3. Computer controller cutting - ADULTS¶
Group Assignment:
Complete your lab’s safety training
Characterize your laser cutter’s focus, power, speed, rate, kerf, joint clearance and types
Include what kind of speeds and power will cut what kinds of materials
Document your group work on your labs group page and link to your individual page
Reflect on what you learned on your individual page
“High frequency on acrylic - high power because you want to melt if it’s acrylic. Low frequency for everything else. Because we want to cut not melt” –Thomas Dubick
Debabrata Goswani discussed the different parameters that we need to understand for the laser.
Our Labs Safety Training¶
Our lab has a Safety Contract that is shared with all students and faculty members who use the equipment in the lab. This link is a copy of the contract.
In our classes, we also review laser specific safety such as fire safety, material safety, what to do in the case of a fire, and how to use the exhaust systems attached to the lasers as well as the air filters mounted to the ceilings.
As a group we reviewed all of the available safety resources.
Laser Settings Tester¶
What is Kerf?
Kerf is the width of the material that is removed during the laser cutting process.
Beam Waste: For many applications the waste will be higher than your focus, therefore less of a concern. But if you are deep engraving/ embossing this can be an issue.
In preparation for learning about our laser cutters, Camile made a Kerf Measuring tool in onshape. It was a parametric design based off of a .125in circle. This made it adjustable so that we can enter in the actual caliper measured material size. She created 10 spaces with a .01mm (.003in) difference between each space and it was designed to generate .1 MM increments for us to test. We used onshape because it has dimensions and its very easy to work together in, since we can all modify it and even be in the document at the same time. We didn’t extrude since all we need is a sketch for the laser.
Kerf tester sketch
We then brought the sketch file into CorelDraw, and Dorian used the transformation tool to created a 6 by 9 square matrix so we can test the Power versus Speed.
We created an indicator box in the bottom left to label our standard values, like frequency and resolution.
We moved the file to the Epilogue Dashboard and Angela and Kim set up the file for engraving and cutting. We used the split by color option and set each color on our grid matrix to a different combination of Speed versus Power.
We checked the standard settings for our laser and materials, and we updated our chart to more closely match the known settings to help prevent fires and issues with our material.
Our first kerf test, on cardboard, had no discernible variation when testing the joint fit of the cardboard. Looking at this screenshot of the kerf tester sketch you can see that the measurements appear to repeat, because of rounding errors. The first set of increments were too small.
Our power versus speed grid showed our ideal engraving settings to be:
1C (P10 S60)
1D (P10 S80)
2D (P15 S80)
2E (P15 S100)
Between our first and second cuts, a brand new laser was placed into the machine and we switched machines from the oldest laser in the lab to the newest laser in the lab.
During the day, Angela created a second kerf testing device with a 1in square and 20 .25in rectangles. Unfortunately it did not cut properly and needed multiple cuts to cut through and we were advised that this could affect our Kerf Value. The data from her testing device gave an average kerf of .01095in.
Since we did not need to do the engraving test again, and we werent ready to redo the slot test to fix the spacing, we decided to cut groups of 1in by 1in squares in different areas of the board to measure the kerf and see if there were any variations due to the location. Some of the first set of squares did not cut all the way through, due to the wood being slightly warped in some areas. We started testing the first set of squares that were cut and realized they were not in fact 1in by 1in squares, they were 1 in. by .9 in.
We cut a new set of 20 squares, confirmed they were 1 in. by 1 in., and used 3D printed bed clips to hold down the wood material. The clips sit slightly higher than the material so we need to be careful not to put them in the path of the laser.
3d printed clip
All four of us took 5 of the newly cut squares and measured two edges to give us a total fo 40 data points. Angela created a Google sheet that calculated the average of all of our measurements as well as our Laser Kerf value. Our final Kerf value was 0.025 in.
When compared to the double cut version Angela made earlier we could clearly see a difference that cutting more than once can make on a material.
After measuring lots of squares, Camille fixed the initial Kerf test based off our measured Kerf value so we can have more prominent spaces for slot testing. Our new slot tester allowed us to easily find the necessary slot size for our wood material which came in handy for us when creating our individual construction kits.
The final testing we did was not a required test, but more of a curiosity. Angela created a test to see the different engraving/dithering pattern types we have available to us on the Epilog Laser.
The first test used solid squares which made the dithering patterns hard to differentiate.
The second test used two different emojis, a gear and a light bulb. The second test, clearly showed a difference in each dithering type as well as a clear difference between 300 and 600 DPI for standard engraving.
For further curiosity, we viewed the dithering patterns under a microscope to see if the pattern affected how the laser layed down the dots.
