What scale to draw an object for printing

john_sucharski

I have a question with a part I designed and am having someone print for me. The part is a cylinder 12” (1’-0”) in diameter and 4” high. I’m assuming that in On Shape I’m drawing full size and not to a scale. The printed part is for HO scale trains which is a scale of 1/87. When printed, the diameter of the cylinder at HO scale should be 1/8”. He is using Chitubox for a slicer program. I gave him the STL file of the part to the size I originally drew it. He said it was too large and tried to scale it down in Chitubox and it didn’t work too well. I then scaled the part down in On Shape using the Transform function so that it was full size for HO scale. Diameter became - 1/87 x 12 in = .1379 in. I gave him the STL file and he said the part was way too small and would need to scaled up about 250% to be close to the 1/8” diameter.

So, do I need to draw the part full size (i.e. diameter 12”0”) or full size for 1/87 scale (i.e. diameter .137”)?

Thanks in advance,

John Sucharski

edward_petrillo

250% = 2.5 times, looks suspiciously like an inch to metric conversion error

eric_pesty

If you have information on the "full size" part I would draw it full size and use a scale (in the "transform") feature at the end.
You definitely want to send something that is the size you want to get it back at (i.e. export 1:1) to avoid issues.

edward_petrillo

250% = 2.5 times, looks suspiciously like an inch to metric conversion error

eric_pesty

If you have information on the "full size" part I would draw it full size and use a scale (in the "transform") feature at the end.
You definitely want to send something that is the size you want to get it back at (i.e. export 1:1) to avoid issues.

john_sucharski

So if I understand correctly, I draw the part at full size then scale it the size I would like it printed? I will need to check to see if they guy printing for me is doing a metric conversion as he did mention he does his work in metric.

Thanks for the help.

eric_pesty

john_sucharski said:

So if I understand correctly, I draw the part at full size then scale it the size I would like it printed? I will need to check to see if they guy printing for me is doing a metric conversion as he did mention he does his work in metric.

Thanks for the help.

Yes, that would be the best approach for sure. This would guarantee that everything that is exported is the correct size.
Then the only remaining question would be making sure there isn't a unit mis-match during the import process by whoever is printing but that would be dependent on the software and process they are using (as well as the export format used) but they should be able to handle that...