Anybody have success with the .25mm nozzle?  

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stl
 stl
(@stl)
Active Member

I am having a great deal of difficulty getting good prints with the default settings in PrusaSlicer using PETG.  The prints are really stringy and I get crash messages on the printer.

What settings should I be using, and does anybody else have this issue?  I get decent prints with the .4mm nozzle.

Thanks in advance.

Posted : 17/09/2020 6:48 pm
bobstro
(@bobstro)
Illustrious Member

I've had good luck with different nozzle sizes on the Mk3. I've got a collection of profiles here and notes here that may be helpful. 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 17/09/2020 8:52 pm
stl
 stl
(@stl)
Active Member

How do you calibrate the nozzle?  I know how to do the live Z.

Also, how different would your profiles be for the MK3/S?

Thanks for your help.

Posted : 17/09/2020 9:01 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @stl

How do you calibrate the nozzle?  I know how to do the live Z.

I use a 75x75mm square for calibrating Live-Z, just like Jeff Jordan's "Life Adjust" but sliced for the 0.25mm nozzle. I stick to the safe parameters based on the nozzle:

  • Maximum height 80% of nozzle size (0.2mm)
  • Maximum extrusion width up to 120% of nozzle size (0.3mm)

Also, how different would your profiles be for the MK3/S?

They are identical. Several Mk3s users have reported no issues with those profiles.

Thanks for your help.

Glad to help. I hope everything works well for you. The Mk3 does very nicely with the smaller nozzles.

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 17/09/2020 11:01 pm
stl
 stl
(@stl)
Active Member

I will try your profiles when I decide to put the .25mm nozzle back in.  I am printing fine with the .4mm nozzle using the PrusaSlicer profiles.

Thank you.

I took a look at some of your notes, and disagree with you about Prusa and the textured sheet.  I have both the textured sheet, and adjusted the z adjust to PETG sticks to the textured sheet, but PLA absolutely will not.  For PLA I use a smooth steel sheet with a PEI sheet attached to it (I got it on Amazon when Prusa was out of them).  PLA works fine with that, but if I try to use that for PETG, PETG sticks too much on that sheet and it is difficult to get the parts off  (I had to use a hammer on some parts).  The .4mm nozzle works great for both PLA and PETG.  I don't think I'll be useing PLA very much because PETG has better physical characteristics.

Regarding Prusa and his printers.  What I have found is that whoever designs the plastic parts for this machine doesn't know much about tolerances.    To get my MK3/S working properly, I had to shim the y axis motor, rebuild the y axis bearing holders, a tensioner on the y axis belt, and it's a good thing I had a stash of metric screws and nuts.  It took a good bit of futzing to get the thing working properly. It was a good thing I had a working ancient Flashforge Creator clone to make some of the missing parts.   Oh, and the Einsy board was bad, and I needed some additional parts from Prusa.  All in all, not a great experience.  Probably should have ordered the assembled printer, not the kit.  I am not a fan of belt-driven mechanisms.  Many years ago, I helped design flat-bed plotters, and we used flexible steel cables to drive the axis and big Slo-Syn servo motors.  I could go on, but suffice to say I am not impressed.  Perhaps my next printer will be a modified  Creality CR10V3 .

Anyway, I'll try the profiles.  I do my design using Alibre Design Expert.  It's expensive, but it works.  Not as good as Solidworks.

 

Posted : 18/09/2020 12:21 am
bobstro
(@bobstro)
Illustrious Member
Posted by: @stl

[...] I took a look at some of your notes, and disagree with you about Prusa and the textured sheet.  I have both the textured sheet, and adjusted the z adjust to PETG sticks to the textured sheet, but PLA absolutely will not.  For PLA I use a smooth steel sheet with a PEI sheet attached to it (I got it on Amazon when Prusa was out of them).

I had major issues with the textured sheet with any material. I think we had somewhat similar experiences, except mine was more extreme. I shipped my textured sheet to @vintagepc and he ran a series of tests confirming that there were measurable differences in adhesion between my sheet and others, so it seems to be a batch thing.

 PLA works fine with that, but if I try to use that for PETG, PETG sticks too much on that sheet and it is difficult to get the parts off  (I had to use a hammer on some parts). 

I've had good luck using Windex on the smooth PEI per the Prusa user guide before printing with PETG. A few wipes with the fingers is usually effective in a pinch. The only exception has been high-temp (270C) PETG which requires glue stick or other release agent to remove from the smooth PEI.

The .4mm nozzle works great for both PLA and PETG.  I don't think I'll be useing PLA very much because PETG has better physical characteristics.

That will depend a lot on what you want to print. I quite like PETG, but it's much trickier with supports and for fine detail like miniatures. Great for PPE and big functional parts though.

Regarding Prusa and his printers.  What I have found is that whoever designs the plastic parts for this machine doesn't know much about tolerances. 

And yet they tend to be among the most precise consumer-grade printers out there. This is a "put your money where your mouth is" issue for me. I compare the prints I get on my Prusa to those I see others getting as well as my own Sidewinder, and the tolerances on the Mk3 are much better. I can print tolerance tests that function with 0.15mm clearance on my Mk3, yet struggle getting to 0.2mm on the Sidewinder. Not to say it couldn't be better, but it's pretty damned good for off-the-shelf stuff. Whoever engineered it managed to put something affordable together that gets me where I need to be.

To get my MK3/S working properly, I had to shim the y axis motor, rebuild the y axis bearing holders, a tensioner on the y axis belt, and it's a good thing I had a stash of metric screws and nuts.  It took a good bit of futzing to get the thing working properly. It was a good thing I had a working ancient Flashforge Creator clone to make some of the missing parts.   Oh, and the Einsy board was bad, and I needed some additional parts from Prusa.  All in all, not a great experience.  Probably should have ordered the assembled printer, not the kit.

Since it was my 1st, I went with an assembled Mk3. Working on that for 18 months prepared me well for all the issues I've had with the Sidewinder. I think that'll cost me as much as my Mk3 before too much longer! By all accounts, the Prusa kits are good, but much like my textured sheet, some turds are bound to get through.

 I am not a fan of belt-driven mechanisms.  Many years ago, I helped design flat-bed plotters, and we used flexible steel cables to drive the axis and big Slo-Syn servo motors.  I could go on, but suffice to say I am not impressed.  Perhaps my next printer will be a modified  Creality CR10V3 .

Interestingly, I was reading up on a highly touted kit recently, a low production design (can't think of the name) with very nice linear rails, the works. They have an option to upgrade from lead screws to a belt driven Z assembly. I think it's a question of how it's all assembled in the end. I've yet to buy a printer that printed better because of the label on the front! I've seen Enders print nicely and Prusas suck. 

Anyway, I'll try the profiles.  I do my design using Alibre Design Expert.  It's expensive, but it works.  Not as good as Solidworks.

Don't know it. Now that Fusion 360 is getting to be a drag, I'm looking at options. Not expensive ones though! Hope the profiles are helpful. Have fun with it.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 18/09/2020 12:57 am
stl
 stl
(@stl)
Active Member

Check out Alibre:  https://www.alibre.com/

It''s a parametric modeller that keeps a feature tree.  If I build my model correctly, I can go back and change an earlier feature, and it gets reflected in the model.  It also lets you set your critical dimensions as parameters.  Change the parameter, and the model reflects that change.  Also, the boolean operations make mating parts a snap.

 

On another topic, I am not sure why a belt drive is better than a leadscrew, unless the leadscrew follower isn't done properly.  If it isn't, it will wear out and get really sloppy.  That's my concern with the Prusa Followers on the Z axis leadscrews.  They should be made of nylon, not PETG.

Posted : 18/09/2020 1:14 am
bobstro
(@bobstro)
Illustrious Member
Posted by: @stl

[...] On another topic, I am not sure why a belt drive is better than a leadscrew, unless the leadscrew follower isn't done properly. 

It was offered as an optional upgrade. The description mentioned inconsistencies with bent lead screws and resulting artifacts. It's the first time I've seen that suggested. I'll update with a post once I find the link. I've got it bookmarked ... somewhere.

If it isn't, it will wear out and get really sloppy.  That's my concern with the Prusa Followers on the Z axis leadscrews.  They should be made of nylon, not PETG.

Do you mean the trapezoid nuts? Aren't they POM?

 I just stumbled on a project replacing belts with lead screws. Looks like there are a lot differing approaches. Would love to see a head-to-head comparison of the results.

This post was modified 2 months ago by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 18/09/2020 1:45 am
stl
 stl
(@stl)
Active Member

Yes, the trapezoid nuts.  They certainly look and feel like PETG, not POM.  Nylon would be better.  Ball screws and bearing followers would be even better, but would cost more.  Instead of direct drive steppers, the motors should  be servo motors and have planetary gears to give finer motion, and closed loop sensors in order to get positive position of the extruder.  But it's more expensive.   Even the expensive desktop printers are open loop.

I could go on.

One of these days, I'll build a big printer.

Posted : 18/09/2020 5:10 am
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