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Machining small laser cut peices

stephon0913

Plastic
Joined
Aug 12, 2011
Location
Portland, OR
A few weeks ago my boss decided on getting these little tabs we make laser cut instead of being machined. now we are talking 3/16 mild steel getting cut into 1" x 2" pieces. we just received the first batch in today, so now all i have to do is drill a single hole in them.now the problem lies whereas i used to stack these pieces about 5 high and drill right thru them no problem, there is multiple issues not only does the hole look horrible the holes wont consistently be in tolerance as far as position(hole diameter is fine) . ive been using a solid carbide 3 flute guhring 6.4 mm drill before plowin thru them like butter. since this change i switched to single part offsets and much lower speed and feed. seems to work fine now but its a little disappointing that this setup will take about 4+ times the amount of time as before. i have a feeling the heat from being laser cut is the problem, seems like its virtually hardening the material (work hardening). my question being is this common and will cutting out on a water jet solve this hardening issue? thanks all comments welcome:cheers:
 
Laser shouldn't have any effect on the material for more than few thou on either side of the cut.
It also wouldn't affect the location of the hole... are the parts all the same size, what about the edge of it, much taper from the kerf?
And as to the holes looking bad, its mild steel, must just a worse than usual batch of it?
 
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Some of that hot rolled and pickled steel that laser cutters like to use is the worst steel to drill. I have a local shop who sends me parts a couple of times each year to drill and tap and I have never gotten them to drill as nicely as regular CRS or the HRS that I can buy.

I suspect it is just cheap gummy steel causing your problems and I dont know if there is a good solution but if you are persistent you will likely find something that is acceptable.

Charles
 
Laser cutting steel is often dead soft - horrible to drill. That said could you not get them to cut the hole in?
 
My laser guy has been holding +-.001" on some stainless parts that I have him run, and that is over 2 years. They may be expensive and fickle, but they can hold crazy tolerances.
 
Heat from the laser is not the issue. I'd look at material first. I would also look at getting the hole lasered, although you run into issues with the pierce making the hole pretty ugly if it's close to or under material thickness in diameter. How are the parts deburred after the laser?
 
Some of that hot rolled and pickled steel that laser cutters like to use is the worst steel to drill. I have a local shop who sends me parts a couple of times each year to drill and tap and I have never gotten them to drill as nicely as regular CRS or the HRS that I can buy.

I suspect it is just cheap gummy steel causing your problems and I dont know if there is a good solution but if you are persistent you will likely find something that is acceptable.

Charles

thats exacly what it is cheap gummy steel , wants to stick to the bit and leaves naasty looking chips.
 
The lazer cutters use special steel I have tons of stuff lazered and whenever I have to machine it I have the same problems. I asked them about it and the told me it has a higher sulpher than regular steel? they gave me the name of the stuff but I forget. You are not alone sometimes they make more work.
 
the material is .187 the hole diameter is .252 lasers dont do to well when youre that close to the material thickness plus the hole finish would be horrible

We cut stuff all the time like that. I don't know what your hole tolerance is, but it's not out of the question at all. As has been suggested you could ream the hole. I also do just fine putting holes in "laser steel" with a stubby carbide drill, one shot no peck. Biggest issue would be load and unload times, make two fixtures, change one while the other is running and swap sub plates. Burr can be an issue, you can use those one shot front back deburr tools as well.
 
Laser the holes undersize and then use a ream to bring the stacks of parts up to snuff?

Agreed.

Second option would be to have the laser drill the hole, then 'redrill' the same hole 2 or 3 times. This acts like a spring pass or spark out pass on the grinder. This adds very little cycle time to a hole this size, but hole quality is vastly improved.
 








 
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