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How do you draw? - T-size or larger and scale down?

Posted: Mon Jan 25, 2016 10:31 am
by DanMacK
So I'm using Sketchup and trying to draw a somewhat complex locomotive (JNR 581 series)

Do you draw your items larger and shrink them or draw them at T scale?

Just curious :D

Dan

Re: How do you draw? - T-size or larger and scale down?

Posted: Mon Jan 25, 2016 12:05 pm
by dkightley
I've heard before this method of designing something larger than is needed and then scaling down to the right scale for printing....and I've always been baffled about why this is done.

I'm not familiar with SketchUp so I have no idea whether there is a minimum resolution that shapes can be drawn in. If there is...then perhaps that's the reason why some people draw big and scale down. If not, I'm confused!

I design using actual size. My CAD package has millimetres as it's default dimension scale....so all I have to do is convert my measurements to millimetres (I'm a feet and inches person) and divide by 450 to get the correct value to use for size!

Something to bear in mind though....if you're designing for 3D printing and drawing as say x10 size, don't forget to multiply the minimum limits of the 3D printing process x10 as well!

Re: How do you draw? - T-size or larger and scale down?

Posted: Mon Jan 25, 2016 3:56 pm
by mattd10
With sketchup you can get issues drawing circles and arcs at T scale. So far I've not found a way around that. I tend to draw at 10 or 100 times the size (keeps maths simple for scaling) and then scale down. Then, as long as you then don't interfere with curves they tend to stay put.
It's not perfect and I think other software is more appropriate for T, but for simplicity sketchup is great.

Re: How do you draw? - T-size or larger and scale down?

Posted: Mon Jan 25, 2016 7:50 pm
by ivanf
I design at the scale size using blender. That saves the extra step of going round fixing all the bits that end up below the minimum size for printing.

I've been playing recently with the solidify modifier in blender - it lets you resize a bit of a model from one scale to another but keeping the wall thickness the same... so going from Z down to T it would still be printable... which is handy.

Re: How do you draw? - T-size or larger and scale down?

Posted: Tue Jan 26, 2016 11:06 am
by NeilM
Yes, working at a larger size is to get round the foibles of Sketchup. Not only the minimum size for a circle, but also the possibilty of your model developing holes in it when you save it (I think saving triggers the minumum line length/point spacing check and Sketchup just throws out anything that falls below the limits, leaving holes where they should not be).

I either just work at a larger scale or use a component to acheive the same thing. I did describe this method fully in an earlier thread, but basically start your model actual size, but before you have done much more than create a recatangle convert it to a component. Then make a copy the component. Then scale up the second component to 10x, 100x or even 1000x. Now do all your editing on the large component when you should not get a problem with size limits during design or during saving. Due to the way Skethup works the original size component will also be correct despite its size. When you are happy with your model then save into another file, delete the larger component, and you will be left with the correct size one ready for export for printing.

This does sound like a complex way round, but is actually quick and easy to do when you familiarise yourself with the process.

Re: How do you draw? - T-size or larger and scale down?

Posted: Fri Jan 29, 2016 6:03 am
by JBModels
Summary of what NeilM did (this is how he explained it earlier in detail)
Summary of what NeilM did (this is how he explained it earlier in detail)
Untitled 1.jpg (82.13 KiB) Viewed 9599 times

Re: How do you draw? - T-size or larger and scale down?

Posted: Sat May 21, 2016 6:39 am
by christspringer271
I downloaded STL first.Some information I get in instructables.