Beer Can mod for Prusa MK3/S/+  

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dimprov
(@dimprov)
Noble Member

I'm guessing you'd get less overall distortion if the shims are steel, like the kind Karl uses, than if they were made using some other metal, which is going to have a different coefficient of thermal expansion.  Call it a hunch.  Would it be significantly better though?  No idea.  I have no hunches regarding that aspect of it.

Posted : 23/02/2021 5:54 am
Antipode
(@antipode)
Eminent Member
Posted by: @dimprov

I'm guessing you'd get less overall distortion if the shims are steel, like the kind Karl uses, than if they were made using some other metal, which is going to have a different coefficient of thermal expansion.  Call it a hunch.  Would it be significantly better though?  No idea.  I have no hunches regarding that aspect of it.

Yeah, I think that this is splitting hair at this point, while theoretically this difference exists, I doubt there would be any meaningful difference in practice.

Posted : 23/02/2021 6:01 am
karl-herbert
(@karl-herbert)
Illustrious Member

@dimprov

I think that at these small dimensions (thickness of a few tenths of millimeters) thermal expansion is not an issue and you can use many temperature-resistant materials (even Kapton, for example) with a clear conscience.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 23/02/2021 4:23 pm
dimprov liked
Dragon1291
(@dragon1291)
Trusted Member

Did the mod to my printer. Got it to a variance of .2 from .4 with a of fiddling, but unfortunately two points of my bed are slightly higher than the center. Will probably end up doing the silicone tube mod in a few weeks time. 

I think in a pinch, this method does help. I did also opt to put the shims on the bottom of the spacer. Was a bit tricky but I was able to slide the shims under the spacer without slicing my fingers open, which I count as a win. 

Posted : 24/02/2021 5:29 am
cwbullet
(@cwbullet)
Illustrious Member

@dragon1291

Any difference in print quality?  Just doing soemthing to do it?

--------------------
Chuck H
3D Printer Review Blog...
Posted : 24/02/2021 10:45 am
Antipode
(@antipode)
Eminent Member
Posted by: @dragon1291

Did the mod to my printer. Got it to a variance of .2 from .4 with a of fiddling, but unfortunately two points of my bed are slightly higher than the center.

Why could you not do to better than 0.2 variance?

Maybe the first step of the process should be to make the center point the highest point of the bed.

Posted : 24/02/2021 2:32 pm
Antipode
(@antipode)
Eminent Member
Posted by: @cwbullet

@dragon1291

Any difference in print quality?  Just doing soemthing to do it?

0.4 to 0.2 across the bed is not going to make much of a difference. In any case, this mod is not really about print quality, it's about printing parts that are square and flat.

Posted : 24/02/2021 2:34 pm
Dragon1291
(@dragon1291)
Trusted Member

@cwbullet

Pretty much just to try and eliminate any stray variables when trying to print this cheap PETG on the textured plate. Was having a weird issue where the layers were perfect in one spot and completely lifting 4 lines over. 

@antipode

TBH, laziness. Getting to the center rear of the bed is a pain, and trying to install the shims on the back row is not a fun process overall. Figure the .2 is going to be good enough for most of my printing needs for now anyways and I can go in and install the silicone spacers once I need 'True level' in the future. 

Posted : 24/02/2021 5:23 pm
dimprov
(@dimprov)
Noble Member

@dragon1291

When you say "silicon spacers," do you mean the ones that are typically used to substitute for springs?  Or something else?

Posted : 24/02/2021 11:56 pm
Dragon1291
(@dragon1291)
Trusted Member

@dimprov

Yup. Like the mod used for the mini and such. 
Why that and not the Nylock mod or use steel springs, you may ask? Just personal preference. All methods are perfectly valid for what plan to use my printer for.  I guess also the silicone spacers can be used on other printers (like my Wanhao i3 for example)

Posted : 25/02/2021 12:14 am
cwbullet
(@cwbullet)
Illustrious Member

@dragon1291

That is pretty much why I have sworn off cheap ABS AND PETG.  Sure it helps increase profit, but it is not worth the down time and headaches.

--------------------
Chuck H
3D Printer Review Blog...
Posted : 25/02/2021 1:15 am
dimprov
(@dimprov)
Noble Member
Posted by: @dragon1291

@dimprov

Yup. Like the mod used for the mini and such. 
Why that and not the Nylock mod or use steel springs, you may ask? Just personal preference. All methods are perfectly valid for what plan to use my printer for.  I guess also the silicone spacers can be used on other printers (like my Wanhao i3 for example)

 

I've heard of people starting with springs and switching to silicone spacers, but not the opposite, so I agree it makes sense to just start with them and be done with it.

Posted : 25/02/2021 1:47 am
Dragon1291
(@dragon1291)
Trusted Member
Posted by: @dimprov
Posted by: @dragon1291

@dimprov

Yup. Like the mod used for the mini and such. 
Why that and not the Nylock mod or use steel springs, you may ask? Just personal preference. All methods are perfectly valid for what plan to use my printer for.  I guess also the silicone spacers can be used on other printers (like my Wanhao i3 for example)

 

I've heard of people starting with springs and switching to silicone spacers, but not the opposite, so I agree it makes sense to just start with them and be done with it.

Curious what made people switch off springs. I wonder if they just picked cheaper/wrong springs that just got weaker over time due to the thermal cycling. To me it's also like, I'm spending $18 for 4.5 m of silicone tubing. That's more than enough tubing for a lifetime of 3D printing, even if somehow the silicone tubing degraded under the heat/pressure. 

 

Posted by: @cwbullet

@dragon1291

That is pretty much why I have sworn off cheap ABS AND PETG.  Sure it helps increase profit, but it is not worth the down time and headaches.

For me, I got this PETG years ago when I wasn't sure if I wanted to even try printing in PETG. So it was between spending "full price" on a roll only to not utilize it at all or half that just to experiment and mess around with. 

 

Posted : 25/02/2021 2:11 am
dimprov
(@dimprov)
Noble Member

@dragon1291

It sounds like we may be talking about different things:  https://www.amazon.com/gp/product/B07RZKF8MB/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It's all anecdotal, but the people who have switched have said that silicone ones mean they don't have to level as often, that somehow the knobs/screws don't hold their position as well with the springs.

This post was modified 2 months ago 2 times by dimprov
Posted : 25/02/2021 2:02 pm
karl-herbert
(@karl-herbert)
Illustrious Member

@dimprov

The springs hold their position very well, if you use high quality heat-resistant steel springs. Only drawback - expensive!

https://uk.misumi-ec.com/vona2/mech/M1200000000/M1202000000/M1202030000/?CategorySpec=00000005916%3A%3Af

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 25/02/2021 2:52 pm
dimprov liked
Dragon1291
(@dragon1291)
Trusted Member

@dimprov

Yeah, like I said silicone tube mod. Like seen here: https://www.schweinert.com/silicone-bed-level-mod-prusa-mk3/
Or the more common version used on the mini: https://forum.prusaprinters.org/forum/user-mods-octoprint-enclosures-nozzles/prusa-mini-silicone-bed-leveling-mod/

As Karl alluded to, it's likely due to heat resistance of the springs that are being used. Some springs take a while to break in and settle, which happens over time with cyclical loading (like the heating and cooling of the bed). So people may be impatient during that break in period and just swap over the Silicone Spacers. Springs that are more heat resistant are less prone to that cyclical loading and will probably hold much better, but of course those will cost more. 

At the end of the day for me it ends up being how much time and money do I want to spend? Sure, in a production environment you should try your best to squeeze every last ounce of performance out of your machines. But for me, a guy who wants a 3D printer to make parts whose dimensions aren't super critical, it's more about getting it good enough for what I want it to do. Did a bed leveling test last night and it looked like I had some weird high and low spots throughout my printbed. As long as I can iron those out, I'll be happy enough. 

In terms of which method is "best", honestly I don't really think there's an answer to that. I think most of the results are anecdotal and you'll have people fighting tooth and nail for their method. Each method has its' tradeoffs in either time, money, effort, or accuracy. Do what works best for you and just stick with it. 

Posted : 25/02/2021 5:17 pm
dimprov
(@dimprov)
Noble Member

Interesting.  Before now I didn't know heat resistant springs were even a thing.  However, I would have thought that springs which were calibrated at a particular bed level temperature would return to the same force level if returned later to the same temperature, but that isn't actually the case?

Posted : 25/02/2021 9:35 pm
Dragon1291
(@dragon1291)
Trusted Member

@dimprov

Depends on what kind of spring you use. But typically speaking most springs need a little bit of time to settle in and set. And not all springs are made equally so some can handle quite a bit of compression while others may deform very easily even before the coils touch. 

And while we're not dealing with temperatures that would cause these springs to set in place, over time heat and force can cause some cyclic loading that just will weaken the springs over time. Springs wear out due to cyclic loading, just kinda their nature. 

Posted : 26/02/2021 5:40 am
dimprov liked
dimprov
(@dimprov)
Noble Member

@dragon1291

Are the silicon spacers immune to those effects, or is it merely reduced?  i.e. is there a settling-in time for silicon spacers as well?  They do seem to be less expensive than heat resistant springs.  Any downsides to them?

This is all quite eye opening, and really useful to know!

Posted : 26/02/2021 6:54 pm
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