I was cutting 1/2" plywood with a 1/8" bit on my Shark today. I have two steps: 1) v-carve lettering and 2) 1/8" end mill drilling/cutting.
When trading out bits, I didn't adjust the X/Y at all, though I did re-zero the Z, of course. In the middle of the end mill cut, the Y developed an offset. This seemed to happen a couple times over the course of the 1-hour cut, but mostly in the first 20 minutes as far as I can tell.
As a result, most of my birch cut is garbage. In the pictures below, the lettering doesn't match the holes. And the holes don't match the spokes. What am I likely doing wrong here?
edit: attached pictures correctly
Cutting offset during cut
Moderators: al wolford, sbk, Bob, Kayvon
Cutting offset during cut
- Attachments
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- It should look like this
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- But it actually looks like this
Last edited by Kayvon on Thu Dec 18, 2014 8:17 am, edited 1 time in total.
Re: Cutting offset during cut
First, the pictures you attached have some sort of malware or something with them when you open them. Please delete them from your post.
Second, make sure the first cut you are doing doesn't come close to an X or Y limit. If the machine hits the hard limit, you will have lost steps and the axis value will be reset and throw off any further cuts.
Second, make sure the first cut you are doing doesn't come close to an X or Y limit. If the machine hits the hard limit, you will have lost steps and the axis value will be reset and throw off any further cuts.
Re: Cutting offset during cut
Fixed the pictures. I didn't realize I could upload them as attachments, so I was using the first image hosting service I'd googled. No problem on my computer, by I saw the pop-ups on my tablet. All better now.
I will double-check the limits. I didn't think I was hitting anything at all--when I ran it a second time (without a bit and with the router off), it didn't seem to approach the limits. The cutting length is 18" while the machine supports ~23". The piece was properly centered. However, the offset occurs just after it finishes cutting the top-most cut of the board (on the Y end). So it's worth looking at. Any other ideas?
I will double-check the limits. I didn't think I was hitting anything at all--when I ran it a second time (without a bit and with the router off), it didn't seem to approach the limits. The cutting length is 18" while the machine supports ~23". The piece was properly centered. However, the offset occurs just after it finishes cutting the top-most cut of the board (on the Y end). So it's worth looking at. Any other ideas?
Re: Cutting offset during cut
I took another look at the setup--you're almost certainly right. Hats off to you for solving my problem. Thanks.
It turns out that "centered on the table" does not mean "centered on the cutting area" because the router is mounted on the side of the gantry. The gantry's movement is constrained about the CNC table as you'd expect (or as I'd expect, anyway), but the router can cut just over one edge of the table and go back only to within a few inches of the other edge. My material was right on the edge of this cutting area, causing two offsets to occur when the farthest cuts tried to exceed it by a half inch or so.
Lesson learned. Now I can go back to using the machine with confidence. Thanks again.
It turns out that "centered on the table" does not mean "centered on the cutting area" because the router is mounted on the side of the gantry. The gantry's movement is constrained about the CNC table as you'd expect (or as I'd expect, anyway), but the router can cut just over one edge of the table and go back only to within a few inches of the other edge. My material was right on the edge of this cutting area, causing two offsets to occur when the farthest cuts tried to exceed it by a half inch or so.
Lesson learned. Now I can go back to using the machine with confidence. Thanks again.
Re: Cutting offset during cut
Glad that worked out for you. It's a good idea to mark out the table with the limits. I have a permanent scarf board attached that keeps me within the limits.