5 Ways to Cut Costs when Designing Enclosures

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5 Ways to Cut Costs When Designing an Electronic Enclosure

19th Oct 2021
by Edward Moss

Designing an electronic enclosure isn’t always straightforward, and keeping costs down can be crucial for making the end product financially viable. From material choice to surface finish, there are decisions made across the whole manufacturing process where you may be adding unnecessary costs. 

In this blog I will lay out five considerations when developing electronic enclosures to make your design cheaper and easier to source. 

1. Material Selection

Electronic enclosure - feed imageChoosing the right material for your enclosure for its physical properties is crucial, but you should also consider raw material costs, availability, how fast a material can be machined, and to what tolerance, as these factors will all impact price.
 
Aluminium, stainless steel and plastic are the materials generally specified for machined enclosures. For detailed information about these materials and others, see our Resource Hub, or if you have a specific question, get in touch with our expert team and we can talk through the benefits of each for your application. 

Aluminium

Aluminium is the most common material that is used for machined enclosures because:

  • It is light weight
  • The raw material is comparatively low cost
  • It is readily available in multiple sizes of plate, round bar and flat bar
  • It generally has shorter run times due to the high rate of material removal
  • Tight tolerances are easily achievable
  • It can be anodised in multiple colours, giving options for branding.

For example, to achieve a consistently superior finish using an anodising process, we recommend choosing 5083 for your enclosure. 

Stainless Steel

Stainless steel is often used where aluminium would fail, for example, in harsh environments, sub-zero temperatures, or when coming into contact with corrosive chemicals. 

Two of the most common grades of stainless steel that I recommend are 304 and 316 because they generally strike the right balance between corrosion resistance and value for money.

If specifying stainless steel, consider:

  • Stainless steel is heavier than aluminium and plastic
  • It is generally more expensive than aluminium and plastic
  • It is less readily available in thicker plate sizes
  • It has lower rates of material removal, meaning longer run times than aluminium and plastic
  • Tight tolerances are easily achievable
  • Adding colour to steel is usually through powder coating, rather than anodising. Multiple colours can be used but this process will add thickness to the machined structure.
Plastic

There are many grades and trade names of plastic. Two of the most common grades for electronic enclosures are Acetal, such as Delrin®, and ABS (Acrylonitrile Butadiene Styrene)

For plastic enclosures, consider:

  • Plastic is light weight 
  • It is low-cost (although some grades are not stocked, so a minimum order value may apply)
  • Some plastics have long lead times
  • It has a high rate of material removal
  • Plastics are more prone to movement after machining, meaning holding tight tolerances is more challenging
  • There are limited options to change appearance of plastics, so only standard colours are possible. 

I won’t sugarcoat it: machining plastics is hard. So if you do specify a plastic machined enclosure, to ensure the best outcome, choose a machining company with extensive experience in machining plastics, who will support you in the design, and communicate effectively with you throughout the process.

Material choice comparison table for electronic enclosures

(Click image to enlarge)

2. Tolerances

I often see designs for machined enclosures where tolerances haven’t been fully considered, and this can push up costs. Penta’s default tolerances are DIN-ISO-2768-mk, but we can support designers on deciding the most appropriate tolerance for an enclosure. By thinking about where tighter tolerances are necessary, and where more open tolerances can be applied, it’s possible to reduce run time on the machine and cut costs. 

Certainly, where tolerances must be maintained, this is critical and should be specified on the drawing, but there may be areas of the enclosure where fit and tolerance can be relaxed. For example, if a cavity has a clearance of 1mm for the mating part, specifying a blanket 0.1mm tolerance will require additional machining time that will add unnecessary costs.

3. Surface Finish

Surface finish comparatorsA simple cost saver when designing electronic enclosures is specifying the surface finish. The majority of designs and drawings we receive have a standard drawing border usually stating a surface finish of Ra1.6µm. This is informally known as ‘a good machined finish’. But is this always necessary?

If the inside of the enclosure is never seen by the customer, or there are sections of the enclosure that are considered less important, the surface finish could be relaxed to Ra3.2µm or greater. By specifying which surfaces are customer facing or need a higher spec finish, the machinist can take greater care on these faces, and then remove waste material faster on the less important faces, saving time on the machine and reducing unit cost. 

4. Corner Radii

I always recommend specifying as large a corner radius as possible on electronic enclosure designs as it allows a machinist to save time on the machine by using a larger, standard, off the shelf cutter.

This is especially important when designing deep enclosures. Standard cutters are available at a length of 6-7 times the diameter, so to produce a 4mm radius for example, an Ø8mm cutter would be able to machine 48-56mm deep. A 2mm radius would only go half as deep, taking longer to machine. And of course the deeper the tool goes the slower the tool feed rate.

5. Tapped Holes and PCB Upstands

Electronic enclosure - upstands featuresSpecifying the correct size and depth tapped hole can also save costs. Generally, to get the maximum strength from a tapped hole, the thread depth needs to be 2.5 x Ø. For example, an M3 x 0.5mm pitch tapped hole needs a maximum thread depth of 7.5mm (3x2.5mm). Going longer than this will not bring any additional strength, but it will add cost through custom tooling requirements.

Similarly, the location of features such as PCB upstands, islands or bosses within enclosures should be considered with tooling in mind. I’ve seen designs where such features are situated as close as 2mm to the wall of an enclosure. Such a small gap means a Ø2mm cutter needs to be used, which will impact on the time taken on machine. My recommendation for such features is to group them together, or consider tabbing them to the wall of the enclosure to save machining time and reduce cost.  

Get the Right Advice

Taking into account the five points above will help you design a financially viable electronic enclosure. Penta has over 20 years’ experience in machining a wide array of materials and components, including hard-to-machine plastics, and by building strong partnerships with our customers, taking care, communicating well, and using our knowledge of machining, we enable our customers to get a product that not only delivers the functionality required but also helps get the project within budget.

Get Penta Involved

Penta Precision is ISO 9001:2015 accredited for quality assurance. Our experienced engineers can alert you to potential design and engineering issues before they become costly, time-consuming and stressful.

Penta is different because we have tried and trusted validated processes:

  • We communicate well 
  • We take care at each stage
  • Our service is consistent.

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