GROUP ASSIGNMENTS

This week we were tasked with characterizing our laser cutters. We set out to record the lasers focus, power, speed, and kerf, in addition joint clearance and types for when we cut out our own parametric construction kits.

As former and current employees of Moonlighter FabLab, Victoria and Augusto have both undergone safety training relating to the laser cutters near the beginning of their employment at the lab. Both went through the Laser Cutting Basics class that we offer with either Tom or Daisy, the founders of the space, and both have completed the neccesary certifications related to operating a Full Spectrum Laser cutting system.

Some of the most important rules to keep in mind for operating laser cutters are -

1. Inspecting laser cutters for breakage or damage before each use.
2. Turning on all auxiliary systems, the air compressor, water chiller, and air exhaust before use. The water chiller is necessary to operate the machine and the other two mitigate potential safety hazards.
3. Never leave laser cutters unattended. Doing so risks create a fire hazard.
4. The red emergency stop button cuts off all power in case of emergencies such as fire hazards. If needed a fire blanket and/or CO2 extinguisher is recommended to put out CO2 laser fires as they are the only approved means of doing so without damaging the equipment.
5. Clean after use. Clear the bed from debris, tapes, jigs, and/or guides to prevent fire hazards. Removing the bed may be necessary.
6. Chemical composition of materials are a good thing to keep in mind. Some materials like PVC and vinyl will harm either you or the machine with toxic and/or corrosive fumes.
7. Keep hands away from moving mechanical parts.

Our laser cutter operates without an auto-focus laser meaning we have to manually measure the distance between the lens and whatever material we cut. With this in mind, we did research on our laser cutter and found out that we are currently operating with a 2.5 lens. The ideal focal distance for a lens of this type is 63.5mm or 2.5 inches. Luckily we already had pre-existing focal ruler templates with our space. We use a robot with a small arm to measure the distance between the midsection of the nozzle, where the lens is located, and the material you are using. To ensure that this ruler was fit for the job we simply measured the distance between its feet and its arm and found that it was 2.5 inches as needed.

Once our focus was in order, we set about shifting our attention towards power and speed which was rather easy thanks to Full Spectrum Lasers, the manufacturer of our laser cutters, vector and raster tests available on their website. We were not satisfied with the tests as they were especially since they were rather small and easy to lose so we chose to modify them. The modifications to their templates included a resizing, making each 12"x12", the addition of holes in each of the four corners, this is for display so members can see what works, and the addition of fonts on the left side of the template, so anyone can see what font sizes are readable and which aren't.

We set out to cut 2 in. (50.8mm) squares in 1/4 cardboard and using a caliper for extra precise measurement we found out that our first cut was off from 50.8mm exact by a bit. We tweaked it further by increasing the size of the square by .14mm and realized we were still short so we increased it by .06mm. This third run allowed us to physically get 50.8mm with our cuts but digitally we had to program the square to be 51mm in both length and width. The odd thing we noted after is that even though we had noticed a 0.20mm difference in the kerf, after measuring our first run again we realized it came up to 50.5mm and our last run was what we needed at 50.8mm. We concluded that our inconsistent power and passes settings may have altered the results so we did three more rounds of testing at 100 speed, 60 power, and 1 pass. Each consecutive set of tests were simpler now that we knew the overall offset of 0.20mm and each test was able to successfully get to 50.8mm physically while keeping the 51mm measurement digitally. In conclusion, the offset we have to take into consideration is 0.10mm for each line cut if we want to get perfect and precise sizes and measurements for any future cuts.

Both of our projects utilize simple joints. We resorted to press-fit and chamfered and that is what we cut and tested. Both worked for what we had but we noted minimal differences between each as they are both essentially press-fit, the only difference being that the chamfers for the chamfered joint serve as a funnel that slides any connections into place. We did take note of the various different types of joints one can cut below.

Press-Fit - The most basic joint. Thin slot on any surface that slides in together.

Chamfered - Just like the press-fit except the chamfers serve as guides or funnels that make it easier to fit connections into one another.

Snap-Fit - Snap fit cuts a box at the bottom of your piece and incorporates prongs into the slot. When two of these pieces slide in together, the prongs snap into the boxes both have at the bottom making for a snug fit.

Flexure - Flexure incorporates prongs with curved heads and spacers on the sides to allow for some flexibility in the prongs. Like the snap-fit, there are boxes at the bottom of the joint so that when two join together the curved heads on the prongs snap into place there.

Pinned - The pinned joint slides together very simply like the other joints do, but there are gaps in the pinned joint that then allow you to drive a pin into it perpendicularly.

Finger - Snug joints if kerf is accounted for properly. Very useful for making corners and building walls.

Snap - They utilize prongs with curved heads at the top of their stems that slide into a slot. The curved heads also serve as hooks because of their flat underside. The prongs are cut in a manner that allows for some flexibility but not enough to move on its own once locked into place.

Wedge - Three part system. Wedge goes into slot, wedge has a hole that has a pin placed in it to lock wedge into place preventing movement.