3D Case Design

If you need a custom enclosure for your electronic product or prototype, perfectly designed for 3D printing, perhaps we at 3D Case Design (3DCD) can help. We design beautiful, effective, enclosures for electonics suitable for printing on your own 3D printers or those of any 3D printing service.

We do great work for a flat rate, so you know exactly what it will cost before you begin!

3D printing, of course, is not the only technology available for producing enclosures. This web site can help you learn,

and decide if our design service is right for your product.

circuit board 2

1 - Is 3D Printing Right For Your Project?

Enclosures can be made of metal, wood, ceramics, plastic and other meterials too. Nearly all electronic enclosures are fabricated from metal or plastic.

Metal cases may be necessary for ruggedization, shielding, or other reasons. Metal cases are generally stronger, heavier and more expensive than plastic cases. They are usually formed from sheet metal by folding, bending, cutting and drilling.

Plastic is a good choice of enclosure material unless you cannot use it. Plastic is inexpensive, readily shaped, fairly long-lasting, and available in countless colors. Many kinds of plastics are available with special characteristics:

  • flexibility
  • strength
  • transparency
  • biodegradability
  • acid-resistance
  • heat resistance
  • non-toxicity
  • conductivity

and more.

Even 10 years ago, the only practical method for producing plastic enclosures was injection molding. Injection molding remains the most common manufacturing method for plastic enclosures, but today 3D printing is an option to consider.

Injection Molding

Injection molding has been around for almost 150 years (first patent in 1872), so it is tried and true. The injection molding process works by squirting molten material (usually plastic) into a mold. Simple molds are two pieces which fit together and include one or more holes into which the molten plastic is injected. Injection molding is a multi-step process:

  1. a two-part mold is machined from metal (molds made from hard steel can be used hundreds of thousands of times)
  2. the molds are clamped together
  3. the molten plastiic is injected under pressure to fill the mold
  4. the plastic is allowed to cool
  5. the two halves of the mold are separated to release the newly formed part

To learn more about injection molding, with diagrams, see: injection molding.

3D Printing

3D printing refers to a diverse collection technologies: FDM, SLA, DLP, SLS, EBM and more. 3D printers do not use molds. Instead, they squirt molten plastic from a moving nozzle (FDM), or cure photosensitive resins (SLA and DLP) with a laser or LED aray, or sinter polymer powders (SLS) or metalic powders (DMLS) with a laser, or fuse metal powder or wire by heating it with an electron beam (EBM) All of these are additive processes because each proceeds by building up (adding) one thin layer of material atop another until the part is fully printed.

Pros and Cons of Injection Molding

To produce one additional part by injection molding requires the execution of steps 2 - 5 of the process described above. Steps 2, 3, and 5 take only a few seconds. Step 4, waiting for the molten plastic to cool, typically consumes 90% of the total cycle time. The overall size of a part does not necessarily affect cooling time but, rather, cooling time depends on the wall (or other) thickness, and the efficiency with which the mold dissipates heat. The total cycle time for an enclosure is likely to be less than 30 seconds. We will see that 3D printing takes much longer.

Injection molding, obviously, requires a mold. It typically takes about eight weeks (after the mold is designed) to have it manufactured, and even a simple mold typically costs $10,000 - $20,000. After a mold is milled, only the most minor changes can be made to it. Beyond very minor changes a new mold must be made for another $10k - $20k. Some products may require mulitiple parts or enclosures and therefore multiple molds.

Also, consider that if you are creating a new product, especially an electronic one, it is possible—even likely—that one of your engineers' design goals will be to reduce the cost and size of the circuit boards in subsequent releases. If they are successful, you will need a new, smaller mold.

Pros and Cons of 3D Printing

3D printing uses no molds. The same 3D printer can produce any number of different cases with no retooling. Switching production from one part or case to another requires nothing more than selecting a different file from the printer's menu interface.

Modifying a 3D part requires no physical changes. Whether the change is large or small, the 3D model gets tweaked using the same program used to create the model. The model gets processed by another program (called a "slicer") and the same old 3D printer, using the new, modified model produces a modified part.

The major drawback of 3D printing is that it is very, very slow. Rather than injecting all the molten plastic for a part into a mold in a second or two, 3D printers lay down (or cure, or sinter) material bit by bit. Printing time is directly proportional to the amount of material, so a 100 gram (~4 oz.) case will take twice as long to print as a 50 gram case. The cycle time needed to produce a case by injection molding is likely to be less than 30 seconds. 3D printing a 50 gram case will likey take 2 - 3 hours.

A 3D printed part or case, depending on the printing technology, may not be as strong as an injection molded part—even when produced using the same plastic material. Injection molding generally produces consisent, high quality, highly detailed parts. 3D printing, again depending on the particular technology, may not be capable of producing the consistency and detail routinely achieved with injection molding.

Injection Mold or 3D Print?

An injection molding machine gets "fed" plastic pellets and produces plastic parts. Those plastic pellets, gram for gram, are cheaper then identical plastic on spools (for FDM printers), or resins or powders used by 3D printers. So, the material cost for injection molding is lower than for any 3D printing process, typically 40% - 80% less expensive. The raw material cost for a single, injection molded, 50 gram case might be 75 cents. The material cost for a similar 3D printed case might be $1.30 - $4.00.

However, even though the material cost of injection molding is lowest, a mold is required, and that may tip the unit cost heavily against injection moldiing. For example, the mold cost per case to injection mold 100,000 cases using a $20,000 mold is:

$20,000 / 100,000 cases = 20 cents/case

Adding in the materical cost of 75 cents, the total cost per case is 95 cents/case, which remains less than just the raw material cost for 3D printing.

If, however, you only need 100 cases then using the same mold, the mold cost per case becomes:

$20,000 / 100 cases = $200/case

Adding in the raw material cost of 75 cents, the total cost per case is $200.75/case. Of course, 3D printing uses no mold, so the cost per case is the same in any quantity.

Don't forget, however, that even though the cost per case to 3D print 100,000 cases might be as low as $1.30, at 2 hours/case it would take 200,000 hours (23 years) to print them. Of course, one could run 23 printers simultaneously and print them in only one year. The obvious point here is that 3D printing is simply impractical for high-volume production.

Please note that the above examination of price looked only at mold and material costs. In practice, injection molding charges will likely be 3 or more times the material (plastic) cost, 3D printing will cost quite a lot more because each print ties up a printer for so long.

circuit board 2 circuit board 2 circuit board 1

2 - Steps to a Suitable Enclosure

Whether you choose injection molding or 3D printing, each begins with a computer model of the enclosure you wish to produce. Every such model is created using computer-aided design (CAD) software.

In the case of injection molding, the computer model is used to control a computerized milling machine which cuts the necessary cavity or cavities into a block of material (usually steel) to create a mold. In 3D printing, the computer model is used to produce a data file which another computer program (called a slicer) uses to create a second data file containing a sequence of commands a 3D printer uses to produce the object described by the model.

On the right is a screenshot of a computer model for the bottom half of an electronics enclosure. Notice the model includes all necessary supports, holes, cutouts, braces, cooling fan supports, guides, tabs, etc. It must also include mechanisms—using fasteners or friction fits or snap fits—to secure the electronics inside the case and to ensure that, once closed, the case remains closed.

The Model Must Match the Process

Please be aware that while a model is required for both injection molding and 3D printing those models will be different in important ways. Due to fundamental differences in mechanical aspects of the injection molding and 3D printing processes, the case designer must know which production process will be used and accommodate the process in the design. A perfecty good design for 3D printing will likely be entirely unsuitable for injection molding and possibly vice versa.

For injection molding, after the model is developed it gets stored in a file (usually in .STEP format) that gets used by a mold maker to mill a mold. After the mold is finished the injection molder can begin production. 3D printing requires another step called slicing.

Slicing for 3D Printing

For 3D printing, after the model is developed it gets stored in a file (usually in .STL format). That file gets processed by a program called a slicer. The slicer takes the model and figures out how to slice the model into the thin, horizontal layers the 3D printer will print, one on top of another, to print the model.

Slicers tend to have many (often hundreds) of different settings which allow fine control over the 3D printing process. This is necessary because getting good 3D prints depends on the particular kind of printing material and the exact behavior of the 3D printer being used. ABS plastic filament, for example, is very popular in FDM printing, but the filament chemistry varies significantly from one brand to another and, even within a brand, the behavior of filaments can differ significantly from one color of filament to another. Variations in printer characteristics, even among printers using the same technology vary even more than printing materials. For those reasons slicers are designed to allow many different adjustments of many sorts. Producing good 3D prints requires skillful use of a slicer.

If you farm out your 3D printing to a printing service you will only provide the model (.STL file), and the printing service will use their own slicer. If you do your 3D printing in-house then, of course, slicing will be your own responsibility.

image of bottom half of spotter case

3 - Should You Design Your Own Enclosure?

If you or one of your team members is experienced in case design, and thoroughly understands the chosen production process (injection molding or 3D printing), then designing your own case may bring little risk.

If you will 3D print your enclosures and your designer is also skillful at 3D printing then there is no risk (beyond wasted time) to the iterative process of designing a case, printing it, tweaking it, re-printing, re-tweaking, again and again until you are satisifed. At that point you can begin your own production printing or send the .STL file to a 3D printing service for printing.

As it can take 10 or 20 (or more) iterations to get a model just right, if you are unable to do the printing and tweaking in-house then, unless you are a very experienced and skillful designer, sending out each iteration for printing may become a long and possibly expensive process.

For injection molding, the risk of designing your own enclosure is much greater. Each design iteration for 3D printing wastes 50 grams (or whatever) of material and a couple of hours on the printer. If the model for your injection mold is not right, maybe it can be tweaked or maybe you get to mill a new mold for another $10k - $20k.

Injection molding companies are generally happy to make molds for their customers, but it is rare to find an injecton molding company that is willing to design a model for milling a mold. If you provide the model and the mold doesn't perform well the cost and loss are yours. If the injection molding company designs the mold and it doesn't perform as required then the cost and loss are theirs. Desiging a model for injection molding should not be undertaken without deep knowledge of injection molding and experience too.


4 - How Long Until You'll Have Cases in Hand?

Whether you choose injection molding or 3D printing a model must be made. Making a model for injection molding takes no more or less time than one for 3D printing. The time required depends on the skill and experience of the person creating the design. Without prior experience, there's a lot to learn and it can take weeks or months to get up to speed.

For injection molding, the model is needed to mill the mold. If cost is not an obstacle the mold can be milled in the US and that might take 2 - 3 weeks. Many molds get milled in China to save thousands of dollars. Molds are heavy so they are usually shipped by sea, instead of air freight, and that adds significant shipping time. It typically takes 8 or more weeks to have a mold milled in China and shipped to your injection molder.

Injection molding is a much faster process than 3D printing. It might take 2 - 3 weeks for your injection molder to fill an order for 100 or 1,000 parts. For 3D printing, 100 pieces mighht also take 2 - 3 weeks, and 1,000 pieces will likely take considerably longer.

If you operate your own 3D printer then you can easily estimate production time based on your experience.


5 - How Much Does a Custom Design Cost?

If you cannot or do not want to design your own enclosure then you must find a designer or design service. There is no uniformitey in pricing and you will likely have to pay by the hour for as many hours as it takes. It is unlikely you will get an accurate time estimate, so cost predictions for model design will be very rough, unless...

Flat Rate Pricing: $500 or $1,000

If you do not want to design your own case, and you will 3D print them, you might be interested in our flat rate design pricing.

if your electronics will fit in a 70mm x 70mm x 70mm cube (internal dimensions) our flat rate design fee is $500. If any dimension of your electronics is greater than 70mm then our flat rate design fee is $1,000.

Here's the Process

  1. send a sample of the electronics to be encased along with a 50% deposit
  2. we design a custom enclosure and e-mail pictures of your electronics fitted in the enclosure for your review and feedback
  3. based you your feedback we will modify the case if needed
  4. repeat steps 2 and 3 as needed
  5. we return your electronics in the 3D printed case
  6. you pay the remaining 50% of the design fee, plus the cost of shipping
  7. we e-mail you the model including the model source code and .STL file
  8. you can slice the model and begin 3D printing your cases or send the .STL file to a 3D printing service
  9. naturally, if questions arise when you or your printing service begin printing we will happily provide telephone support

Our flat rate pricing eliminates all surprises and lets you budget accurately.


6 - Why Trust Your Design to 3D Case Design?

At 3D Case Design we specialize in designing 3D enclosures for electronics. We do not design cases for injection molding because, while our experience in 3D printable case design is vast, we are not expert in designing for injection molding; we know what we know and we know what we don't know.

Modeling With OpenSCAD

We use the OpenSCAD CAD modeling program for all case modeling. It is mature and stable with many users around the world. OpenSCAD runs happily on Windows, macOS and Linux.

OpenSCAD is open source and completely free. You can install it in only a few minutes. When we design a case for you, the model is yours. We send you the .STL file, and also the source code for the model. You are welcome to view and modify the model as you wish, but to do so you will need the same modeling software used to develop the model. Were we to use one of the expensive modeling packages you would need to buy it too in order to view or tweak the model.

OpenSCAD is pretty easy to pick up and use. Though it is not a programming language, it encourages designs to be described parametrically which is pretty natural for progammers. However, programming skills are not necessary to use OpenSCAD effectively.

We Enhanced OpenSCAD

OpenSCAD is a great modeling tool. There is no modeling software specifically designed for modeling enclosures, but there are many elements of enclosure design that arise again and again. OpenSCAD was designed to make it easy and practical to create "reusable parts," and over our years of using OpenSCAD we have developed a library of such parts that we use and reuse in the cases we design.

Our library allows us to add,

  • support blocks
  • braces
  • guides
  • alignment pins
  • friction fits
  • snap fits
  • cooling fan supports
  • fillets
  • cooling vents

and more, each with a single statement or two.

Our library lets our designers specify parting-lines and rectangular, round, and oval wall cutouts, again in a single statement. Our designers can round courners, parts, and openings simply by providing an addtional parameter when describing the component. It allows our designers to place parts relative to the case walls and/or specify the direction a part should "face" with a single parameter (EAST, WEST, NORTH, SOUTH) when specifying a part.

It also lets the designer number each part and displays the numbers alongside the parts (but does not print them), so you can ask a question about, "part #6," instead of "that funny looking thing near that other funny looking thing."

We design our models such that setting a single parameter shows the electronics and connectors exactly as they will fit into the enclosure. Setting another parameter displays the top and bottom halves of a case as they will fit together, and another parameter specifies how far the top should be displayed above the bottom.

It is this library that makes it possible for us to offer great models and flat-rate pricing.

Please don't hesitate to give us a call or send an e-mail to discuss your needs. We're happy to answer questions and offer advice.

cable tester model
cable tester model
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