Scaling model before or during 3D printing

jack_erhart

If anyone has had the experience of 3D printing a part they have modeled here on Onshape, I could use some advise.

I have modeled my part in full size, but need to scale the indivitual parts down for 3D printing.

There is a scale feature here in Onshape, but there are scale options within the slicer software for most 3D printing machines.

I'm curious to know, is it better to scale within Onshape, or do the scale process within the slicing software?

Appreciate your input.

michael3424

I'd probably scale the model within Onshape if it was going to be used many times by myself or sent to many others and within the slicer if it was going to be used only by myself.  Just be careful that the object isn't scaled down so much as to be unprintable.

jack_erhart

I'm modeling a full sized locomotive, and scaling it to 1/10th scale. I'm testing my finished models in the Cura slicer software. I'm exporting my model out to STL files. The full sized parts seem to come into the Cura software fine, but when I bring the same part in already scaled in Onshape, it doesn't seem to view it, or handle it the same. Which is why I asked the question. I started here where I developed the part, but I will follow up with Cura to see if it's something on their end. I'm hopeful that the question will also bring clarity to others who may be dealing with this issue also.

konstantin_shiriazdanov

STL do not carry units of measure, so this can be tbe case. I'm not familiar with the slicer you using, but can it be that it scales the model automatically for best fit into the working area you defined, and because of this you don't see the difference.

michael3424

One problem with scaling down something so large as a full-size locomotive into the work envelope of a 3D printer is that the printer resolution may not be fine enough to actually print all of your features.  For example, most printers use a 0.4 mm nozzle, which prints a layer (wall) thickness of roughly 0.4 mm.  If a feature on your full-scale model is 2 mm thick (say a window or some sheet metal) is 2 mm thick that would scale to 0.2 mm thick on a 1:10 model and the slicer may not actually print the feature since it is significantly thinner than the layer width.  Hope that makes sense.  I've been burned by that issue before when trying to 3D print embossed text and very small text ends up printing like hieroglyphics.

jack_erhart

konstantin_shiriazdanov said:

STL do not carry units of measure, so this can be tbe case. I'm not familiar with the slicer you using, but can it be that it scales the model automatically for best fit into the working area you defined, and because of this you don't see the difference.

So what format would you suggest I save my scaled models out at?

jack_erhart

michael3424 said:

One problem with scaling down something so large as a full-size locomotive into the work envelope of a 3D printer is that the printer resolution may not be fine enough to actually print all of your features.  For example, most printers use a 0.4 mm nozzle, which prints a layer (wall) thickness of roughly 0.4 mm.  If a feature on your full-scale model is 2 mm thick (say a window or some sheet metal) is 2 mm thick that would scale to 0.2 mm thick on a 1:10 model and the slicer may not actually print the feature since it is significantly thinner than the layer width.  Hope that makes sense.  I've been burned by that issue before when trying to 3D print embossed text and very small text ends up printing like hieroglyphics.

I'm modeling in full size so that I can eventually produce actual tech drawings of the locomotives I model. And I am modeling, and will be printing indiviutal parts, not the entire locomotive. Would that make any difference as to what the software sees? 

konstantin_shiriazdanov

jack_erhart said:

So what format would you suggest I save my scaled models out at?

The best would be to export in any b-rep format like .step but i think there are not much slicers which can work with it. So you should make sure that you defined correct units of measure on import STL into the slicer, and no implicit scaling is performed by the slicer.

jack_erhart

michael3424 said:

One problem with scaling down something so large as a full-size locomotive into the work envelope of a 3D printer is that the printer resolution may not be fine enough to actually print all of your features.  For example, most printers use a 0.4 mm nozzle, which prints a layer (wall) thickness of roughly 0.4 mm.  If a feature on your full-scale model is 2 mm thick (say a window or some sheet metal) is 2 mm thick that would scale to 0.2 mm thick on a 1:10 model and the slicer may not actually print the feature since it is significantly thinner than the layer width.  Hope that makes sense.  I've been burned by that issue before when trying to 3D print embossed text and very small text ends up printing like hieroglyphics.

I'm modeling in full size so that I can eventually produce actual tech drawings of the locomotives I model. And I am modeling, and will be printing indiviutal parts, not the entire locomotive. Would that make any difference as

jack_erhart

Thank you. I'm not sure how to define measurments when exporting in Onshape. I just transform the full sized pieces down to 1/10th of their original size.

Any special instruction on exporting stl files out of Onshape I should be aware of?

konstantin_shiriazdanov

The units of model representation should be set on import in slicer, i believe. If you use stl its the only option, as again - the stl file itself doesn't carry units info, and it can't be set on export in OS side.

jack_erhart

Solved the issue. I modeled in full size using imperial measurement, then scaled the model so that the largest part would fit on the printer bed. (1/10th) Then I took each part and exported it out to STL file format in MM. The slicer software, Cura only reccognizes MM, so it worked perfectly. Thanks for everyones help in working through this, and for your input.

eileen_thoe

The scaling model is a very useful tool for evaluating designs. It gives you a feel for the size and shape of an object before you even begin printing it. However, after printing, you might find that your 3D printed scale model is too big or too small.

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