Facing Your Material (Otherplan Classic)
This guide refers to Otherplan Classic, OMC’s legacy application for Mac OS X. The cross-platform version of Otherplan does not include the Facing Plan feature. We recommend using Fusion 360 or VCarve to generate G-code for facing material.
Facing your material is the process of milling down the surface of the material to be as flat as possible, using a flat end mill to mill across the entire surface of the material, often in multiple shallow passes. This guide will show you the process of facing your material.
Why would you want to face your material? Because even a piece of material that looks flat may be just a little warped or bowed, which means that some areas of the material will be higher than you expect. When you mill it, your tools will cut too deep when they encounter those areas, and they may break.
This is especially true when milling harder materials and/or using smaller tools, so it’s important to make sure that the tool is removing the correct amount of material on the first pass. All subsequent passes will be correct, but the first pass can be affected by anomalies like tape thickness, burrs on the material edges, and material warping, all of which can increase the height of the material surface, causing the tool to cut too deep.
To guarantee your material surface height is correct, face your material with a 1/8" flat endmill before milling. The Othermill can mill the surface to within +/-0.001" (0.025mm), which will ensure your endmills cut at the right depth later on.
Here’s how to do it:
Enable BitBreaker Mode (Otherplan menu > Preferences > BitBreaker Mode checkbox).
From the BitBreaker menu, choose Add Material Facing Job. It will come with a 1/8" flat endmill automatically selected.
In Setup Material, make sure your material thickness is what you expect it to be.
In the material facing job plan, set your facing depth between 0.004" and 0.008", depending on how uneven the material looks. It’s often better to start with 0.004" and see how deep the tool is cutting. You can always cancel after a few passes, increase the facing depth, and start again.
Click the Start Cutting button.
Optional for advanced users: In the Advanced settings for the facing plan, change your feeds and speeds to match the advanced feeds and speeds in the guide for your material. This will make facing a lot faster. Aluminum and brass are the most important materials to face because they’re the hardest and most likely to break tools, so the advanced feeds and speeds for aluminum are shown in the screenshot below. If you’re using the alignment bracket and you get a collision warning, look to see if your material height is taller than the bracket screws. If it is, you can safely ignore the warning. Otherwise, you’ll have to remove the bracket or move your material away from it.
Once the facing plan finishes, Otherplan will automatically reduce your material thickness to compensate for the material that was removed. If there are patches on the surface where no material was removed, it’s up to you to decide whether the entire material surface needs to be uniform (which would require additional facing) or whether you just want to guarantee the maximum height of the material.
Now you can go forth and mill your material knowing that your tools are safe!