We're going to machine a simple two-material sign using MeshCAM and the Nomad 883. This is a great example of a project that's simple with a CNC machine, but difficult to do by hand.
You'll learn how to do some basic editing of the toolpath parameters that are automatically generated by the Carbide Auto Toolpath.
This is a picture of what we'll be making. For size reference, it's about 3″ square and about .25″ thick.
Start with a CAD file
You can download this file from: carbidelogo.stl
It's simple enough that you may want to take the time to make something more meaningful to you as you follow along.
Load the file in MeshCAM
- Start MeshCAM
- Load carbidelogo.stl
- Select mm and click Ok
Click 3 Axis
Set the maximum machining depth
We want to cut out the whole part from our block, not just cut the top surface. Whenever that's the case, I like to change the Max Cutting Depth to force MeshCAM to cut below the bottom of the stock. This ensures that the finished part is not still connected to the rest of the stock by a thin layer of leftover material.
Click the Set Max Depth button on the left
Enter a max depth of 9 mm.
Carbide Toolpath Wizard
Click on the Tools->Carbide Auto Toolpath menu entry
- Select Wood - Hard for the material
- Select a #102 Flat cutter
- Click the Review toolpath settings option
- Click OK
Normally you'd never have to look at this screen for a simple toolpath but we want to make a few changes.
First, we want to cut out the whole part from a larger piece of material, not just cut the top surface and assume the the rest of the part is cut to the correct dimensions. By default, MeshCAM will set the area to be machined as the stock size, we'd like to machine the whole geometry.
Second, MeshCAM assumes we need a roughing toolpath to machine a lot of the material away before the the finishing pass, which is responsible for applying the final surface finish and cutting everything to final size. Since we know that there's very little material to be removed, we can skip the roughing pass to save machining time.
- In Global Parameters, select Machine geometry only
- In Roughing, uncheck Enable Roughing Pass
- Click OK
Review the toolpath and click the Save button.
To get a more intuitive understanding of MeshCAM, it's worth repeating this process without making the changes to the toolpath parameters in the last step to see how the toolpath would be different.
Select two contrasting materials
It's time to prep your stock for cutting. I chose some 3″ x .25″ walnut and some white oak veneer.
Laminate them together
Laminate the two together using an appropriate wood glue and pressure to keep the whole thing flat while it dries.
I'll admit to cheating for this tutorial — I used 3M Super 77 spray adhesive to attach the two pieces of wood. If you were to cheat too, be sure to spray both surfaces and wait 30 seconds before attaching them.
Add double side tape to back of stock
Cut the stock to length, it should be about 3″ x 3″.
Attach a couple of strips of double-side tape to the bottom of the stock. It's not necessary to cover the whole surface completely.
Tape the stock to the wasteboard in the machine
Startup Carbide Motion and Cut the Part
From here, you just need to run the toolpath "The Typical Way". This can be found in more detail at: http://carbide3d.com/docs/tutorials/1-wrench/
Zero the mill
When you set the zero on the mill, be sure to set it just inside the bottom left-hand corner of the material, on the top surface.
The finished part...
Pry the part from table
Note the edges of the wood. This is completely normal and can be cleaned up very quickly.
We like to use 3M foam sanding pads for wood finishing. For a small part like this you don't need to start coarse and work your way to fine, you can start with a fine grit.
It took less than 5 minutes to get the finish shown it in the photo.
We brushed on a quick coat of General Finishes High-Performace Polyurethane to darken the colors.
Start to finish this project took about an hour. Machining time was only about 8 minutes, the bulk of the time was taken waiting for glue and paint to dry.