Your Printer has Poor Resolution….


I have been told this a few times when sent STL files to print but I know from printing I do for my own kits and for others `in the know”.  I now have an example to hand with the advantage of also having the original drawing to work with so this would be an opportune time to explain.

First up, what’s an STL file. Over to Wikipedia for this bit…………

Granted its a bit tricky to read but if you click on it it’ll take you to the Wiki page. The gist of  it is that it a format for 3D printers and it takes the outer skin of you model and describes it as a series of triangles.  So in your CAD program you save your model with the file extension .stl and you get a faceted version ready to load into your printer.

So here’s a very simple example of a cube. It takes very few triangle to described that. Moving onto an actual example and just doing a print straight off a supplied .STL file for a firebox you get a print like this

Its quite hard to photograph but can you see the ribbed effect along the length of the curve. When that came out of the cleaning process my thoughts were that it didn’t look right and that my printer does better than that (and has done for this customer).

Tine for a bit of an investigation. I opened the .STL file in the CAD program and viewed it as this.

The conversion for CAD format to .STl has done a fair job of converting the flat bits to triangular facets but around the curve where you could see the ribbing its done more, but not enough faceting to describe the complex curve smoothly.  I suspect the file was saved on the default settings with the user probably unaware you could change them.

Luckily, he also sent the original CAD file and this is what it should look like.

Now the trick is to up the resolution on the conversion to .STL

I use SolidWorks CAD and on the save as .STL dialogue there is an options button. Default is probably as shown on the left (but with fine ticked) and the settings I use are with the two sliders as far to the right as you like. You might think just stick them all the way to the right but there is a cost. On the default settings the file is 403Kb whilst the more you slide the right the bigger the file gets. All the way over makes the same object 29.5Mb. This is fine working all on the one PC but can be a problem if e-mailing files.

What it produces is this


Lots more triangle everywhere and very finely spaced on the all important curves. In truth this is denser than it needs to be but I did it like this to demonstrate the point.

And the print?

No sign of the ribbing on that curve.

So in short, if the print file is low resolution then so will the print be


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