View Full Version : Scaling Issues with .stl Export

07-07-2009, 05:56 PM
Hi Everybody,

I am running Lightwave 8.5 on a Mac. It is stable, and I am able to model, texture, render images and movies no problem.

Recently, I have been asked to model items, which are out of production, or were a part of a prop item, and output to a 3D printer for replication. I have been having success on Dimension Printers Intermediate-Priced ABS Fused Deposition Modeling Output Devices of making digital files into tangible items from the Lightwave models I make.

I am running into scaling issues though. Example: I was asked to make a microphone tip a HOVI-MIX that is 1.07" inches tall, and .98" in diameter. So, I use Adobe Illustrator, draw a path, which is the profile for a radius lathe. It is very precise... I draw it 1:1 scale in Illustrator and save as a Version 8 .eps file (which, oddly, is about 4-5 versions ago).

So, I toggle to Lightwave Modeler, I use EPSF Loader, the shape comes in fine, and I use the lathe tool. I set Numeric to 120 sections. And it looks good, lots of polygons, and no smoothing in texture required (and Dimension software ignores texture smoothing). I clean out the skinny little polygons in the center, then weld the points at the top and bottom and the model is made of 4-point-polygons, or less, and I export to .stl format.

I go to the Utilities Menu, select export SHM_STL_Exporter_v1.10, and set it to "Binary" and "Intel" since the Processor in my Mac is Intel, and the Engineering Firm who print my files are using Dimension software.

Despite me drawing the lathed radius design with precision, and scaled within 1/100" of an inch... the Engineering Firm says they have to scale my files up, or scale down. The thing I drew today needed to be increased by 30X to match the 2D schematic.

Items that could affect scaling...

Is the EPSF Importer changing my scaling? Or perhaps a combination of these
- Inch to Metric conversion? Unintended.
- Mac-to-PC issues?
- EPSF Loader has a scale window that defaults to 0.01. Why?

Or is the SHM_STL_Exporter just making random sizes when converting the quad polygons to triangles?

HELP... Please. I sent 4 files today, and I think they are jacking the price a bit for schematic scale matching. I would like to provide 1:1 scale files for the Dimension to just open and print. Please view images of the items I am making...

Thanks! And you may e-mail me at [email protected] if you have answers.

Light Beams... Abound!


07-07-2009, 09:12 PM
Following is the email I sent to John:

STL files only use triangles so you don't have to be concerned about using 4 point polygons in LightWave.

The unit of measurement in the LightWave file is the meter.

You are building in LightWave with the display set to show inches. Behind the scene LightWave is storing your measurements as meters in the LWO file.

I haven't used the SHM_STL_Exporter plugin and I assume it is saving one LWO unit as one STL unit.

Different companies assume one STL unit as different units of measurement.

As the Engineering firm said they have to scale your file up by 30 times they must be using one inch as one STL unit. Ask the firm if they consider 1 STL unit is 1 inch.

There are 39.37 inches in a meter so you have to scale your LWO mesh by 39.37 to get it to the correct size in inches.


07-08-2009, 11:27 AM
Use Accutrans to rescale it 39.7 times larger as mentioned. Of course they still may have (and usually do) have problems printing files made in this way because they are almost never water tight. There is a great program that can fix that but it costs $8000 (not kidding)

They have a viewer that lets you know if it is watertight for free: