how to smooth stl before machinin

Hi. I am a complete CAD Blender novice and not very computer literate so please bear that in mind if answering.

I am using Blender to covert a 3d map from shapefile format to stl format for physical machining.

I have imported a digital terrain model/map into Blender as a shapefile. I have triangulated it and then exported as an stl file for machining.
The terrain model is now made of millions of tiny triangles, which are visible when I zoom in with an stl viewer.

I am wondering if there is a simple way to smooth the model so that the flat faces will not be visible in the finished product?
Can I increase resolution somewhere or interpolate between the faces or something? I want to make it look more natural with no straight lines visible to the eye. This applies to the output stl, not just the image visible in Blender.

If you answer, please assume that I know nothing about CAD or Blender and tell me where to find the tools I’m looking for, if they are available.

Many thanks in advance for your help.

You haven’t shown us anything so we can only guess what you have and what you want. Have you tried adding a subsuf modifier to make smaller faces. You will always have faces so you can only make them too small to be relevant http://wiki.blender.org/index.php/Doc:2.6/Manual/Modifiers/Generate/Subsurf

If you want smoother cuts on your CNC from an STL file, you need to post process the G-Code.
Here is a script that converts straight-line (g1 cuts) to g2g3 arcs.
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?LinesToArcs

Hello, blender has a “laplacian smooth”. Maybe that helps. Go to Edit mode, press w, select Laplacian smooth. In the toolbar (press “t” in the 3d viewer), options will become available, also see http://wiki.blender.org/index.php/Doc:2.6/Manual/Modifiers/Deform/Laplacian_Smooth. There are some sample pictures. There is also a free tool called meshlab (http://meshlab.sourceforge.net/) which can do a quite a lot to an stl file. Maybe it’s worth having a look at it.

It doesn’t matter what you do to an STL file in Blender or Meshlab, an STL file will still translate in point to point machining which will not be smooth. It will always have ‘facets’ or faces and the smaller you make those, the more G-code you generate and the machine just moves to more points meaning more run time.
If you do an impression from a sphere for example, it will have those faces, whereas if you supply a formula to the CNC machine it can do arcs and make the impression as if it were made from curves. That is why post processing is needed such as the script I noted.
The script takes three points for example and creates and arc out of it to make smoother machining.
I know because I am working with a local CNC machinist in bringing in files from Blender so he can machine more ‘organic’ shapes.

Thanks for the replies. Sorry to be a bit thick; I keep reading that it is possible to set the resolution (i.e face size) when exporting an stl file, but when I export I can’t find any such options. Can someone point me to the relevant options please or explain in simple terms how I go about exporting my stl with maximum resolution and minimum face size (I tried following the link pasted above but am not experienced enough to understand all the terminology).
Many thanks in advance.

I have had a look at the lines to arcs script and I am sure it will work well if I had the ability to implement it. Unfortunately it is beyond my current skill set.
I need a simple command in Blender to increase the stl resolution to the point where the flat faces are not visible on the finished model. I have looked at the link provided above about subdivide but again am struggling to implement it. I have read about resolution options that appear when you export an stl. Can anyone direct me to them please?

I have read about resolution options that appear when you export an stl. Can anyone direct me to them please?
Where have you read this ? For blender or for some other application. You mention CAD in your original post. Blender is not a CAD application so don’t confuse it with one. The size of each face in the stl export is dependant on the size of the face you see in blender. There is NO export option to change it.

You also still haven’t show us what you have or a link to your blend file.

I must have read about stl export resolutions options on a cnc forum. I don’t think it was referring to Blender in particular (it can’t have been by the sound of it).
I will try machining at current output resolution and check the result before looking further at the suggestions made above. Thanks for your help so far.
Chris

Every CNC i know of so far is stepper motor driven; there might be some using different tricks but i assume you have first. Which means your tool is transferred non linearly. Could you make an estimation what edge length on your object would be close to that tool step, set appropriate subdivision level and go from there? You can check edge lengths on N-panel in blender.
Of course, see first 2 sentences in #5.

I am slowly working my way through the various useful advice given on here. I am now playing with Meshlab (as suggested - thanks) to try and smooth my stl, but am having trouble saving changes. I am applying smoothing filters successfully to my mesh, but can’t seem to export the changes I have made. What are the steps I need to follow after applying a filter? Do I then go straight to export mesh? When I try this, the exported file has no change to original file i.e the smoothing filters have not been applied to the export. It feels like I am missing a crucial step. Any advice much appreciated (again). Sorry it’s not Blender specific question but I tried the Meshlab forum and it seems deserted.
Here is a pic of my mesh. Thanks. Chris


Meshlab 64 bit v 1.3.3BETA here. If i export obj file from blender, use different smoothing algos in Meshlab and hit Apply button on filter box
exported and in blender again imported obj looks like this: