We recently heard from one of our intrepid community members, Dave Cox, who reached out to share a guide he's written about using the Othermill and Otherplan to make mechanical prototypes using Altium. Dave is an engineer at SeeScan, a company that specializes in designing, manufacturing, and supporting diagnostic and utility-locating equipment.
We have several high-end PCB prototyping machines with features such as optical alignment, which let us make working boards down to 0.006” trace and space with 0201 parts (and a lot of hand-holding). But they're difficult and slow to use, very finicky, and often non-operational. We regularly have to try several times to get a working or acceptable board.
We bought the Othermill in order to make quick mechanical models that didn’t need to be electrically functional but that we could solder connectors to, screw into the prototype plastic enclosures, and test for wire routing and clearance.
I created this guide to take designs from Altium and create a single-sided, mechanically accurate prototype board on the Othermill. Though I haven’t tried to make two-layer boards yet, this should at least be a good starting point.
So without further ado, we present to you Dave's guide. Be sure to check out our Gerber Files guide as well as Altium's Importing and Exporting Rules as a foundation. Dave's guide summarizes his findings for designing single-sided mechanical boards with large holes and pads.
Guide to Using Altium with the Othermill
- Because changes are needed to the PCB in order to make Gerbers that will work in Otherplan, make a copy of the PCB doc and work with the copy.
- Otherplan only wants to see the board in the files — no peripheral text or measurements. On the Top, Bottom, and Board outline layers, delete anything that isn’t in the area of the board.
- After the above-mentioned clean-up, I was able to use the default Board Outline GM3 layer for a simple board outline. If this doesn’t work, you can create a board outline on a different layer by using the Place Line tool. Then import and rename this to GM1.
- In order to have clearance for the milling bit to isolate annulus around the pads, shelve the flood on any layers of interest.
- In terms of building a single-sided, mechanical model, it's easiest to use just the 1/32" flat end mill, which is 0.031”, since it's sturdy and fast-cutting.
Create Gerbers and NC Drill for Single-Sided Mechanical Models
- You'll need to create both Gerber and NC Drill files. Start with Gerbers. Use the following settings.
- Gerber settings:
- Leave the Drill Drawing and Apertures tabs as default.
- Make sure all “Other options” are off.
- Then create NC Drill file:
- Place all the files in one directory (a folder on the desktop is currently the best solution on Windows).
Start Otherplan and Mill
- Start Otherplan, specify a material of Single-Sided FR-1, and click File —> Open files.
- If all goes well, you should get a screen like this one:
- Click “Okay” and Otherplan should load and display the file.
- It’s important that you specify a Z of 0.002" in the Material Placement, so that the bit clears the aluminum machining bed. This value represents the thickness of the adhesive tape.
- Using 3M double-sided adhesive, cover the bare PCB material backside. Leave about ¼-inch extra on each side to ease removal when done milling.
- Click the Loading button in Otherplan with the covers on the Othermill, to move the machining bed to the loading position.
- Stick the FR-1 to the bed so that the left and front edges of the FR-1 overhang just beyond the left front corner of the aluminum machining bed.
- Press the board material down to adhere it to the machining bed. Return the safety window and press “Start Milling.”
I did two passes and will likely require a little X-Acto work from the back to do the final perforation of the holes and edges.
Here's the final board after a little cleanup. Obviously the lower connector is not isolated, but because I’m just using this as a mechanical, that’s fine — and I didn’t have to change bits!
Thanks so much for sharing, Dave! Do you have a tip or trick that has worked well for you? We'd love to hear about it! Always feel free to reach out at firstname.lastname@example.org.