Small parts on P2P

Using a spoilboard to solve problems of no suction with small parts. March 20, 2001

We have a P2P machine with a pod type rail system. How do you deal with small parts that do not vacuum down because they are not large enough to create the suction needed?

Also, let me know how you deal with through-line drilling, as when the drills pierce the bottom surface, you lose suction and the machine stops the program. Sometimes it is impossible to move the vacuum pods where they do not cross the drilling line.

Forum Responses
I sometimes use a spoilboard. Often I use a piece of 1/4 melamine with a gasket around the perimeter of the part, to accomplish what you are talking about. Depending on the quantity of parts, this may or may not be cost efficient.

I know the smallest cabinet that I can process on my P2P without having to jump through hoops, and try to design around those parameters. If I positively have to have something smaller, I price accordingly.

One problem you may encounter with the spoilboard option is horizontal boring. You will need to do some setup and measuring, and keep an eye on your horizontal holes to ensure that they are staying in the same location as the gasket material keeps compressing. Also, if you are going to be running the same parts over and over, make a 3/4 thick spoilboard with laminate on both sides and edgebanded--this will help maintain a constant size.

Another option with through bore holes if you will miss the vacuum cup but still hit the pod is to drill part of the way on face 5, and then drill the rest of the way on face 6. The main thing is, of course, positioning. It can be done, but it can be difficult to get the things positioned correctly. Keep in mind that if you are off .1mm, its going to show up in the holes.

Brian Personett, forum technical advisor

We use spoilboards every day for drawer box parts. You will have to experiment with the size hole you drill on the spoilboard--this is tricky as far as adequate suction is concerned. We have also used C Clamps on certain occasions to clamp a part down to a spoilboard. You better make sure you know where the tool is going when you do this, otherwise it's going to be expensive. Seems like a single 1/8" hole works best per vacuum pod and the gasket area needs to be as large as possible to allow as much surface area as possible to suck with.

When routing small parts that are difficult to hold down, we typically leave 2-3mm without going through, using a 3/4 downspiral bit. We then take a 1/2" bearing router bit and hand route out the rest of the part. You would be surprised at the small parts we produce on our machine with this method.

As for holding down parts where you drill through on system holes, we do not drill completely through because this would require a through-bore bit, and unless you have several tooled up in a row, you will have several plunges for the entire row of holes. We mirror those parts, but it sounds like your parts are too small to be held by the small set of cups on your machine. Or do you even have them? Your only solution is to make a spoilboard.

If you are doing solid wood parts, you can route almost all the way through, leave 1/32 or less, then run through a wide belt sander. We also use the hand held router.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
When I have small parts to cut, I usually do what is called onion skinning. This is done by making a few passes at different depths each time (i.e. for a 1/2" thick piece, I may make the fisrt pass at 1/4" deep, a second pass at 15/32" deep, then cut through on the final pass). The disadvantage to this is the time involved to make the extra passes, but for me the time is better than useless parts.

Comment from contributor B:
To address the problem of machining small parts on a pod system PTP 5 axis machine, I have used a few different tricks, depending on the part and the machine limits/capabilities.

On a machine that had square pods with round suction cups that required the material to be at least 125mm wide to get suction if based of the rail and I had to run narrower parts, I would use a spacer rail between the rail and the part. Then remove the spacer after suction if I needed to machine the back edge (against the rail) before running.

If the part was actually smaller than the minimum width of the suction cup itself, I used what we called a form board. Like a router that uses form boards instead of suction pods, I used that tactic.

I machined a form board with the pattern of the parts, but only about 1-3mm deep in the form board, then bradded stops onto the form board judging by the outline that I machined. If I have to machine all 4 sides, then the parts need to be rough sized to allow the router bit to miss the stops so it is reusable.

Then I drill holes the form board to mate up with the suction cups in places that will not be drilled/routed through by the program. Then apply regular 1/8 weather stripping to the form board, tracing the inside of the outline that I routed 1-3mm deep to hold the part down. These form boards can be used repeatedly if stored properly (reduce warping to maximize suction and life).

Sometimes I've had to "lie" to the tooling and head configuration files to get the edgebore to drill deep enough on the back edge(against the rail). I have also extended the drill bit by their length adjusting screw in the rear of the bit and by using adapters between the collet and bit to extend their length.

To get a lateral boring tool to go deep enough on the edge of the board that is away from the edge (5 axis), I have "lied" to the program by telling it that the piece being machined is smaller than it actually is on some machines that drop the lateral boring tool directly above the point that it is about to bore. If the machine drops the tool then moves to position, then this isn't recommended.

I have run into limitations with this technique. The smallest width of the board that you can "lie" to the machine is equal to or greater than the distance from the rail to the farthest vertical hole from the rail.