[Philosofy]

Hi everyone. I'm new to this forum, and a complete novice with regards to CNC. A friend of mine, who shares my passion for playing harmonica, bought a Sherline CNC mill some years ago. He could never figure it out, and asked me to try for him. Since I travel quite a bit, I have not had the time to spend at his house learning all the intricacies of programming the machine. (I've tried the book and manual he has: I'm not bad with computers, but I was lost.) We only want to make one thing (a harmonica comb), and it seems like it would be pretty straightforward. Here is a picture of what we want to make:


We would want to try different materials: wood, acrylic, corian, and brass. One characteristic of a good harmonica comb is that it has to be dead flat. Also, the holes need to be precise. I'm not sure the mill he has can drill the holes, but a V groove bit could be programmed to dimple the precise spots, then drilled on a drill press by hand.

How difficult is this project? Is there anyone here who can volunteer to write the code for us? I hate seeing the money my friend spent on the machine and having it sit in his garage.

[awerby]

The Sherline mill shouldn't have any trouble making that part. If the holes aren't the same size as the collets available, then you'd want to get a Jacobs chuck to hold the right size drill bit: Sherline Drill Chucks But the mill has more than enough power to drill the holes.

If you don't want to dive into CAD and CAM, this part is simple enough to hand-code. Get a piece of fine-ruled graph paper, and plot out the locations of all those slots and holes, in reference to the bottom left top corner, which you'd call 0,0,0. Touch the tip of your tool to that spot and zero all the DROs. This way, all the X and Y values will be positive, while the Z values will be negative. To make the slots, you'd put an endmill into the collet that's no wider than the slots, and move it to a location above the part. Then use the command "G01X*Y*F*" to tell it to go to a certain XY location (that's Gzero, not GO, and the * is a random value) at a certain speed denoted by the F value (go slowly at first, with feedrates about 10 ipm or less). Then move the tool down the same way (G01Z*F*) and into the first slot. If your tool is the exact width of the slot, you can do it all at once, but if it's smaller, you'll want to go in on one side, over at the end, and out the other. Repeat that for each slot. You might want to repeat this at several depths, especially if your tool is very small. The drilling can be done the same way, with a drill-bit in the Jacobs chuck. There are also special peck-drilling commands you can use, but for this it's probably not necessary.

It's important to support your workpiece properly, with a spoil-board underneath so you don't damage the mill when you cut through the part. Leave some extra material on the edges to hold it down by, using the Sherline hold-down kit, and trim it to size afterward. If the material you'd got isn't perfectly flat, you can use a fly cutter to surface it with: Fly Cutter

[691175002]

G-code is almost never shared for several reasons. It is machine, material, and cutter specific. Incorrect (or incorrectly used) g-code has the potential to do serious damage to the machine.

At some point you are going to need to learn CAD/CAM or at least basic g-code if you want to use the machine. Without a working knowledge of CNC concepts you are unlikely to be able to set up the machine for a cut even if we could provide a g-code file.

There is free software and plenty of learning material available.

[Philosofy]

The problem I have is trying to learn all this without actual access to the machine. I have the book "Table Top Machining" by Joe Martin. Are there any other good learning materials? Could I enlist the help of a high school kid in the shop program?

[Fastest1]

Everyone has given you sound advice. It will take time unfortunately.

On the other hand, what control software is the machine using? If it is Mach 3, download it to your computer. Run it as a simulation. It will give you the ability to see the part and the steps created by said GCode. Most CAD programs have the simulation too. Might be a bit early for that just yet. Awerby gave great advice on the hand coding. That is most likely the route you should take. It will give you the best understanding of GCode in the future. I can draw and generate code as a novice. I am not able to see the commands in my head by reading the code. I am better than I was and learn as I go.

Though many of us here are hobbyists, the art or profession of machining is just that, a profession. Doing something fast with a CNC is a misnomer. Doing a part multiple times accurately is a better description but that is only after many runs, corrections and adjustments to the machine and files. Wood and the Sherline will both be pretty forgiving. By all means the Sherline can handle the task. If in doubt check out "Tryally" on YouTube.

[awerby]

High school kids are not likely to be interested in writing G-code by hand, although you might find one who's good at CAD and CAM. If you want to go the hand-coding route, you're better off looking for a retired machinist.