Cutting at below 10% power.

Hi all.

I'm doing some Christmas baubles etc for my family and I'm trying not to get any laser burn..

I can cut with masking tape and it doesn't leave on burn marks on the front of the wood but it is a nightmare to peel it all off afterwards as the design is very small.

I've tried to cut at a very low power and I can get down to 8% and it looks ok even tho I haven't got masking tape on but I think it needs to be lower..

But once I go below 8% the laser doesn't fire at all..??

Can anyone help me with this please? I have a Redsail x700 and auto laser but I cannot figure out how to do it.

Thanks Callum

what material are you using we can't help with half the information. wood what kind of wood
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You're using a DC glass laser, and due to their nature (which Dave can explain better than me) they have a 'low point' at which they'll fire reliably, below that they can fire sporadically or not at all.

You've found your low point, and it's 8%. There's not much else you can do aside from buffering the beam with tape and dealing with the cleanup.

You shouldn't have a lot of burn marking at 8%. Mineral spirits or turpentine will probably clean the excess soot off, just dab a little on a rag and see what happens.

Another option is to cut faster, if you're not already at full speed.

If so, then 'loosen' your resolution ('gap' or 'scan interval' or whatever your machine calls it) -- I don't know your current setting, but as an example, if your gap is currently at .05mm, extend it to .1mm. Wood is very forgiving. You may have to bring it down to .08 maybe, but that should be as low as you need to go.

A .1mm gap will hit the wood 50% less than at .05mm which should really help with the overburn.

Not getting the tube to fire below 10% is very common, to reduce burn, you might try speeding the machine up. What focal length lense are you using? I'm wondering if you tried to use a longer focal length lense if it would reduce the power density of your output beam to an acceptable level.
Scott

One thing that helps with cleanup of intricate parts is to leave them in the laser after you cut and clean them before you move them. If you have a lot that are the same then cut them on a piece of mdf and that will help keep them in place while you clean. This may allow you to cut with higher power and faster speed AND reduce the difficulty of cleanup.

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Originally Posted by Bert Kemp

what material are you using we can't help with half the information. wood what kind of wood
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Im using 3mm clear acrylic and 3mm oak veneered birch. Sorry about the late reply. I forgot to click the "update me via email" section when I wrote the post

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Originally Posted by Kev Williams

You're using a DC glass laser, and due to their nature (which Dave can explain better than me) they have a 'low point' at which they'll fire reliably, below that they can fire sporadically or not at all.

You've found your low point, and it's 8%. There's not much else you can do aside from buffering the beam with tape and dealing with the cleanup.

You shouldn't have a lot of burn marking at 8%. Mineral spirits or turpentine will probably clean the excess soot off, just dab a little on a rag and see what happens.

Another option is to cut faster, if you're not already at full speed.

If so, then 'loosen' your resolution ('gap' or 'scan interval' or whatever your machine calls it) -- I don't know your current setting, but as an example, if your gap is currently at .05mm, extend it to .1mm. Wood is very forgiving. You may have to bring it down to .08 maybe, but that should be as low as you need to go.

A .1mm gap will hit the wood 50% less than at .05mm which should really help with the overburn.

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Thank you Kevin these are brilliant ideas!! I'm actually cutting no where near full speed.. I think on my last try I had it set to 15 or 20.. I didn't want to try any faster as I thought it might lose the quality?? But I guess it is worth a try. Also increasing the gap is a genius idea! I would of never of thought of that! I will give it a try this morning and report back. Thanks again!

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Originally Posted by Scott Marquez

Not getting the tube to fire below 10% is very common, to reduce burn, you might try speeding the machine up. What focal length lense are you using? I'm wondering if you tried to use a longer focal length lense if it would reduce the power density of your output beam to an acceptable level.
Scott

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the focal length is set at about 1/2 an inch... I use the little acrylic spacer I got with the machine to set that before I cut. Does that seem about the right length..? I keep reading and seeing things where other lasers are on 2-3mms in focal length..??

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Originally Posted by Gary Hair

One thing that helps with cleanup of intricate parts is to leave them in the laser after you cut and clean them before you move them. If you have a lot that are the same then cut them on a piece of mdf and that will help keep them in place while you clean. This may allow you to cut with higher power and faster speed AND reduce the difficulty of cleanup.

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Thanks Gary, some great suggestions there. Going to try soma others today that have been suggested and report back.

Kev is spot on about the power :)

Try using loads of fast air in the air assist, that will remove all staining if enough air is provided

OK every ones saying your cutting , but at 8% power you have to be rastering as my 60 watt needs at least 65% power to cut 3mm wood.
anyway acrylic will clean up easy with some DNA or mineral spirits. The wood if you clear coat it before rastering it to will clean up very easily with a quick wipe of DNA or mineral spirits.

Excellent answer guys.

thank you very much for your help and apologies for not using the right terminology...

heres a couple I did real quick. I clear coated this BB and rastered at 325mmps and 50% trying to get burn marks and soot. as you can see I got very little. then I cut it out at 65%pwr and 12mmps speed still very little residue or burn marks. a quick wipe with some DNA and they look pretty good.
So if your getting burn marks and lots of residue , I think theres something else going on. Most likely a focus or alignment issue.Attachment 343124Attachment 343125Attachment 343126

Im setting my focal length with the acrylic piece provided but there is a setting on the machine for setting the focal length... This is currently set at 2mm and the acrylic piece is about 12mms.. Should I change this on the machine to match??

2mm focal length does not sound correct. Are you sure it is not 2 inches (very common)?