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camhguh
03-09-2012, 04:02 PM
Hi Folks

Has anyone got experience of laser cutting 10mm acrylic sheet?

Feedrates etc?


What power laser would be required (budget machine - hopefully)


We are trying to get some general idea (ok , guess) of what our maximum throughput might be on a daily basis compared to say cnc milling?

Robin Hewitt
03-09-2012, 04:53 PM
I had some 10mm PVC lasered once, the bloke said, "We can cut it, but they are going moan at me down in't shop because of the smell".

Could be a job for abrasive water jet which I have never quite figured out. The flow is easy, you simply use hdraulic pumps to move the water, but how to add the garnet? Some kind of venturi?

camhguh
03-09-2012, 05:06 PM
Thanks Robin,

yes, water jet cutting has intrigued me since i first heard about it but the machines seem expensive and then you have the abrasive material usage costs.

I did a lot of work on hydraulic production machinery at one time..injection moulding, template copying etc and the idea did pop into my head that i might be able to build one but that will have to be another project for another time i think :)

Desktop water jet cutting...way to go...

Can the abrasive be reused or does it just recycle until its no longer effective?

m.marino
03-09-2012, 06:41 PM
Having helped assemble a water-jet cutter that was used for cutting headliners for cars, I seriously doubt you could make a desktop version as just the bath depth required to absorb the stream makes that a non starter. Back to the original question of laser cutting 10mm thick acrylic, I would go with milling as the power of the laser would have to be strong enough to not only cut the acrylic but also resist the tendency of acrylic to transmit light along and across its structure. I have seen laser etching into acrylic and that works but has limits as well.

What are you using the acrylic for?
Is there another plastic that will do the job and be easier to work?
Is the possible production level high enough to offset the cost of the laser and the cooling equipment needed?
If you are looking for finished edges, is milling the item then having it flame polished by an out source or buying a unit to do that reasonable to cost?

Those are just some questions that came to mind about where you are in this project and things that you might want to look into.

Michael

Robin Hewitt
03-09-2012, 07:21 PM
Can the abrasive be reused or does it just recycle until its no longer effective?

I think someone has to empty the filter tank once a year, supposed to be one pig of a job.

I did see someone offering a gizmo that separated out the garnet from the dross but no details.

I find milling acylic requires something to get the heat out, once it starts melting the tool bit is doomed. I usually just put the suds on. Icky.

Wonder if you can get an Abrafile blade for a bandsaw? That'd do it.

m_c
03-09-2012, 08:26 PM
Wonder if you can get an Abrafile blade for a bandsaw? That'd do it.

I've cut acrylic with the bandsaw and jigsaw, and the only way I've found to avoid clogging, is to cut as hard as you physically can. By that I mean full weight behind the jigsaw, and worry about not being on the line later!

John S
03-09-2012, 08:34 PM
Hugh.
Recently bought a 40 watt unit and it will cut 10mm perspex at 1mm/sec at 100% power.
Not a bad but but a little bit of striation marks on the bottom part of the cut.

Can post a pic if you want.

camhguh
03-09-2012, 09:28 PM
Having helped assemble a water-jet cutter that was used for cutting headliners for cars, I seriously doubt you could make a desktop version as just the bath depth required to absorb the stream makes that a non starter. Back to the original question of laser cutting 10mm thick acrylic, I would go with milling as the power of the laser would have to be strong enough to not only cut the acrylic but also resist the tendency of acrylic to transmit light along and across its structure. I have seen laser etching into acrylic and that works but has limits as well.

What are you using the acrylic for?
Is there another plastic that will do the job and be easier to work?
Is the possible production level high enough to offset the cost of the laser and the cooling equipment needed?
If you are looking for finished edges, is milling the item then having it flame polished by an out source or buying a unit to do that reasonable to cost?

Those are just some questions that came to mind about where you are in this project and things that you might want to look into.

Michael

Thanks for the info on water jetting Michael! Thats out then :)

Didnt know or think there might be a the light transmission problem, never worked with plastics before this project so its a learning curve!

Production levels are unknown at this stage but we are exploring our options to try and figure out (guess) how many units we could produce on a daily/weekly basis!

We have tested flame polishing the milled edges but could not get a satisfactory finish (or even come close) using a butane blowlamp. lol

camhguh
03-09-2012, 09:40 PM
Hugh.
Recently bought a 40 watt unit and it will cut 10mm perspex at 1mm/sec at 100% power.
Not a bad but but a little bit of striation marks on the bottom part of the cut.

Can post a pic if you want.

Thanks John ! now that sounds interesting!

yes please, a pic would be nice if you have one to hand!

How expensive was the laser unit?

m.marino
03-09-2012, 09:47 PM
No I can't either and use polishing compounds to finish the acrylic I work with. Most of the folks I know who get good flame polish on acrylic are using one of two systems. The first feeds the acrylic through a machine that puts a focused flame along the edge and in a very controlled method keeps any surface or edge melting/burning from happening; the second uses A fire resistant lined edge jig that allows you to use a hand held unit to control where the flame is hitting (thereby stopping over melt or burn) and with practice they say you can get a very high quality finish that way. I can afford the equipment to do the first way and have not looked seriously in the other.

Depending on your machining I would look at doing a final pass with as large a end mill as you can use in the single flue type and that does tend to give a very high quality finish I have found. Just remember to only use Cast or it will go gooey on you every time and cost you tools and material (money). If you are using air with vacuum up pull at the milling point you would be surprised at the cutting you can do at speed. I have done DOC from .3 mm for engravings to 3 mm passes for general milling and that is without good air cooling. Just getting the feeds and speeds right with tool type can give you a lot to work with. I am working on adding air cooling as I have clients that want me working in Brass, ABS and one who is asking when I can cut 306 or 316 (not to crazy on that idea).

Hope that helps.

Michael

camhguh
03-09-2012, 10:10 PM
No I can't either and use polishing compounds to finish the acrylic I work with. Most of the folks I know who get good flame polish on acrylic are using one of two systems. The first feeds the acrylic through a machine that puts a focused flame along the edge and in a very controlled method keeps any surface or edge melting/burning from happening; the second uses A fire resistant lined edge jig that allows you to use a hand held unit to control where the flame is hitting (thereby stopping over melt or burn) and with practice they say you can get a very high quality finish that way. I can afford the equipment to do the first way and have not looked seriously in the other.

Depending on your machining I would look at doing a final pass with as large a end mill as you can use in the single flue type and that does tend to give a very high quality finish I have found. Just remember to only use Cast or it will go gooey on you every time and cost you tools and material (money). If you are using air with vacuum up pull at the milling point you would be surprised at the cutting you can do at speed. I have done DOC from .3 mm for engravings to 3 mm passes for general milling and that is without good air cooling. Just getting the feeds and speeds right with tool type can give you a lot to work with. I am working on adding air cooling as I have clients that want me working in Brass, ABS and one who is asking when I can cut 306 or 316 (not to crazy on that idea).

Hope that helps.

Michael

Yes it does indeed, thanks for the tip re single flute tooling, we have been using three and four fluted cutting bits and the finish has been dissapointing so far.

We found out about using cast acrylic the hard way! Didnt realise there was any difference to begin with but we know now! lol

John S
03-09-2012, 11:31 PM
Hugh,
Picture as promised, actually looks better in real life, more polished but the striations are still there. The other bit is 3mm and this cuts OK.
I'd imagine that 8mm will cut OK without marks but not tried it because i don't have any.


http://www.stevenson-engineers.co.uk/files/perpspex.jpg

Michael makes a good point over cast and extruded but to be honest I don't know what this material is? just some kicking about.

Laser is an A3 unit and cost 3K but you can get some from China for about 1.5K

I bought from the UK, HPC laser as I wanted UK support.

Perfectly willing to run some test pieces for you.

camhguh
04-09-2012, 12:50 AM
Hugh,
Picture as promised, actually looks better in real life, more polished but the striations are still there. The other bit is 3mm and this cuts OK.
I'd imagine that 8mm will cut OK without marks but not tried it because i don't have any.


http://www.stevenson-engineers.co.uk/files/perpspex.jpg

Michael makes a good point over cast and extruded but to be honest I don't know what this material is? just some kicking about.

Laser is an A3 unit and cost 3K but you can get some from China for about 1.5K

I bought from the UK, HPC laser as I wanted UK support.

Perfectly willing to run some test pieces for you.

Cheers John!

That gives us something to go on for comparison purposes.

If its ok with you and you have the time, we would like to arrange with you to see the unit in action so that we can get a proper understanding of whats involved in running a laser unit.

Never seen one before (except ebay pics) let alone used one!

John S
04-09-2012, 12:56 AM
No problem Hugh.
Can pick you up as before, just let me know.

They are very very easy to use, easier than a CNC mill, no tooling worries for a start. You select either engrave or cut and the speed and power and that's basically it.
One hours training is virtually all you need, after that it's a self taught learning curve of the settings for different materials but easy enough to get a library sheet printed out.

camhguh
04-09-2012, 01:51 AM
No problem Hugh.
Can pick you up as before, just let me know.

They are very very easy to use, easier than a CNC mill, no tooling worries for a start. You select either engrave or cut and the speed and power and that's basically it.
One hours training is virtually all you need, after that it's a self taught learning curve of the settings for different materials but easy enough to get a library sheet printed out.

Thats exactly what we need John....the simpler the better.... :)

Will be in contact to arrange time/date

Thanks once again!