Before I get into parts/design discussion, I’d like this subject to just sit for a bit to make sure it’s allowed to be discussed.
I think a lot of owners who do large sheet work could benefit from these.
There are a lot of options (stroke length, mounting, seal type, rigidity, etc…) and price points, as well as methods to both manually and automatically control them - Masso controllers especially would make this easy.
Depending on the stock used, they could even be modified to act as both alignment pins on the upstroke, and pneumatic hold-down clamps on the downstroke (for double acting cylinder types).
There exist 90 deg and 180 rotating pneumatic cylinders that would serve this function admirably.
I’m looking at dual action pneumatic compact cylinders at the moment for my own use. I’m open to discussion to help figure out solutions for anyone interested in participating, but I’m not looking at supplying or making kits or anything like that.
So “SDA” type in various bore and stroke are super easy to find, with either internally or externally threaded piston rods. Plain unthreaded rods seem to be custom order and heavier-duty “STA” “stopper” cylinders much more expensive - this looks to be what some bigger machines are using.
So because of the easy availability of the threaded SDA type, I was thinking of using externally threaded ones, then threading on an also readily available smooth shaft. Putting that through a metal flange of appropriate size, and mounting the whole thing so the top of the pin and flange are flush with the board when in the downward position.
I’d only been thinking about them for positioning sheets and holding with lateral force, using dogs and cams on the opposite side(s)
I like the idea of the shaft extension and flange, as I think in this application the lateral force will be the one to eliminate/reduce. If you are not using them for clamping then the extension/retraction forces are of no real consequence.
One thing I might consider is making the three parts - cylinder/extension shaft/flange - one single mountable unit. Even though my current machine has very high position repeatability, I would still want a little wiggle room to adjust the pin locations if needed in the future.
I was looking into those for another application - retracting dust shoe - and one thing to watch out for is the clearance available before and after the ‘twist’ motion as they warn about not having any force exerted during that movement.
1 Like
I just ordered a couple of samples for testing and they should be here next week - verify piston size/strength and mounting options. The two I ordered are internal thread, the external ones will be a longer lead time from overseas.
1 Like
So, wouldn’t you know it… this morning I find ready-made cylinders that satisfy the features I was trying to put together (using additional parts) with the other sample cylinders I ordered. Doh! Sometimes you have to think INSIDE the box when searching. 
I’ll post some details when I get them.
Well done.
I have been honing my search skills over the last 3 years while sourcing components for my CNC build. I have gotten much better at defining search terms/key words, but often still just get lucky.
One strategy that works for me is to initially search the images section of the search engine. I find it allows me to quickly discern if the product is what I am interested in, shows often unexpected alternatives, identifies the source (helpful as I have gotten to know which suppliers are more expensive than others, or if it may be a longer wait for overseas product), compares prices for the same products, and identifies new manufacturers I may not have known about.
Looking forward to your next update.