Week 04. Computer Controlled Cutting¶

This week I began to learn about tools in computer-controlled cutting. There are many tools/machines that we can use for computer-controlled cutting at various price scope. And the tools range from knifes to laser, from waterjet to hot wire etc. Our main focus lies in laser-cutters and vinyl cutters.

And starting from this week, we will have group assignment apart from the usual individual assignment. And they are:

Group Assignment: characterize your laser-cutter, making test part(s)
Individual Assignment: (1) cut something on the vinyl cutter;
(2) design, laser cut and document a parametric press-fit construction kit.

Laser Cutter¶

Laser cutters are the most commonly-used machine in Fab Labs and maker spaces. It can be used and engrave many materials, among which acrylic, wood and cardboard are most used in our Fab Lab.

Due to Chinese New Year holidays, we just came back to the office this Monday, and I couldn’t do the group assignment with my classmate at SZOIL as planned, so I asked my colleague CY to walk me through the usage of our laser cutter at Chaihuo x.factory today.

Laser Cutter profile:
- brand: Han’s Yueming Laser
- model: CMA1610
- max dimension of cutting: 1600mm*1000mm

SOP of using the laser cutter:
1. turn on the power of the laser cutter.
2. turn on the power of the PC.
3. open the client of Han’s Yueming Laser on the PC.
4. File => choose file => select the file (should be a dxf. file) => double click.
5. check “divide by layer” => click “ok”.
6. choose melimeter (which is usually the default setting).
7. change size (click the “click” icon to make the size change by equal ratio) => click “apply”.
8. click the icon of “put to origion” at the lower left corner.
9. set the cutting sequence by setting different colors for different layers.
10. change the power value to set the cutting strength. For not cutting through, I chose max 30%, min 30%; for cutting through, I chose max 80% min 80%.
11. calibrate the distance between the laser optical and the surface of cutting: it should be 5mm.
12. set the origin for cutting (use the arrows on the laser cutter to move) => click “Go Scale” on the PC to check whether the chosen material and origion is correct and macthed. If not, repeat the previous step and recheck until it’s confirmed.
13. turn on the fan and ventilation system.
14. close the cover of the laser cutter.
15. turn on the laser switch.
16. click “start” and the cutting started. (Cutting finished) 17. turn off the laser switch 18. turn off the PC 19. gather the projects that have been cut. 20. clear the left-over materials from the machine.

Since this is the first time, I did not want to waste materials in the trial and error phase, I chose a deserted wood to cut the 2D design that I made during my Week 03 assignment.

(my laser-cut objects)

There are some lessons learnt during this process. And I will need to spend some time in exploring the cutting process, when apply different powers, what will be the outcomes of the cutting; and hopefully I will try different materials as well.

Press-Fit Construction Kit¶

My mind was a total blank when it came to this part of the assignment of making a press-fit construction kit, because I did not have any idea, not a picture in my mind what it will be and how to get started. So I decided to go from the very beginning of doing some research.

Research & Study¶

Thanks to the tutorials (links below) I got a better understanding of the press-fit construction, and also grasp the basic usage of Inkscape in creating 2D designs for some simple projects.

First of all, I got fond of this press fit construction kit on Instructables. I downloaded the files and cut out the project and study the structure and learn how to design one myself. Since the project was designed for 6mm plywood, and we only have 3mm plywood at our Fab Lab, so I doubled the pieces and it worked. See the picture below.

And then I designed a similar one, but it’s neither pretty nor stable/robust enough. Here is a picture of it.

(First Press-fit Construction Project)

My Press-Fit Project¶

I have been thinking what press-fit project I should make. Then this idea came into my mind. Since the Lantern Festival was approaching, I was thinking why don’t I make a lantern! Since the number 6 means “things go on smoothly” in Chinese culture, I decided to make a lantern based on a hexagon. And here is the calculation part:

Each side: 20mm
The width: 40cm
The height: 34.64mm
Kerf: 2.8mm width; 5mm depth (The plywood was 3mm, however, when I cut a 3mm kerf, it’s not fit well, so I changed to 2.8mm)
Chamfer: 45°
The middle cube piece: 20mm each side, with the same kerf as previous size.

I created a key, and used “clone” to make other parts for making kerf and chamfer for each side/edge.

And here comes the final result. Yay!!

(Lantern V1)
My colleague loves the lantern, and would love to co-make & make it more festival. So Lily suggested combining yarn with the wood to make it more pretty. So we added some cuts at each edge to make it possible to knit the yarn onto the wood lantern. Here comes the updated version （with grooves on the surface of the lantern).

(Lantern V2)

And here is a video showing the final festive version that combines yarn knitting with wood laser-cutting press-fit kit. Thank you Lily for making it more aesthetic! Happy Lantern Festival!

Other Project - Fix my Calendar¶

Apart from making the press-fit project, I also tried the Box Designer to make a case. Why did I want to make a case? I had this calendar kit that my friend gave me as a gift. And I lost one part, which made it impossible to show the date properly. So I decided to use the Box Designer to make a cube to fix my calendar. See the comparison below.
(I used the Box Designer & Laser Cutter to fix my Calendar)

And while using the Box Designer to make this tiny cube, there are some tips I learnt:
1. The downloaded file are consisted of short lines by default, so it’s suggested to group the lines of each side of the cube to make it a whole. In this way, it will go more smoothly during the cutting, which will save energy & time!
2. When adding numbers on each side of the cube, it’s text by default, and it won’t be recognized or shown on when export for laser-cutting. Need to use the following functions (on Inkscape): Path => Object to Path. In this way the text will be converted as path for cutting or engraving.

Vinyl cutter¶

I realized we actually have a Cricut Explore at Chaihuo x.factory, which can work as a vinyl cutter. So I designed a simple sticker that I intended to use the Cricut Explore to vinyl cut it and stick it on my laptop. Since Cricut has a design space that works directly on Chrome, I made the sticker design on it directly. And here it is.

(Cricut Explore for vinyl cutting)

And here is an overview of the Cricut Explore.

(Image Credit: Cricut)

However, since the Cricut machine was not used for quite a while, and we couldn’t find the mat for cutting. So I have to wait for the new mat to be delivered.

The mat arrived, together with the PVC sticker I bought from Taobao. And I started exploring how to use this machine to vinyl cut some stickers.

After checking its website, I realized that Cricut has its own design platform called Cricut Design Space. So I designed a simple sticker on the Chrome extension of Cricut Design Space. See the screen shot below: Fab Academy + heart.

And then I made another two-heart shape.

The Cricut Explore is very easy to use, with very straight-forward instructions.
1. Turn on the switch of the Cricut Explorer
2. Press the Open button on the left side of the machine
3. Put the PVC sticker onto the mat
4. Put the mat (with the PVC sticker on it) on the storage compartment (make sure the edge of the mat toughs the rollers)
5. Press “Load/Unload” button to load the mat
6. Click “Make It” on the Cricut Design Space
7. When the “Go” button blinks, press it to start cutting
8. When it finishes cutting, press “Load/Unload” button to unload the mat
9. Peel off the stickers and here is how it looks like on my laptop.

(My first sticker from vinyl cutter)

Another good function of Cricut Explore is that I can print the sticker and then cut it. Since we are going to organize a Raspberry Jam event at Seeed in Shenzhen, I was thinking about making a Raspberry Jam sticker. And luckily we had some blank A4-size stickers available in the office, so I plan to have a try. I imported the file into the Cricut Design Space and it looks good. However, the cut result was horrible, so I paused the cutting without finishing it.

(Raspberry Jam Sticker Design)

With the image above, the Cricut Explore will cut each of the lines in the image, and I won’t be able to have a sticker as expected. This is how I learn about about the term “bleed”. I can either redesign the characters and add “bleed” to make the letters “fatter” to be cut out. Or I can make a frame for the whole sticker and then ask the machine to cut the frame only. In this way, I can have a sticker as a whole instead of a piece of paper with many lines cut into the image. I will try print & cut another time :)

Another skill I learnt through this process is calibration. When choose to print & cut, Cricut Explore will require you to calibrate before the actual cutting. When you agree to calibrate, it will print out a A4 paper, with small and large squares in the middle and lines on the top and the right side. Stick the A4 paper on the mat, and ask the machine to cut. It will cut all the lines and ask you which lines are cut in the middle. Through this process, the machine is calibrated and you can start cutting.

(A4 Paper print for collaboration Image Credit: Cricut)

Update June 21st
As my local instructor pointed out my press-fit design did not show parametric design. When I was using Inkscape to design the press-fit lantern, the main function I used for parametric design was the “clone” function, but I did not save the parameters of the “clone parts” in my previous design.

And this time, I tried Fusion 360 for parametric design. I searched for a few tutorials (links at the end of this article) and made my own design.

To set user parameters, I followed this path: modify => Change parameters => click “+” at the section of “User Parameters” and start to set my own parameters. I decided to make a rectangle with kerfs so that the rectangles can be fitted together. So I set the following parameters.

And then I began to draw my design.

(1) draw the rectangle

(2) draw the kerf

(3) use “mirror” function to copy the previous kerfs to the other two sides.

When I had the rectangle with kerfs ready, I thought everything is set. I canged the parameter to see the result, and noticed the following error: some of the kerfs are not in the mid-point of the rectangle sides.

I realized I did not set enough constraints for design, so I updated and make sure the “sketch dimension” of different parts of the design is set and constraint to the parameters.

So I had the following design:

length/width of the rectangle: 50mm
material thickness: 3mm

And when I changed the parameters to the followings, the design changed accordingly.

length/width of the rectangle: 30mm
material thickness: 3mm

When I changed the parameters to the followings, the design changed as well.

length/width of the rectangle: 30mm
material thickness: 6mm

I exported the previous two designs as .dxf files for laser-cutting. Please refer to the following picture for the path of exporting .dxf files in Fusion 360.

And here is the press-fit projects I made.