Technical IntroDesign CriteriaMaterials - TechnicalGenl Specs - TechnicalOverview - Technical
 
 
 
Overview - Design Criteria
PEI Standards
Types & Styles
Bends & Curves
Openings & Cutouts
Panels & Joints
Recesses & Pockets

 

 

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Overview - Design Criteria pdf
Overview -Design Criteria

 

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OVERVIEW - Design Criteria

PEI's revolutionary process allows for most of the features and functionality that you would typically find in injection molded or thermoformed enclosures. As for sheet metal fabricated enclosures, we can provide all of those features and much more.

We define enclosure features and functions as all of those attributes that do not involve the shape or basic construction of the product. In particular, we look at those enhancements that make an otherwise six-sided box into a functioning enclosure.

While it would be nearly impossible to list every possible feature or function that a customer may require or that PEI has provided, we have selected a number of key features and functionalities that we find our customers consistently request. Among those are:

Standoffs and Spacers
- for mounting PCB's and other components

Metal Inserts and studs
- to allow for the use of machine thread screws and nuts

Vents
- both straight through and offset

Openings and Cutouts
- for any shape or style connector or piece of hardware

Windows
- for displays

Pockets
- for labels, overlays, and membrane switches

Shielding
- for RFI/EMI protection

Silk-screening
- for labeling and aesthetic appeal

Painting
- for color matching and advertising

As stated before, this list is not "all inclusive" and if you have features or functions that you would like to include in your enclosure, be sure to bring them to attention. You may be pleasantly surprised to find that we can meet your request.

Construction - Shape, Style, and Materials
By construction we are referring to the physical make up of the basic enclosure including those items that involve the construction of the enclosure as well as the overall shape, size, look, and feel of the housing.

On that note, we can supply enclosures with curves, arcs, and rounded corners, as well as multiple surfaces and angles. The easiest way to envision what we can and can not do is to think of how you would form an enclosure by taking sheets of paper to develop the walls of the box. As with a piece of paper, we can bend, fold, and cut individual and multiple surfaces to develop a fabricated final product. Furthermore, because the plastic sheets we use have a thickness to them, we can incorporate pockets, recesses, angled vents, decorative emblems, engravings, embossings, and many other features that require a 3-D surface.

As for limitations, ours are simple. To eliminate the cost and time consuming process of utilizing hard tools and molds, we do not plasticize the material. This means we do not melt and re-form the plastic in such a way that we alter its original dimensional size. Because of this, we design and manufacture all of our enclosures without utilizing spherical shapes such as 3-D domes and contours.

However, this does not mean we can not incorporate eye-appealing designs into your enclosure. On the contrary, due to our years of experience in designing highly aesthetic enclosures, we have developed techniques that allow us to go beyond the 'boxie' cube look of typical fabrication. With over 8 years of experience and thousands of custom designs to our credit, we can offer any low volume enclosure customer attractive enclosures that can be customized for a company's own unique look and feel.

Before deciding to take on the time constraining and capital-intensive investment of molds and hard tooling, you should talk with us about the kind of enclosure PEI we can provide. You may be pleasantly surprised that you can get what you want, when you want it, and without the compromises that come from other enclosure sources.

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PEI Standards pdf
PEI Standards pdf

 

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PEI STANDARDS - Design Criteria

Many of PEI's design and technical standards come into play after the customer has approved the assembly drawing and we are developing the panel details. As such, it is not necessary for our customers to deal with those standards when developing their basic enclosure design.
However, there are some issues that our customers need to address so as to save time and eliminate costly features or attributes. In particular, we recommend that our customers adhere (or try to adhere) to some basic PEI guidelines.

PEI Standards and Specifications Guidelines

  • Keep the edges of holes and cut features a minimum of .200/(5mm) away from a bend joint. Closer placement is possible, but is more difficult to control deformation and should be avoided whenever possible.
  • Dimension from only one surface of a plastic wall...either the inside surface or the outside...but not from both.
  • Specify screws no smaller than #4 self-tapping or 4-40 machine thread. Smaller screws and threaded inserts are very difficult to handle and seldom provide a better alternative to a larger size.
  • Use threaded inserts for applications where the screw will be removed repeatedly.
  • Use self-tapping screws for fastening items that are never or seldom removed, such as a PCB or small LCD display.
  • Keep curves, arcs, and rounds to a minimum. These are costly features and should be used effectively. Extensive use of these features can increase the cost of an enclosure by 10 to 30 percent!
  • Use clear panels or windows judiciously. Clear plastic is more prone to scratching and can render an enclosure useless when marred or damaged.
  • Do not specify a material thickness that is either too thick or too thin for the application. Most enclosures have an ideal thickness and using something that is not ideal will ultimately drive up the cost.
  • Select the plastic material type, color, texture, and thickness as recommended on our "Material Specification" sheets.
  • During initial design, allow for flexibility in connector hole and/or PCB board placement. Standoffs come in specific lengths and being able to adjust your height specifications can reduce assembly costs.
  • Do not specify that the enclosure pass a drop test that the internal electronics will not! If the unit is dropped and the electronics will fail, then over engineering the enclosure will only add cost without a payback.
  • For 90 degree bends, the outside radius will be equal to the material thickness; i.e. 0.125" thick material will have 0.125 outside radius when bent to 90 degrees.

Because many standards and specifications are complex and difficult to summarize, we offer downloadable documents listed elsewhere on this web page.

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Types & Styles pdf
Types & Styles pdf

 

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TYPES & STYLES - Design Criteria

When discussing enclosures for electronic devices, the terms 'type' and 'style' have two distinct yet related meanings. 'Type' refers to where and how the device will be used while 'style' refers to the ergonomics and visual or 'look and feel' aspect of the unit.

Enclosure Types
For the most part, an enclosure type is determined by the environment in which it operates. By understanding the environment, our engineers can better suggest not only the type of unit you will need, but also the materials, fastening system, and general construction of the enclosure.

Examples of enclosure types include:

  • Pocket
  • Handheld
  • Portable
  • Mobile
  • Desk Top
  • Wall Mount
  • Hazardous
  • Dusty
  • Oily
  • Submerged
  • High Temperature
  • Vibration
  • Electrical Shock
  • Floor Mount

Enclosure Style
Enclosure style refers to the appearance, the ergonomics, and the specific construction of the enclosure. That is to say, style refers to how the enclosure will interface with the operator or other individuals including those involved with assembly and service of the device.

As with enclosure type, PEI can assist in your selection of style by fully understanding how the enclosure will be assembled, operated, and serviced. In particular, by knowing the assembly method, we can make style recommendations that may reduce the time it takes to assemble the device in the factory or to service the instrument out in the field.

Examples of enclosure styles include:

  • U-channel Removable Single Panel
  • Front Sloped Removable Double Panel
  • Body Wrap Seven Sided Front Sloped
  • Curved Front Flat Panel Display
  • Bezels

Finally, any decision on 'type' and 'style' must take into consideration the functionality and ergonomics of how the electronic device will be used or operated. Handheld devices should fit the hand; desktop units should be operational while the user is sitting or standing at a desk or counter; portable devices should be mobile and manageable by the operator...you get the picture.

With our years of experience in developing enclosures for an extensive customer base, we have learned what works and what doesn't. Once we fully understand your expectation and your customers' needs, we can offer the best advise possible in determining the type and style of enclosure to consider.

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Bends & Curves pdf
Bends & Curves pdf

 

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BENDS & CURVES - Design Criteria

When most people think of fabricated enclosures, they think of square, sharp cornered, boxie cubes. However, over the years, we at PEI have continuously pushed our design capabilities such that today we can offer enclosures with very attractive curves and contoured surfaces.

Among the more popular features in this area are:

  • Front Panel Arcs
  • Rounded Front Bullet Nose
  • 3 Corner, Single-round
  • 2 Corner, Double-round
  • Full Wrap, Quad-round

Technique
In order to minimize the deformation of the plastic during the forming of a curved or rounded surface, we minimize the amount of heat, which can cause texture degradation or panel shrinkage. As such, our method for developing curves involves special surface machining and cold-rolling of the plastic panels which allows for a smooth, continuous, and uniform flowing of an arc throughout a bend radius.

As a visual aid for those engineers attempting to develop an enclosure design specifically for our process, we suggest you envision how a piece of paper would be manipulated to form curves and non-flat surfaces. Just as you can bend paper along a single axis, you can also bend plastic sheets along an axis.

Furthermore, depending on the complexity of the joint and the angles of attack, you can have two curved surfaces meet in such a manner as to form a very complex shape. In this manner, your enclosure can have curved shapes from multiple angles thus giving a very dynamic overall appearance.

Finally, on this subject, as with all complex features, we recommend you use them judiciously. While curved surfaces and rounded corners can add sex appeal to the look of your enclosure, such features add cost and should be used to accent and enhance the products marketability.

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Panels & Joints pdf
Panels & Joints pdf

 

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PANELS & JOINTS - Design Criteria

The PEI process for manufacturing enclosures involves cutting flat sheets of plastic into panels that are bent and assembled into a fabricated assembly. As such, how the panels are designed to fit together is a key factor in the success of the enclosure. Panel joints that have gaps or misalignments can be a major detractor to an otherwise functional enclosure. Furthermore, poorly fitting joints have less strength than those that are made to within established tolerances.

To improve the mechanical strength of the joints and to eliminate problems associated with misalignment, all of our joints are developed using a tongue and groove interlock. Because the plastic panels have a wall thickness, we are able to cut slots or grooves into one panel while machining a step into the mating panel. Then, during the bonding process the mating materials are melted and re-fused as a continuous plasticized weldment. For glued joints the process is the same but the welding medium is the epoxy chemicals instead of the polyolifins.

At PEI, we have developed machining, bending, and assembly techniques that ensure that the fit of all joints is never compromised. With our specialized cutting equipment and tools, we have developed methods and specifications that allow us to mate surfaces within .003" of each other. Furthermore, through controlled research and development projects we have established manufacturing specifications that reduce the introduction of human error and increase the tolerance window such that process variations have a minimum or no effect on part quality.

If you are in the process of designing an enclosure that PEI will be building, you do not need to be concerned with the construction of the panels or joints. That is what PEI will be doing after the assembly drawings have been approved. What you should be considering at the early design stage is the general shape of the enclosure and the location of components, PCBs, displays, panels, etc. Once we are brought into the project, we will work with you in defining which panels are bent, which ones are bonded and which ones are fastened with screws, inserts, and other types of hardware.

If you have any questions about how you should be constructing your enclosure, please do not hesitate to call our technical group for guidance and direction. As a customer of PEI, you will always be entitled to early-stage technical assistance at no charge.

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Recesses & Pockets pdf
Recesses & Pockets pdf

 

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RECESSES & POCKETS - Design Criteria

For most enclosure applications, plastics has a distinct advantage over sheet metal in a number of basic areas; with one of those being the ability to incorporate pockets or recesses into the material sidewall. Yes, with a punch and die operation you can offset sheet metal surfaces to include pocketed areas, however, this means investing in a tool (punch and die set) for every different size recess. Additionally, you may also find yourself living with dimensional variations that could be functionally unacceptable and visually unattractive.

With a plastic enclosure, you can include recesses and pockets to handle functional details such as labels, overlays, or membrane switches. Additionally, the shape of the recess can be infinitely modified to add aesthetic features such as decorative lines or logo engravings. Furthermore, text or international emblems can be etched directly into the plastic providing a permanent 3D marking.

As with cutouts and openings, the primary design criteria that must be taken into consideration when designing for a recess pocket is the sharpness of the corner along the X,Y axis. With that in mind, the smallest diameter cutting tool that we can use to economically cut plastic material is .039"/1mm. This means that for applications where the recess or pocket requires extremely square inside corners, the sharpest we can cut the corners is .019"/.5mm.

From a practical perspective, our experience has been that very few customers design their labels, overlays, or membrane switches to such a tight tolerance that they must have perfectly sharp corners. Furthermore, even fewer assemblers have the ability to place a self-adhesive label or similar item inside of a pocket when corners are perfectly square and tolerances are tighter than what PEI can provide. The bottom line being that if you are designing an enclosure that requires perfectly square inside corners, then you may be looking at higher costs, greater reject rates, and longer lead-times from PEI as well as your other component suppliers.

Beyond the location and squareness (X,Y dimension) of the pocket, the other measurement that must be addressed is the depth or Z dimension. For PEI, many of the features we cut into the plastic panels rely on our CNC machines to accurately control the depth, which we can do to within a few thousandths of an inch. This allows us to locate components, PCBs, connectors, and other items precisely where they are needed. As an example, the location of standoffs used for fastening PCBs can be accurately located in order to align them with a side wall opening or other component. This is crucial when locating board-mounted components that must protrude through an outside wall.

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Openings & Cutouts pdf
Openings & Cutouts pdf

 

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OPENINGS & CUTOUTS - Design Criteria

There are few enclosure applications that are totally self-contained whereby there are no openings or cutouts in at least one exterior surface. As such, our process is not only capable of handling a wide array of such features, we can do so with a degree of accuracy and tolerance that is difficult to match by injection molding, thermoforming, or sheet metal fabrication.

Because our process does not involve the restrictive lateral movement of a molding press, we can incorporate very complex holes and patterns without incurring excessive costs. Through the advancement of our technology, we have developed equipment and methods that allows us to affordably machine both sides of the plastic such that components not only fit securely, they will have a greater aesthetic appeal due to our ability to custom fit such items to the finished product.

Among the more standard cutouts we encounter are for such items as connectors, buttons, switches, magnetic card readers, LCDs, LEDs, membrane switches, overlay panels, and virtually every type of component imaginable. Additionally, we have extensive experience with incorporating virtually any type of hardware needed for an electronic enclosure including hinges, latches, slides, knobs, handles, feet, bumpers, windows, doors, etc.

Finally, our process is capable of handling custom or unique cutout shapes including such features as recess pockets, special speaker hole patterns, designer vents, flush mounted windows, engraved logos, and raised text to name just a few. As always, we suggest to anyone looking for a special feature or function to let us know what it is you want to accomplish and we will do everything possible to see to it that your needs are met.

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