Hi All,
I’m still a relatively new user. Made a pocket cut home address sign and while the letters/numbers cut itself looks good the pocket isnt very smooth. Is this an issue with leveling or perhaps the bit? I reran the Job a couple of times with limited improvement. Any suggestions would be appreciated.
How are you holding the part down ?
It seems that the part lifted somehow or your z-axis is walking a bit.
I’m using the Shapeoko essential clamps that I got with the machine. I have the CNC on a Rockler framed table with the casters locked. I did notice some movement of the table when the CNC has a more abrupt change in direction.
The MDF may be flexing as the bit cuts - an upcut bit will try to lift the stock. In particular, the problem looks worse as you move further away from the outer un-cut areas, suggesting stock movement.
You could try doing a finishing pass with a downcut bit, or use double-sided tape so the stock isn’t held only at the edges.
OR, you may have some slop (looseness) in the Z axis. With the machine powered on and the spindle off, grab the nose / collect nut and see if there is any vertical play.
The above comments are all valid. Try decreasing your step over. When the upcut bits stop to change direction the upcut bit tries to lift the material. So decrease your step over and maybe increase the feed rate. Make sure your bits are clean. As this is your first post they are likely clean but regular maintenance with bit cleaner is necessary. MDF is sawdust and glue. Glue gets on your bit when it gets heated up.
May try a down cut bit if you have one in the size you need.
What is the Depth per Pass? Max Depth?
Have you tried adjusting them to get a very shallow (effectively a finishing pass) as the last pass?
e.g., if cutting to a Max Depth of 0.5" w/ a Depth per Pass of 0.125" which results in 4 full-depth passes, instead reduce the Depth per Pass to 0.124" — four full-depth passes will still be made, but also a fifth pass which removes just 0.004" of material.
Kind of looks like the House Sign i posted on here a bit ago. Try Wills suggestion. Adjust your Depth Per pass so you get multiple cuts with the last pass being a finish cut.
Example: Max Depth 0.190 Inches
Depth per pass: 0.047 (5 Passes)
That will give you four passes for a total of 0.188
The last (Fifth) pass will be 0.002.
This should give you a smoother bottom finish.
That’s probably where I got the design idea!
Thanks for everyones input-
MyDepth per pass = 0.6. ( In retrospect perhaps this was the problem)
I’m going to rerun with the parameters suggested. I looked back at a few of my other cuts and the depth of pass is usually much lower.
Also going to try the double sided tape - I have noticed some issues with other cuts/stock and some slight movement. (No veritical play in the router and bit looks ok)
Will report back when I’ve finished the cut.
Just an update. Took the suggestions and cut was significantly better. I did have some sanding to manage in the bottom left corner of the sign buit overall I was prettty happy with the end results.
Thanks to everyone for the input.
