Low-End Options for Bleed Board Vacuum

      A small bleed-board parts hold-down setup for occasional use can be practically powered using shop vacuums. September 3, 2010

I have a CNT Motion 900 5x10 CNC. Since we primarily make hardwood parts our hold down system consists of an MDF table surface and screw down pods. An SL-Laser provides the layout for pod placement. Occasionally though I want to cut some sheet stock. This can be done with pods, or carefully located screws to hold down the sheet. However I'd really like to have a bleed through system for these occasions.

I've already cut a couple 4' x 4' x 3/4" base grids and have a plan to access these two panels with 3" vacuum lines once they are set on the 5x10 MDF table. I can put either one or both 4'x 4' panels on the CNC depending upon what size material I need to cut.

The question I have is just how small a regenerative blower can I get by with for each of the 4' x 4' bleed board sections? I was thinking that perhaps two smaller blowers might be the way to go, but one large blower would be fine too. Since this isn't going to be used very often I obviously don't intend to spend $3k to $5k (or more) on a vacuum pump or regenerative blower. My pump for the pod system is a 5hp rotary vane pump that pulls 26" with a low air volume so won't work with the bleed through panels.

Forum Responses
(CNC Forum)
From contributor B:
Here's my situation, your’s may be different. I'm only cutting at 480ipm. I do all perimeter cuts in two passes, leaving a skin on the first pass, the second pass is a cleanup pass. I use lightweight MDF as a spoilboard, edges banded. Within those limits it works very well.

From contributor L:
How much vacuum you will need depends on the size of your parts. Small parts - lots of vacuum. Onion skinning works well but doubles the time. We use regular MDF, banded or painted edges. Use a 4" diameter resurfacing bit when you get too many leaks. If your drill box has Thru bore bits you will be limited to about 5/16" min. SB thickness. We run conservatively at 900"/min in 3/4" melamine using 3/8" compression spirals. Block off un-used areas of the spoil board with pieces of HPL. We have a 40hp Quincy on a 5x10’ Komo.

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