Levelling CNC Work Area

[Atomic_Sheep]

Hi Guys,

I have one of those Chinese 6040 machines and I made a spoilboard for it which I then levelled however I still get variation. I tried making circuit boards and in some areas of the table the variation is quite significant. My PCB was around 15cm wide and it was taking a decent chunk of material on one end and then pretty much not even skimming the surface at the other end. This is WITH the spoilboard. What am I missing? Why do I have such a warped work area even after levelling?

I have done quite a bit of work from large 12mm sheets that cover the whole work area and in some areas the 12mm depth of cut makes it all the way to the spoilboard, in other areas I need to cut the piece out with a knife. It's not a massive cut mind you, it's not like I have to cut through a mm of material, probably no more than 0.5mm but still, that's quite a lot especially for PCB making. (I did manage to find spots on the table where I could make PCBs without a problem)

Why is a levelled spoilboard producing such results?

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[CaptainVee]

If the rails are not flat/straight, the work area, and the result will never be flat either.

[RCaffin]

You are expecting stability from an MDF spoilboard on a Chinese 6040?
Good luck.

Cheers
Roger

[Atomic_Sheep]

Ok, so I guess I'll just have to live with it as it is now.

The best thing about MDF for spoilboards is that it doesn't break apart like plywood would if you sticky tape stuff to it, so it remains nice and flat in that case - lasts longer at least from what I've experienced.

[CNCMAN172]

Mount a dial indicator in the spindle and move it across the table and determine exactly what is going on with your machine. MDF is actually pretty stable provided the environment is kept at a constant temperature and the same humidity, like indoors. In a garage you can't control the humidity very well. Regardless is the MDF is dry it can be pretty stable. Also a good idea when you first start is to spray the MDF with a clear poly coating to help keep moisture from impacting the MDF. As others said the rails need to be well secured and straight and if that is all good then you should be able to level the table using shims and when you get it close then you can take a skim cut and you should be able to get it very close all the way across the table. Cutting PCB boards on a CNC table requires it to be very close to flat since you are only removing .003 to .006" of copper, so you can't have .020 to .040" difference across the table it need to be close to perfect.

Russ

[Atomic_Sheep]

Yep, I have been very impressed with MDF. For the price you pay for it, I don't think anything can beat it as a spoilboard.
Although my machine is in my bedroom, I sleep with the window open, so my room conditions equal outside conditions for 3/4 of the day. But I haven't noticed too many issues with my MDF. Have been using the same spoilboard for roughly half a year now, and it's still going strong.
All roads seemingly point to a dial indicator. Have always wanted one. It's definitely on my to do list. Need to finish my limit switches and get one of those fancy XHc Remote Pendants. Getting tired of pressing e-stop and manually moving the motors to zero and not having a reliable zero.

[CNCMAN172]

Atomic,
Yup, we all buy that stuff over time because of the costs. But, as you add them you will be happy with the investment.
Russ