What is the Difference Between an Industrial Designer and a Design Engineer? incl. Polymer Part Design Checklist [Guest Post]

Our guest author and polymer design engineer Vatsal Kapadia presents in this post the difference between an industrial designer and design engineer. This post reflects his personal experiences in this area and he wants to share them with us. 

As an engineering tool for your next plastics part project, we worked on a Polymer Part Design Checklist which can be found in the end of this post.

What is the difference between an Industrial Designer and a Design Engineer? 

An Industrial Designer creates the concept for a part with major emphasis on aesthetics and innovation. A Design Engineer designs a part considering functionality. Thus, dimensions, tolerances and limits are established according to the technical requirements of the envisaged product. 

A refined part is the one which satisfies all expectations including performance and appearance and is commercially economical to produce. Different other factors contribute to the dimensions and properties of a part, i.e. utilized machines, processes and skill level of workers. 

Dimensions and tolerances are fundamental for manufacturing any polymer-based part. This leads us to the following question: How do you choose a tolerance? You should start by consulting the tolerance chart available for the materials you want to produce your part with and review these together with the manufacturing team. Resulting manufactured prototypes shall subsequently be inspected for obtained dimensions. In the final drawing sheet, all the tolerances along with the dimensions in an orthographic view are necessary. Such process is crucial for concept to completion or design to manufacture. Concepts of GD&T (Geometric Dimensioning and Tolerance system) have allowed designers to work more precisely with datum points facilitating efficient exchange of part’s design data between involved parties as well. 

A foolproof design engineer and/or tool designer shall also be thorough when it comes to material selection as the choice of the right material is crucial for part design and manufacturing. Important material properties influencing part’s design include e.g. mechanical, thermal, electrical and chemical properties, shrinkage factor, surface finish and material recyclability. Selection of a suitable processing technique accordingly completes the whole part design process. 

Finally, I would like to share a non-technical experience: Cooperation and communication between industrial designers, design engineers and tool designers can save time by ensuring that the product is not only accurately designed to accomplish its functionality, but also that it can be molded and assembled. 

The following Polymer Part Design Checklist will allow you to gather all necessary information about the part. Having such a checklist not only allows the present job work to be systematic, but it should also help in the future when a part failure occurs in any real life application.

Thank you and #Findoutabouplastics!

Vatsal & Herwig 

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Polymeric Material Selection: In 6 Steps To The Optimal Polymer For Your Application

If you are a designer, application engineer, material engineer, or material purchaser dealing with e.g. automotive parts, you will have one major question in mind to bring forward your projects: which polymeric material fulfills the job based on the set criteria in the optimal way and costs? To take the guess work out, I will show you in this blog post how you can determine the optimal polymeric material in six steps [1]. In this way you can keep track of your material decision making process.

Step 1 - Define key criteria for your part: Main task here is to proper estimate the requirements of the part which can be based on performance criteria, appearance criteria, and cost targets (part costs, tooling costs and equipment costs). Step 2 - Selection of the manufacturing process: there are several things to consider when selecting the manufacturing process of your part. On one hand, it is the part size, part complexity, and allover product volumes. On the other hand, you have equipment costs. For example, costs of an injection moulding machine in case a new one is needed and tooling costs. Production volumes are the driving force here, followed by tooling costs. The material cost can vary from 50% (technical parts) up to 80% (consumer parts) of your manufacturing costs. The economic batch size varies for the different processing techniques:

- Injection moulding: 10^4 – 10^6 units

- Blow moulding: 10^5 - 10^7 units
- Compression moulding: 10^3 – 10^5 units
- Rotational moulding: 10^3 – 10^4 units
- Thermoforming: 10 – 10^3 units
- Polymer casting: 10 – 10^3 units
- Resin transfer moulding: 10^3 – 10^6 units

Step 3 – Create a short list of materials: After we estimated the key criteria and manufacturing process it is time to create a short list of potential material candidates. A grouping into chemical family such as polyolefines, aliphatic nylons, semi-aromatic nylons, polyesters, polysulfones, fluoropolymers, polyketones, polyimides, and so on is useful. Furthermore, grouping by primary additives such as fiber (glass, carbon) reinforcement, tougheners, heat stabilizers, flame retardants is helpful at this stage too. Additionally, you can look for plastic material suppliers in online databases such as Pro-Plast  or you can work with online selection guides such as these ones: Omnexus and PlasticsFinder. Furthermore, CAMPUS material database offers a comparison of hundreds of grades and their properties in an uniform way (every resin supplier who contributes to CAMPUS tests their materials in the same way).

Step 4 – Evaluation of your data: now the feasibility study can start by evaluating the material data of the chosen polymers for mechanical, chemical, electrical, process ability, post-processing capabilities such as laser welding, painting or metallization. Since some load cases of the final part are available, structural analysis can be done too. Cost analysis is crucial for some end markets such as automotive and it needs to be included at this stage. The same is valid for supply chain and global availability of the suggested materials. The complexity of the analysis can vary and timewise it can take days or some months to obtain conclusive results.

Step 5 – Develop your prototypes: now you dive into the product development phase, which has an iterative character. In this phase, the focus is kept on detailed engineering. It is usually the longest phase and it allows you to create prototypes, test them, and re-iterate. Your material selection list will get more focused and some materials might fall off the list. In corporations, this phase can take place in the Research & Development (R&D) departments. There, engineers and scientists test and approve the different materials or they approve a process where the material is integrated. Product development groups have usually the product itself as an output. In some cases, the material needs to be first approved by the R&D for general design use that it can appear on the selection list for certain parts in the Product Development group.

Step 6 – Selection of the material: in the final step, selection takes place. The selection should be already pretty obvious and it should be not a surprise anymore which material will be used in the product. The selected plastic fulfills all the set criteria, including cost effectiveness. Implicit knowledge is turned into explicit results which allow a fact-based decision. If the decision is not yet easy and clear to take, then it is best to revise some of the steps, especially the starting steps. It will cause some time delays and is still better to take the extra loop since a wrong material choice now will lead to potential higher costs in the future. It is always useful to cross-check the results and the suggests with the resin supplier since they have in-house know-how build up on their materials including lots of testing and actual applications.

So, those were the 6 steps for selecting an optimal polymeric material for your application. You can use it as a checklist when you make your next material selection. For further reading I would like to recommend this post dealing with big data and material selection.

Thanks for reading & till next time!
Greetings, Herwig Juster


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Literature: [1] Eric Larson - Thermoplastic Material Selection: A Practical Guide