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Ask the original manufacturer to configure the enclosure to the project

Author : Russell Irvine is with Hammond Electronics

05 December 2016

The main advantages of standard enclosures are that there are no up-front non-recurrent design, engineering and tooling charges; products are on the shelf ready for immediate delivery, so the time to market is as low as possible; the unit costs are attractive and the design will have been field proven in many different applications.

Compared with an application-specific custom enclosure, designed specifically for the project, standard products are immediately available and, certainly in volumes up to the low thousands, are extremely cost-effective. However, standard products are exactly that: standard. To meet the needs of a specific project, they will typically have to be machined with suitable apertures to accept switches, displays, I/O connectors, keyboards and other components. They will probably need to be printed with legends and logos and they may have to be finished in a non-standard colour to meet corporate or product branding requirements. 

To modify a standard enclosure to meet the requirements of a project, the purchaser has three choices: 

1. Purchase standard products, either directly from the manufacturer or through distribution, and then modify them as required in-house. However, many electronic OEMs may not have the plant, equipment, expertise or interest in undertaking machining and painting procedures in their own premises. If there is in-house capability, to modify the housing as a part of the overall assembly process could be the best way to proceed. However, more standard units than are actually required will have to be purchased to allow for set-up procedures and wastage. 

2. Buy standard products and outsource the modification processes to external contractors. In this scenario, there are the additional costs, time penalties and logistics complications associated with managing the process of sub-contracting.

3. Perhaps the best option is for the original manufacturer to provide a modified enclosure configured to the specific requirements of the project. With this option, there is no need to over-order to allow for set-up and wastage quantities. Arguably, given that the original manufacturer is best positioned to understand its own products, potentially expensive problems can be avoided during the initial design phase. It is certainly of great benefit to involve the standard enclosure manufacturer as early as possible in the development cycle. While many international standards, such as Eurocard, define basic PCB dimensions, smaller PCBs would not normally conform to any external size standard, so modifying a PCB layout and size at an early stage might enable it to fit a standard off the shelf enclosure, rather than ending up with a size that will definitely require a custom box. 

What sort of modifications can be done?

Hammond Electronics is a supplier of moulded plastic, metal, extruded and die-cast aluminium enclosures to the electronics industry, offering more than 5,000 different sizes as standard products. 

Hammond has the capability to undertake many different types of modification; the choice of method will obviously depend on the tasks required to achieve the required result. 

• Milling: CNC XYZ milling allows cutouts and rebates to be achieved. A comprehensive library of standard apertures exists and custom shapes can easily be achieved. A corner radius of 0.75mm can be created, enabling complex shapes to be readily achieved with high precision. 

• Drilling: Large and small holes can be positioned to tolerances of 0.005mm relative to each other, allowing holes to be positioned close together when required. 

• Punching: In sheet metal enclosures, punching is a very economical way of creating apertures of various shapes in flat panels. Metal enclosures would normally be punched in the flat before assembly.

• Engraving: Legends can be engraved in both plastic and metal using traditional techniques.

• Screen printing: Traditional screen printing enables single or multiple solid colour legends to be applied to enclosures and panels in a durable finish that resists erosion through normal wear and tear. Screen printing allows logos and gradients to be achieved on panels and enclosure bodies, opening up many design possibilities for the appearance of the finished product.

• EMC coatings: Moulded enclosures have one specific weakness: by virtue of the intrinsic properties of the material itself, plastic, unlike metal, offers no inherent attenuation to the passage of electric or magnetic fields. In many applications, this deficiency is of no consequence, but if radiation emitted by the housed electronics or their susceptibility to external fields is a potential problem, the lack of screening could be an issue. Internal coatings in a variety of materials can be applied to the inner surfaces of a plastic enclosure to give different degrees of attenuation dependent on the project requirements. By offering different materials in a range of thicknesses, the most cost-effective and technically competent solution can be provided. 

• Custom moulding colours: Hammond plastic enclosures are available in ABS, flame retardant ABS and polycarbonate. All plastic enclosures are available ex-stock in a variety of colours and all materials can be moulded in any custom colour subject to a minimum order quantity.

• Painted finishes: Aluminium die-cast enclosures are available as standard in natural and black finish. A wide range of different finishes and colours can be applied to both enclosures and panels; ranging from a deeply textured finish to an ultra-high gloss piano black paint, the appearance of the unit can reflect corporate or product identity.

• Overlays: Overlays are specified as the front panel finish in standards such as IEEE1101.10/11 used in cPCI applications. Overlays can be added to any size of front panel if required to give a durable and attractive appearance.

In addition to the fabrication capability, service is another key focus. To specify the modifications required, customers can download PDF drawings or 2D and 3D CAD files for all products from the Hammond website. The required modifications are marked up on the drawings and returned. A quote is prepared and upon receipt of order, approval samples are produced. Once the samples are accepted, volume production starts. This streamlined process reduces dwell time and removes possible errors if information from a customer drawing is re-entered into Hammond’s CAD system.

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