Now let me get this clear, as machinists our job is to produce exactly what the designer asks us to produce. We often have no idea what the component does, where it is used or how it functions and even if we do, it is is not our place to question or interpret the design. We know that the drawing or CAD model is everything and it is our job to make it as perfectly as possible, as the designer intended.

Of course this means that when a designer or mechanical engineer designs something, what they do (or fail to do) has a direct impact on the manufacturing process which in turn impacts the components aesthetics, quality, delivery and of course cost.

Every time the component is re-produced any inefficiencies inherent in the design will create those negative impacts, year in and year out. Spend some time thinking about Design for Manufacture (DfM) at the beginning and customers will reap the benefits for years.

As machinists we see the same costly features time and time again. Adding cost, reducing quality and impacting delivery. In the days when designs were produced in large companies by people who had gone through an exhaustive apprenticeship, they would hopefully have included some DfM thought, Designs often went through several layers of checks meaning they were suitable for both their purpose and for manufacture.

However, with the advent of low cost CAD and smaller companies where people are required to undertake multiple roles, we see more and more designs that have had only limited thought about how they will be produced. Of course for machinists that means we get to do more machining which takes longer and costs more. Good for us on the face of it but not good for the supply chain, overall productivity or your bottom line.

Now there are many design issues that I could mention so these are just a few of my personal favourites!! I have put them in reverse order with the most expensive last!

6) Threads - Think about your threads. Have you left as much hole as possible at at the bottom of the thread? have you drilled through where you are able? Do you leave enough run-out on external threads? Does the hole need to be tapped as deep? Can you use a larger thread? - Threads are a constant source of concern for machinists and as a result they have the potential to add cost and increase scrap. We can produce any thread in the book ( and even those that aren't) but get it right and this will reduce your costs.

5) Surface finishes - I suspect your drawing border states all sorts of things and one of them might well be surface finish. In the absence of any other information whatever we see there we will have to apply to the entire component whether you need it or not. Like tolerances below, better surface finishes demand a slower and more refined machining process adding cost and time. Don't rely on that coverall note on the drawing border and give your surface finish requirements some really good thought if you want to decrease costs.

4) Internal corner radii. - The larger the better, always - whether you are designing a milled box or turned shaft make your internal corner radii as big as you can and this will feed through to the cost. Why? Well a larger internal rad means a larger cutter can be used which can run faster and so will reduce the component cycle time. As a by product the cutter will be more stable so the finish will be better. Machinists love big corner radii!!

3) Stock bar size -When designing a functional part ( ie one where the appearance is less important) are you able to produce it from a stock bar size? I have lost count of the number of times I have had to remove 0.8mm from a face just because the designer asked for 50mm when the stock bar of 2" (50.8mm) would have done just as well. Stock bar sizes are all available on the web or speak to your local material suppliers to check. This would save industry thousands.

2) Be really clear - A big issue is uncertainty. If we do not know then we have to assume the worse. By worse I mean we will give you the best finish we can, the tightest tolerance and the best overall quality. Great you might be thinking but this does not come for free. We will be assuming this from the point we quote the job. This impacts directly on what prices you will receive. If you can give as much information on what will be fit for purpose and where you need it to be top notch then we can do things to meet those needs, reducing the price as a consequence.

1) Tolerance - Tolerance has a direct and exponential impact and is my number one area that could be used to reduce costs. There are many issues but as a starter think about two areas before , during and after the design process.

do you really need that tight tolerance you are about to use?

does it really need to apply to the entire feature?

Give more thought to when and where you need to apply a tight tolerance and equally be really clear where it is less important and this helps reduce set-up time, scrap and means a less rigours process can be applied reducing production times.

Summary

I started by outlining that the machinist jobs is to produce what the designer wants and nothing I have outlined here changes this relationship. What I hope to show you however is that the more time you spend understanding the needs of manufacturing the more that will positively impact your costs. Spend time on Design for Manufacture and you win every time.