CNC Shark Forum

Hey folks - was playing with making friction top boxes, and noticed that something was really off with.. well.. something. It took a lot of sanding to get the top and bottom to fit together. Much more than I'd expect. So, I pulled out the micrometer and did some tests. Hopefully the following makes sense, and hopefully it helps point me in the direction of how to fix this:

Setup Details -
* router bit is just a standard upcut spiral 1/4" bit, 1/4" shank, brand new
* using a Shark HD510 w/ the spindle that nextwave provides
* using vcarve desktop 11.006

I did a test square - 3 inches, and the end result was almost right. 2.9975 right to left, 2.9965 top to bottom. Material is MDF

The box I'm trying to cut out is supposed to be 3 inches square, with a 1/4" lip and a 1/4" "upper lip" (i.e. where the top fits on). The measurements that result from cutting that box bottom from walnut are:

Pocket: 2.4800" left to right, 2.484" top to bottom. This is supposed to be 2.5"
Pocket + lip: 2.7285" left to right, 2.7465" top to bottom. This is supposed to be 2.75" (which would then be reduced a touch by some sandpaper)

The top's pocket which should sit over the bottom's pocket + lip is 2.7075 left to right, 2.7375 top to bottom, cut from cherry. It should be 2.75"

So, something's not right. Am I expecting too much precision from this machine? It seems like things really go off the deep end when it starts cutting the pocket for the top, though I'm surprised at the pocket bottom being .02" off as well.

Are you using climb cut or conventional cut? There is a difference on how it cuts. Check out the coupling on your y axis, make sure it's tight. check these out https://www.youtube.com/watch?v=MPsGQjjZpKE
https://www.youtube.com/watch?v=meBT2758pik&t=159s

Tony

I've used both, honestly. Was using climb when I first noticed the issue, then figured I'd try conventional to see if that would make any difference. It did not, unfortunately. I managed to lift the cnc up and check to make sure that the threaded rod that controls the Y axis wasn't loose, and all was well there.

I'm wondering if this is a software issue more than a hardware one - the 'cut a square' seems to work fine and isn't all jagged or jacked up (which is what I'd expect if one of the axis isn't moving quite right).

Is Correct Post Processor being used?

Have you Checked your post processor for the G64 tolerance setting?

I have mine set to "G64 P.005"

You also must watch your feed and speed rates with the Shark machine for they are not as rigid as some other machines out there!!!

Just my Thoughts/Opinions!!!

Sharkcutup

Well, I played around with the postprocessor settings and nothing really worked. So.. figured what the heck and tried a different bit that I had just ordered for a backup. Cut perfectly (within .01).

I'm thinking, and this is just a wild guess, that the bit I was using was perhaps too long or something and maybe had too much deflection (is that the term?) when cutting solid wood. <sigh>