week 3. Computer-controlled machining

1.1 Cutting a Simple Shape on the Roland GS-24 (Instructor Tutorial)#

My instructor walked me through the basics of vinyl cutting on our lab’s Roland CAMM-1 GS-24. We started with a simple experiment - cutting a rectangular and star shape - before moving on to more complex work.

The Machine#

This is the Roland CAMM-1 GS-24, the vinyl cutter we use in our lab.

The specs label on the side. It’s a Roland CAMM-1 GS-24, a pretty standard vinyl cutter used in fab labs.

Sometimes you use mats for stability when cutting vinyl, but this machine already had its own built-in mat so we didn’t need a separate one.

Blades and Blade Holders#

This is the blade of a vinyl cutter up close. It’s tiny but precise - just enough to cut through the vinyl without going through the backing.

This is a blade holder. My instructor showed me some cool ones that were 3D printed in the lab too.

A whole assortment of blades and blade holders. The 3D printed ones are interesting - shows how fab lab tools can be used to make more fab lab tools.

Setting Up the Machine#

We decided to experiment with simple shapes first before doing the actual assignments.

First you have to set up the blade and make sure it’s seated correctly in the holder.

Then you set the rollers so they sit within the white strips on the machine. After that, turn on the cutter and choose between “Roll” or “Piece” mode. We chose “Piece” first and let the machine measure the width of the vinyl.

Next, put the vinyl sheet in and align it properly.

The screen on the machine displays the width and length it measured. This is important because the software needs to know the cutting area.

Software Setup: Roland CutStudio#

You need to install the Roland print drivers and CutStudio software, then select the correct printer from the settings.

You can configure the cutting force and speed in the software. You also need to match the width and height to what the machine measured.

Instead of typing the dimensions manually, you can just press “Get from Machine” and it pulls in exactly what was measured. Much easier.

Drawing and Cutting#

We first tried drawing simple shapes directly in Roland CutStudio - a rectangle and a star. It worked well for a quick test.

Here’s the star shape we drew in CutStudio, ready to be sent to the cutter.

And here’s the first star sticker we cut! It came out clean. A simple shape but satisfying to see the whole workflow end to end - from drawing in software to a physical cut piece.

1.2 Cutting a Little Prince Sticker Using Inkscape#

For my actual vinyl cut assignment, I wanted to cut a Little Prince logo on gold vinyl.

Machine Setup#

I chose a gold vinyl sheet for this one - felt fitting for the Little Prince.

This time I selected roll mode on the machine instead of piece mode.

In roll mode the machine assumes the length is infinite, since the vinyl can keep feeding through. It only measures the width.

Switching to Inkscape#

I couldn’t download CutStudio on my Mac, and it wasn’t accepting SVG or AI files anyway. So we switched to using Inkscape with a Roland print driver instead, which worked great.

In Inkscape, I had to configure the design with no fill and a hairline stroke. The vinyl cutter follows the stroke path, so fill doesn’t matter - only the outline gets cut.

I also had to set the document properties to match the dimensions measured by the machine, plus set a fixed height since roll mode doesn’t give you one automatically.

A Positioning Mistake#

Initially I made the mistake of placing the image at the bottom left of the canvas, which wasn’t where the roll actually starts cutting from. Had to reposition it to align with the cutter’s origin point. Lesson learned!

The Cuts#

This was my first test cut. It came out well enough to confirm the workflow was right.

And here’s the final cut on the gold vinyl! The Little Prince design came out clean. The whole workflow - from SVG in Inkscape, through the Roland print driver, to the physical cut - worked smoothly once I got the positioning right.

2.1 Designing a Press-Fit Pentagon in Rhino 7 + Grasshopper#

For the laser cutting assignment I needed to design a parametric press fit construction kit. The idea is pentagons with grooves at the midpoint of each side so multiple pieces can interlock with each other.

The Goal#

This is what we want to cut. A pentagon with grooves cut inward from each side so the pieces can slot together.

We sketched this out on paper before starting. The plan is to draw a pentagon, find the midpoint of each side, then subtract rectangles inward from those midpoints. You can see the notes at the bottom right, Polygon, Find center point.

Step 1: Drawing the Pentagon#

In Grasshopper I created a Polygon node with 5 sides and a radius of 36. The radius is 36 because we want 3.6mm at the actual scale and the mm is the unit that gets specified at printing time.

And this is the output of the polygon in the Rhino viewport.

Step 2: Finding the Side Midpoints#

Now to make the grooves we need to find the midpoint of each side of the polygon and cut a rectangle inward from there. So I used Explode to break the polygon into its 5 individual sides, then piped those into a Curve Middle node which gives us each midpoint.

You can see here the side midpoints are marked (green crosses) and note how Grasshopper automatically took care of mapping the Curve Middle function to the five elements outputted by the previous Explode node. No loop needed.

Step 3: Drawing Lines Inward from Each Midpoint#

Now to draw the rectangle we need a line going halfway to the middle of the pentagon from each midpoint, then we offset it. So first I used the Area operation on the polygon since it also gives us the centroid, created a 2 point vector (Vector 2Pt) from each midpoint toward the center, and used Line SDL to draw the line.

Output of the operation. Here I’m only showing the polygon and inward lines for clarity.

The length of the line was defined parametrically, half of the radius minus material thickness (3.1mm). This way we can ensure that the press fit of two components dont overlap into each other. You can see the Division and Subtraction nodes computing this.

Step 4: Creating the Rectangle Lengths (Offset)#

Now we want to create the lengths of the rectangle so we offset the previous line in both directions using two Offset Curve nodes.

As you can see here only the sides are included so the widths of the rectangle are still open. We’ll close them next.

Another thing you’ll notice is that the width of the rectangle is material thickness with kerf of the machine subtracted (0.10mm), and so for the offset we had to take half of that value parametrically: (material_thickness - kerf) / 2. You can see the Subtraction, Division, and Negative nodes computing this before feeding into the Offset Curve.

Step 5: Closing the Rectangle Widths#

Now we create the nodes to draw the small width lines by finding the endpoints of the length lines and drawing a line between them. Used End Points on both offset curves to get their start and end points, then drew Line segments connecting them across.

Heres the output of the lines. The viewport shows all the endpoint pairs as red crosses, 10 pairs total (2 per rectangle, 5 rectangles).

And we merge the output of those lines to combine them with a Merge node into a single set of curves ready for the next step.

Step 6: Region Difference and Fillet#

Now to put it all together. We take the whole pentagon and the 5 rectangles and do a Region Difference operation so the rectangles are cut out from the sides inwards towards the radius, and then round the corners with Fillet. I also had to use Flatten Tree because the output of Join Curves was a list of lists with one curve in it and we needed to convert it to a flat list of curves.

And thats the final output! The pentagon with all five grooves cut in and corners filleted. Ready to be baked out and sent to the laser cutter. In part 2 I’ll cover the actual cutting process.

2.2 Cutting the Pentagon on the Epilog Zing Laser#

Kerf Test#

In a previous session we had printed a kerf test that let us see at what kerf amount the slotting of the material fits tightest. We figured out it was about 0.1mm for this machine, which is why we used that value in the Grasshopper definition.

The Machine#

We used the Epilog Zing laser in the fablab. This one.

These are the specs of the Epilog laser, its a 40W Zing 16.

Safety and Exhaust Setup#

This is the fan speed control. For safety we need to turn it on before use.

The different cutters share the exhaust system so you need to be mindful of that.

Need to make sure to pull out this extractor sliding stopper for the air to flow.

This is the actual extractor (fan? motor? whatever its called).

Connecting and Setting Up Inkscape#

We plug in the ethernet cable from the PC to the cutter.

In the lab we have a dedicated PC for the cutter which means you dont have to install the software on your own machine.

Then we open Inkscape on that PC.

We set the document properties to landscape since thats the shape of the laser bed.

Importing the Design#

We open the pentagon press fit DXF file we exported from Rhino and Grasshopper.

We set manual scaling.

There we have imported our design and positioned it in the top left corner.

Ensure fill is set to no paint.

Set stroke paint to flat color.

And set the stroke to hairline. Thats what tells the laser its a cut line.

Measuring the Material#

Then we measure the thickness of the material. Here its 2.95mm.

But the different sides of the material have different thickness, here it is 3.14mm. Its a natural material after all so thats expected.

Setting Focus#

We place the material on the cutter and now we have to set the focus of the laser. See this metal thing, we have to let it hang and just barely touch the material. Its a manual adjustment of focus.

As you can see its barely scraping it when we let it hang. Some machines do auto detect of focus but not this one.

Printer and Cut Settings#

Now in Inkscape we choose the Epilog Engraver as the printer.

When you print it opens up the Epilog software. Under Process click the folder icon to find a preset configuration for wood.

We start with the vector cutting preset for wood 3mm.

We can adjust speed, power, and frequency. For wood we dont want it to be too frequent or powerful as it may burn through, so we want the laser to be in and out as quickly as posible.

First Cut#

Now we click print from the software and we can see the job appeared on the machine. The display shows “Job1.Print”.

We click the play button to start cutting. Make sure the lid is closed.

So thats how our cut came out. The first one was fine but the second one wasnt fully cut through. Like we said the material thickness is different across the board so we needed to readjust some settings.

Second Attempt#

So we remeasured and got a piece of material without too much variation across the sides we want to cut. Here its 3.08mm.

And here its 3.13mm. Much more consistent.

We also noticed that the press fit was kinda loose. We realized in Rhino we were adding half the kerf to each offset instead of subtracting, so we fixed that.

And yay thats the cut we got! The press fit was better now, not too loose, but could be tighter tbh. Something to iterate on next time.

3. Lecture Notes#

Parametric Design#

This was probably the most interesting concept from the lecture. The core idea is that your design parameters are all correlated, so when you change one thing, everything else updates automatically. Like if you scale the length of a table, new legs get added where they need to be. You don’t manually go back and fix everything, the model just knows.

In FreeCAD specifically, parameters can be all sorts of things: physical quantities like weight or material type, geometric dimensions, even the number of elements in a pattern. FreeCAD has a built in spreadsheet (kind of like a mini Excel) where you can define all your variables before you even start designing. You can also add parameters later in the workflow, which is nice. For example you’d set up variables for slot length and side length, and then reference those throughout your sketch instead of hardcoding numbers everywhere.

This is what makes parametric modeling so powerful for things like press fit construction kits. You define your material thickness and kerf as parameters, test them, tweak the numbers, and the whole design updates. Neil showed some examples of parametric joints and construction kits on the course site, including clearance testing and stress concentration considerations.

The Tools Landscape#

There’s a huge range of cutting tools beyond vinyl cutters and laser cutters that I didn’t fully appreciate. Vinyl cutters (like our Roland, plus Cricut and others) use a knife, but there are also ultrasonic cutters. Laser cutters come in tons of flavors: Epilog, Universal, Trotec, GCC on the professional side, and then more accessible ones like xTool and Full Spectrum. And then there are plasma cutters, waterjet cutters (OMAX, Flow, even a desktop one called WAZER), hot wire cutters for foam, and wire EDM machines. Each one has its own sweet spot depending on material and precision.

On the CAD/CAM software side, there’s more options than I realized. Beyond Fusion 360 which I’ve been using, there’s Inkscape with extensions for 2D vector work, Rhino with Grasshopper for parametric stuff, Blender with geometry nodes, FreeCAD, SolidWorks, Onshape, and a bunch of specialized tools like Cuttle and Kyub for specific fabrication workflows. For CAM, there’s Inkcut (which I’d been wondering about, turns out it’s basically open source software for driving vinyl cutters and plotters) and the mods project which Neil demonstrated.

Vinyl Cutter#

Interesting take from the lecture: the vinyl cutter is apparently the least appreciated tool in fab labs. But it actually does way more than just stickers. (google tells me: thermal transfer prints onto fabric, pop up cards, screen printing stencils, sandblasting masks, and even cutting copper tape for flex circuits and antennas). The materials list goes beyond regular vinyl too.

Laser Cutter#

Apparently, the laser cutter is the most overused tool. Everyone gravitates towards it because it’s fast and versatile, which is fair.

Laser Safety and Practical Stuff#

Safety is a big deal with lasers. There are different laser safety classes, and you need proper venting and airflow. The air assist blows debris away from the cut, the exhaust pulls fumes out, and filters clean the exhaust before it goes outside. Some materials are straight up dangerous to cut: PVC releases chlorine gas (you can do a flame test to check, PVC burns green). Polycarbonate doesn’t cut well either, it melts and discolors.

Materials that work great: cardboard (check the Edge Crush Test rating, and grain orientation matters), wood, acrylic/PMMA (which you can also glue and bend), delrin/POM, and fabric.

The practical settings you dial in are focus (distance from lens to material), power, speed, rate, and number of passes. Kerf is the width of material the laser removes, and you need to account for that in your designs, especially for press fit joints where the fit tolerance matters.