Vacuum Hold down kit: Real world reviews please.

[aluomala]

I recently ordered the AR4Pro and I also ordered the vacuum hold down kit (link) - neither have arrived yet. The only concrete video evidence of this product in action I found thus far was the promotional video (YouTube video)

I come from a hobbyist background and I have tried pretty much every DIY (and commercial) solution from low-low tech (double sided tape; screwing the piece (either from top or through the side on a 45 degree angle) to the spoilboard (brass screws are good, but break very easily if you don't drill a pilot hole of suitable size and depth) to more high(ish) tech: hold down clamps; side clamps; etc.

I looked at the CNC machines by other companies that have built-in vacuum beds and the thought of buying one quickly evaporated once I saw the sticker price! Definitely for full-on production environments!

For the cost ($220CDN), I'm not overly concerned if I don't use it for every project I do, but I do have high hopes for it for things like acrylic and smaller part (i.e slightly larger than the little suction devices).

One question I do have is how smooth does the surface have to be? I saw that in the video they have (link) at the 1:30 mark they have a piece of wood placed on there that looks fairly rough (on the top) but it's impossible to know from angle if it has been machined or sanded to any degree. I have some rough cut wood that I surface planed one side to a fairly smooth surface in anticipation of using it on my Axiom with the vacuum hold down kit, just to be on the safe side.

I have a compressor that slightly exceeds the required spec's (1.5CFM of compressed air at 90PSI ). I don't want to have to buy a bigger compressor, but I might if it means that my compressor will be running non-stop (and the possible loss of vacuum could be catastrophic I image if nothing is in place to hold the item (I was thinking about always having side guides or similar just to make sure it stays in place laterally).

Anyway, I would appreciate if anybody has any real world experience with this kit.

Allan

[gerry]

I ordered a set with my machine, but haven't had time to play with it. You do have to have a pretty smooth surface for this to work reasonably. The smoother the surface, the easier it is to hold a vacuum. A planed surface should be OK.

[germanguitars]

I used the vacuum hold-down earlier today to cut out a fretboard. Instead of the pucks that came with the kit, I made a custom shaped jig for fretboard blanks. The material does need to be pretty smooth to hold a seal. I'm using a small 4-gallon compressor which does need to run most of the time while I use it. It would be annoying to do a project that took hours to machine. The Venturi device works well enough for my purposes.

[gene35146]

I tried it on several things and didnt have much luck. I have one I got from Lee Valley and it works but only went you pretty much cover the whole square. I was trying to do something smaller than the size and after readjusting the seal still didnt have much luck. My next one will have a full vacuum table, pop up pins, and a tool changer.

[Deleted]

I've seen many vacuum tables that have design issues. The strength of hold down is a function of the difference between the vacuum pressure and atmospheric pressure as well as the area under the workpiece that is subjected to that differential pressure. That is, the amount of area NOT supported by the table, so a few little grooves will provide little holding power. You want a large percentage of area under your workpiece subject to vacuum and not in contact with the workpiece. If your material is porous or you have leaky sealing then your vacuum pump needs to have a CFM rating that can overcome the leak rate.

The Axiom pucks are similar to the Rockler ones in size. They use compressed air and the venturi effect to pull a vacuum, which many others do because it's lower cost if you have a large enough compressor available, but an actual vacuum pump lets you get a higher vacuum or larger differential pressure and thus more work holding power. The downside is that you need a vacuum pump which fewer people already have unless they deal with air conditioning systems.

[aluomala]

Dec 22, 2017 11:27:34 GMT -5 @fean said:

I've seen many vacuum tables that have design issues. The strength of hold down is a function of the difference between the vacuum pressure and atmospheric pressure as well as the area under the workpiece that is subjected to that differential pressure. That is, the amount of area NOT supported by the table, so a few little grooves will provide little holding power. You want a large percentage of area under your workpiece subject to vacuum and not in contact with the workpiece. If your material is porous or you have leaky sealing then your vacuum pump needs to have a CFM rating that can overcome the leak rate.

The Axiom pucks are similar to the Rockler ones in size. They use compressed air and the venturi effect to pull a vacuum, which many others do because it's lower cost if you have a large enough compressor available, but an actual vacuum pump lets you get a higher vacuum or larger differential pressure and thus more work holding power. The downside is that you need a vacuum pump which fewer people already have unless they deal with air conditioning systems.

I think that is the million dollar question: How big is big enough? As I said, my compressor meets the minimum requirements (I originally purchased it to do hardwood flooring, so it's one of those pancake portable ones), but is that good enough? Or do I need to go out and get one of those monster sized ones? I have a feeling I might be disappointed by the vacuum hold down kit.... Although I think I will only really break it out for projects that are short(ish) in nature, like cutting acrylic, or a bunch of items out of largeish flat stock (plywood). I think I will create jigs (using friction fit wedges) for other items that can't be held down by traditional methods.

[gene35146]

I am not sure having a big compressor will help. I have a huge one that you can crank up to like 200 psi but most of the kits have a max psi so I have a regulator in front of mine as long as you have min pressure it should not matter. Again haven't been happy with result even with a big honking compressor to put on them.

[aluomala]

Dec 22, 2017 23:34:45 GMT -5 gene35146 said:

I am not sure having a big compressor will help. I have a huge one that you can crank up to like 200 psi but most of the kits have a max psi so I have a regulator in front of mine as long as you have min pressure it should not matter. Again haven't been happy with result even with a big honking compressor to put on them.

OK. That makes a certain amount of sense (the fact that they [the kits] have a max psi). Otherwise your 12"x12"x1" piece of wood might get sucked into another dimension!

For the price I paid ($220CDN) I'm not expecting miracles, and I have other alternatives (or things to augment the vacuum) in mind, so knowing ahead of time that it isn't an "all singing, all dancing" solution helps.

Thanks for the input.

Allan

[Deleted]

PSI is not normally the issue but the CFM.

[mnwoodbee]

I built my own modeled off a cnc at work. This is the 3rd time building it for 3 different machines I’ve owned. I’ve never looked back on using clamps unless it’s logical to do so, otherwise this has sped up production and even eliminated the use of tabs 90% of the time. It uses my shop Ridged vac, and holds very well- 1/8 BB to 3/4, acm, even solid glue ups to flatten. No gaskets used, but ultra lite mdf is the spoil surface.

1st version was for a 2x3 axiom
2nd for. 4x4
3rd is for my new AR 16 with minor changes to design.

Compromised of a -
-single sheet of 3/4”mdf
-Some piping/ fittings to attach shop vac hose
-Single sheet of mdf ultra lite which gives you 1 extra top for a 4x4

[gerry]

Do you realize you're responding to a 3 year old post?

[mnwoodbee]

Feb 2, 2020 13:28:47 GMT -5 gerry said:

Do you realize you're responding to a 3 year old post?

No 😆, just signed up and was surfing the topics. Thanks

[1lilkraut]

Trying to determine the height of the Axiom overhead dust arm. Ceiling height might be an issue so I want to know before purchasing.

[gerry]

Feb 29, 2020 20:38:57 GMT -5 1lilkraut said:

Trying to determine the height of the Axiom overhead dust arm. Ceiling height might be an issue so I want to know before purchasing.

Is this question related to this thread in some way?

[lesad]

Feb 29, 2020 20:38:57 GMT -5 1lilkraut said:

Trying to determine the height of the Axiom overhead dust arm. Ceiling height might be an issue so I want to know before purchasing.

Did you get this info? If not I may be able to help?

[1lilkraut]

Thanks lesad - I figured it out. Appreciate it.