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Designing for manufacture; the role of tolerancing software

11 March 2011

Martin Raines suggests five steps that the product designer can take to improve the manufacturability of his designs and achieve big reductions in rework and waste

A design engineer doesn’t always have all the necessary experience of manufacturing materials, processes and treatments to produce a design that will result in a product that requires minimal engineering change and will keep scrap and wastage to a minimum. Here are five things the designer can do to improve the ‘manufacturability’ of his designs:

Encourage feedback: encourage feedback from the machine shop and associated manufacturing specialists and absorb as much of it as you can. Don’t be the designer that takes offence when someone suggests a change; an improved design can only reflect well on you.

Spend time on the shop floor: it’s a good idea to spend a few days helping a machinist make one of your more complex parts. As part of this process, tell your machinist which features are absolutely necessary and which can be tweaked; he or she may well have some good suggestions to improve the machinability. If a machinist tells you that a particular aspect of a component is challenging, consider simplifying it.

Invest in tolerancing software: parts that don’t fit together are not necessarily the fault of the manufacturing department. Double check your tolerance stack, and then check it again, visualise it and write it down. And don’t just use your calculator – there is very good software out there to help you.

Consider material and process: you should consider the material and process you are using as a priority. If the material isn’t crucial to the design, simply choose the easiest material to machine. This will reduce capital expenditure as well as reducing scrap and wastage attributable to machining difficulties. 

Equally, if the process is producing a tolerance that is better than required, choose a different process to reduce the cost. It may well be that the component doesn’t really require a fine process, such as grinding, for instance.
Spend time with the QA department: while your new part is being qualified and tested, spend time with the quality assurance team and whoever handles industrial compliance in your business. It isn’t worth designing an easily machinable part if it doesn’t have the physical attribute required to pass muster and reach the end user.

Of course, if you work in a multinational manufacturing organisation many of these suggestions may be difficult to follow up, because your design department may be on a different site to that of the production plant. In fact, it’s frequently in a different country! So spending time with your machinist is impossible.

If this is the case, then the software route is the only way you can get the benefits that closer integration brings. By investing in tolerancing software, far fewer potential problems will get through to the shop floor. As a result, waste is minimised and the design is more elegant, more efficient and less costly.

Martin Raines is with tolerance software provider, Tolcap

Tolerancing software hints:
Bear in mind that, in tolerancing stack design, it is absolutely crucial that any software employs capable tolerances. If it doesn’t, it really isn’t worth the code it is written in. If it does not work with capable tolerances, then it needs to be used alongside Tolcap, which will allocate process capable tolerances to any design characteristic.

Tolcap manages tolerance allocation and predicts process capability at the early stages of design before production starts. This reduces production costs, improves product quality and increases product profit. The software is web based, readily usable and fully supported for business. It is also available for the education and training of engineering students.

Good tolerancing software will help you select the right process and material. By predicting tolerance you can choose exactly the right level of accuracy, without expensive over-specification.


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