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Thread tolerances on Prusa mk3s+?  

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Armin
(@armin)
Active Member
Thread tolerances on Prusa mk3s+?

Hello, I recently bought a Prusa mkrs+ kit and I am satisfied so far. However, I am now trying to print PLA screws (diameter 7mm) with a matching nut with a layer height of 0.15mm and a 0.4mm nozzle. I've read on other forums that people only need a thread tolerance of about 0.25mm for this with Prusa mk3rs and other printers. For me it only works with about 1.3mm after I tried different sizes. What are your tolerance levels? Thanks and regards, Armin

Posted : 17/07/2022 5:03 pm
JustMe3D
(@justme3d)
Reputable Member
RE: Thread tolerances on Prusa mk3s+?

What do you need tolerances for? I construe threads (both for screws and nuts) in Fusion 360 with the standard sizes. I don´t need to set tolerances between the screw´s and the nut´s threads because these are already contained within the definition of standard threads such as metric threads.

If you print a 7mm screw I wonder what your thread distance is. E.g. an M10x1 does not make sense to be printed in .15 mm layer height as the layers will not correspond to the thread which will make the thread pretty much insufficient; printed with .10mm instead there are 10 layers from one thread to the next, meeting the exact distance; printed with .20mm there are 5 layers but the thread will be more coarse. 

Cheers

Chris

 

I try to give answers to the best of my ability, but I am not a 3D printing pro by any means, and anything you do you do at your own risk. BTW: I have no food for…

Posted : 17/07/2022 7:40 pm
Armin liked
jsw
 jsw
(@jsw)
Famed Member
RE: Thread tolerances on Prusa mk3s+?

For any close-fitting pieces, such as threads, registration pegs, rod holes, etc., trial and error is the only way to do it.

There are so many variables involved, and the only practical way is to tweak the sizing as needed for the desired fit.

Posted : 17/07/2022 8:15 pm
Armin liked
Armin
(@armin)
Active Member
Topic starter answered:
RE:

Yes, I also think that you have to try different thread tolerances. However, the difference to me is far more than a factor 5. So I think maybe I'm doing something wrong with my workflow.

I use the Bold Mesh in Blender and I haven't found any automatic thread tolerances yet, like maybe with Fusion 360.

Screw: Thread Length: 15mm, Major Dia: 7mm, Min Dia: 5mm, Pitch: 1.1mm, Crest Percent: 20, Root percent: 10, Div count: 36

Nut: Major Dia: 8.3mm, Min Dia: 6.3mm, Pitch: 1.1mm, Crest Percent: 20, Root percent: 10, Div count: 36

Prusa PLA, Prusa 0.15mm QUALITY @MK3 Setting, 0.4mm nozzle.

Stupid question, but what is the minimum horizontal tolerance for a Prusa mk3s+ with a 0.4mm nozzle? If 0.4mm then it should be 0.2mm on both sides of the thread or am I wrong? Thanks and regards, Armin

Posted : 18/07/2022 6:41 am
Neophyl
(@neophyl)
Famed Member
RE: Thread tolerances on Prusa mk3s+?

For a start up your div count , lots.  You are basically creating 36 sided circles, which is very low resolution.  You want at least 90, preferably 120 for anything even vaguely smooth.  And yeah the bolt tool in blender is not really for real world bolts, its designed for game assets and visual rendering.  Although once you have figured out the tolerances for your particular printer/filament setup it can be used. Making the threaded cross sectioned rounder can help a bit too.

I will also point out that the meshes created from the bolt tool arent particularly error free for 3d print use.

Posted : 18/07/2022 7:53 am
Armin liked
Diem
 Diem
(@diem)
Famed Member

If you need to match an existing part (eg. a screw on accessory for a workshop tool) then you are stuck with threads intended to be cut in metal.  If you are making both male and female threads there is no need to stick to standard sizes.

I find 2-3mm thread pitches much easier to work with and I tend to use slightly rounder thread profiles. With a 0.4mm nozzle tolerances down to 0.1mm are possible but I mostly use 0.125mm. Be aware that the strength of a bolt will vary depending on the orientation on the bed.

Cheerio,

Posted : 18/07/2022 11:23 am
Armin liked
hawai
(@hawai)
Reputable Member
RE: Thread tolerances on Prusa mk3s+?

I don't want to sound too smartarsey, but as brilliant a piece of software Blender is, it is not really the right tool for technical designs.

You can still get a Fusion360 license for free if it's for non commercial use. It might seem a bit tedious to learn to use a new tool (especially after you spent the huge amount of effort needed to come to grips with Blender), but for a relative straightforward design like a bolt and a corresponding nut F360 is pretty easy to use. Just give it a shot.

Not everything is a nail, even for the most skilled hammer user 😉

 

jm0.02$

Hansjoerg

Posted : 19/07/2022 6:11 am
RussG
(@russg)
Eminent Member
RE: Thread tolerances on Prusa mk3s+?

 

Posted by: @neophyl

For a start up your div count , lots.  You are basically creating 36 sided circles, which is very low resolution.  You want at least 90, preferably 120 for anything even vaguely smooth.  And yeah the bolt tool in blender is not really for real world bolts, its designed for game assets and visual rendering.  Although once you have figured out the tolerances for your particular printer/filament setup it can be used. Making the threaded cross sectioned rounder can help a bit too.

I will also point out that the meshes created from the bolt tool arent particularly error free for 3d print use.

I was just perusing the forum and found this thread. I'm new at printing, so new I don't have my printer yet. LOL. It's been ordered. So, my question is, what is "div count", how is it adjusted, and how does somebody learn about it?

Thanks

Posted : 08/08/2022 4:37 am
Neophyl
(@neophyl)
Famed Member
RE: Thread tolerances on Prusa mk3s+?

'div count' has nothing to do with 3d printing as such. The original poster was using Blender for modelling and div count is specific to it. So unless you are also using Blender to model then its not going to mean anything. If all you are going to do is print other peoples models then you will never have to worry about any of it. If you intend to create your own designs though then its worth learning about the basics.

In general though the thing that is relevant is model resolution. Even if your CAD software models with proper arcs/curves the output of that CAD when exported to use in a slicer is made up of an approximation of those curves. Different software handles it in their own way, might be called resolution, might be segment length etc etc. There are as many terms as there are modelling programs.

Take a cylinder as an example. The circular cross section would be split into a series of short straight lines to define that circle when its created or exported. If you only have a low resolution then the circles aren't very circular. Using the Blender example a circle with a div count of 6 is actually a hexagon. Increase the div count to 8 and it becomes an octagon. Increase it to 36 and it starts to look more circular but when examined in detail you will see the faces that make up the circle/cylinder. Increase it to 120 and those faces become smaller, in effect making it smoother. Increase it to 360 and its smoother yet. Go to 960 and it looks very smooth.

You can create models with a very detailed output, unfortunately the downside of that is that they become large and use lots of memory. Some of the very large ones can cause some computers to slow down or even crash and high resolution models can cause slicers problems due to their complexity.

You want to save your designs with enough detail for the printer you intend to use. A balance between file size and detail. For example if you are modelling and printing for a filament printer like the MK3/Ender type then there's only so much detail the printer can reproduce. So having a massively detailed mesh can be over kill. However if the model is going to be printed on something like a resin printer that can handle more detail then a higher mesh density makes sense. What level of detail to use is up to the designer. You find a lot of models on the usual sites that are pretty low resolution and so can cause problems. Then again I've seen ones that have 10x more detail than even a resin printer can use which is a waste.

Posted : 08/08/2022 7:05 am
Swiss_Cheese
(@swiss_cheese)
Noble Member
RE:

Despite @neophyl's great explanation, it's even more involved then that. Once you get a 3D program of Note under your belt you will understand. AND Then after all that you will have to learn what it means to bring a model from 3D Space into the real world, That's what 3d printing is doing.

 

You have support.

 

Regards

 

Swiss_Cheese

The Filament Whisperer

Posted : 08/08/2022 7:20 am
RussG liked
RussG
(@russg)
Eminent Member
RE: Thread tolerances on Prusa mk3s+?

 

Posted by: @neophyl

'div count' has nothing to do with 3d printing as such. The original poster was using Blender for modelling and div count is specific to it. So unless you are also using Blender to model then its not going to mean anything. If all you are going to do is print other peoples models then you will never have to worry about any of it. If you intend to create your own designs though then its worth learning about the basics.

In general though the thing that is relevant is model resolution. Even if your CAD software models with proper arcs/curves the output of that CAD when exported to use in a slicer is made up of an approximation of those curves. Different software handles it in their own way, might be called resolution, might be segment length etc etc. There are as many terms as there are modelling programs.

Take a cylinder as an example. The circular cross section would be split into a series of short straight lines to define that circle when its created or exported. If you only have a low resolution then the circles aren't very circular. Using the Blender example a circle with a div count of 6 is actually a hexagon. Increase the div count to 8 and it becomes an octagon. Increase it to 36 and it starts to look more circular but when examined in detail you will see the faces that make up the circle/cylinder. Increase it to 120 and those faces become smaller, in effect making it smoother. Increase it to 360 and its smoother yet. Go to 960 and it looks very smooth.

You can create models with a very detailed output, unfortunately the downside of that is that they become large and use lots of memory. Some of the very large ones can cause some computers to slow down or even crash and high resolution models can cause slicers problems due to their complexity.

You want to save your designs with enough detail for the printer you intend to use. A balance between file size and detail. For example if you are modelling and printing for a filament printer like the MK3/Ender type then there's only so much detail the printer can reproduce. So having a massively detailed mesh can be over kill. However if the model is going to be printed on something like a resin printer that can handle more detail then a higher mesh density makes sense. What level of detail to use is up to the designer. You find a lot of models on the usual sites that are pretty low resolution and so can cause problems. Then again I've seen ones that have 10x more detail than even a resin printer can use which is a waste.

A truly awesome and very generous explanation! Thank you!

I am using FreeCAD. I will look into what settings are available to control resolution.

Posted : 08/08/2022 12:55 pm
RussG
(@russg)
Eminent Member
RE: Thread tolerances on Prusa mk3s+?

 

Posted by: @swiss_cheese

Despite @neophyl's great explanation, it's even more involved then that. Once you get a 3D program of Note under your belt you will understand. AND Then after all that you will have to learn what it means to bring a model from 3D Space into the real world, That's what 3d printing is doing.

 

You have support.

 

Regards

 

Swiss_Cheese

Understood. As a photographer who has a good grasp of the subject I know well what novices need to learn and that they have no idea what is involved. I am the novice here, learning a lot and my brain is loving it. 

Posted : 08/08/2022 1:00 pm
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