I'm setting up my SCV44 and wondering how others setup and attached their spoiler board. First question is on the gasket tubing for the vac table, do I silicone seal in the channel before installing? Once I spoke with Nick last year about the board setup. That I needed to surface both sides and than silicone sealant about the edge and seal the edge of the board with lacquer. Is there anything else I need to hold done the MDF board? Sorry, last question. Do I drill small holes in rows to improve the SUCKING power.
Brian
there is a lot here to unpack, brother.
You can use the gasket material to further isolate your zones- and it works like a charm. a dab of silicone in the corners is all that's needed.
the MDF or LDF (which is even better) is factory sealed on the faces- you have to cut through that when you surface- so the air can be pulled through it... that's both sides... plus, as flat as we think MDF is, it isn't.. you'll have to go as deep as required to make sure it's flat in relation to your gantry. as an example, I shave a 32nd off for the first pass and "see what that leaves"... usually I end up shaving at least another pass to a 16th". for the first side only shave off enough to get through the factory seal... it'll be obvious to you once you get through... no more- then flip it, and this time do as many passes and as shallow of a pass as you can to make sure it's flat- really flat- and there you have it.
the sides of the MDF/LDF are not sealed.. you MUST seal them or all your vacuum will escape through the sides... contact cement works... silicone works... a few coats of latex paint works... i've even used hvac tape and that works... don't be shy with it- make sure it's sealed.
for affixing the MDF to the bed, the most secure way is with screws into the bakelite material- which is some kind of tough and will need to be pre-drilled with a smaller diameter bit... and then countersink a screw that has a dab of silicone on its threads. that is the easiest way. another way is to use the rails and clamps, but i find they can get in the way sometimes...
here is the tricky business:
you're not actually 'sucking' material down.. you're lowering the air pressure below the bed as compared to the air above it. yeah, i know, same thing- but this trick relies on volume of air not pressure- the more volume of air you can remove from underneath that MDF the bigger a hole the material you're cutting tries to fall into and the greater holding power you get- you're actually making the material 'heavier' as it falls into that void... that's what this vacuum hold down thing is all about- it's about volume removed, not a silly high negative pressure that can only be achieved when the volume being removed is slight... .. the zones are nice to have, but you may find leaving all zones open allows for greater removal of air (especially if the gasket material between zones wasn't used)... it's counter intuitive sometimes... better yet, and as a for instance- leaving the zone you're cutting in and an adjacent zone(s) open often times provides more hold down than just the one zone isolated. i had a helluva time wrapping my brain around that for the longest time..
