17. Go Wild

This week is “Wildcard Week”, where we must try a technique not covered in other classes.

The technique I chose to try was characterising FabLab Kamakura’s Laser cutter to bend acrylic. The goal was to find a fail-proof method for mass-manufacturing transparent cases that would connect my spice bottles to the shelf.

After many failures, I retorted to bending manually

This week's assignment:

- Design and produce something with a digital process (incorporating CAD and manufacturing),
- not covered in another assignment,
- documenting the requirements that your assignment meets,
- and including everything necessary to reproduce it.

Bending Acrylic with the Laser Cutter:

I’ve been thinking a lot about the approaches to manufacturing the spice bottle cases. I’m quite interested in acrylic because of 1. their transparency, which would help users to identify the spice easily, 2. the material’s versatility, and 3. because they can bend a little, potentially adapting to a range of bottle sizes.

I thought that if I could identify a method for automatically cutting and bending the acrylic to exact measurements, I could mass-produce these cases easily on-demand. A research paper published in 2017 first proposed such a method, calling it “LaserOrigami” (Youtube video).

A quick search in the FabAcademy repository returned few students who have documented their attempts, although it seemed that only a limited percentage succeeded. The idea sounded simple enough to me, so I decided to give it a try myself.

The Plan

I started by listing up the parameters used by past students.

Person	Thickness	Result	Offset	Passes	Power	Speed	Frequency
Abdul (Bahrain, 2020)	2mm	Success, but fragile	4.5cm	17	40	600mm/s (21%)	-
Adrian(Leon, 2020)	3mm	Failure (cut)	40pts	20	90%	7%	5000
		Success	60pts	18	30%	30%	5000
Pamela (Shanghai, 2019)	2.5mm	Failure	6-7cm	20	95%	5%	-
HCI Engineering Paper (2017)	1.5mm	Success	5.0cm	20	30%	40%	-

It seemed that the Offset is ± 5.0cm, and passes of around 17 - 20 times was necessary.
Some claimed that turning off the fan is necessary to keep the temperature high, but this was not possible in our lab.

There were also a few pointers about the acrylic;

• The acrylic must be the “Extruded type”, not “Cast”
  
• The thinner the better, as the heat of the laser must reach all the way inside the acrylic.
  So I got a 2mm Extruded Acrylic.

The Case Design

The Case:
We don’t need a perfect design right now so I drew a simple paper prototype, and modelled it on Fusion360.

The areas to bend are marked by dotted lines (they were changed to a different color on Adobe Illustrator, so the Trotec Laser Cutter can identify it as the part to “bend”.)

The Support Structure:
I eventually realised that I needed to make a support structure to hold the above design in place above the bed. I made this make-shift structure using scrap MDF.

In my 2nd design, I added the pulling force of an elastic band to 保管 the gravity . The acrylic depends on its weight to bend downwards, but since it was not heavy enough, . (However, securing the elastic band each time proved to be quite a hassle.)

The Progress

My plan was to start at slightly weak settings and gradually increase the power/speed.
So I started with Power 30%, Speed 30%, Frequency 4000, with offset of 5cm. This did nothing to the acrylic, but I kept tweaking little by little.

I spent a lot of time tweaking each parameters, but this was a struggle because there were so many combinations and working the laser cutter machine also takes a fair bit of hassle. I also had to keep finding a new area of acrylic to focus the laser, after each trial.

After many gruelling hours of failures after failures, I did eventually make it bend, but found the bent part too weak from all the heat. I continued trying to find a good balance between bending and durability, but ran out of time.

The parameter I got it to bend was; 40 passes, Power %, Speed %, Frequency 4000.

The Verdict

After giving my best for 2 days, I couldn’t get it to bend without making the it fragile.

My conclusion was that while it’s not impossible, it’s not worth all the effort.

I realised that the key is to keep the temperature of the bed constant at the melting temperature. But this is almost impossible because of the fan, and setting the machine also takes considerable time. It might be more realistic if we could achieve below conditions, which doesn’t seem viable;

• The fan needs to be turned off but this is a dilenma because of the toxicity
  
• Ideally the laser cutter machine should have features to facilitate the process; such as more flexibility around adjustment of power/speed midway.
  
• A proper jig needs to be made for more precise control of the degree of bending, but choosing a material and structure that would not be affected by the laser beam would be a challenge.

Bending manually with a Heat Gun:

I found out that there is a Heat Gun at FabLab Kamakura, so I tried bending acrylic manually.

Useful links:

• LaserOrigami
• How to Bend Acrylic Using a Laser Cutter: Tips and Techniques
• アクリル曲げ加工のノウハウ

Reflection:

This week I learnt to…
- Demonstrate workflows used in the chosen process
- Select and apply suitable processes (and materials) to do my assignment.

Assessment Checklist:

• Documented the workflow(s) and process(es) I used
  
• Explained how my process is not covered on other assignments
  
• Described problems encountered (if any) and how I fixed them
  
• [] Included original design files and source code
  
• Included ‘hero shot’ of the result