Hello all and thanks again for all the feedback, Well, to clarify a little bit more this is what I have and I what I intend to do:
I'm planning to use the router to cut just sheets of MDF and Melamine with compression toolbits mostly, and some drilling too, all carbide off course. I do have a 3 hp side blower that was used to suck wood chips from another machine. My idea was to start with that pump to see if it can handle the task. I can't try all this already because the router is almost finished but not yet. But since it's almost the end of the project I think this is the moment to start worrying about the bed subject. So basically, I will have to try the MDF spoil board without holes to see if that works and if not, just try another material not so permeable with the pellets and springs. I have several weeks yet to decide what to do. Best wishes to all! El jue, 10 jun 2021 a las 10:28, Les Newell (<les.new...@fastmail.co.uk>) escribió: > That's very good info. If you are doing mass production and starting > with blanks or pre-machined parts then pods are the way to go, no doubt. > However if you are machining parts out of sheet then you want vacuum on > the whole table. Table vacuum is generally more versatile but usually > needs some creativity when it comes to holding smaller parts. > > I see a few suggestions to skim your spoil board to improve flow. In my > personal opinion that is not always a good thing. The higher the > permeability of the board the more flow you get in exposed areas. Flow > rate and pressure drop are directly related. If you decrease the flow > rate the pressure drop across the board decreases. > Take two areas of the board, one is covered with an impermeable object > and the other is open. The open area has no limit to the available air > so the pressure drop across the board is high and the flow rate is high. > However in the case of the covered area, little or no air flows through > the covering so there is very little pressure drop across the board. > Your part sees nearly the full vacuum. > If you are cutting impermeable materials such as plastics or alubond > you want a very restrictive spoil board to reduce lost vacuum in the cut > areas. If you are cutting permeable materials such as MDF you need less > restriction in the spoil board to compensate for the flow through your > work. It's a complicated subject and the only real solution is to > experiment and see what works for your setup. > > Les > > On 09/06/2021 21:00, Todd Zuercher wrote: > > There is a wide discrepancy between the levels of vacuum that different > types of vacuum pumps and blowers can generate. Some kinds are rotary > screw pumps, liquid ring pumps, rotary vane pumps, positive displacement > blowers like a roots blower, or regenerative blowers (which are more like a > fan). You need to consider both the level of vacuum you need to attain and > the amount of air you need to move to get there. Compare a 10HP regen > blower, vs a 10HP rotary vane pump. The regen blower can move 4 times as > much air as the positive displacement vane pump. But the vain pump can > draw more than twice the vacuum level. Which would hold a part better will > depend a lot on table design and area. An open hole table with small > pockets over the holes can work very well with the blower, but the blower > will struggle trying to hold small parts on a fall board. The vane pump > would work great on closed pods and jigs or a smaller fall board, but if > the table is very large or an open flow design it won't be able to keep up > and vacuum levels could fall too low. > > > > A 5ft x 10ft fall board (sheet of MDF that has been skinned can flow > nearly 300acfm (maybe a bit more) of air when a 15inHg vaccum is applied to > it. But if you need 20inHg to hold your parts, you're going to need a much > larger and more powerful pump to get there (probably at least double). But > if you only need 10inHG the flow through the board will be much less > probably closer to 100ACFM. The greater the pressure differential the > higher the flow and leakage. This is why gasketed jigs and pods work so > much better for holding pieces. You don't have the flow to contend with, > you only need a pump capable of generating the pressure level you need and > the ACFMs of the pump are less important. > > > > Todd Zuercher > > P. Graham Dunn Inc. > > 630 Henry Street > > Dalton, Ohio 44618 > > Phone: (330)828-2105ext. 2031 > > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
