Printing/Modelling in scale and a few other questions

[Shagohod]

Hello everyone,

 

I did a lot of 3D modeling in the past, but mainly for video games. Ten years ago, I changed jobs and somehow dropped 3D modeling completely, even as a hobby. Now I have a 3D printer and am getting into it again.

 

Now to my questions:

-How important is polycount? Sure, it takes a bit longer to load a high-poly model into the slicer software, but does it also affect the final print? Or how the printer handles the piece?

-How do you print models in scale, let’s say 1/35? Do you use "real world" scales in your 3D program and then scale it down in the slicer software? What do you do when you can’t get your hands on measurements? Yes, I’m a noob when it comes to 3D printing. 

-I’m currently using an older version of Autodesk 3dsMax as I still had a license for it lying around (and because I’m used to it). But I see a lot of people using Autodesk Fusion or other CAD software for creating models for 3D printing. Is CAD the better choice? Or is it just a matter of personal taste?

 

I would really appreciate any answers. Thank you. 🙂

[gamblor916]

I would use a high poly model to print. More polys, more detail. As for scaling I always model at full size then I make an instance at the scale I want and export that for print. I also use 3dsmax as it's great for modeling and it's what I know. Definitely personal taste when it comes to modeling.

[Mig Eater]

The higher the poly count the better especially on larger rounded/curved surfaces. I will personally increase the poly count of a part based on its size, so if I'm making a circle that is under 1mm I'll make it 16 sided, if its over 1cm I'll make it 200 sided etc.
As an overall example I like to print 1/35 scale tanks and my 3D models can often be made from several million polygons with the most detailed one being nearly ten million.

It's best to design the 3D model in the scale/size you plan to print it in as there are limitations in how big or small you can print parts, if you design the model at 1:1 and then scale it down for printing it will be difficult to take these limitations into account and it is highly likely that you will lose detail or some parts might become unprintable. If there are parts that need to be fitted into each other (a peg an a hole etc) then you also need to take the size tolerances/variations of the printer into account. I always add a 0.1mm gap between such parts, if I dont I will need to sand down the edges of the peg and/or drill the hole larger to make the parts fit together correctly. Such fine control over the size of the parts can't be done if you need to change their scale for printing.

I have 3dsMax's scale set to 1 point = 1mm, and will convert the real life sizes down to the scale that I wish to pint at. If I dont have any overall measurements of the subject I will then try to find a single part that I can measure and then use that as a point of reference to calculate the size of the rest of the model. For example if you have a drawing of a car and you don't know its dimensions but you do know the size of the wheels, you can resize the drawing to match the wheel size and then work from that etc. On a recent project I had the opposite problem of having the overall dimensions but I didn't know the size of the individual parts, so I had to just eyeball the sizes and then compared renders of my work to the few photos that I had and then adjust as needed to try and get the size/proportions of the parts as accurate as I could.         

I started making 3D models for games too and have stuck with 3dsMax as its what I know. I think it's the same situation for a lot of other people who have learned to use CAD software as part of their job and have continued to use that knowledge for personal 3D printing. Polygonal and CAD programs use different methods to make 3D models but the resulting STL files will be pretty much the same so its really down to personal preference which one you use. 

Edited November 20, 2024 by Mig Eater

[Ebf2k]

On 11/20/2024 at 4:19 AM, Shagohod said:

-How important is polycount? Sure, it takes a bit longer to load a high-poly model into the slicer software, but does it also affect the final print? Or how the printer handles the piece?

-How do you print models in scale, let’s say 1/35? Do you use "real world" scales in your 3D program and then scale it down in the slicer software? What do you do when you can’t get your hands on measurements? Yes, I’m a noob when it comes to 3D printing. 

-I’m currently using an older version of Autodesk 3dsMax as I still had a license for it lying around (and because I’m used to it). But I see a lot of people using Autodesk Fusion or other CAD software for creating models for 3D printing. Is CAD the better choice? Or is it just a matter of personal taste?

 

I would really appreciate any answers. Thank you. 🙂

• Go for as high a polycount as you can handle with regards to file size and CPU power for slicing.  If the poly count is low, in extreme cases you could see those polys in the printed model.
• I always design in the scale I intend to print.  This is particularly important for smaller scales and small detailed parts.    In many cases you will need to take artistic license with the dimensions of things you are printing because of the limitations of the print medium.  It will vary depending on the printer, resin, orientation, etc. but you will soon find the limitations of your printer set up.  For example, I tend to make any free-standing details, like individual bolt heads, panel gaps, etc. no smaller than 0.05mm.  For sheet like surfaces (e.g. rocket or bomb fins, stabilizers, doors) I try to make them no thinner than 0.2mm.   If you simply scale down a full scale model in your slicer, you might have problems with the smaller features.
• Use whatever works for you.   I use Fusion360 because I primarily work on hard surface models, and I find it easy to visualize and build models using the sketch/extrude process.  It also lends itself to working off blueprints and scale drawings.   Some other people prefer other methods, and especially for things that Fusion360 isn't great at, like softer surfaces such as seat cushions, flat tires, and figures.

 

[Shagohod]

Okay, I did some test prints and printed a few simpler models. Now I'm trying to print my first "real" piece that I want to use on a scale model.

 

It turned out pretty well, except the "inner circle" isn’t completely round. What could be causing this? I printed the tire several times with different settings, but it basically stayed the same.

 

 

Thanks for any input and/or ideas.  

[Jo NZ]

I think it's because of the size of the unsupported part. As it prints it's dragging down slightly - assuming that the hole is stretched vertically. You can put longer supports in attached to the inside of the tyre, if you don't want to do more cleanup on the outside.

[Shagohod]

Thanks, this solved the issue. 

 

After successfully only printing the tire, I tried to print the whole wheel. Aaaaaand, another issue occurred:

What's that solid "plate" doing there?

 

For reference, a screenshot from Chitubox:

 

Could the hole be causing this?

Edited December 28, 2024 by Shagohod

[hendie]

I had a very similar problem when I was designing/printing my AVRO504 a few years back

 

Everything looked good in the slicer (I also use Chitubox)  - this is a view looking down inside the fuselage

 

 

 

But when I printed it, I had a phantom "plate" printed across the fuselage blocking access and leaving a very obvious  elephants foot flaw on the outside - seen here just forward of the pilots position 

 

 

this is the mystery "plate" on the inside.

 

 

Eventually, after stepping down through the slices I found this mysterious plate showing up in only a few of the slices. It was not present in the model and I couldn't edit it out, no matter what I tried

 

 

This is a link to the post in the thread and an explanation of how I eventually fixed the issue.

 

 

Basically, after a couple of false starts, I believe it was down to a corrupted stl and I had to rebuild part of the model. 

 

 

[Ebf2k]

I was just going to suggest regenerating the STL file.  I had not seen that before until last night when I went to slice a file in Chitubox.  There was this large disc shape around the entire model but only when viewing from one specific angle.  I definitely did not design that.   I just re-exported the STL and the problem went away,

 

Also, for your tire, you don't really need any supports other than those on the bottom, and especially not those on the upper face like in the screen shot.  Print the tire vertically, not on an angle,, and you should't have to support anything at all except along the bottom.  The center axle hub should print fine as well, but you could put one support near the outer edge, at the bottom of the circle if needed.  Things like the axle nut and the rim of the wheel don't need any support at all.