My workshop neighbour has a surfboard factory with a CNC machine, he's offered to CNC my next board. His machine uses suction cups to hold the blank, I have my doubts that this will work with very breathable 13kg foam. I can just see the cutters throwing the blank across the room.
Has anybody any experience with this?

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decrepit said..
My workshop neighbour has a surfboard factory with a CNC machine, he's offered to CNC my next board. His machine uses suction cups to hold the blank, I have my doubts that this will work with very breathable 13kg foam. I can just see the cutters throwing the blank across the room.
Has anybody any experience with this?

Please ensure you have camera set up to record slinging of blank across said room.

I cut 13kg EPS on my machine almost every day, the only time we have problems is when we receive poor quality foam from our supplier.

Using a machine with a vacuum pump is a great way to check foam quality. If it doesn't stick, you have a poor bond between the beads in your blank.

Vacuum has been used by the body board industry to hold blanks+boards through the bulk of the construction for decades. Shouldnt be an issue &
agree with above, good blank=good vacuum.

Good quality tape stuck to the foam then suction onto that ?
I wouldn't think there is much push on the cutter .

good thinking Imax1, easy to test the adhesion first and apply tape if necessary. All I've got to do is figure out how to do rails in shape3D light

So does what is being said here mean better quality foam will have less air gaps and less chance of delam due to heat expansion?
Decrepit you used to be able to pay for a 1 month license on Shape3D. If you struggle with the lite version. It wasnt too much. Get a load of boards done and save the files.

I've only got one board to do. I've no idea about the foam, but that does make sense. I've seen delamns that were obviously really well wet out and the foam has failed centimetres inside the board.

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tarquin1 said..
So does what is being said here mean better quality foam will have less air gaps and less chance of delam due to heat expansion?
Decrepit you used to be able to pay for a 1 month license on Shape3D. If you struggle with the lite version. It wasnt too much. Get a load of boards done and save the files.

Possibly, there is always a reasonable amount of air in any polystyrene blank that expands & contracts with the temp. I've found the most common cause of heat induced delams are low or poor adhesion of the inside skin to the blank or moisture in the blank. Dark colours in the sun don't help either. All parts of the reason why it is so important to dry out and seal/fix a polystyrene board that has been damaged. Modern Gortex valves go along way to eliminating pressure building up in a board.

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Brent in Qld said..
>>>Modern Gortex valves go along way to eliminating pressure building up in a board.

Last time I tested one possibly 10years ago, moisture on the inside stopped it breathing for months. I advice against using them, I've repaired a couple of very well constructed boards, resin has penetrated a centimetre or more into the foam, but there's a very bad delam, starting well into the foam, these all had goretex vents, can't prove the vent was the problem, may have been lousy foam seeing how far in the resin penetrated. But I'll still always go with the standard bung.

Fair enough, will pay that scenario. Maybe dodgey blanks but certainly seen what you've point out & in bone dry boards. Can't be 100% sure but the deep separation within the blank can often be traced back to high load zones like heels or mast track. Sometimes an old impacts & point loads appear to transfer undue stress to the inner core. In essence, the blanks are not static in use and are subject to wear & tear, it's just not visible until the skin goes pop.
An advantage of the Gore-Tex valve is it considers good old human error. A reasonable amount of boards get water in them because the driver forgets to do the bung up or check if the O-ring is in working order ;-)

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Brent in Qld said..>>>
An advantage of the Gore-Tex valve is it considers good old human error. A reasonable amount of boards get water in them because the driver forgets to do the bung up or check if the O-ring is in working order ;-)

Yes it's that old trade off, a damp board because you forgot to do up the bung, or a blown bottom because you forgot to undo it. Or a complete unknown, is the vent still venting. Granted it should be if there hasn't been any damage to let water in. So it may be OK if there's a policy to replace the vent with a bung when a damaged board gets fixed. But then the owner isn't used to having to attend to the bung.