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- Route mold (roughing pass + finishing pass)
When using a router, you first make a roughing pass that removes most of the material in rough steps, then goes over and smooths it with a finishing pass (because starting with a finishing pass would take way too long)- Prepare CAM and tool
- Set finishing passes (the step size for the roughing cut should be no greater than 1/2 the diameter of the tool you're using). Make sure the step size for the finishing cut is small enough or there will be ridges (as shown in the picture below). You might have to test on a spare piece of MDF to make sure the step sizes are correct.
- Verify that the tool head would not run into the wall of the nose cone while routing (this can happen if you're cutting too steep of an angle: see images below)
- Insert tool into the router
- Attach mold to router bed. You want this to be secure because if the mold moves around while you're routing, your mold will be ruined. (if you didn't cut slots into the MDF layers before epoxying them together, add brackets so you can attach securely to the routing table)
- Zero the router (zero for router and CAM file will be different so make sure you're zeroing correctly)
- Route!
- Don't wear clothes you care about. Have vacuum ready because lots of sawdust will be generated.
- Make sure to wear safety goggles and earmuffs. It's going to be pretty noisy. Also offer earmuffs to anyone in the vicinity. Protect everyone's ears!
- Ground yourself by touching the router (but make sure not to be in the way of any moving parts) or you'll probably get shocked.
- Do a test pass offset above the mold
- MAKE SURE THE ROUTING TOOL DOES NOT CUT INTO THE ROUTER BED
- If anything goes wrong, pause if necessary (instead of stopping the router altogether, set the speed to 1% so you don't have to re-zero everything after. It won't technically be "stopped" but it will be moving very slowly so you're effectively pausing it). Or if you're panicking and don't have time to set the speed to 1%, you can also just press the E-stop button.
- Prepare CAM and tool
Mold Preparation
- Sand mold to 500-grit. Sanding takes a long time so prepare for this!
- When sanding, make sure to protect the edges of the mold with something straight like a piece of aluminum. If you don't do this, the edges will be curved and when your part comes out of the mold it will have an annoying seam that you later have to sand off.
- Wet sand mold 800-2000 grit
- Add one layer of epoxy
- Mix epoxy (slow-cure)
- Apply thick layer to the inside of the mold, the top, and sides of the mold. Let sit for 20 minutes so that it soaks into the mold. Make sure you get epoxy on the top too, but not in the alignment holes if you have them.
- Wipe excess epoxy away. If you don't wipe it well, sanding will be more difficult later.
- At least 24 hours later, sand back up to 2000 grit. Shouldn't take too long because the mold should have been very smooth before epoxy was applied in the first place.
- Wax the mold
- **Note: wax is difficult to sand off, so make sure you're ready before you apply it. (i.e. you still need to sand more epoxy, etc.)
- Using a shop towel, get a dab of Meguiar's mold release wax (or other suitable mold release wax) and apply a moderate amount to the mold (wherever you applied epoxy, so the inside, top, and sides)
- Rub in circles until there are no more streaks
- Get a fresh shop towel
- Continue to rub in small circles (this is called "buffing") until the mold is really smooth. You'll feel the resistance decrease a lot suddenly, and you'll know it's ready when it's super easy to glide the towel along the mold.
- Let the wax sit for 15 minutes if you're using Meguiar's (read instructions for different wax)
- Repeat this 4 times (so you want 5 layers of wax)
- Apply PVA film
- Using a fine-haired brush, apply PVA film to the inside, top and sides of the mold (everywhere there's epoxy and wax).
- Let sit for 20 minutes.
- **Note: be careful not to wipe any of the surface with acetone as this will dissolve the PVA film and make mold release more difficult.
