I’ll start things off by stating the obvious. This is well, well, into “wrong tool for the job” territory and you would be more than justified in saying explaining that “you’re better off buying the part instead”. I’ll reiterate, but more clearly this time, this project isn’t well suited for the MPCNC. That said… We’ve all been stuck at home and bored for a while so… why not? Worst case the part can be purchased and I’ve learned what not to do
I’ve set off to make a triple tree clamp for a friend’s motorcycle. The part is roughly 260mm x 170mm x 25mm in size. Here’s what I intend to make:
We’d joked that the part didn’t look that hard to make. My bluff was called and a piece of 1" 6061 plate was dropped off the garage the next day. I took plenty of time to ensure the the machine was leveled, squared, trammed, legs dropped to the lowest level possible, spoil board surfaced, etc to give myself a fighting chance. If this is to work at all then all of those things need to be spot on. The 6061 plate was rough sawed to size and the work was held down with cap screws + t-nuts.
The rough cut stock was modeled in fusion so that I didn’t waste quite as much time cutting air. I wasn’t happy with the estimated cut time and got more aggressive with cut. I suspect that the steps visible in the perimeter of the part are from tool deflection. They’re uniformly facing away from the part with the bottom of the endmill pushed out further than the top.
Fortunately I’d left stock all of the way around sufficient to be cleaned up with a finishing pass.The camera exaggerates the steps, I swear! Things turned out about as well as I could have hoped up to this point with every dimension that I could measure being within 0.2mm.
I chose to use a 1/4" single flute cutter for the entire job. In theory I would have gotten better cuts by shortening up the machine and using cutters with less stick out but I’m not confident enough in my fixtures/indicating to do so. I was worried that I’d end up with lips half way between the part. Not great for clamping! The 1/4" endmill has held up like a champ for the tool paths that have been used thus far.
Chamers and spot drills marked out with a 90* vbit.
Drill press is much better at plunges than my router.
Where I’m leaving it for now:
I’m doing my best not to scrap the part by taking test cuts on scrap and templating out my cutting parameters in fusion before applying them to the real work piece. This just might work.
More to come…