Week 4

The week with "problem of plenty"

1. Laser and Vinyl cutter both are fast and would would easily make a designer think more and do more in a week's span. Hence, it gives lot of room for experimentation.

2. Miscalibration is truely a nightmare especially when it happens to a laser-cutting machine. A bad calibration results in lot of charring and ends up .

3. The neglected one, "a vinyl cutter" would leave you amazed if you get the design right. PS: you can put in anything else too instead of a vinyl sheet, the machine isn't intelligent enough to detect it.

Laser Cutting

Brief Overview

I had some experience with Laser cutting before, while designing my 3D Printer at Fab Lab CEPT. At Vigyan Ashram, Pune we are using SIL Laser(CO2 las in a glass tube). On one hand it is a very important tool in the lab but a special importance has to be placed on safety above everything else. A laser cutter has its own limitations, while it can cut smoothly through MDF, Acrylic and Cardboard it shouldn't be used for materials such as metal as it can bounce the laser back. One of the important instructions we were given was to use laser cutter only in the presence of Lab Instructors. For this week, I used Laser Cutter on three different occasions, firstly to calculate the kerf for acrylic, secondly to cut a living hinge and lastly a waffle structure for press fit construction.

Things to remember

a. Check whether the material to be cut is straight or not, from my personal experience, MDF and acrylic sheets are usually bent. This can result in varying level of cutting and inaccurate results.

b. Check how many files the laser cutter can store in its memory and keep removing the ones that are not required.

c. Do not leave the laser cutter un-attended while in use.

d. Wait for a minute after the laser cutting is finished. The exhaust takes a while to remove all the fumes.

Kerf Calculation for Acrylic(Group Assignment)

SIL Laser used at our Fab Lab in Vigyan Ashram, Pune, India. Photo Credits: SIL Laser

One of the key steps is to have a certain distance between the bed and the laser. It had been predetermined by our lab instructors.

I made the base file to be laser cut on Rhinoceros 3D software

We did our first Kerf test on acrylic and it didn't go accordingly. We wanted to engrave the names but accidently we also cut them through.

The first proper Kerf test on acrylic with constant speed of 10 mm/s and variable power. We also realized that the power of Laser was too low to engrave but also thought that maybe due to paper it was happening

Kerf calculation with speed 15mm/s and variable speed

We noticed that it was easy to cut acrylic at 30 power at 10 mm/s and wanted to go a bit lower that that but unfortunately it didn't cut.

Results of Kerf Calculation: Speed=10 mm/s and variable speeds

Results of Kerf Calculation: Speed=15 mm/s and variable speeds

I partnered with Tushar Kukreja to explore the kerf of 3 mm acrylic using SIL Laser at various settings. One of the main aims of this exercise was to calculate the amount of material lost during the laser cutting. We took a series of steps to calculate the kerf (defined as the width of material that is removed by a cutting process). We took the following steps to calculate kerf. It is described as follows:

a. Designed on Rhinoceros 3D: Made squares of fixed size 30 mm x 30 mm with corresponding speed and power labled on them.

b. Commands to machine by RDWorks: Made different layers for scanning and cutting. Mentioned command for power and speed for every square.

c. Laser Cutter: Standardized the distance between the acrylic sheet and laser tip(z axis distance), origin and frame to cut the pieces.

d. Measured Kerf: The length of the sides of the squares ws measured using Vernier scale.

Conclusion

a. The minimum Kerf keeping speed at 10mm/sec is at 30% power and at 15mm/sec is at 65% power for acrylic.Thus, characterizing the laser cutter.

b. Applying this data will will save power and cut acrylic precisely.

c. Minimum Kerf data will be useful for press-fit designs, adjusting Kerf values in slot thickness.

Living Hinge(Parametric Hinge)

I started with a predefined pattern of a living hinge on a 2 mm MDF by Kofactor Lab to see how it fares to bending.

The results were pretty good displaying bending in two directions

After looking at various examples of living hinge or lattice hinge. I wanted to explore and create my own patterns for pre defined bending. Before that, I took a predefined pattern created by Kofactor Lab and laser cut it to see how it bends. I took a power setting of 60W and 10 mm/s. I personally liked how density, length of cuts can have a major effect on the torsion of the material. The predefined custom cut pattern created the effect of a rubber sheet and was bending in both sides behaving as singly curved and doubly curved surface.

Download the file here

New living hinge pattern developed based on tiling geometry

The base tiling pattern

Bending test in one direction

Bending to an extreme limit

Twisting in two directions

Twisting in

Twisting in two directions

After laser-cutting a pre-designed living hinge, I decided to evolve it and create my own living hinge based on similar lines(one that could be bent and twisted in multiple directions). I have been obssesed with geometrical tiles for a long time and wanted to use a one of them consisting of parallelogram and square. Unlike the previous living hinge that used only one geometry getting reapeated, this tiling uses two geometries getting repeated again and again. These living hinges can be further evolved with some level of variations in geometry and lines. Also, one can observe as compared to the previous lasser cutting that the cuts are much better in terms of precision. This is a result because of the calibration of the laser.

Download the file here

Parametric predefined bending

Experimentation with predefined bending using curvature lines. Important parameter being the length of the cuts

The laser settings were again creating some issues and a lot of charring was happening and it didn't cut through properly

I finally got successful in cutting a part of my final living hinge and checked whether it was bending accordingly

Creating a script in grasshopper helps in managing the distance between the lines, the intensity, the rotation and other factors

The start of the final laser cut for parametric bending

The finished product

The lines came out well except for charring, attributed to calibration of the laser

Predefined bending

For my custom shape, I used straight lattice in the form of a whirlpool and started with cutting a part of it at a setting of 50W and 24 mm/s. The laser wasn't calinbrated and the pattern didn't cut properly, hence I had to go back to my previous tried and tested setting of 60W Power and 10 mm/s speed. I had to force a bit to take the pattern out. Since it was a whirlpool and it would be bent in a certain way when the pressure is applied to designated places, it was doing so and I was satisfied with it. I also did certain changes for the final cut. I made the cuts longer and calibrated the laser cut machine(by local instructor Suhas Labade). I also found out that closer the lines, the more the elasticity. One important aspect here to pay attention to the fact that the space left between lines has to be in an alternative zig-zag manner.

Download the file here

The following links helped me in understanding bending, curvature and torsion
a. Bending Radius
b. Understanding Curvature

Press fit construction

Press fit construction using two different material, acrylic and MDF

A custom script made in Grasshopper for two different materials, including the Kerf for each material

Before fabrication, a comb test helps in determining the kerf and best fit

The Grasshopper script generates fabrication ready 2D curves that can be exported to RDWorks for laser cutting

Kerf at the point of fitting

Applying the script on a Gyroid, a minimal surface but with fail

Fabricating MDF and Acrylic parts to check which fits the best

Assembled piece

I wanted to create a waffle/rib structure on a doubly curved surface using Grasshopper(again) for the press fit assignment. This might seem a very common thing around, but most of the scripts available online didn't include the kerf. Also, I wanted to make the waffle/rib structure using two materials i.e. MDF and acrylic, hence I had to use comb test to check which settings fit in properly. MDF is 2 mm and Acrylic is 2.58 mm thick respectively. While performing comb test, on both MDF and acrylic, I took increments of 0.08 mm based on kerf. The comb settings that allowed for perfect snuck fit are:
2.26 mm for the acrylic on MDF, and
1.92 mm for MDF on acrylic.

I further went ahead and tried to apply the script on a gyroid surface, a minimal surface as mesh in Grasshopper, but since it was a mesh and my script only took inputs as "surface" it failed to generate a ribbed structure. But then I decided to create some changes in the mesh but still there were some issues with the script and it failed to create the final product intended. I also realized that having so many parameters in a script/code helps in more control over changes to be done in the future. I made the script, fabrication ready, hence the workflow was faster.

Download the Grasshopper code here and 3d file here

Brief Overview:

I had never tried Vinyl Cutting but had already heard a lot about it and as mentioned by Neil, it is the most underrated machine in the lab and so I wanted to challenge myself in this assignment. I started with one vinyl cut and enjoyed it so much that I made two more vinyl cuts. We used, Roland CAMM-1, which was slightly on the older side and clear instructions were given to us before using it. It was connected a lab computer using Linux, hence we had to generate our final png files and transfer it to that computer. I enjoyed this assignment more than any other.

Steps

The final product

Using grasshoper to create a wave pattern

Roland CAMM-1 used in our lab

Exporting the file in .png format using Adobe Illustrator

Using the Linux terminal window to setup the cutting process

The final window before cutting displays the dimentions and other parameters to be customized

Opening the lever to load the vinyl and closing to start cutting it

Force and Speed settings

Slowing peeling the vinyl off the laptop (clean the laptop before sticking the vinyl.

I started with a straightforward and popular wave pattern by creating a script in Grasshopper, a plugin for rhinoceros. When I started making it, I was challenged by my local instructors that it would be tough for me to stick it on the laptop. The vinyl cutting machine also needed some hacking to make it work. The sensors weren't initially detecting the vinyl paper, and the machine had to be turned off and then back on. Steps followed to generate and initiate cutting:

a. I measured the size of my laptop and how I wanted to place the vinyl over it. After creating my graphic in Rhinoceros, I exported the file as .ai and opened in Adobe Illustrator.

b. In abode Illustrator, I exported the file as 600 dpi .png image.

c. Next up, I opened Terminal on the Linux PC and typed "sudo fab". It asked for an input and output format.

d. After uploading the .png file and creating the tool path, I sent it to the Vinyl Cutter. I set the speed to 1cm/s and force to 120gf.

e. The cutting took about 15 minutes and then I followed the process below to stick it.

I used a very different technique by "removing the vinyl completely" off the backing paper and then sticking it directly on the laptop and then slowly peeling it off, using X-ACTO knife. The whole process involved lot of patience and slowly peeling it off. I really got the knack of it and was amazed by the final product.

Download the grasshopper file here and the png file here

Creating another graphic for vinyl cutting in Rhinoceros

One issue that still remains is that the toolpath isn't very smooth

I stuck the graphic "This isn't Helvetica" on the front page of the diary. PS: nt was too small

The QR code was a failed experiment since it couldn't be read.

I then moved on to make another vinyl-cut and thought of a QR code(to see how small the Vinyl Cutter can cut) and a quote "This isn't Helvetica" (a kind of oxymoron, since "This is Helvetica" is written in Arial). Again I was surprised how small the Vinyl cutter can cut but the issue from my side was that the barcode didn't stick properly and hence I couldn't scan it.

Download the file here