Assignment:
For the third weeks activity, I started looking into creative uses for a Laser Cutter; one of the most versatile tools in manufacture if you know how to use them. These machines are commecially available, but are not usually in the hobbyist arsenal due to their size. The Laser cutters I’ll be using for this assignment are:
The assignment itself was to produce a small “Push Fit Model” out of Card, MDF or Acrylic. A push fit model is a model that holds itself together through clever joinary and minimal tolerance. The goal of this project was to use the in built “Perameter” function of Fusion 360 to minimise the tolerances as much as possible and prduce the tightest possible fit; accounting for veriables such as the thickness of the used material and the Lazer Kerf.
Terminology
Tolerance: The possible range of allowable veriation in a given dimension. Example: this part has a tolerance of +/-1mm
Laser Kerf: The thickness of the lazer itself.
Initial Settings and Tests! (With some Engraving!)
The very first task was to decide on which parameters we’d be using for this project. Overall, there will be four; Material, Kerf, SlotH and SlotW. They’re written like this because Fusion doesn’t recognise spaces as a character.The reason we need to set up parameters is because every dimension which is tied to that parameter can be changed at once using this method, instead of having to go through an alter each on individually.
Deciding the size of the material was easy, 2mm is readily available in all three of the materials and quick to cut while still being sturdy enough to be used for a model.The slots will all be 2mm deep and 6mm long for this first prototype. Finding the Laser Kerf for this assignment will prove to be a problem however. Every Laser cutter is slightly different, and the laser itself is tapered; meaning its cut gets very slightly wider with each extra mm added to the material thickness.
To find this Kerf, I cut two a small test pieces with slots cut at 2.05mm, 2.04mm, 2.03mm, 2.02mm and 2.01mm. This lets me experiment with the fit and see which one of these creates the strongest fit.
Methodology:
Setting the Parameters
Thanks to that test, I now know the laser cutter I’ll be using has a kerf of 0.07mm with 2mm material.
I can now set up the parameters for the next stage of the assignment.
Methodology:
You can find the Parameter settings under the modify tab of Fusion.
Just click the + icon and give the Parameter a name, unit, and … Parameter!
For this first test we’ll be using 4 parameters, Kerf, Material, SlotW and SlotH
Press Fit Model 1: Basically just a box! (With some Engraving!)
The first model was a very simple one; a four piece model that will form a tunnel. I’ll be using very simple push fit joints for this part of the assignment.
Methodology:
Start by drawing a box, of any size, then another rectangle which will form the slots! But instead of an ordinary dimension, type in the name of Parameter, which in this case is SlotH
This will cause the dimension to be constrained to that parameter, which in this case is 6mm + the Laser Kerf.
Now do the same, except with SlotW, which is set to 2mm (The thickness of the material + the Laser Kerf.
So now that we’ve tested the theory, lets test it out on a real model! This model is a bit more complicated and features a clipping system that should make the model more secure.
There’s also two 9.8mm holes being laser cut for 10mm dowel, remember the laser kerf will actually mean those holes are 9.94mm in diameter so the dowel should fit.
It works! This model was made out of 2mm Card and used tolerances to create a tight fit!
Laser Cutting Scale Models
Pythagoras
A 1/3 scale model of my furniture Project from earlier in the year. Made using 2 different thicknesses and an emphasis on the tolerance of the joints.
This is one of the laser cutting nests for the project, Tolerances were considered for the slots in the legs. they are 6mm slots designed to hold two 3mm sheets of MDF tightly through friction. Understanding Laser Kerf at the time would have given this model the extra level of natural strength it needed to work as an effective prototype
The Akari!
As part of my end of year usable project, I needed to product a model of the outer-shell with Acrylic sheet.This requires an amount of precision in both the lazer cutting and the making of the final piece.
Project Downloads
Press Fit Tube Model – Downloadable
Further Reading/Referencing
Assignment Documentation – Andrew Sleigh
minimal-parametric-laser-cutter-demo – Andrew Sleigh
