Hello there. I’ve been having this problem with a 5x10 laguna cnc with 2 10HP regenerative vacuum motors. ultra light MDF spoiled board where small and fairly large pieces move when cutting. At 600 inch per min set up. Base on vortex site. Any suggestions on how to improve vacuum holding will really appreciate. Thanks.

Has this worked in the past and it is no longer working or is this something new?

Get a liquid ring Dekker of travinni ,makes a big difference.

Quicktrim is right. a liquid ring vacuum is far superior to a regenerative blower, but my guess is guy doesn't want to drop that kind of cash on his issue. I haven't priced one, but guessing a new vacuum would be in the ball park of 30k.

make sure your spoilboard edges are sealed very tight & gasket underneath is correctly installed. make sure any surface area that is not sealed by material is covered so you dont have any loss that way either.
as far as liquid ring goes i wanted 1 for 18 years. i bought the 40hp vfd model, either i dont have it set up right or it is a totally different style of vacuum. will not work good at all with ldf . was told to go to mdf & that does not work near as good as the old blower style i had. if material is really flat it does ok. if not flat it does not pull it down like the old roots blower style did. just my 2 cents worth but study real hard before making that high dollar purchase.

You have tons of vacuum with what you described.
So, the following things need to be checked.
First off like Bill asked is this a new problem or has it always been this way?
Is your spoil board clean? are you surfacing your spoil board often enough? are your vacuum pumps maintained and hoses maintained?

Really small parts will have to be onion skinned for the average cnc.

If a sheet has a bow to it and it bows away from the table on the edges then chances are it will not pull down with any type of vac.

If it bows up in the middle no problem.

I have had to make custom gasketed spoil boards or use pods when I have a particularly bowed sheet . Sometimes the forces in the material just can not be over come with vacuum and you have to get creative to cut it out in alternate ways or get another sheet .

I have exp with a dry vane Becker 10 hp and a liquid ring Dekker 20 hp so don't know about the roots type people talk about .

I use rangerboard for my spoil boards and it works pretty well .
But some materials require custom gasketing or fixtures / pods / etc...

2 10 HP regen blowers on a 5X10 is not "tons of vacuum". Regens only pull 7" to 10" vacuum best case. They are used because they are inexpensive.

It can be made to work but a liquid ring or rotary screw is better - they will pull over 20".

There are 3 types of pump - Regen, low vacuum high volume, Vane, high vacuum low volume and Liquid ring, high vacuum high flow.

What size sheets are you cutting? If 4X8 then you are losing 1/3 of the vacuum around the perimeter of the board - 32 square feet of board vs 50 square feet of spoilboard. The rest is just sucking air. Cover the open space with something.

In some certain cases LDF can work better, but 99% of the time MDF is what you need. This is an article I wrote many years ago which still holds true today. You can also run your spoil board through your edge bander with no tape to seal the edges. Just don't forget to back off your pressure wheels.
https://www.woodworkingnetwork.com/custom-woodworking/wood-cutting-shaping/Five-St
eps-to-Surfacing-a-CNC-Spoilboard-177128671.html

Agreed. Change to regular MDF and see if it's better. LDF is too porous for us.

is 1" mdf ok or does it need to be 3/4" ?

thx
mike

One inch is just as good as 3/4.