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I know I haven’t posted on here for a while, but that certainly isn’t because I gave up on the project. I just had some more pressing work to attend. Recently, I finally got back to it, and I had my first two successful large scale carves! They look excellent, and I couldn’t be happier.
Now, that’s not to say that I don’t have more questions, haha. On the JP’s Woodworks sign, one issue that came up is that when the bit lifted off the surface to carve elsewhere, it didn’t ascend all the way back to zero, and thus carved shallow tracks all over the piece. I’m not sure why. I zeroed it properly (the same way I always have). I planed it down to get rid of the tracks, but I was still disappointed by the issue and can’t figure out what I did to cause it.
Secondly, I’ve noticed that I’m getting some less than accurate cutting from my machine. I discovered it while cutting fidget spinners from acrylic. The circles for the bearings have come out a hair too small or a hair too large, often with the circle slightly deformed. Any advice or tips for me?
Thanks again to all of you who have helped me so far. I am seriously loving CNCing. Now that I have a decent grasp of what I’m doing, I have so much enthusiasm for the hobby again. I very much appreciate the assistance!
I use chalk paint from Michael’s. I think it’s actually Martha Stewart brand, haha. I like chalk paint because it absorbs finish, so it blends in nicely with the finished product.
Thanks Robert! I suspected that was it. I’m using F-Engrave and UGCS. When I used Easel for other projects, I never had that issue. But, I also never touched the Z Safe in Easel. The Z Safe was set to only .04. I think I meant to set it to .4. That stinks about your router table top. I hope it wasn’t anything too expensive.
For tips, check that your belts are all properly tight, and that the set-screws on the belt pinions are tight. If you have the machine powered up, grab a pinion and try to move it - you shouldn’t be able to. If it’s got some play that’ll mess with your accuracy. This is often referred to as backlash, and it causes issues whenever an axis changes direction - the motor has to eat up the slop in the pinion or belt before the carriage starts moving again, which leads to things like ovals instead of circles.
For things being slightly too big or too small, but properly shaped, check to make sure your bits are actually the size they advertise. Some bits, particularly if they’ve been resharpened, will be a little off. There’s also the fact that wood is both porous and expands when heated. When the bit goes by, heating an area, the wood may expand, leading to wider than expected cuts. When it cools off again, the wood retracts back to shape. That’s more of an issue with softer woods. If you’re pocketing and need a precise size, leave about 1mm of material on the sides, then do a finishing pass to remove that last bit. That will help.
Great advice, guys. Thank you. I didn’t think to check the belt pinions. Will do that tomorrow. I also notices some of my v-wheels were a tad loose, so I think I might have a go at those as well. I did check the tension on the belt and tightened all of them a tad.
I hadn’t considered measuring the bit! I’ll definitely check that out as well. I think some of it might’ve been due to a dull bit. I swapped it out and got a MUCH more accurate cut.
Okay, one last thing that’s been irking me, then I promise I’ll clear the floor. How do you set up the limit switches so that they actually home to the lower left corner? I installed them at 3/4" like the assembly guides instructed, but when my machine homes, it stops a decent bit off the corner of the work area. I assume I just position the carriage where I want “home” to be and then move the bumpers against the switches, but I figured I’d check.
