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Wildcard Week

This week I intend to learn about composites. This will include:

Unit Description

Group assignment:

  • I found the following in the Assessment Guide: Do I have to do the group assignment if I choose to do composites? Answer: Yes, you have to make test coupons.
  • Document your work on the group work page and reflect on your individual page what you learned.

Individual assignment:

  • Design and produce something with a digital fabrication process (incorporating computer-aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it. Possibilities include but are not limited to wildcard week examples.

Learning outcomes

  • Demonstrate workflows used in the chosen process
  • Select and apply suitable materials and processes to do your assignment.

Checklist

Linked to the group assignment page

  • Linked to the group assignment page:

  • There are two types of assignments, one group about composites and one individual, since I am alone in my personal Fab Lab I will do both. All of my work will be documented here, so there won’t be a group assignment page.

To complete my Final Project, I will need to learn how to skin my cardboard kayak. I intend to use a polyester matrix as the skin, so I will need to learn how to do this with digital fabrication as part of the process. Originally, I intended to use fiberglass and epoxy, but I remembered my experience with covering a Radio Controlled (RC) Glider with the same material and thought that would be a cleaner option. I looked in the composites and found that this is an acceptable material.

Further, I researched covering wood boats with monokote and then whether anyone has cut the material with a vinyl cutter. I was very encouraged to find out that others had done this. Since I have the material, the iron, and a vinyl cutter, this seems like a reasonable spiral.

The material is Hangar 9 Ultracote; a “multi-temp thermal shrink covering” made of “high-tech polyester”. The vendor claims it is “fuel proof and waterproof”, so it should work for a cardboard kayak:

The iron was purchased long ago when I explored RC model building. It is a Hobbico Custom Sealing Iron, rated at 115V and 170W.

The vinyl cutter is a Vevor KI-870 Cutting Plotter. I have only used it as a plotter in my personal Fab Lab since I did my vinyl cutting assignment in my previous Fab Lab. This will be a good test for digital fabrication.

I watched a video on Applying Ultracote If you watch it, the first minute is blank, so be patient or do a little scrubbing forward. My first test was to find out what temperature the iron would have at various settings. The instructions call for 220F for sealing edges and 300F to shrink and eliminate wrinkles. Using a non-contact IR thermometer, I found that the “2” setting fluctuates between 200F and 225F; the “3” setting fluctuates between 300F and 360F. Makes it easy to follow instructions ;)

My first test coupon was with a small 1 inch square piece on cardboard. At first I used the “2” setting to seal the edge on the cardboard. It worked great! Then I smoothed the whole piece. I tried to remove the coupon from the cardboard and it was stuck very good. I was able to pull it off and reapply it without damaging the material. Lastly, I used the “3” setting to apply it again; it was an excellent seal. This test proved the viability of using polyester matrix on cardboard. In the image you can see the edge of the cardboard imprinted on the material. The cuts are from manually testing the dragknife as explained below.

Setting up the Vinyl Cutter

  • Adjust the cutter so the tip is barely visible. Use a piece of the material on a hard surface to manually drag the knife. You want to cut the polyester, but not the backing. It took me several tries to get it right; then I tightened the lock nut. You can see the cuts in the test coupons below:

  • Place the drag knife in the vinyl cutter and tighten it. The pinch rollers were set at the lightest setting. I used the default settings for vinyl in the cutter: Speed 660 mm/sec, Force 150 grams. Communications 9600 baud. To setup communications in SignMaster, Click on Tools > Plugins & Modules > Vinyl Spooler; this will open the Vinyl Spooler window. Click Connection in the right panel > Select Cutter KI-870 for Current Cutter > Select Direct COM Port for Port Type > Select USB-SERIAL CH340 (COM4) for Port Name > Select 9600 for Baud Rate > Select Hardware (CTS/RTS) for Flow Control (Advanced unchecked) > Click Detect

Click Next > Click Next > When ready, Click Yes to test. It will move fast, so be ready. If it worked, Click Yes; if not, Click No or Cancel. You will do this for three tests and then you will see the below screen if it is successful. Then Click Done:

Digital Fabrication in Composites

Now I will make some test coupons with the vinyl cutter. I used the design software that came with the vinyl cutter, SignMaster. I wanted to take small step, so my first trial was with vinyl material. I wanted to see how the cutter would respond before risking my precious covering material. I designed a small rectangle:

I sent the job to the cutter and it cut/etched the shape very quickly on the vinyl, but did not cut through since I had it adjusted for the thin covering material. Then I loaded the covering material and cut the material. It cut it perfectly as you see on the test coupons below on the left:

I went in spirals and cut progressively more complex shapes as you can see above.

Larger rectangles:

Circle:

Arrow:

This is the screen you see just before you cut after Clicking “Cut Selected” under the shape.

You Click “Cut Now” and then Yes to cut.

This is the covering material after I had cut the test coupons:

As you can see the material is slightly wrinkled. First, the pinch rollers really press on the material and this causes a bumpy surface. I didn’t like it, but it was a necessary evil to keep the material under control. Second, the material is not held to the backing with an adhesive, so it easily delaminates during use. I suspect that once I run through the kayak shape, it will not be useable, so I better get it right the first time :) Finally, if it is delaminating, the cutter will bunch up the material; I had this happen once and I learned to stay away from the edges. As I cut the test coupons, I repositioned the cutter and pressed “Origin” to reset X-Y zero; this gave me control of putting the cutter over good material that was fixed to the backing.

You can see the upper rectangle on the far right has sliced backing; this is where I sent the job a second time and it cut the at the same location (before I learned about “Origin”). It cut the backing; whereas on the first cut, it does not cut the backing. This proves that the dragknife is properly adjusted for the material thickness. This is so cool! I hope you enjoyed the learning journey as much as I did :)

After all of the learning and cutting, I will show you how fast this cutter moves.

This is the weeding process after cutting the coupons.