Some of your most frequently asked questions answered
At Lawrence Engineering, we deal with people from all areas of businesses from a wide variety of different types of engineers, to project managers, to founders and CEOs of medical device start-ups. Because of this, we encounter a wide range of experience levels when it comes to injection moulding and the moulding process itself. We’re regularly asked a variety of questions, and we’ve gathered the most common ones here to give you a clearer understanding of injection moulding, and how we can help solve your technical or business challenges.
Q: What variables effect the cost of an injection mould?
The cost of an injection mould tool can vary significantly depending on a number of key variables. These include:
- Tool size – Larger moulds generally require more material and machining time
- Number of cavities – Multi-cavity moulds increase production efficiency but can raise upfront tooling costs
- Part complexity – Intricate geometries, tight tolerances, and undercuts add to the design and manufacturing time
- Material selection – The type of steel or alloy used for the tool, as well as the plastic material being moulded, impacts both performance and cost
- Projected volume – Tools for high-volume production often require more robust design, automation features, and longevity considerations
Designing and building the mould correctly from the outset is one of the most effective ways to control costs. Choosing appropriate materials, designing with manufacturability in mind, and ensuring the tool is qualified to meet regulatory standards can all help prevent unexpected costs later in the process.
Q: What size moulds do you specialise in?
Injection moulds come in all shapes and sizes, depending on the application. At Lawrence Engineering, we specialise in small to mid-sized precision moulds, typically ranging from 5kg to 500kg.
Q: What is the difference between prototype moulds and production moulds?
The main difference between prototype moulds and production moulds lies in their intended purpose, materials, and expected lifespan.
Prototype Moulds
Prototype moulds are typically used for early-stage product development. Their purpose is to produce a limited number of parts quickly and cost-effectively, allowing for testing of form, fit, function, or regulatory evaluation before committing to full-scale production.
Key characteristics:
- Made from fully hardened Stainless Steel
- Typically, manual de-coring of undercuts
- Lower upfront cost
- Faster turnaround times
- Ideal for design validation and iterative testing
Production Moulds
Production moulds are designed for long-term, high-volume manufacturing. These tools are made from high-grade tool steel and are built to withstand the repeated stress of full production cycles while maintaining dimensional accuracy over time.
Key characteristics:
- Made from hardened steel for durability
- Higher upfront cost, but lower cost per part over time
- Designed for efficiency, consistency, and regulatory compliance
- Suitable for tens or hundreds of thousands of cycles
- Often incorporate features like multi-cavity layouts, hot runner systems, and automated ejection
Q: How can sustainability be incorporated into the injection moulding process?
Sustainability is of key importance to us at Lawrence Engineering, and we do always look to keep this in mind in the design process. While injection moulding for the medical device sector involves strict regulatory and performance requirements, there are still a number of meaningful ways to improve environmental impact.
Here are a few key areas where sustainability can be built into the injection moulding process:
- Design for minimal waste: Where possible, we focus on optimising part and tool design to reduce material usage and minimise waste during production.
- Efficient tooling and processing: Well-engineered moulds run more efficiently, produce fewer defective parts, and consume less energy per cycle. By investing in high-precision moulds, you can reduce material waste and lower your environmental footprint. Optimised process parameters also make a significant difference. For example, clamping force has a major impact on energy usage, so it’s important to apply only what’s necessary and avoid over-clamping
While sustainability in injection moulding can be challenging, especially in regulated industries , it is something we actively consider at every stage. From initial design to final production, we aim to deliver solutions that support both your business goals and environmental responsibility.
Q: What is DFM and what are the main benefits?
DFM (Design for Manufacturability) is the process of designing parts in a way that makes them easier, more cost-effective, and more reliable to manufacture. At Lawrence Engineering, we apply DFM principles early in the design process to help our customers streamline tooling costs and avoid costly processing problems further down the line.
Key benefits of DFM in injection moulding:
- Improved part quality and consistency – Optimising different areas of the mould tool reduces defects such as warping, sink marks, or short shots.
- Fewer mould modifications – Catching design challenges early on prevents delays and rework during tool build or validation.
- Longer tool life – A well-designed part places less stress on the tool, extending its lifespan and maintaining consistent performance over time.
Our experienced designers work closely with you to assess your design from every angle considering the geometry, material choice, projected volumes, and regulatory needs and develop the most suitable mould solution. By integrating DFM from the outset, we help ensure a smoother transition from design to production, while reducing risk and controlling costs.
Q: What are the main quality control challenges with injection moulding?
Injection moulding is a highly reliable manufacturing process, but achieving consistent part quality requires careful control of both design and processing parameters. At Lawrence Engineering, we place strong emphasis on Design for Manufacturability (DFM), thorough tool design, and a robust First Article Evaluation (FAI) process to ensure reliable performance from the outset.
Some of the main challenges that can happen include:
- Warpage and Shrinkage: As molten plastic cools and solidifies, it naturally contracts. Uneven cooling, inconsistent wall thickness, or poor material selection can result in part deformation (warping) or dimensional inaccuracies (shrinkage). Through DFM, careful material selection, and uniform wall design, we minimise internal stress and promote even cooling.
- Surface Defects: Some surface defects including flow lines, sink marks, and weld lines can be common problems. We use advanced design tools, including Moldflow analysis, to identify and resolve potential problem areas before tool manufacture. Proper gating, venting, and cooling channel design also play a crucial role.
- Flash and Burrs: Flash occurs when molten plastic escapes the mould cavity, often due to poor parting line design, worn tooling, or excessive injection pressure. Burrs are sharp edges or unwanted material often seen after demoulding. Precision tooling, optimised clamping force, and carefully designed parting lines are key to preventing these defects.
- Demoulding Issues: Getting parts to come off core pins without distortion is a challenge. Certain materials like Pebax for instance are more challenging in this regard. Here, specialised coatings, mould finish, and in-depth process knowledge are essential to achieve clean release.
- Blowouts of Tubing: In overmoulding applications, issues like tubing blowouts, pinched extrusions, or hypo damage can occur. These are primarily influenced by pinchoff design and require expert knowledge to address effectively. Understanding the interaction between tooling and process is vital for success.
Maintaining quality begins in the design phase. By identifying risks early and applying best practices in tool design, materials, and process control, we reduce the likelihood of defects and ensure consistent, production-ready parts.