Help! My quote is just too high!

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Help! My quote is just too high!

21st Apr 2022
by Edward Moss

There are three main areas that make up a cost for a machined component: raw material, machining time, and any finishing processes required.

In an environment where both raw materials and energy costs have shot up, looking at practical ways to reduce the usage of both in the manufacture of your component is one way to cut costs. 

In my experience, if you’re struggling to get your precision machined components within budget, it is always worth reviewing your design to see how you could optimise it without affecting the form, fit or function of your component. 

Design your components in relation to standard plate, bar and tube sizes

Stock material on rackAn easy start is to consider the standard sizes of plates, bars and tubes. If it is possible for your component to align with standard sizes, you may be able to both reduce machining time and material wastage, and consequently reduce the cost per component.

For example, if your aluminium turned component has an outside diameter of 33mm, this would be machined from a Ø38mm stock bar. 

However, if the design allows, you could reduce the outside diameter of the finished component to Ø31.75mm (Ø1.25″). This is a standard size for aluminium bar, meaning that you would reduce the amount of raw material required, and therefore the cost, and potentially also cut machining time. 

Similarly, if you are designing an enclosure that requires milling and your design stipulates a depth of 48mm, a standard 50mm billet would usually not be suitable: we generally allow 3-5mm of material to hold the part for machining. Therefore, the next available size billet would be 57mm, meaning a lot of additional raw material is required. 

In this case, I would ask if it were possible to change the design to a 45mm depth, which would enable the machined parts supplier to use a standard 50.8mm billet, and still have enough material to hold the part.

Leave some faces ‘as stock’ where possible

Another way to optimise your raw material usage is to leave all or some faces of a component ‘as stock’ i.e. not machined. This is a particularly good option for components that are part of an assembly where some or all faces will never be seen.

Let’s return to that 33mm diameter turned component. Sizing down to a diameter of 31.75mm and leaving as stock would save costs in two ways: a smaller diameter bar of raw material could be purchased, and less machining time would be required.

Acetal billetsIn the case of a milled component, there may be a customer-facing ‘front’ that needs to look aesthetically pleasing, but the back may rarely or never be seen, and could therefore be left unmachined. 

As well as reducing machining time, this approach also decreases tool wear – reducing cycle times and associated consumables. This can reduce the overall cost per component. 

It is worth noting that some materials are more suitable for this than others. Aluminium, for example, usually has a cleaner finish than stainless steel, so there may be more opportunities where an aluminium component can be left as stock than stainless steel. 

One final aspect to consider is the material tolerance. If your component has a blanket tolerance of ±0.1mm, but the tolerance of the stock material is ±0.2mm, you will need to decide whether it is appropriate to relax the tolerance of your design, either for the whole component, or on specific faces. If not and the tolerance must be met across all faces, leaving as stock would not be an option.

Other ways to optimise your design

Aluminium component on machineOnce you’ve checked that your raw material usage has been optimised as much as possible, there may be other features of your design that could be changed to help get costs down. 

For example, if a design features complex pockets or recesses to reduce component weight, it may be possible to adjust this to a simple circle or square which would be far simpler to machine. While the precise ratio between weight and strength could be compromised, it may well be possible to create a design with comparable strength, that is just a little weightier than ideal. Of course, it may not always be acceptable to make this compromise, but where budget is tight and there is some design flexibility, small savings such as this can be very handy.

Other aspects of the design to review are material selection, tolerances, surface finish and corner radii. My blog post 5 Ways to Cut Costs When Designing an Electronic Enclosure has some excellent suggestions for ways you could adjust the design of an electronic enclosure to keep costs down, and many of these tips are applicable for other types of component too.

Partnering with a CNC machined parts supplier

When the economic environment is challenging, it’s vital to choose a supplier with considerable experience and expertise in machining design to help you keep costs down whilst not compromising the form, fit or function of your component.

Here at Penta Precision, machining design advice is offered as part of our service. All our estimators are time-served engineers and can advise you on optimising your design.

Call 023 9266 8334 and ask to speak to the Estimation team. We look forward to your call.

"Highly recommended and customer orientated company. Professional team which meet requests in a timely manner, supportive and cooperative." Nadiya - Purchasing Officer

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