[JerryBurks]

I don't know if this is a common thing to happen. But I have ruined a bunch of jobs with the work piece or even the waste board slipping on the smooth and slick anodized 80/20 table surface. Obviously that happens more with larger bits and higher feed rates. I can prevent this by clamping down harder but at some point the clamps with mar the wood.

Lately I have been using a few pads of non-slip shelf liner (approx 60/1000" / 1.5mm thick) between the table and the waste board and under the work piece as well. This prevents the problem but makes it harder to get an even surface because the non-slip pads compress a bit.

Is there another proven way to make sure the work piece stays put?

Thanks, JB

[Walky]

What about using some wood between the workpiece and the clamp so it won't get damaged?

Clamping wood stops near the workpiece to prevent sideways movements can work, too. Depending on the situation one or more of them can even be pre-routed in a way so they fit on the slots so it's even harder for them to move.

Maybe use a fixed stop on one side and a plunger on the other side? I mean something like this:
Rubber Cap Spindle Horizontal Push Pull 45Kg 99 lbs Toggle Clamp | eBay

Or even better: two stops and two plungers to press in both X and Y directions. Then add some way to press the workpiece down (shouldn't need much force as the sideways slipping problem would be solved).

[DonFrambach]

Lots of way to do things but what works for me is to:

1) bolt the waste board (3/4" mdf) to my aluminum slots

2) screw the workpiece to the waste board

3) leave small tabs on my workpiece that I sand off later

Here's a photo of a project that I just cut:

[aarggh]

As has been mentioned, an MDF spoliboard is the best, it protects the aluminium table from damage, and gives enough grip for machining. Another thing that works great is the cheap silicon "grip mats" from the $2 or Reject shops.

cheers,
Ian

[louieatienza]

You can try using or making cam clamps, that hold the board on the edge. Woodpeckers sells hold down clamps with rubber coated edges to help prevent slipping. For multiple copies making dedicated fixturing might make sense.

[JerryBurks]

Thanks guys for the tips!

Looks like always...the best option depends on the application.

Actually I use screws quite a bit to affix the blank to a waste board and maybe I should just bolt that down instead of using clamps. But this only works if there is some material in the blank to screw into, like if it is a cutout or has anyway some holes.

Sometimes I have already a final shape that just needs additional machining. I will try the silicone pad for that.

Otherwise a fence and cam clamps seem to be a good option but I have not tried this. Not sure how firmly the side cam clamp will hold the piece down, though.

Another thing I learned is using bronze carriage bolts for the aluminum T-slots. The steel bolts leave sometimes nicks on the inside of the T-slots that make the bolts harder to slide back and forth.

[ger21]

Otherwise a fence and cam clamps seem to be a good option but I have not tried this. Not sure how firmly the side cam clamp will hold the piece down, though.

I use cam clamps almost exclusively, with excellent results. A simple cam made of scrap pine can easily provide enough force to move my bolted down fence. I've never had a part lift in the 3 years I've been using them.

[DonFrambach]

Another thing I learned is using bronze carriage bolts for the aluminum T-slots. The steel bolts leave sometimes nicks on the inside of the T-slots that make the bolts harder to slide back and forth.

I use 1/4 20 T-bolts that I get from Woodcraft (the Rockler version don't fit well in my machine). T-bolts have a large surface area so they slide well and don't nick the soft aluminum when tightened down. Here's a photo:

[harryn]

McMaster sells sand paper in rolls with a sticky back. I have not tried it on cnc, but in manual use on my work bench I have been happy with the results.

[RomanLini]

You could try some paper masking tape layed down over the "slick" 8020 metal table (under the workpiece obviously).

That should provide a lot more grip than the slippery metal and is fairly non-invasive and easy to remove if needed.

[kinghong1970]

or spray the 80/20 surface with some plasti-dip rubber spray?