Cannot shrink drawing enough to print


Kvalve top half - 10X step 3.skp (2.2 MB)
I am a model railroader and have been using SketchUp Pro 2016 & 2017 to draw up parts which can be 3D printed. I have learned that it’s much easier to draw an item many times larger than needed and then scale the finished drawing down to the size to be printed.

The drawing I uploaded is one I drew large, but cannot shrink enough to print. I drew the part ten times as large as the real life prototype part. The scale I model in is 7/8" per foot which is one 13.7th of real size. First, I used the SketchUp “Size” utility to bring the drawing down to full size. Once the scaling frame was in place, I entered 0.1 in the “Scale” box and the drawing shrank to a full size representation of the real part. Then, I tried to repeat the process to get down to one 13.7th of full size by entering 0.073 in the “Scale” box. This yielded a bug-splat dialog box.

Next, I tried to shrink another copy of the part in a single step by entering 0.0073 in the “Scale” box and got a bug-splat.

Finally, I tried saving the full sized file to SU 2016 format and tried the process again with the same results.

The drawing I uploaded has already been shrunk to 1/10 of the size it was drawn. So, it needs to be reduced to 1/13.7 of current size to be of use for 3D printing.

Effectively, I drew the part 137 times life size. Was that too much of an expansion? Is there some specific limit to how much a drawing can be resized downward? Is there something else going on which I don’t understand? I’ll appreciate any advice I can get.


It’s not too large to scale down. You just need to do it correctly. I drew a line 12 in. long in the model space. Then I measured that line with the Tape Measure tool making sure to click at each end. I type 7/8" and hit Enter. SketchUp asks if I want to resize the model to which I agreed.

Just a note, your model needs some cleanup before it’ll be printable. Currently it won’t make a “solid” group or component.


First: Put your part in a component!
Second: Make a copy of your component using the Move tool with the ctrl modifier.
Third: Using the “Scale” tool, scale one of the components by clicking on one corner of the bounding box, then type your scale factor (.00729927 …) and hit enter.

Presto! You now have your original model and a copy at the size you want to print. When you’re ready to print, save the actual size copy and print only that.

The beauty of using components here is that any changes you make in the big part are reflected in the small part automagically!

Edit: Looks like @DaveR and I posted simultaneously. His comments regarding the need to fix your model so that it’s a “solid” are spot on!

In the future, I’d recommend drawing at a power of 10 (10, 100, 1000) of the actual size. It’s a lot easier to scale down when ready.


That little tidbit of knowledge just made my DAY! Thank you!


Okay What are you using for G-Code maker ? I use Slic3r . . And it has Scale with which I used to make a Farrari down to where ti would fit on my Printers area . . of 195 by 195 by 185 tall .( about a 6.5 inch cube ) .I use Repetier -Host to Print with . . Exported to a STI file and took it into Slic3r then scaled it down to 50 % ( took a bit of time ) and then made G-Code for the Printer
Says it will take about 2 hours to make the Red Car
Heated Bed size is 200 X 200 by 190 tall . .


@Robajohn: One caveat: This is true as long as you keep having the component instances share the same definition. This relation is severed if you apply “Make Unique” to one of them - so don’t do that!


I leverage this frequently for drawing small details. I generally start drawing at actual size. Before doing anything that would result in problems like missing edges or faces (such as Follow Me) I make a component of the geometry. Then I make a copy of the component, scale the copy up and work on it. When I’m finished with the large copy I close it and delete it. then I return to the original which has everything done to it.


Credit where credit is due department: I learned this from @DaveR!


Ah, yes. Success. I like the idea of using components. I now have a drawing with components in both the as-drawn and as-needed scales.


Note that instances of a component are created from the component’s definition every time. So, you don’t need to retain both the enlarged and the real-size instances; you can create a new instance and scale it any time you want.