Parametric Press-Fit Modeling

Parametric is an approach in design and modeling, where design is driven by parameters and relationships between different elements. It works by defining parameters (design variables), setting constraints (rules that govern how each parameters relate to each other), and relations between parameters and constraints, either mathematical or logical.

Parametric Designing

Inspirations

For my parametric design, I’m interested to make something that is more abstract. My strategy is I want to focus less on the ‘object’ or aesthetic, and more on the design process and ‘module’ –make it modular utilising one module only that is varied in size and let it surprises me with what form configurations can be generated from that. Is tarted by finding inspirations and I know I want to do something with curve and playful.

Design plan / sketch

I decided to design one module that loooks like this

Parametric Modeling with Onshape

First of all, we need to learn how to model ‘parametrically’ by using Onshape. As I’ve mentioned above, there are 3 aspects of parametric design: parameters (variables that are changeable), constraints, and relations. Each of these aspects are done differently in Onshape, here they are:

1. Setting Constraints

There are 2 ways of setting a constraint in Onshape. Either a) manually by hovering, or b) running command

a) manually by hovering

Enabling constraints are only doable when you are sketching (as far as I understand). So, for example when you’re doing a sketch, and you want to make a square that are parallel to each other, you can do that by first hovering over the reference point and dragging your cursor over to the spot that you want to start drawing

I will draw 3 rectangles that are tied to each other. I started off by drawing a rectangle sketch. And then hover over a point that I want to start drawing the next rectangle.

And then I draw the next rectangle from that point. This will create a coincidence constraint.

b) through the constraint command toolbar

From the command toolbar you can search “Constraints” and you can see there are many options that you can choose from:

Here I am demonstrating how to make a coincident constraint. First, by making rectangles for the slots. And then I put a midpoint in each of the small rectangle, as well as in the big rectangles.

Next, go to the Constraint > Coincident (i) and then select the two points that we weant to meet together.

How to check if your constraints are working

2. Setting Variables

3. Relations

After all the parameter works, what I do next is basically continue on making it curvy by using a 3-point arc tools in each of the corners.

And then by using the “Equal” constraints, I make the radius of the arcs the same to each other

And next, I’m continuing on extruding the plane.

Now that we have the parametric design. Whenever we have to change the module size or material thickness, which results in change of the slot width, we can just edit the bodyLength and/or slotWidth value and it will automatically adjust the all design elements for us.

Assembly

To simulate what it look like when assembled, we can go to the Assembly Studio tab, and use the ‘Mate Connector’ features. Here I’m using ‘Fastened’ mate connection, to simulate the slot connection.

with 2.7mm thick cardboard

with 6.6mm thick cardboard

If all is well with our design, we can save and export the design module into .svg format file.

Laser Cutting

Next step is to lasercut the modules! You can follow the general instructions on how to operate the lasercut machine by following the step by step process mentioned in our group assignment here.

Transfering Files to Machine with RetinaEngrave control software

Okay, so to cut our model, we have to send the design to the machine through a control software. At Fab Lab Bali, we’re using the Muse Core Laser Cutter. Apparently it comes with a browser-based control software, called RetinaEngrave v3.0, which already incorporates necessary design adjustment features! The control software can be accessed through a browser using the machine’s IP address when we are connected to the same network.

• Once you open the software, go to File > Import, and load your design.

  

  The tools that we’ll be using the most are the job control tools (to run perimeter and run job), the engraving parameters, and the machine indicator control tools. Also, notice the emergency stop button on the top right corner.

• Once you load your design, position the object according to your material workspace in the laser cutter machine. And Run Perimeter by clicking the square icon in the job control tools, to check if the object’s position is within the intended area.

• Then, in the Vector Engraving Parameters, set the cutting power, speed, current, and passes value. If you have multiple path-types to cut, you can differentiate their settings by assigning different colors, and you can also arrange their cutting order.

  

• You can automatically duplicate and arrange your object by using the Grid Array feature. Just set the number of columns and rows, as well as spacing and click Apply.

  

  for example, here’s the result of my array:

  

• Important! Before running job, don’t forget to turn on the the Exhaust Fan, Cooler, and Toggle Air Assist! in the bottom right corner. You can also alternatively do this directly from the machine.

  

• Finally, close the laser cutter lid. When all is well, the indicators should show no red colors. And you can go ahead press Run Job icon to start the laser cutting process.

Cutting Process

Never leave your lasercut unmonitored!

Cut Test Module

6mm cardboard:

The fit is nice! meaning that our kerf value is right!

More cutting results

Cardboard is not a homegenous material. Even with the same thickness, sometimes one cardboard is more dense than the other. As you can see here, I was using the same cardboard thickness, but one cardboard, it didn’t cut through at all. Therefore, always try to do a test-cut before any job, because the settings that works before might not work this time, even when it’s with a seemingly same-looking carboard.

Because of our lab’s limited cardboard, we have to change to the thinner cardboard, the 2.7mm thick one. I even ended up utilizing leftover cardboard from mineral water box, so, there’s some design value needed to be adjusted.

Assembling

6mm vs 2.7mm cardboard

Overall Result