5. Computer Controlled Cutting
This week's assignment tasks are listed below:
- group assignment:
- test the design rules for your 3D printer(s)
- individual assignment:
- design and 3D print an object (small, few cm3, limited by printer time) that could not be made subtractively
- 3D scan an object (and optionally print it)
2025/02/20:This week I wanted to change my documentation style to something that was more blog like, I'll be testing if I like it better this week.
The first thing I have to do is look at the evaluation criteria in Nueval Academany
Checklist
- Linked to the group assignment page
- Explained what you learned from testing the 3D printers
- Documented how you designed and 3D printed your object and explained why it could not be easily made subtractively
- Documented how you scanned an object
- Included your original design files for 3D printing
- Included your hero shots
Work Plan
I now spent some time (too much time to be honest) on making a workplan and detailing all the tasks for the week. Also I will be documenting in a rough format like a log as I perform the task instead of leaving it for after I am done with the task. Instead I will use that time only for formating it in a presentable manner.
Also, moving forward, I want to treat each week as small mini-project, ie. I have to create a product prototype in each week using the tools I learn in that week. This week I will create a poseable model of my final project that I will use to create a simple stop motion animatin. To make sure I complete the project, I have set a deadline for myself; 20/02/2025.
Group Assignment
21/07/2025: While I originally planned to complete the documentation for our group assignment yesterday, I was not able to complete it on time, so this was the first thing I did when I came to the lab in the morning
5.1. Test the design rules for your 3D printer(s)
Individual Assignment
5.2. Design and 3D print an object
Once done with group assignment documentation, I started to look for design inspiration for what I wanted to make. I wanted to make a parametrically designed print-in-place hinge joints because my final project involved two rectangles that had three hinge joints at the foot, knee and body. Also print-in-place joints are hard to make through subtractively so it met the assignment requirements. Also, since I wasn't able to properly explore other CAD software in the CAD design week I wanted to give FreeCAD one more try.
I followed this tutorial to make my design. If it works well I might print a foldable phone stand as shown in this tutorial.
After some tinkering with constraints, I was able to constrain the sketch fully after adding in the dimensions
Note: I noticed that it is easier to first select the constraint you want to use before selecting both edges/vertices, which was opposite to the way I operated in Fusion.
I then looked back at the tutorial, realized I had made some unintentional design changes which I then changed.
There was an error in the sketch, wherin the arc passing through the shape cut the shape into two sections that cannot be padded.
I'm assuming that you cannot select each individual plane and apply the 'Pad' function, similar to how you can do so with 'Extrude' function in Fusion
At this point in the tutorial I realised I missed addding a Part and nesting the Body inside it, so I did so now
I noticed that many of the tools like the arc tools were missing. I'm sure they are just hidden somwhere
At this point, my instructor saw what I was doing and instead suggested to focus on the aim of this weeek, which was to explore different 3D printing processes and explore FreeCAD only when you have some free time. I found his advice sensible, so I switched approaches and went with Fusion which I am most comfortable with.
First I started with the sketch for the cylinder that will form the hinge. I will be using parameters here also to make iteration easier.
I then created a sktech of the joint, which is fully parameterized
The revolve tool wont work since the projected surfaces would overlap, ie. you only need to make one half of the cross section about the axis of rotation, so I made the necessary changes by removing the mirror half.
I then able to remove the Revolve tool
Note: Only sketch one half of the sketch about the axis of rotation to use the Revolve tool
I then constructed a midplane and used the Solid 'Mirror' option to Mirror the faces on the other side.
In hindsight, I shoul have just made the cone that would the hinge joint and mirror opposite to the midplane, and then offset the faces to make the clearance
However, once I apply the operatin, it removes one of the outer cylinders as well
So I used the Mirror tool once more, this time mirroring the body about the same midplane
Now I have to make the main frame of my phone stand. To do that I took reference of my previous phone stand design.
I realized I made an error with my sketch, I had added an extra point, which I then removed and the sketch was readjusted
I then extruded the face connecting the cylinder to the cylinder surface, creating a curved surface
I then offset the of the middle section to give it a 1mm clearance.
I also used the Design History feature to go back and make minot changes in the design so that it would stay completely flat on one surface.
Just like before I created a mirror image of the sketch I made
This time I performed the same extrusion as before, but this time, I hid the body so that trhe Join operation would only affect two instead of all three bodies.
Now I have to add fillets so that to add strength to my model once I 3D print it
I realized I will not be able to fold the structure, so I have to reduce the extrusion now
When I presented the model to my instructor, I was told that it was still millable, even though it would be difficult
So I wanted to modify my original design to have a cylinder through a hole that is printed in place, making it truly impossible to mill
I was also given some advice to increase the diamter of the top of the cone
Based on instructer feedback, some chamfer was also added to the cylindrical portion of the hinge joints. The final model looks like this.
Added chamfer/fillet to cylinder sections
Download & open Bambu Studio
Connect wth printer by LAN
Slice model, no automatic message saying supports are required so I will not enable them
I removed the shell layers to expose the solid infill beneath
As you can see the layers do not completely cover the hinges. so we
Set colour,
Following first print failure, I added an outer brim of 5 mm
Following failure number 2, I was forced to increase the infill density to 20% so that the print would not tear off.
Failure number 3 because the print bed was not aligned properly.