Week 3

Assignment - Computer-Controlled Cutting

Group assignment:
Do your lab’s safety training
Characterize your lasercutter’s focus, power, speed, rate, kerf, joint clearance and types.
Document your work to the group work page and reflect on your individual page what you learned.
Individual assignment:
Design, lasercut, and document a parametric construction kit, accounting for the lasercutter kerf.
Cut something on the vinyl cutter.

From Assignment Details.

Group Assignment:

Group Assignments Page

Laser Safety Training

[x] Did the laser introduction with my instructors.
Notice: Fire Point and Assembly Point notice
Notice: Controls, End Stops
Make Sure Extractor/Filter is working, and the duct gate is open
PPE: Safety Glasses (not required for normal use)
Never: PVC/Chlorine!

In case of Emergency:

Fire Blanket
Extinguisher
Raise alarm
Exit calmly to assembly point

Standard operation:

Epilog

Epilog Pic

Starting up,
- Turn on the computer.
- Turn on the Epilog and the extractor(s). (On the Zing machine, open the duct gate also).
- Place your material flat within the hard rulers,
- Focus, with the spring depth gage, and the up and down buttons on the top surface of your material.
Preparing and sending your file,
- Open Inkscape, and open your SVG or DXF file,
- File > Print or Ctrl+P to send to the Epilog Dashboard program.
In the Epilog software,
- Assign your cut strategies and material settings.
- You can use the preconfigured materials, and make tweaks for the specific mateial you are using.
- Position your job (with cameras, in case of Epilog Fusion Pro).
- Print and select Run on the machine screen.

Trotec

Trotec Speedy400

Turning on the machine (usually for staff):
- Turn on the computer, Open Trotec Ruby in Edge.
- Log in
Import,
- Import your file. AI, SVG, DXF, and image formats.
- Check scale (in particular if DXF), position and set up colours for vectors and raster layers.
- Defaults are Black for Raster Engrave, Red for Vector Engrave, and Magenta for Cut. But it’s really easy to reassign them. Just make sure your graphics are recognised colours (RGB spectrum).
- Click Create Job.
On the Prepare page,
- Select material
- Adjust material power and speed by clicking on the settings. Click on the coloured square to reassign.
- Position job(s) on the bed,
- Drag and align to material area. Use the red dot, updates on screen live to check the positioning relative to your material.
- Click Send to Laser
Prepare the machine,
Extraction is switch on automatically, and runs for 2 mins after the job is complete.
Load material flat on bed
Set your focus (auto-focus or manual gage)
Press the Play button to send from Ruby to laser
Afterwards,
- Wait for extraction to clear fumes
- Remove parts carefully
- Clean edges / bed if required

Checklist and agreement:

Laser Safety Checklist

Laser Cutter Characterisation

Creative Spark has a Beambox, an Epilog Zing, an Epilog Fusion Pro, and an xTools F2 Ultra.

Fab Lab Limerick has a Trotec Speedy400, and an old Lasersaur.

Epilog Fusion Pro

Epilog Pic

Focus: 2.0" Lens
Power: 120W.
Work Area: 1219 x 914 mm
Speed: up to 4.2 m/s
Rate: Pulse configured through the Epilog Dashboard material settings, depending on the material
Kerf/Joint Clearance: To be characterised.
Type: CO₂.

Trotec Speedy 400

Trotec Pi

Focus: 2.0" Lens
Power: 80W, …however this is an older machine and recent maintenance measured a power drop of >10W between source and cutting position.
Work Area: 1000 x 610 mm
Speed: Original Specs for the machine state Max. processing speed: 4.32 m/s. The software presents each material speed as a % of this value.
Rate: The software uses 1-60 kHz, depending on the settings for that particular material. Timber and Card are at the lower end, and plastics like Acrylic seem to be at the higher end.
Kerf: 0.4mm (see below)
Joint Clearance: 0.2mm (see below)
Type: CO₂ CeramiCore® laser source produced by Iradion GmbH

Kerf Test

Steps

Measure material thickness with a callipers (note that it could vary from the nominal thickness and that it could vary across the material!)
- Cut a square of a known dimension. Use a calipers to measure the inside of the hole, and the outside of the positive part
- And then you can calculate, $$ kerf = \frac{s_{inner} - s_{outer}}{2} $$
To be sure, based on the measured thickness, make an array of slots, that vary (negative and positive). For a timber/timber product, a series of thicknesses ±0.2mm is a good guess.
Cut both parts, and mark which is which(!)
Try it out for the desired tightness.

Material 1.: MDF, 2.5mm (adapted for Trotec bulb)

100% power
0.6% speed
2 passes
1000 Hz
10 Power Correction
0mm Z-Offset
Air-Assist On
Source CO₂

Material 2: Plywood, 3mm (adapted for Trotec bulb)

100% power
0.9% speed
2 passes
5000 Hz
10 Power Correction
0mm Z-Offset
Air-Assist On
Source CO₂

Measured: 24.6mm (meant to be 25.0mm) So Kerf = 0.4mm, and Joint clearance = 0.2mm

Material 3: Acrylic, 3mm

100% power
0.2% speed
1 pass
6000 Hz
10 Power Correction
0mm Z-Offset
Air-Assist On
Source CO₂

Kerf Test 2

Tested best fit, “2.7mm”, so kerf is 0.15mm (each side)

1st Laser Cut

The first step was to get familiar with the Epilog. In this case I used the Epilog Flux, and a 3mm Plywood offcut.

Laser_1

The drawing was in Inkscape. The Epilog software understands fills and hairline vectors. You can, additionally, add more to the list on the right. Have them filtered by colour, or type to set up different operations, with different speed and power settings. The open folder icon allows you select a material from the existing library. (Note as you do this may overwrite tweaks you made up to this point, and job-level settings, like resolution).

Laser_2 Laser_3

Grasshopper Parametric Script, pt 1.

Then, I experimented with a Grasshopper Script to slice a 3D object with an interlocking pattern. It uses the Contour node and the Region Slits node to do this efficiently. And I will apply OpenNest to lay out a cut sheet.

Grasshopper is a node-based, low-code parametric program that works with/within Rhino. ‘Flows’ work from left to right, and data passes along wires between nodes. Often the biggest challenge is managing data and lists of data.

Nodes allow you to use data from inputs, collections of data, series and psuedo-randomised data, and apply in a parametric CAD environment. Script nodes allow even further customisation in Python or C# or Net Basic.

Plugins like Kangaroo, Human, Lunchbox, Wasp, and Ladybug are popular, and available with downloads and discussion forum, on food4rhino.

Grasshopper_1

This is the most basic version of the Box Split node.

From the ribbon menu, go to Intersections > Shape > Box Slits.

Box (thin line) is the horizontal box.
Box (with the ticker line) are the two verticals.
Input (“G”) of 0.18, which is the Gap, i.e., 0.18mm (clearance for kerf, 0.09mm either side).
The output Brep (“B”) goes to the List Index node, so I can show one result, moved +15 in Y.

Grasshopper_1a Grasshopper_3

However, this version uses the Contour node as mentioned above. Allowing me to seperately deal with the X and Y slits.

OpenNest, then takes the combined list, and fits it to a rectangular shape provided, as best as it can nest. OpenNest’s second output is a transformation, or list of transformations (vector + rotation + scale) that transforms a list of text objects to end up in the same place relatively without having to recalculate!

Transfer to Inkscape Lasercut, during cut Lasercut Finished Cut

Grasshopper Conclusion

I wanted to experiment with grasshopper for this assignment. The limits I found were:

Could not adjust the slot depth (always 50/50)
Could not add notches at opening, or taper, or added clip features.
RegionSlits component produced some self-intersecting boundaries.
RegionSlits missed some intersections entirely.
The assembled model was not assemble-able, numbers not in order and direction of slots not consistent.

Laser_4

Grasshopper Contd.

I used the Contour node to make a stacked model, based on a BREP (ie a NURBS rhino shape, or a polysurface).

OpenNest 2 is the plugin I used to nest the slices. It’s a little buggy sometimes, and I find it’s best to disconnect, and reconnect the nodes. There are examples on food4rhino.

Laser_4

File:

simplecontours.ghx

Cut something on the Vinyl Cutter

To make use of the Vinyl Cutter, I drew something in Inkscape. The Vinyl Cutter is a Roland GS2-24, and I used a laptop in the lab with the Roland DGA Print Driver.

Vinyl_1

From the roll, cut roughly to length. This is a 300mm roll of polymeric adhesive vinyl.

Vinyl_2

Release the lever at the back left of the machine. Feed the vinyl through the machine from the front. Adjust the wheels. The white stickers correspond to the knurled parts of the bar underneath, so make sure both wheels are within the white demarkated sections. Make sure the edge is parallel with the lines marked on the machine, so that it doesn’t misalign itself too much as it moves.

Vinyl_Now_Loading

From the menu, select “Piece” to add.

Vinyl_Putting_In_Page_Sizes Vinyl_Width_And_Height

The carraige travels the width of the machine, and rolls the piece through. It returns the width and height on the display. Update this in Inkscape (Document Preferences).

Vinyl_Arranging_Your_Page