Summary
It was fun getting to know the laser and vinyl machines (and materials), but a lot of time was wasted trying to get the parametric designs to be constrained in the correct way.
A lot was learnt regarding the importance of testing of materials in the different machines before the final cutting run. As well as luck being a variable in the success of the cutting due to variations in 2 pieces rated as the same type / thickness of material, and individually within the same piece of material.
Learning Outcomes
Theory and use of things i learnt from this assignment:
-
The theory and practical use of Laser/Vinyl cutters.
-
The definition of Kerf and how to measure it accurately.
Lessons to take away
Understand the definitions you use. The internet is full of differing understandings of the same standard definition. Be sure you understand your definition, so that you minimise errors when working with others.
Kerf values vary. Even on the same machine, the value can vary depending on the thickness/density of the material. Even with the same material but a different thickness. These differences are negligible with this laser cutter.
Operating the laser cutter at a slower rate with half the power gives a better cut than faster with at full power. Under magnification, the quality of cut is better and sharper when the cutting process takes longer. This should minimise any burning/scorching of the material either side of the cut.
There is always a little amount of luck involved in the success of every cut. Natural variations in the material can mean that you can get differing results from repeating the same cutting job.
Check the laser focus each time you place a new piece of material under the laser. Even if the piece of material was part of the same larger piece as before, there will be natural variations in the manufacture of that piece. These manufacturing variations minimise the greater the thickness or density of that material.
Check your file is the one being sent to the Vinyl Cutter. Make sure that your file has been “calculated” before sending to the cutter.
Parametric designs don’t scale. The design won’t scale everything at the same time like using a ‘scale’ function. The design will scale as many of the parameters as possible at the same time, but be limited by the constant variables in your parameters list. E.g. The thickness of the material will limit how small you will be able to get your design.
Group Assignment
- characterize your laser cutter’s focus, power, speed, rate, kerf, and joint clearance.
Kerf: Kerf is an old word of English/German derivation. Used to explain the width of material that is taken away when sawing wood. Defined as the width of the saw blade and the offsets of the saw teeth on both sides. The teeth are pushed out either side to allow the blade to move freely.
Kerf = Diameter of blade or laser + material taken away either side of the blade
or, (Radius of laser + material) * 2
Offset: Where to place the centre of the cutting line if you want to get an accurately measured piece.
Offset = Kerf / 2
Clearance: The extra space beyond the offset setting to allow easy fitting when joining/fitting different parts. Remember this is also applied to the opposite joint. Values can be negative as well as positive, depending on the nature of the material.
Measuring formulas
Male joint
Total width = Desired Width + (2 * (Offset + Clearance))
Female joint
Total width = Desired Width - (2 * (Offset + Clearance))
Laser Cutter
(image from Henk)
BRM 1600 (x 1200) - CO 2 laser - Water cooled
| SPEC | VALUE |
|---|---|
| Focus | 17 mm |
| Power | 100 W |
| Max-Width | 1600 mm |
| Max-Length | 1200 mm |
| Max-Thickness | ~10 mm |
| Max-Speed | 1000 mm |
| Kerf | 0.152 mm |
Risk Assessment
| RISK | WHO IS AFFECTED | CONTROL MEASURES | RATING | DEFENSIVE MEASURES |
|---|---|---|---|---|
| Eye Damage | You | Machine lid contains an glass/acrylic window. | LOW based on low rating of laser. | Don’t look into/at the laser beam. Wear safety glasses |
| Cutting effect diminishes due to dirty lens. | You | none | LOW | Clean regularly with lens cleaning fluid. |
| Fire | You, surroundings. | Fire extinguisher on hand. | MEDIUM | Big red emergency stop button. Don’t leave the machine whilst running. Careful adjustment of settings. |
| Toxic Gases from burning of material. | You, surroundings. | Extractor fan. | HIGH | Turn on extractor fan before starting job. Wait before opening the machine cover after job finishes. |
Available Settings
Speed: the rate at which the laser moves.
Minimum Power: the amount of power needed to cut corner or angles that acquire a longer exposure to the laser than a straight cut.
Maximum Power: the amount of power needed to just cut through the material in a straight line.
With the weighting of significance on the formula being on the side of speed rather than power. A change in speed has a greater effect than changing power.
Operating instructions
(image from Lucia)
Operating the laser cutter is as simple as 1,2,3! The buttons have been helpfully labelled in order of operation. And a BIG RED BUTTON for emergency stop!
For safety there are several steps to turning on the machine. First, is needing a key, and turning the switch to which you activate the electrical system to the machine. Next, arming the machine and placing the systems on standby with the green button. At this point, the machine is capable of doing a ‘dry’ run to test placement of the material and the working area of the laser. To activate the laser, the final switch must be turned to warmup and activate the laser generator. An audible alarm alerts you (and others in the area), of the readiness of a firing of the laser.
The control pad allows you to perform different functions such as moving the initial placement of the laser cutting head. However, it is much easier to control the machine from the computer connected to it. Using a piece of software such as ‘lightburn’.
This software accepts 2D design files such .DWF file formats, and allows you to perform functions such as scaling and adding multiple copies of the design to be placed in a pattern and cut at one time. The ‘Frame’ buttons allows you to see where the boundary of the laser will perform it’s cutting, to double check if the placing and the dimensions of the material is correct. Calibrating the laser’s focal point is also advised each time a new piece of material is used.
With the desired settings in place, closing the safety cover will disable the last safety feature and allow the machine to fire the laser. It is advised to activate the attached extractor fan to begin extracting any noxious gasses from the cutting process. Only then is it acceptable to press ‘Play’ and watch your design being cut out.
Group Assignment
- characterize your laser cutter’s focus, power, speed, rate, kerf, and joint clearance.
Kerf: Kerf is an old word of English/German derivation. Used to explain the width of material that is taken away when sawing wood. Defined as the width of the saw blade and the offsets of the saw teeth on both sides. The teeth are pushed out either side to allow the blade to move freely.
Kerf = Diameter of blade or laser + material taken away either side of the blade
or, (Radius of laser + material) * 2
Offset: Where to place the centre of the cutting line if you want to get an accurately measured piece.
Offset = Kerf / 2
Clearance: The extra space beyond the offset setting to allow easy fitting when joining/fitting different parts. Remember this is also applied to the opposite joint. Values can be negative as well as positive, depending on the nature of the material.
Measuring formulas
Male joint
Total width = Desired Width + (2 * (Offset + Clearance))
Female joint
Total width = Desired Width - (2 * (Offset + Clearance))
How we defined Kerf and joint clearance.
We created an .svg file that included 10 cut lines surrounded by a frame. The idea here was to be able to measure the space left inside the internal frame, once the pieces we place back in. The space measured would equal the amount of material “cut” away from the material 10 times. Since the measurement of the Kerf would be so small, and taking in the possible variability of the material’s thickness, having 10 cuts would make a give a reasonably accurate average value for the Kerf.
To get a value for the clearance needed to apply to joints, we designed a “comb”. Each tooth of the comb would be an incremental step increasing in width. When finished, we would be able to fit a thickness of the same material into the slots to find the best fit. The idea was to have a range of widths spanning either side of the theoretical “line fit” of the material (with a circle denoting our believed optimum value). However, something went wrong in the calculations, and our range began much smaller than expected. This didn’t matter much in the end as the nature of the material (~3mm corrugated cardboard) had lots give/flex anyway.
Optimal Settings
| MATERIAL | THICKNESS | SPEED | POWER (min) | POWER (max) |
|---|---|---|---|---|
| Paper 80 gsm | 0.1 mm | 100 mm/s | 10 W | 12.5 W |
| Cardboard (corrugated) | 2.75 | 100 | 20 | 28 |
| Cardboard (high density) | 2.91 | 65 | 40 | 85 |
| 3 ply | 4 mm (3.91mm) | 90 | 35 | 85 |
| 3 ply | 6 mm (5.81mm) | 50 | 30 | 85 |
| 3 ply | 9 mm (9.02 mm) | 10 | 40 | 50 |
How we came up with these values
Whilst in our small group, we took it in turns to operate the laser cutter, and gain experience operating the machine. We made a simple shape in the cutting software (Lightburn) and started cutting with a low setting until we found a combination of settings that would cut out our shape with minimum burning/ scorch marks to the finished piece. As we tested we were sure to change only one parameter at a time to best understand the relationship between the individual settings and their effects.
The most logical setting to start adjusting were the power settings. We noticed that the ‘Max power’ settings related to the cutting out of the ‘continuous single’ lines. Whereas the ‘Min power’ setting related to the power needed to cut out any ‘corners’ or line angles where the laser briefly cuts over it’s Kerf for a second time. The finish in these areas we found would suffer burning/scorch marks, so tried to eradicate or minimise these as much as possible.
We started testing materials based on material thickness. Going from the thinnest (paper) to the thickest (9 mm 3ply plywood). Each time starting our test settings on the optimum values of the last material.
When the results failed to cut through the material completely at 100% power, we then changed the varying parameter to ‘speed’. Slowing down the laser to leave more time to cut through the material.
However, there were some unexpected results. At one point lowering the settings to refine the amount needed, it caused more burning and scorching damage than the higher settings. After much confusion, we repeated both sets of values to try and replicate the same results. We couldn’t replicate the burning / scorching damage as before so decided that it must be due to an internal variation of the material.
At a thickness of 9 mm, the material was nearing the maximum thickness possible in the cutter, so its possible that variations in the performance of the machine could also be a factor. (image from Lucia)
Individual Assignment
- Design, laser cut, and document a parametric press-fit construction kit, which can be assembled in multiple ways. Account for the laser cutter kerf.
What I did
The original concept was to create a one piece system that would provide as many angle possibilities of joining together. Other systems I have seen are based on multiples of one angle setting.
I planned to have 2 sides to this piece, one based on 45' angles, the other side based on 30' angles. Rotating and flipping the piece would give the multiple options for mixing the angles.
First i worked out which parameter variables i would need to describe the different measurements of the design. I tried to relate the parameters to each other to minimise the number of parameters i would need to alter at any one time.
Drawing the shape in Fusion360 as a 2D sketch and adding parameters to these measurements was next. In combination with constraints, I tried to constrain the design so that the liens of my shape turned black (showing the shape was fully constrained). This was where time disappeared. I struggled to get all the lines to be black. Taking constraints away, adding different ones in a different order. Eventually (more by accident) i took away one constraint to find that all lines suddenly went black.
I managed to do some basic cutting and fitting tests to work out the clearance two pieces would need. Testing for the ‘clearance’ needed to ensure a tight fit, my initial value was too loose, so i doubled it to a value i believed to be extreme to to make sure. This fitted really snug to each other, which i think was more due to the flex in the material. Once i had perfected a good fitting at a size that was reasonable, i decided to add fillets to the design to ease fitting of joints.
Attempting to do this ruined the constraints of the shape, and I had another round of ‘find the right combination of constraints’. Hours later, as a final thought before i turned the computer off i remembered that 2 lines at 45' angles to each other (as in a triangle) are equal in length. So in order to constrain to each other, i could just use the ‘equals’ constraint instead of using a 45' radius measurement constraint. This worked!
Testing of the parameters performed, I tested a couple of settings in the design, and it performed well. As the fillet setting was related to the thickness of the material, and the size of the piece cut, it was hard to see the rounded edges. But the design worked so i can take that experience to larger designs in the future.
To try and extend the possibilities of the design I added some ‘long’ connectors. On the final cutting run, I added the connectors to the original piece (which function now just as a joint). At a ratio of 1 ‘joint’ to 4 ‘connectors’, i realised when i tried to build something that this mix of pieces wasn’t very good. I ran out of joints quicker than the connectors. Next time i would change the ratio drastically.
What I’ll probably do next time
In the case of designing, (i’ve since found out), there are other methods of constructing that would possibly be quicker. Namely, not constructing something with one line like i have, but keeping the different shapes that went into making the final design separate. Relating and constraining them to the other parts. Selecting only the lines needed to include in the final design.
Turning these shapes into ‘bodies’ by giving them a 3rd dimension and perform more functions, from which the dimensions can still remain parametric, can also help. Even though its another step in the process, the final body can then have a 2D outline projected and exported from it.
Vinyl Cutter
(image from Lucia)
Roland GX24
| SPEC | VALUE |
|---|---|
| Force | 30-250 gF* |
| Speed | 10-500 mm/sec |
| Kerf | negligible |
‘*’ 1 gram-force [gF] = 0.00980664999999998 newton [N]
Risk Assessment
| RISK | WHO IS AFFECTED | CONTROL MEASURES | RATING | DEFENSIVE MEASURES |
|---|---|---|---|---|
| Cutting your finger | You | Difficult to place fingers near the cutter. | STUPID | Don’t place fingers near cutter |
Optimal settings
| MATERIAL | THICKNESS | SPEED | FORCE |
|---|---|---|---|
| Vinyl | 0.16 mm | 2 cm/s | 50 gF |
Operating Instructions
(images from Paula)
With a few simple buttons on the pad, the machine is very intuitive to use. Turn on the machine and place either a piece or a roll of material into the aperture. Having clamped the supporting rollers within the white lines, the machine will self test the positioning of the material. Use the different buttons to enter the settings you wish, and follow the instructions on the screen should there be any.
Import the file (.svg or .png) into the Mods program. This node base program will take your file and prepare it, based on your input settings, and calculate/compile the data into machine code that the cutter understands.
When ready press ‘Send file to machine’ and let the cutter run.
Individual Assignment
- Cut something on the vinyl cutter.
What I did
Something quick and simple to print on the cutter is a sticker. Here i traced the logo of the building that the FabLab occupies in Illustrator and exported the ‘.svg’ file.
The assignment to create a sticker was fairly easy task. I re-created the logo for the ‘building’ that the Amsterdam FabLab is situated in. I exported from Adobe Illustrator as an .svg ready to import into Mods program that compiles the svg XML data into machine code that the printer can understand.
However, someone had already had a problem (and found a solution) directly importing an .svg file from illustrator. Apparently, the Mods program is looking for a couple of extra parameters so it understands the boundaries of the graphic. This was done in quickly in a text editor and saved. (see mistakes below).
Upon setting up the machine, one thing to take care moving the support rollers to sit inside the white lines. This is used to help understand the width of the material. Get this wrong and it will throw a ‘Bad position’ error.
The machine can handle a ‘piece’ or roll of material. Which option you have will need to be specified in the cutter and the lever clamping the material flat onto the cutter, pulled down.
Communication with the the cutter is possible just with commands via the terminal. To test the communication path (once you know the websocket port):
echo PD
This tells the cutter to briefly place the knife down (‘Pen Down’).
In the Mods software, a system of nodes allows you to import an .svg vector or a .png raster image. Creating outlines of the raster, or scaling and computing sizes and other parameters of the file to be sent to the cutter. (image from Paula)
Once happy with the settings, ‘calculate’ the data and compile it ready to ‘send to machine’.
Mistakes & Issues
Double lines. When making the Illustrator file to measure the Kerf, i made the lines using the rectangle tool and snapping multiple copies together. This made the laser cutter cut double lines and obscure the accuracy of our measurements.
Inconsistent results. When attempting to find the optimal settings to cut 3 ply wood of a 9mm thickness, we got results that were inconsistent with the idea of using less power would minimise burning/scorch marks. One result showed that less power caused considerably more burning. By repeating the same settings again the results showed less burning. Without the ability to run more scientific tests, We concluded that there was a natural variation in the material causing this confusion.
Use of Constraints in parametric design. I spent many hours trying to place the correct constraints to my design. This was more difficult than expected, as it took a long time to get correctly constrained “black lines” in Fusion. This happens due to a combination of the correct constraints in the correct order. The only strategy i can think of at the moment is to start from “the outside in”, measuring and constraining the most significant lines first.
Black lines in Fusion don’t necessarily mean a parametric design. Whilst cutting different sizes of the design, the lengths of 2 faces changed when compared together. The the lines had adjusted to the smaller size to make sure that the slots cut into it stayed at the required angle. N.B. Upon thinking about this more, i believe that i had gone smaller than the threshold of the design, where would kept its original shape based on the constant “thickness of the material”. Made even smaller, and i think the dimensions would raise a an error in Fusion. These different shaped pieces did still fit together with the larger pieces too.
Not pressing the “calculate” button before sending the file to the vinyl cutter. Calculate compiles the instructions of your .svg into the machines intern code. Not pressing it effectively leaves the last user’s calculations in the internal memory and prints it instead of yours. (The previous user had left the cutting machine to fix the file that was then considered too big to cut, not before pressing “calculate”. It did print out quite big.)
Mods program needs specific metadata from your .svg file. When creating a .svg from Adobe Illustrator (2021), the metadata does not include 2 parameters that Mods needs to function correctly. Adding, for example, width="600px" height ="600px" to the XML metadata gives it the information that it needs to work.
Conclusion
A fun and frustrating week in all. Cutting things with a “laser” is cool, but parametric design can be a pain in the “bum”. Defining what parameters to use and how they relate to each other is the easy part, getting the correct constraints, in the correct places, in the correct order is the difficult part. Throwing every possible constraint on the design isn’t the solution. The best strategy i guess is to start applying the the most significantly important parameters and constraints, and working towards the less significant and smaller measurements.
FILES
Further Study
Software that was popular with other students that i didn’t use:
DeepNest Deepnest is an open source nesting application, great for laser cutters, plasma cutters, and other CNC machines. Deepnest
Cuttle Cuttle is a design tool for digital cutting machines. Laser Cutters • Digital Die Cutters • CNC Routers. It’s both a vector editor (like Illustrator) and a programming environment (like Processing or OpenSCAD). Cuttle