How would you go about making this?

This is a part that I plan to make, have it drawn up in Fusion 360. As I am very new to the CNC world (not design, but the making part) I am not sure how to approach this from the CAM and fixturing side of things. I have the SO3 XXL and have no means of holding parts yet (as in a sea of holes or t-track board).

Here are some questions and considerations:

  1. Would you drill the holes first and use those to clamp the part?
  2. Or make the entire part including the holes (perhaps leave just a few thou of material on the bottom to retain the part)?
  3. How would you go about setting up the CAM file (i.e. do all with a small ball end mill, except counterbore holes probably have to be done with flat-end end mill, rough first with larger end mil, finish up with small ball nose end mill, etc)?
  4. How would you go about setting up multiple items at one time?
  5. Consideration: I may leave off the top edge radius of the part and sand that by hand. It seems like that might be difficult to machine w/o a radius bit.
  6. Consideration: I will be making several of these, both a LH and RH version (they are not true opposites)

Thanks for any assistance offered.

Mount the stock firmly either with a few screws or however you feel comfortable.
Drill the two holes to the thickness of the stock, then switch to a 1/4 end mill and use that to plane the profile roughly. You could then switch to ball to make it even smoother if you wanted to.
Then switch back to 1/4" end mill to cut the part out from the stock.
You could at that point maybe use a v-bit to add chamfer to the top edge but will have to probably put the 2 screws into it to hold it still so you can remove the surrounding stock.
Sand it until round when finished.

Hi Chris,

Welcome to the team. Roger’s approach is correct but I think a little to advance for you. While I have 40+ years of machining and 20+ of CNC experience I believe in the crawl, walk run approach. My early programs dealt with a single cutter so that I could learn the machine and I also recommend that for you.

First I assume that this first part is made from wood. You can machine the entire part with a 1/4 Ball End Mill. (Go buy one now fro EBay/Amazon, about $9). Granted you cannot drill the holes complete, but you can Spot Them. And I’m sure you have a hand drill to finish drilling then. And you will mount your wood on top of a piece of sacrificial waste board so that the ball end mill can cut 1/8 deeper.

Make your stock big enough so that you can use some flat headed screws to screw the board THROUGH a piece of 1/4 waste Board and into the MDF machine backer board.

I don’t recommend double sided tape in the beginning. Also the flat head screwes will also remove the possibility of hitting something taller then your work. All part of taking it ONE STEP AT A TIME.

I also recommend that you practice on some scrap wood because you ARE going to make some mistakes. We ALL do.

As you get more comfortable with this part, you can even mill the top edge radius…eventually.

Most importantly, have fun.

Absolutely agree, have fun experimenting. Everyone has a different approach. But as you learn, remember your mistakes and think of ways around them. One thing that everyone has to learn is how to think in layers and tools. Once you think of each part as inside cut, outside cut, this tool that tool, this layer first that layer second then it becomes easier. Also another thing you may learn is don’t make the CNC machine do EVERY part of the job. Sometimes you think that is the way to go, but you soon realize it may be faster with a saw or a sander to complete the job then the CNC. CNC is great for some awesome things like engraving and VCarving text and making just about any shape, but it’s not always the fastest. Yes you could probably use an end mill to cut a piece of wood in half, but then if thats all I want to do, a cheap saw could do that in half the time and no programming involved. Same thing with shaping, a rough shape on the CNC is great, I normally follow with sanding because it’s so much faster then trying to make the cnc do it exactly smooth with the smaller ball mills.

Have fun and if you make a mistake learn from it!

Absolutely agree gents. I don’t plan to make this right out of the gate, but this is largely what I bought the rig for, along with signs and other woodworking projects. I do plan to make several test pieces first to learn the ropes. Even for this project, I will likely just make a simple 2D version of it that is only the outline so I can verify the shape. In any case, just wanted to get some feedback on how to go about this particular project though I know I am not ready to jump into just yet. Thanks!

Perhaps this will make more sense as I get into it, but how do you go about re-zeroing a new bit (Z-Axis) if none of the original material remains? Isn’t the re-zeroing exercise predicated on the original material thickness?

That is where a tool change post can help. However you can still cheat with out one. You have a few options. The best option you have would be to have some extra material left and space somewhere to touch it. Another option is to move the machine to a known height above your waste board where the original bit just touches, note the Z coordinates at that time.
Then put the new bit in and move back to the same position and when if just touches note the Z axis at that time. Subtract the 2 to get the difference and then return to Z then set 0 to the offset that you calculated. (This by the way the software does when you have a tool change post) But it works as long as you get the offset correct with the + or -. You will have to try it a few times to understand it.

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What about just zeroing the z-axis off of the tooling plate (bottom of the part) and working UP instead of DOWN for the z-offset?

you can do that as well just have to make sure you have the cam program generate the gcode accordingly.