Deep Engraving Cast Acrylic

[Jack Harper]

I am trying to quote a large job deep engraving cast acrylic. I need to go about 1/16 (.063) deep into the 1/2" thick sheet. I did a time study for my 60 watt laser and found it will take me 1979 hours of laser time to complete the 1000 sq feet needed. I tried to drop the job but the customer came back and still wants me to give them a quote. They claim sand blasting will not work because it melts the acrylic. So my question is, if I upgrade my machine to a 100 or 120 watt laser, how fast can I laser to a depth of 1/16, assuming a 300 dpi file? While normally this would depend on the laser, I think the speed would be slow enough here that most lasers would be fairly equal. If some of you with the 100 and 120 watt machines would not mind sharing this number, I would greatly appreciate the information. Thank you.

[Dave Johnson29]

I am trying to quote a large job deep engraving cast acrylic. I need to go about 1/16 (.063) deep

Hi jack,

Is this all the one depth?

Could this not be better done on a router or a CNC mill. One of my metalworking mills can cut up to 100"/sec and hold 4-tenths (0.0004") accuracy and repeatability. I have cutters up to 3" diameter for roughing.

[Scott Challoner]

What are you engraving? If it's letters or shapes, can you cut them out of 1/16" acrylic and laminate them to the 1/2"? Just a thought.

[Jack Harper]

Hi jack,

Is this all the one depth?

Could this not be better done on a router or a CNC mill. One of my metalworking mills can cut up to 100"/sec and hold 4-tenths (0.0004") accuracy and repeatability. I have cutters up to 3" diameter for roughing.

Dave - Yes it is all the same depth. I wondered about a router. The pattern varies in width so you would have to use a smaller bit and do several passes in some areas and the bottom would have to be smooth with no router marks/tracks. After all that, the design would have to be frosted. They want a deep sandblasted look that would be see from the other side.

[Jack Harper]

What are you engraving? If it's letters or shapes, can you cut them out of 1/16" acrylic and laminate them to the 1/2"? Just a thought.

Scott - It is a pttern, it is kind of like the postscript bubble pattern in Corel. The bubles are as large as 4" or so and smaller. The pattern will be back-lit and it would be difficult to get a perfect lamination on all 1000 sq ft. Thanks for the idea though.

[Gary Hair]

Jack,
What about routing part and sandblasting the rest? They are right that sandblasting does tend to melt acrylic if you are trying to go too deep, but it will work fine for frosting. Use the router to get the depth and then sandblast to remove the tooling marks. If you leave the protective mask on the acrylic then you have a built-in sandblast mask. Do some testing and see if you need a stronger mask, you can use plain-old vinyl if needed.

Gary

[James Stokes]

Jack, A 100 watt laser would probably reduce the time by a third. Myself though If I am cutting deep in to the acrylic I get ridges in it but I am usually going at least .125 deep. If not deeper. If I am doing a color fill on it the deeper the better. Also I generally use 300 dpi on my engravings. If you use a higher dpi and take your lens up so it is out of focus. That will make it a little smoother.
Sandblasting I have never been able to get any depth just a frost.

[Scott Balboa]

1979 hours? That's almost 3 months of running the laser non-stop, or 247 days straight if you are running it for 8 hours a day. What's the problem?

[Jack Harper]

Thanks everyone for your input. I really appreciate it.

1979 hours? That's almost 3 months of running the laser non-stop, or 247 days straight if you are running it for 8 hours a day. What's the problem?

Scott- It actually ended up at around 2600 hours when all said and done. And yes, I quoted the job using a 24/7 schedule. I have done big 24/7 jobs before but this one will be the largest for the laser to date.