked).

RE: Beer Can mod for Prusa MK3/S/+

I just now looked it up, and according to BlTouch:

"BLTouch’s Standard Deviation in repeatability is around 0.005mm"  https://www.antclabs.com/bltouch

That's for version 3.1.  Earlier versions weren't as good.

RE: Beer Can mod for Prusa MK3/S/+

@dimprov

Sure it is.  That is so small it makes me suspicious.  I replace my BL touch on my ender with an inductance PINDA type because I could not get reliable results with a BL Touch.  

RE: Beer Can mod for Prusa MK3/S/+

@cwbullet  Which version?

RE: Beer Can mod for Prusa MK3/S/+

Posted by: @cwbullet

@dimprov

Sure it is.  That is so small it makes me suspicious.  I replace my BL touch on my ender with an inductance PINDA type because I could not get reliable results with a BL Touch.  

I'm surprised, too, that's almost accuracy of a micrometer, but from a non-substantial plastic mechanism. I wonder if it stays as accurate with use, or gets sloppy after time. PINDA is still 20 times more accurate.

RE: Beer Can mod for Prusa MK3/S/+

The PINDA V2 on my MK3 has been working reliably for years with a repeatability of approx. 0.02mm, which is sufficient for determining the firstlayer with a preheated print bed. I use these inductive switches partly also for referencing on my CNC milling machines.