Polymers Project: Mold Making and the Manufacturing Process

The introduction of molds in the Bronze Age elevated the crude manufacturing processes practiced by our ancestors. Mold-making techniques have been on the rise ever since, as manufacturers using advanced manufacturing techniques such as injection molding, thermoforming, or casting continue to rely on molds to create the majority of plastic, silicone, rubber, composite, and metal parts around you.

Professional manufacturers as well as hobbyists interested in taking advantage of these processes must understand how the mold-making process works, how they’re used, and how to optimize usage to meet specified throughput requirements.

We will be using Mold Star's 20T translucent platinum silicone, and Brush-On Series 40 as part of our polymers unit to create reusable molds - to cast concrete figures as part of our composites unit. Some of you will also be utilizing the 3D scanned resin prints as the positive model for mold making.

ASSIGNMENT: READ THIS ARTICLE AND TAKE THE SHORT QUIZ.

How to Choose a Mold-Making Technique?

What’s the best mold-making technique for a given application? It depends on a couple of important factors, including the desired end-part material, the intended manufacturing process, the geometry of the model, and the production volume. 

A simplified, step-by-step approach to choosing the best technique for your manufacturing project is covered in stages below: 

1. Outline the Development Criteria for Your Project

A manufacturing master plan can help create clear-cut details of what is to be expected from a project, its development timeline, and the available budget. Whether you’re planning to create custom parts or mass-produce thousands of the same item will define what options to pick in the next steps. The development criteria might vary depending on the project, but generally include the design of the part, size, material, quality, required tolerances, timeline, required production volume, cost constraints, etc. 

In product development, the initial document that answers many of these questions is often the product requirements document (PRD), while the bill of materials (BOM) is the comprehensive list of parts, items, assemblies, and other materials required to create a product.

HRG Project Options: A) Cast from original figure (bird, duck, frog, turtle, laying rabbit, crouching rabbit, large rabbit, bird, gnome or owl)

B) Cast from a 3d scan and Resin print - original size (owl 1/2 scale, Felix 1/2 scale))

3. Select the Mold-Making Technique

Once you settle on the right manufacturing process, the type of mold for the process is also largely defined by the development criteria. While the exact factors are dependent on the manufacturing process, here are some of the most important considerations when choosing a mold-making technique:

• Design of the part: Try to simplify the design as much as possible and align it with the design rules of the given manufacturing process to be able to choose the technique that can achieve the lowest costs. Simple designs might only require molds that can be created with manual techniques, while complex designs often require multi-part molds and digital manufacturing tools like 3D printers or CNC machining to create. 

• Production volume: Large-volume production runs require durable molds that can accurately replicate models without wearing out after a few uses. However, fabricating such tools comes with high costs and lead times. For one-off parts and lower volume batches, it might be more efficient to choose cheaper molds that can be created faster, such as sacrificial molds or soft molds that can be discarded when they begin to show signs of irreparable wear.

• Quality: Tighter tolerances require more precise molds and tools to create, such as digital manufacturing tools, and need to be more durable to ensure consistent part quality over multiple cycles.

• Timeline: Producing complex metal molds often takes months through a service provider. If you’re working on a shorter timeline, try to look for alternatives that can shorten the lead time, such as 3D printed rapid tooling.

• Material: Materials that have a higher melting point or are more abrasive will require molds that are more durable and can create the required volume of parts without degradation.  

HRG Project Options:

Moldstar T20

A) Single Part Mold (bird or duck)

B) Two Part Mold (duck, frog, turtle, or small bunnies, 1/2 scale owl or 1/2 scale Felix)

Brush On Series: (gnome, large bunny, owl full scale)

Link to Mold Making Instructional Power Point