Week 15

Wildcard Week

For wildcard week, I explored vacuum forming using the Mayku FormBox. I designed a custom volume control knob for a rotary encoder (used in my final project), modeled it in CAD, and created a two-part mold using vacuum forming sheets

The process that I dedcided for my Wildcard Week is making moulds using vacuum forming. The process involves 3D printing a positive form of the required end product and then vacuum forming it and then resin casting it to get the required end product. The process is not covered in the rest of the Fab Academy weeks, that's why I wanted to explore it in the Wildcard Week.

CAD Design

I used Autodes kFusion 360 to model the volume knob. The design was created with both form and function in mind, matching the retro-futuristic theme of my final project while fitting securely on a standard rotary encoder shaft. To prepare for mold making, I designed the knob in a way that would allow easy casting and de-molding, incorporating appropriate draft angles and splitting it into two halves for a two-part mold.

Design for Vacuum Forming

The Mayku Formbox comes with a manual which includes all instructions for using the machine, it also includes a section which talks about the design rules and tips.

Mayku FormBox Starter Kit

When designing for vacuum forming, it's important to consider the following:

Rule 1:Remove all undercuts

Undercuts make it difficult to remove templates once they have been formed. Make sure your design doesn't have any ledges or indents that could stop a template from being removed.

Rule 2:Add draft angles

Draft angles are slopes on the edges of your templates. They help you remove templates from the vacuum form very easily. The slopes on the edges of your forms should point outwards not inwards, so templates come out with little effort.

Rule 3:Add air holes

Adding air holes will allow air to flow freely through your design to the vacuum plate. This will help your Mayku Sheet get into the tiniest of spaces.

I designed the knob according to my needs in Fusion 360 to fit the rotary encoder, for volume control. I duplicated the knobs for making the two separate vacuum formed molds, to get the inner and outer features of the knob.

Designing Process

The first thing that you need to design for the process of vacuum forming is make sure there is a minimum draft angle of 3 degrees on the sides of the design. This is to ensure that the formed part can be easily removed from the mold after vacuum forming. The draft angle allows the formed part to slide off the mold without getting stuck, which is crucial for successful vacuum forming.

But I gave only one degree of taper angle here.

Air Holes

The next important features are Air Holes. Air Holes are necessary for getting negative features in the design while Vacuum Forming. Therefore I have added multiple holes on the surface to get the inside features of the knob and one for the depression on the top surface. Lack of air holes would result in bad mold outputs with incomplete features.

The extrusions on the base knob are for matching the molds when casting so that we don't need to care for aligning the the two part mold.

This is the final part ready for 3D Printing

3D Printing

For the 3D printing process, I used a BambuLab A1 printer with PLA filament. The knob was printed in 3 parts. The main knob outer surface and two supporting structures for forming two different molds: One for the upper/outer Surface of the knob and one for the inner surface of the knob.

Vacuum Forming

For vacuum forming I used the The Mayku Formbox, a compact vacuum forming machine that allows for easy and efficient vacuum forming at home or in a workshop.

Mayku FormBox

Vacuum forming is a process where a sheet of plastic is heated until it becomes pliable, then stretched over a mold and vacuumed down to create a shape.

Mayku FormBox Starter Manual

The above link is for the Mayku Formbox Starter Manual

Materials

The Mayku Formbox can use a variety of materials for vacuum forming, I have used the Mayku Formbox sheets which are specifically designed for the Formbox. These sheets are available in different thicknesses and materials, allowing for a range of applications from simple molds to complex shapes. The below linked PDF includes the specificaions of the Mayku Formbox Compatible Materials which are sold by Mayku.

Mayku Formbox Material Spec Sheet Mayku FormBox Material Safety Datasheet

The material used here is called is Mayku Clear Sheets, which is made mainly of PETG.