how to get precise dimensions in ReplicatorG

[Michael Shiloh]

I'm having scaling problems getting student's work from SketchUp, Maya,
and some other CAD package (Vector Works?) into ReplicatorG.

I've read the wiki and the mailing list, and I've the references to the
mm/inch settings. I have verified that we've all set that correctly.
Still bad scaling.

Long term, I would like to solve the fundamental scaling issue, but
short term, we have lots to print before an exhibition on Tuesday, so I
have a workaround that needs help:

I can use the scale tool to make things look roughly the right size, but
I'd like to be certain so I've asked my students to create a 1cm cube.

When I import their stl into RepG, I will scale their image until that
cube is exactly 1cm.

Is there a ruler in RepG so that I can verify the size of this cube
before I print, without digging through the G code?

Alternately, what is the spacing of the blue grid in RepG? I could have
my students make a cube of exactly that size.

Thanks,

Michael

[Jordan Miller]

simplest solution for you given the time crunch... use a Mac and install the free application Pleasant3D. You can enter the precise dimensions and it will auto-scale for you...

http://www.pleasantsoftware.com/developer/pleasant3d/

watch the videos to see how...

jordan

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[Greg Thorstad]

Sketchup is relatively easy to scale. You can take a measurement on any
dimension you know what the measurment should be once you have the tape on
it just type the actual measurement in the box in the bottom right hand
corner and it should ask if you want to scale the whole drawing.

If you have an stl file viewer(mini magics is a free one) you can use it get
measurements on your drawing. Then once you get into replicatorG you can do
the math on what your drawing is compared to what you thought you were
drawing was and enter the appropriate scaling factor.

I think the squares on the platform are 10 mm x 10 mm if I remember
correctly.

Greg Thorstad, B. Comm.
Thorstad Computer/Thor3d.ca/Canadian Makerbot Distributor
Box 268
Outlook, SK
S0L 2N0
306 867-9596

[Michael Shiloh]

Sorry, I guess I didn't do a good job of explaining our problem.

We know how to get very precise dimension in the authoring tool. The
trouble is when we open it in RepG it is wrong.

E.g. create an object of 3cm in SketchUp (using mm setting). Open it in
RepG and it's enormous, too big to fit on the platform.

I know how to scale in RepG but how do I measure the object to know that
I've scaled it properly?

Or, better yet, what mistake are we making that makes the object's scale
wrong in RepG?

--
Michael Shiloh
Artist, designer, tinkerer, teacher, geek
KA6RCQ
www.teachmetomake.com
teachmetomake.wordpress.com
http://groups.google.com/group/teach-me-to-make

[ddurant]

> E.g. create an object of 3cm in SketchUp (using mm setting). Open it in
> RepG and it's enormous, too big to fit on the platform.

 

Probably exported it in inches instead of mm..

 

STL files don't have a units specifier so it's sorta honor-system between the bits of software to keep the units the same. RepG (and, more importantly, skeinforge) assume everything is in millimeters, not inches.

[Doug MacDonald]

ReplicatorG has an option to switch between inches and mm.  If the part appears huge in RepG, try toggleing to the other measurment unit.  Sometimes the units just get mixed around.

 

Doug M

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[Owen M Collins]

You mentioned Vectorworks, I use that all the time. I do make sure to switch the units of the file into Millimeters before exporting as an STL. Sometimes I have forgotten to do that and it was fine. But As other people have said, STL don't have a unit specifier so keeping everything as MM makes it easier.

O.

On Feb 12, 2012, at 11:57 AM, Michael Shiloh wrote:

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[randyzimmer]

My first thought was ABS shrinkage but it sounds like you have a
tougher problem.
Is there a universal factor that covers any part and dimension for
shrinkage?

[Michael Shiloh]

We thought of that, but I double checked the units in sketchup and it
was mm.

I will do this test myself. One issue is I'm on Linux and I haven't been
able to get Sketchup to run reliably on wine, so I depend on my students
to do this portion.

[Michael Shiloh]

yeah, we tried that. interestingly neither inch-mm nor mm-inch fixed the
problem, which leads me to believe there is some other fundamental
misunderstanding we are having.

i'll keep digging.

meanwhile, i appreciate all your support and answers.

i love mailing lists, and i love the supportive communities that (often)
grow around them.

m

--

[Michael Shiloh]

the magnitude of my scaling problem is much, much greater than shrinkage.

--

[Emery Roth III]

I found specifically with the sketchup exporter I have to open the box to select what units select something OTHER than MM's click ok, open the box up again and reselect MM's.  It sounds stupid, but it works.  Also you didn’t mention which exporter you were using, try this one: http://www.guitar-list.com/download-software/convert-sketchup-skp-files-dxf-or-stl

--E

[Greg Thorstad]

What your are describing sounds weird. Maybe if you post an example stl,
what the dimensions are supposed to be and a sketchup document we can have a
look and figure it out

Greg Thorstad, B. Comm.
Thorstad Computer/Thor3d.ca/Canadian Makerbot Distributor
Box 268
Outlook, SK
S0L 2N0
306 867-9596

----- Original Message -----
From: "Michael Shiloh" <michaels...@gmail.com>

[Ethan Dicks]

I would like to know this, too. I printed out a 20mm calibration cube
out of ABS on a CupCake last week, and measured 19.66 mm x 19.80 mm
and since it was under 2% undersized, it was ABS shrinkage.

What _is_ close enough on the calibration shapes? 1%? 1.5%?

-ethan