Frequently Asked Questions for the Design of Plastic Injection Moulded Products

Partnering with a leading manufacturer to help design and produce your specific plastic parts can be an excellent alternative to using pre-designed parts. It can offer you a larger sense of control, better cost savings and can meet your specific requirements.

This article sets out to answer a few of the frequently asked questions surrounding the design of your plastic injection moulded products, providing you with all you need to know before starting your product design process.

What plastic should I use?

When selecting the plastic you want to mould, it is essential to consider the properties of each plastic to ensure functionality. Therefore, selection depends entirely on the desired application of your product.

For example, Polypropylene (PP) is versatile, strong, and known for its excellent chemical resistance and lightweight nature. Whereas, Polycarbonate (PC) is a clear, tough thermoplastic known for its impact resistance and virtually unbreakable nature.

We’re happy to discuss your options with you to ensure you select the right material for your requirements.

What needs to be considered when designing a mould?

Wall thickness

Wall thickness should be as uniform as possible to prevent warping, sinking and internal voids. For most applications, we recommend keeping wall thickness between 1.5-2.5mm as thinner walls use less material and cool faster. This reduces running times and overall costs.

Drift angles

It is ideal that you add a draft to all vertical walls to allow the part to be released from the mould without causing damage to it.

A 1-2° angle is recommended for simple designs, but if your part is textured, you should add an extra 1.5-2° of extra draft for every 0.001 inch of texture depth.

Ribs

These are used to add stiffness without adding significant material, helping to keep your products' wall thickness consistent with the surrounding areas.

Rib thickness should be limited to 40%-60% of the nominal wall thickness and height should be less than three times the thickness of the main wall.

Undercuts

These features work to lock the part in the mould for additional security. Therefore, this typically increases complexity and the cost of tooling. To reduce the need for this it is ideal to try and redesign the part to eliminate this or use pass through cores instead.

What are the common issues and solutions for plastic injection moulding?

• Warping or sink marks - this is typically caused by wall thickness or rapid cooling. Ensure uniform cooling and gradual transitions between thick or thin sections to prevent these issues occurring.
• Flow lines or weld lines - these typically occur when plastic flows meet but can be controlled by gate placement, as well as better fill speed and pressure.
• Short shots or voids - which are seen when plastic doesn’t completely fill the mould. Thin walls, low pressure, or low temperature can cause this. Increase the pressure and temperature or optimise the gate location to reduce the chances of this happening.

How can Insignia help?

Our extensive facilities and capabilities allow us to take your project from start to finish, helping with the initial design, production and even your packaging requirements.

We can even produce prototypes for you to assess before committing to a full production run, ensuring your satisfaction with the end product. Or, if you’re looking for a pre-designed product, we have a range of expertly designed and manufactured products for you to choose from.

So, If you’re in the market for a reliable manufacturer to help you bring your idea from concept to reality, get in touch with us today.