Unfinished Kerf

[Peter Meacham]

Another post on the forum regarding Kerf Removal prompts me to ask how engravers deal with uncut kerf on wood - this would be an unfinished vector cut on plywood, for example, due to warped wood (resulting in out-of-focus cutting).

I don't have any method of holding down warped wood to ensure in focus cutting.

Hope I am making my question clear.

Attempts to use an Exacto type knife to finish the kerf are OK, but not totally satisfactory. I have also used a Dremal tool with a small bit to finish an uncut kerf as well.

I was thinking an extreamly thin bladed saw with very little blade set, something a jeweller might use, would work if I could find such a saw blade. Such a blade would be OK for straight cuts, not so good for curve cuts.

Any thoughts or ideas on this

[john banks]

Redo the piece.

[Richard Rumancik]

Peter, John's suggestion may sound blunt but most attempts to salvage a part tend to require more effort than practicable and the end result is a poor-looking piece. For parts where appearance is an issue you end up with a mark and color difference where you cut/sanded etc. For non-appearance parts it still gives a bad impression to the customer.

You need to figure out how to deal with the warpage issue - maybe cut some stress-relief slots in the sheet before starting the vectoring and then add weight or clamp down in some way. Cutting slots will take a bit of machine time but if it results in good parts it might be acceptable.

If some parts did not cut through then I'd try to use the laser to repair them - a second pass or partial pass (before anything is moved). But it is a tradeoff between rework time and material cost. Sometimes it is worth trying to save a part, but other times it is more efficient to make a new one.

I have rarely had success with trying to salvage parts not completely cut. After spending 5 minutes trying to get it from the sheet intact I usually ended up scrapping it anyway.

I'd suggest that you focus on a procedure for making good parts instead of developing a procedure to salvage bad parts.

[Peter Meacham]

Thanks for your inputs - I think a more powerful laser is what I need...

[Larry Bratton]

No amount of power will make that wood flat. We cut a good bit of 1/4" birch plywood and I agree it can be a pain. You can complete those cuts with a scrollsaw. The design of a scroll saw will allow you to release the blade, put into the cut and finish it. Again though, you will have a difference in appearance, but it may not matter, dependent upon how it is to be finished. That and a little sanding can get you by sometimes.

[Steve Clarkson]

I'd suggest that you focus on a procedure for making good parts instead of developing a procedure to salvage bad parts.


What a great piece of advice!

Larry, yours was pretty good too ("No amount of power will make that wood flat")!

[Joe Pelonio]

I have a method that has worked. After the artwork is prepared, use the laser to mark the warped wood in a location (one or more) between the parts to be cut. Then remove it and at the marks screw it onto a thicker, flat piece of sacrificial wood. Place back into the laser and cut. The best thing, though, is to always select flat wood.

[Peter Meacham]

Again, thanks for the inputs.

My comment about a more powerful laser is because I really want a more powerful laser.

All good ideas - however, Joe's method of securing to a flat piece of sacrificial wood is great.

If I do multiple sheets of the same pattern, one after the other, which I do, I can put standoffs in clear no-cut areas underneath the sheet being cut (to keep an evaculation plenium open as I would with a cutting grid) and fasten the sheet being cut to the standoffs to flatten the sheet.

I could even have multiple sacrificial sheets to speed workflow - clear one sheet and prepare for the next cutting as another sheet is being cut.

Thanks again!!

[Rich Harman]

I use a bunch of .5" x .5" x 2" neodymium magnets doubled up in pairs to hold the piece down. I also have a .5" plate of aluminum that works well to hold pieces down. Ideally I would have several 4" x 8" .5" plates of steel to use along with the magnets. A warped piece of plywood can distort the honeycomb because the magnets pull up on it. Weights are better, no distortion.

At .5" there is plenty of clearance for the head to travel over the hold downs.

I have also made a 4" high box frame that goes under the honeycomb. This serves two purposes. One, it gets the work piece far away from the reflective table and two, I have wired the honey comb to the box frame to combat against it being pulled up by the magnets on warped plywood.

[Mike Null]

Pete

I, like you, would like to have a more powerful laser. I don't think that's in my future but in the meantime I use a chisel. I'm usually cutting 1/8" ply into squares or rectangles and if it's even slightly warped there may be spots where it doesn't cut through even with two passes. Sharp chisels will salvage the piece without any damage.