Work surface not level half an hour after surfacing

1

Hi all,

I am looking for some wisdom as I ran into a situation that doesn’t make sense to me
I have a Pro 48x96 recently upgraded to the EX Controller with servos
The sequence of events goes like this

  1. Set work surface level a little under the spoilboard top surface (MDF)
  2. Run surfacing program with 2.5" surfacing bit (it cut a little over the whole table, I kept watching it and always saw a difference in level between the current cut and the original surface level)
  3. Checked WCS table to make sure the Z is 0 (work surface level)
  4. Run program to cut 2 big rectangles from a sheet of 1/4 plywood, origin was set at the bottom of the stock and double checked in Fusion 360 that the bottom level is stock bottom
  5. I ended up with cuts that were supposed to be all the way that had 0.5 mm left, I made the cuts with a downcut bit and then was wondering if it’s pressing the plywood into the mdf so I ran the program again with an upcut bit but it didn’t make any difference. Just to clarify, in some areas the depth was perfect so the material left was between 0 and 0.5mm

The only thing related that I found reading other posts was that MDF absorbs moisture and will not stay flat but doesn’t seem likely to happen in 30 min

Please help, I am completely clueless on what to try next
Thank you in advance for any ideas,
Cristian

PS: I tried uploading the GCODE as files but it wouldn’t let me because I’m a new user

4

I am pretty sure this is your answer right here. You’ll find with an MDF table you’ll always want to cut a bit deeper to get through your material reliably.

When I used to production but materials on MDF I could see the surface of the table raise/lower over 1mm in a day.

For through cuts like you’re doing I’d set your bottom depth .75-1mm below your workpiece to get consistent through cuts.

5

Thank you for the quick reply!

Agree, that happened to me a lot but I forgot to mention an important detail: this is with a vacuum table which I built for this exact reason so this is why I was so perplexed that it didn’t solve the problem.
I noticed that the problem was mostly in the middle-ish and them I realized that I did the surfacing with the vacuum off and that might be the problem so today I re surfaced with the vacuum on and now I get close to perfect results (I still have to lower the surface level in the config a very very small amount) all the material that was left was the same thickness and almost see through