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Week 3

Computer-controlled cutting

Summary

The goal of this week is to get decent understanding of the possibilities of computer-controlled-cutting and get more familiar with the lasercutter and vinyl cutter in our local lab.

Approach / idea / acknowledgements

This was not my best week, so I decided to try and get through the assignments and documentation without aiming for the stars (though Henk still told me I'm over-complicating things, try again next week!). To help me through I stared at projects by previous Fab Academy students and I would not have made it through this week without Fab's open learning model. Pray!

Assignment

Safety

This week our local lesson on Thursday started out with safety instructions. Henk explained to us that the lasercutter at de Waag is a 130 Watt CO₂ BRM laser cutter. The laser beam is generated at the rear of the machine by a large water-cooled tube. It is then guided by mirrors along the X and Y axes into the upper compartment, where a head with a fixed lens is mounted on the X-Y gantry. To use the lasercutter you must:

  • Turn the red nob on the right side of the machine
  • Always press reset to move the head to 0.0
  • Turn on and log into the computer below the machine
  • Open up Lightburn, load your design and configure the cutter settings
  • Place your material on the lasercutter's bed
  • Focus the laser
  • Turn on the laser, water cooling, air extraction etc with the switch on the bottom right of the red knob
  • Turn on the BOFA extraction fan by turning on the power strip next to the computer screen
  • Press start and keep an eye on it as you go

As for safety, pay attention to these things:

  • Make sure you're not the only person in the room, someone else needs to be present
  • The lid is a bit broken, watch your head!
  • In case of anything, open up the lid and the machine stops
  • Don't leave the red marked area on the floor while the laser is running
  • In case of fire use the "plantenspuit"
  • When you move the head on the machine directly instead of using Lightburn the computer will not update the heads position and you'll get unexpected results
  • There's a big red stop button on top of the machine

Getting to know the laser cutter

Former Fab Academy student now instructor and teacher at the HvA Bas Pijls came to talk to use about parametric design and the pipeline he used when doing this assignment in 2022. Then he showed us how to make a comb which is used to test the joint clearance of our material in OpenSCAD. Unfortunately I fell ill that afternoon of our local lecture and had to miss some of the group assignment. Remco coded along with the Bas and shared the script with us after. This allowed me to make my own comb at a later moment to test my joints.

Some of the experiments my classmates did where explained to me later. I used them to study the kerf, focus, power and speed effects on the cardboard we were planning to use for our construction kits. They've documented these experiments here: Remco, Christian.

Using a speed of 100mm/s and a power of minimum 20% maximum 30% I made a comb with cardboard of around 2.8mm. With a joint depth of 5mm I settled on a joint width of 2.4mm.

Document

We don't have a group page Henk told us, so I've documented it here and referred to my classmates documentation.

Construction kit

Talk knex, fischer technik and mechano, add pictures. Looking for inspo on a simple kit.

After looking at kits from previous years and noticing the definition of a construction kit in this weeks assignment I wanted to make a something similar to my favorite toys as a kid: K'nex, Meccano and Fischertechnik. Kits with simple parts that you build endlessly with.

What is valid for a construction kit? Answer: Something more than a finger joint box that you can assemble in multiple ways. The pieces must stay together without the use of adhesives and not fall apart when lifted.

One of the kits from a previous student I really liked was Akila Surendran's kit from 2018, who in turn took inspiration from Jaclyn Berry's kit from 2017. I decided to take the latter as a jumping of point.

It was recommended in week 2 that we experiment with parametric CAD. I spend some time trying to wrap my head around Blender's Geometry Nodes, but this seemed quite a steep learning curve so I decided to opt for FreeCAD's Spreadsheet instead. To get myself familiar with it I watched a tutorial. Then I started building the most basic shape from the original kit constrained by value's from FreeCAD Spreadsheet.

Now I wanted to add a chamfer to my joints, but wasn't sure how, so I looked for another tutorial. It took a bit of trial and error to get the hang of, I started over a couple of times either cause FreeCAD crashed, or I got some strange results.

But once I understood how to properly constrain fillets with values in FreeCAD Spreadsheet it went pretty smoothly.

Happy with this first piece I modeled the other three parts from the original kit by Jaclyn Berry. I first modeled each piece in a separate file. If you're consistent in the naming of your parameters across files, it's easy to copy objects into one file without having to set your parameter dimensions all over again.

Good trick is to first add all the parameters to a spreadsheet in an empty FreeCAD file and then copy over the object from each file without it's spreadsheet. That way it will use the parameters in the spreadsheet you just made.

Next up I added some parts to make the geometry more like the K'nex I grew up with.

Now it was time to do some cutting and test my kit parts. First up: the axel, cause it would let me test a very deep and a more shallow joint, as well as the strength of the axel with the chosen cardboard. I used the settings that came out of the group assignment and was quite happy with the result.

I proceeded by printing some of the other parts and noticed the joints were a little shallow and the connectors had some very weak points where the cardboard was too thin. This made the kit quite unstable, so I changed the parameter for the joint depth and the connector's size and printed some more.

Henk wasn't too happy about my wheels, they were fitting snugly, but more relying on friction than a good fit, so instead of just a hole in the middle I added a cross. For this I could use the axel width and joint depth parameters to calculate the dimensions. The fit was a lot cleaner but Henk still noticed my wheels we're wonky. I tried to argue, but he was right.

I stared at the file and my calculations and couldn't for the life of me figure out why it wasn't fitting. Of course I started the blaming the machine and my materials, but nah, after some rest it turned out I hadn't accounted for the chamfer depth in my calculations, the cross in the wheel was indeed 2mm to big (sorry Henk). Some of the connector parts felt like overkill so I settled on a set of parts I liked both from the original kit and some new ones, as well as an improved wheel.

Time to cut some parts and build some stuff!

Vinyl cutter

At de Waag there are two different vinyl cutters. There's a Roland CAMM-1 SERVO GX-24 and Circut Maker 3. For the Circut the mat that keeps the vinyl in place was a bit overused, so we played around with it, but didn't use it to cut our stickers.

The Roland uses a drag knife instead of a differ knife to cut the vinyl. The drag knife drags along the cut and rotates freely, while the differ knife of tangential knife has a motor on top that directs the knife. For a better explanation have a look at this video.

When selecting your vinyl you should always run a test cut, to check which force you need to get through the material. On the Roland this test cuts a little square within a circle, you can tell by how many of them are on the machine itself.

To run this test you first insert your material and use the arrows on the machine to guide it to where you want it to start cutting. You then set the force, press the origin button until the machine says ORIGIN SET and you press the 'test' button. Once you've found the desired force you can move to a computer to send your design to the machine.

To send your design to the machine we use the website modsproject.org. I wanted to make a dolphin sticker, so I took an svg of the world wide web. On the mods project website go to programs > open program > Machines, Roland, GX-GS 24 vinyl cutters, cut. This gives you an interface that shows the steps the program takes to translate your design into instructions for the vinyl machine.

First upload your design by using the 'select SVG/png file' button depending on what filetype you're working with. Then press calculate to get a preview of the cuts the machine is planning to make.

Make sure the machine is plugged in via USB and click get device and select the Roland GX-24.

Then press send file and wait for the machine to start. Once it's done you cut off the bit with your sticker and use transfer paper to transfer it to wherever you want it to stick.

What would i do differently

Keep it simple, stupid.

Files & resources

Leftovers previous week

  • week 2 documentation

Further exploration

  • Some day I'll be a real pro and master Geometry notes in Blender, watch this space!
  • Would love to work on this kit further and cut a more durable set for my wonderful nieces Ies and Cato <3