Here’s where the difference is.  Most engineers never have to make, punch, bend, machine, etc., the parts they design.  We do.  Over and over and over again!  When engineers have to personally manufacturer what they’ve designed there is a fundamental shift in the way one designs.  The design rules change.  The path through design is more precise.  Part quality and consistency become more repeatable . . . and less expensive.

Noteworthy electronic products begins with a well balanced design definition – electronic, mechanical, manufacturing, etc.  Next comes product design architecture and engaging experienced and talented resources . . . NETBased has both the experience and talent in both enclosure design and manufacturing to develop and produce your next custom electronic enclosure.

Preparing Your Product Definition

When preparing to design and produce your next product we’ll recommend a path for concurrent engineering between electrical, mechanical and manufacturing to expedite the process.   In our first meeting we’ll:

• Discuss your product’s features, performance, thermal requirements, regulatory compliance, etc., and their priorities.
• Consider initial production volumes, ramp-up and product life cycle.
• Determine enclosure materials and processes.
• Define areas for product differentiation beyond features and performance.
• Collaborative design resources for concurrent engineering.
• Strategic product introduction, dates and shows.
• Understand user expectations.
• Review competitive products.
• Discuss your production logistics and methodologies.

These factors are part of a well planned product definition, design process and schedule for your product and it’s enclosure.  This is not a long drawn out process.  We make it quick.

 Innovating

It’s not uncommon to find engineers spending their entire carriers within one or two industries. Many industries essentially design products the same way and competitors go down similar paths of design and manufacturing. Sometimes with good reason and sometimes for no obvious reason other then copying. This often thwarts innovation.

This is where NETBased makes another valuable contribution. We work within many industries. We routinely interject proven methods and technologies from different industries to bring about further differentiation. For example, something that’s being done in medical electronics just might have value in consumer electronics.  Or, crossing between RAID and home entertainment might be a more obvious combination.

 Controlling Costs

Our roots are in manufacturing coupled with great strength in product design and development. This background in precision sheet metal, injection molding, RIM, pressure forming and die casting gives us the shop floor “tribal knowledge” to design differently, cost effectively – we instinctively know how to get the most out of each machine and associated processes.  This kind of knowledge just isn’t taught at universities or written in books or even trade magazines.  Our expertise combined with well planned product architecture results in enormous cost benefits.

 

Minimizing your reoccurring costs is always a primary goal at the onset of any new design.  Attempts to lower costs after a product is in production results in only half measures of what could have been achieved during initial design. One cannot typically make the necessary design changes to the enclosure because it would effect so many other things.  One may need to make changes to PC board design, existing component inventories, etc., to get to the most meaningful costs cuts.  If the engineer or designer does not know the difference between a shaker part and a reshear part or when to use half-shears vs. Clecos.  Or if he/she doesn’t know when to design for and use MUD or the difference between lifters and pecker-pins, or blade, sleeve, two stage, three plate, etc., then the engineer is designing on the hope everything will come out OK.  Without fully understanding these differences, he or she will invariably design in features that will increase your tooling and reoccurring production costs.  It can quickly get expensive.

If you’re not intimately familiar with those terms and associated design rules, you need to be talking to us.  Attempting to regain those lost dollars never amounts to a satisfactory result.  We see only half-measures in redesign, degradation in cooperation and reputation with suppliers and time wasted looking to replace suppliers in the hope of finding that holy grail.  It never pans out.

Proactive Design Cost Management

To achieve lowest cost manufacturing, product definition must be balanced with a properly conceived design architecture which may include:

• Major component arrangement
• PC Board component placement for optimal thermal dissipation
• Connectorization
• Watt density management
• Board level thermal issues
• Thermal dissipation (Airflow, conduction, convection)
• Emissions and immunity
• Regulatory compliance
• Product service (FRUs vs. return)
• Production levels and life-cycle
• Electronic enclosure materials and processes
• Manufacturing methodologies and logistics

A well balanced team includes everyone at various times, including marketing and sales, service and not just the engineering and manufacturing disciplines. Some projects warrant customer/end user focus group studies.

We have been involved with developing and manufacturing custom electronic enclosures for so long that the aforementioned bullet points are a way of life for us.  Also having our roots in the trenches of manufacturing, NETBased is in a unique position to get you to market quickly while understanding the holologation process and how to drive your tooling and reoccurring costs to a minimum.

 

Meeting safety and RoHS is relatively straightforward.  For now, we’ll look at thermal and then EMC.

Effective Cooling of Enclosed Electronics

Achieving proper or adequate thermal dissipation is affected by many variables such as:

• Total watts dissipation
• Watt density per square inch
• Type, volume and material of enclosure
• Type dissipation, conduction, convection, forced air
• Elevation
• Solar Loading (ODUs or Outdoor units)

While we developed and produced conducted and convection enclosures, the majority are forced air (containing fans or blowers).   To approach proper cooling the pure scientist would say “We need to do an FEA” (Finite Element Analysis).  While FEA works well in some instances, it fails to yield accurate outcomes for forced air electronic enclosures.

Flow FEA uses predominantly fluid principles.  If, for instance, we analyze how plastic might fill a mold, FEA works relatively well.  Plastic flows into a mold like toothpaste.  It has a know mass and viscosity, etc.  Air, on the other hand, has no mass.  Well, technically it does but its mass in forced air cooling FEA analysis doesn’t provide much value.  Force Airflow is finicky, squirrely and doesn’t behave in obvious ways.  It’s speed and direction are affected by too many things:

• Pressure (negative and positive)
• Having to change directions
• Square corners
• Obstructions
• Topology
• Chamber volume
• Inlet and outlet size and location

Let’s take a moment and look at just one issue.  You put a heat sink on a BGA for example.  The data sheet graphs watt dissipation effectiveness given a characteristic of air parading through the pins/fins of the heat sink.  That’s all well and good, but . . . Airflow doesn’t like heat sinks.  Moving air sees them as obstructions.  Heat sinks cause pressure and directional changes resulting in added turbulence.  Air prefers the path of least resistance – to go around or over heat sinks, not through them.  Not very effective for cooling electronics.  Over the years we have developed numerous strategies to positively effect airflow for improved cooling.

EMC – Dealing With Emissions and Immunity

This begins with two primary questions:

1. What is your clock speed?  Leading to what’s the ¼ wavelength?
2. What is the enclosure material and process?

These two basic questions will tell most of the story.  More specific questions about the board design will lead to what design direction needs to be taken.  It is more cost effective to manage radiation at the board level then to contain it on a global (enclosure) level.  For example, can traces be buried between ground planes or add a small localized EMI containment can soldered to the board?  When that won’t meet EMC requirements we have to resort to enclosure containment.  This sets in play a different set of design rules.  We begin with enclosure part geometry, but this may not do all that is needed.  Then, having to add grounding materials to the enclosure (beryllium clips, conductive elastomers or fabric over foam, etc.) quickly adds cost.   In the case of plastic enclosures, resin selection, and coatings are often the direction.  Again, at additional cost.

Depending upon the enclosure materials  and processes, we’ve developed inexpensive techniques to circumvent many of these cost adders.  We’ll present what can be done early in the design process of your next custom electronic enclosure.

An area where 1U chassis are unique is internal volume.  How much can you stuff inside, AND, can you properly cool it under all the conditions in which it will be deployed?  The issue of watt density vs. thermal dissipation in a 1U chassis begins with reduced ratio of internal air volume.  Now, if you’re only dissipating a few watts then conduction or convection may be adequate.  But, when power goes up, things get more interesting.  There’s more airflow back pressure, air is more turbulent and luck would have it, air doesn’t flow where you need it most.  Actually, luck doesn’t have anything to do with it.  Can you get enough air in and back out again (fast enough to cool adequately), etc? If airflow isn’t uniform under pressure (negative or positive) then what makes air flow the way it does . . . relatively unpredictably.  Getting air to flow how you might think it should flow is like herding chickens.

We’ve had great success and have developed numerous cost effective techniques and strategies.  Some of these strategies go beyond just the enclosure, fans and holes in the chassis.  It often begins at the board level.  While we don’t design PC boards, if we are involved early enough in the product design process we can provide valuable input into component placement that can yield significantly improved thermal dissipation.

In this example, even though all the air intake was in the front 25% of the enclosure and there was a spread of 4 high-volume fans, the majority of the air would go around the heat sinks, not through them.  We suggested separating the hottest components from each other.  We also employed zoning and compression airflow techniques resulting in successful cooling of this 375 watt 1U chassis.

 

Fan Performance vs. Thermal Reliability for 1U Custom Chassis

Due to their restrictive height, 1U chassis are fan challenged.  When we look at today’s 1U servers, RAID or 40GbE+ switch enclosure, etc., they are jam packed.  There is little space left for air and still they need to be cooled.  These dense systems are also pushing limits on power consumption.  Many of these are considered mission critical and failure is not an option.  Therefore, adequate sustained cooling is crucial.  But when a fan fails, what do you do?  Are you dead in the water, can you schedule to take the system out of service, remove it from the rack or what?  Well, what if the fans were field replaceable and low tech to replace in the field without a service shutdown?

Fan Strategies for Thermal Reliability

• N+1 Fans
• Counter Rotating Dual Rotor Fans
• Reducing Speed to Increase Fan’s MTBF
• The Dirty Truth
• Hot-Swap Field Replaceable Plug In Fan Modules

Or . . . Schedule and switch systems provided it has adequate airflow capacity to sustain itself.  The amount of time before system swap could be long or short depending upon its deployment.

N+1 Fans

This should always be the case in any mission critical chassis.  Knowing how close to the edge of adequate airflow is also important and needs to be taken into account for all deployments.  The greatest factors in deployment are maximum ambient temperature and elevation – both affecting air density and pressure.  (Relative humidity also plays a part.)  The higher the elevation the less efficient your cooling system will be.  For example: at 70°F/21°C at sea level, air is 14.7psi and at 10,000 feet it drops to 10.1psi.  So airflow volume needs to compensate.

When a fan dies, say locked rotor, you loose more than the output of a single fan.  If the fans are exhausting hot air then the dead fan becomes another intake because the chassis has a negative interior pressure.  This reduces the efficiency of the remaining fans.  When using single rotor fans, with one in lock rotor condition, will not maintain the system temperature then this is where dual rotor fans may be considered.

Counter Rotating Dual Rotor Fans

These are a fairly new breed of axial fan.  A typical 40mm square fan may be 56mm long then a more typical size of 28mm or less.  Each rotor is independently powered and controlled.  If one rotor fails the remaining rotor continues to power through the dual rotor venturi.  This eliminates the airflow reversal that occurs when a single rotor fan locks.  Doing a quick search on DigiKey I found over 200 40mm single rotor axial listings (in stock and RoHS compliant).  In contrast, there were only 9 listing of dual rotor fans.  Choosing wisely, one could still second source dual rotor fans.

Reducing Speed to Increase Fan’s MTBF

Another strategy is to employ that under general conditions may be throttled down to a less the maximum speed.  This will increase the fan’s MTBF.  This also provides the option that if conditions radically change, i.e. the air conditioning fails in the building, the fans can be sped up to better support cooling under the higher then planned ambient conditions.

The Dirty Truth

Most systems are installed in a rack buried in a closet, NOC, etc., never to be seen again until something goes wrong.  What about the fans and is there something here that should be taken into account when initially designing the system beyond maximum ambient and elevation (aka worst case air density)?

Fans will over time load up on particulate.  If there is a dirt/dust load factor of 10% then airflow will drop 10% . . . 15% = 15% loss and so forth.  The knee jerk reaction would be to say “lets add filters.”  If no one is their to remove the dirt/dust from the fans then who’s going to be there to replace the filters (where are they installed, how does one replace them)?  Filters, depending upon their efficiency will load up much more quickly the letting the vast majority of dirt and dust just pass through the system and fans.

This begs the question, how much additional drop in fan efficiency do you design for do to fan dirt/dust fan loading to determine a useful predictive field life between installation and maintenance?

One more thing, dirt/dust loading on heat sink fins – how or do you account for that?  Frequently BGAs, etc., have the ability to report their temperature . . . is anyone listening?

Hot-Swap Field Replaceable Plug In Fan Modules

We routinely suggest using one of our field replaceable (removable) fan modules that allows for quick, simple routine scheduled maintenance.  Depending upon the system (normal operating temperature and it’s max temp) and the speed at which your tech works, the system may remain live in many cases during the fan removal, clean and replace procedure.  We have the same capability in 1U Chassis as in 2U, 3U or more.

Incremental design reviews are critical to the process of concurrent engineering within any design process.  It keeps management and design team members in sync and abreast of progress.

• In person, at your facility.  We can project models that can be manipulated, disassembled and individual parts examined.
• Remotely, with 256 bit encryption, sharing our desktop.  We can simultaneously broadcast to numerous people in multiple locations bringing everyone together online for the review and discussion resulting in better oversight.

With today’s technology, the process of review (and its frequency) is more real-time.  We often conduct these reviews using our live CAD database.  This allows for greater depth of review and analysis.

Remote design reviews permit more frequent progress review and tighter management of the process as well as the results.  When issues arise, impromptu reviews may be called by either your engineers or management to quickly raise and resolve issues with little or no impact to schedule.

For enclosure design been using SolidWorks since 1995 and have found it to be a robust design tool.  It has the capacity to import and export in many file formats to support collaborative efforts.  It dominates the mechanical design world and manufacturing has increasingly adopted it.

The application we use for online remote design reviews is Mikogo, a 256 bit encryption desktop sharing application.  We have the master license.  Review participants need only the single user free application.  It is multi-platform ported and can run on many different devices.

You may download the free app at:  https://www.mikogo.com/download/
This is a very quick download and one-time install.

You may run it from your Web Browser by going to:  https://go.mikogo.com/
Remember to select the “Join Via Browser” button after entering the Session ID and your name.

In either case when you “Join A Session” you will need a session ID number which we will provide.  Session ID numbers are unique to each session.

Based on decades of experience collaborating with customers, we frequently perform multiple reviews where the board design is overlayed into the enclosure CAD model.  We do this frequently to track and validate form, fit and function.  Depending upon your PC board design tools, we can accept various files you export.  The import and export procedure between your board layout application may vary with SolidWorks, which we use.  We begin by determining if 3D data can be acceptably translated.  As a fallback, we can use a .dxf exported from your CAD package.

It is important for emissions and immunity that there be coordination between the enclosure design and connector selection and placement on the board.  For instance, connector manufacturers like Tyco, Molex, FCI, etc., will provide a board layout document for holes or pads placement.  Component manufacturers often define this placement with a distance to edge of board.  This distance to edge of board is often incorrect for many connectors such as RJ, SFP, XFP, the list goes on.  When using the “recommended” distance to edge of board, we frequently find connectors with grounding spring fingers or EMI gasketed flanges do not make proper contact with the chassis (or no contact at all).  This can impact EMC and ESD compliance.

We solve this through collaboration with your PC board designer.  You tell us the order in which components need to appear and we determine exact placement.  Then we provide a drawing and CAD files with exact hole, pad or component placement.  Later, once your board designer has placed the component and is preparing to route the board, we will have him or her feed back to us and IDF, STEP or DXF file for a double check.  We import the data from your CAD tool’s export back into our enclosure design and look for issues so they may be immediately resolved.  Sometimes it’s a correction to the board while other times it’s easier to change the enclosure design.  As you can tell, this process provides for concurrent engineering of both PC boards and the enclosure with attention paid to thermal, safety, emissions and immunity.

Another thing we look at during this process is do we have enough space between connector, LED, switch components for placing intuitive and legible text for user identification?  This will often times push connectors, LEDs, etc., to the left or right.

You may anticipate that we’ll want a conversation with your board layout designer to discuss where locations of greater heat dissipation will be.  Once we understand higher watt density areas, we can turn our attention to airflow.  We may ask if there is a possibility to adjust the placement of some components to minimize too much heat concentration in one area or to put components in an increased airflow path.  We fully understand that these kinds of requests may not always be accommodated.  Either way, we will be considering intake and exhaust and airflow volume.  Next, do we need to add cooling techniques such as air compression, redirection, funneling, etc.  As a side note, we might suggest placing hot component on the bottom of the board where we may use the enclosure as a heat sink and heat spreader.  The bottom line is, we will consider multiple means to inexpensively cool your product before resorting to more expensive techniques such as heat pipes.

Whether you’re in a fast-paced technology market or a more moderate one, these are appropriate strategies.  There is not a single tactic that fits all approach.

Fast-Paced Technology Markets

When you’re late to market you lose more than the upfront lost sales. The typical bell curve associated with a products’ revenue life-cycle gets compressed in length and height. This life-cycle loss of revenue comes from:

• Being late to market
• Competitive encroachment
• New technology advancements

Being first on the scene with anything new is critical.  As soon as you begin shipping your product, a competitor will be deconstructing units from your first production run. As the saying goes, “imitation is the highest form of flattery.” While the competition is developing their knock-offs, you should be collecting user data for your next generation. When timing works in your favor, you’ll be introducing your next generation product rendering obsolescence to the competition’s introductory knock-off.  Speed may mean the difference between success and failure.

It was reported that General Electric sponsored a study to determine how other multinational companies were able to introduce so many new products and be successful.  It was also reported that the number one thing to do was to establish a design aproach/spec. and stick to it.  Bring the product to market per the spec.  This would indicate that it’s better to introduce a new technology quickly, well in advance of competitors rather than insert delays in the schedule with changes (creeping elegance) from the marketing department as they gain new tidbits and preferences of intelligence from the field.

Moderate-Paced Markets

Where product life-cycles are longer or production runs are shorter, it may be prudent to take an extra breath along the way. In these cases, hitting the market with the exact right product, without the ability to follow it with a newer technology product in 9, 12,18 months, may be in order. Nevertheless, with well conceived and structured product design architecture, we can still move briskly. – See Custom Enclosures – The Process.

Maintaining On Track

There are plenty of distractions that could arise. Program Management can play a key role in constraining creeping elegance influences as well as managing resources to stay on target.

Trade publications frequently wave the flag over something new and novel that they’ve discovered. What would you expect . . . it builds readership, buzz and sells advertising.  These publications are a major way engineers maintain awareness of evolving technologies. We’ve seen numerous companies lured in thinking that what the trade publications are reporting is mainstream when in actuality is a process developed by a single supplier to solve an otherwise overwhelming design issue.

We know the differences between the latest industry manufacturing hype and what is mainstream. We keep you out of the trap that leads to very limited manufactureability, higher costs and longer lead-times.  This plays very heavily into the approach we take in designing your custom electronic enclosure and manufacturing. Utilizing the best mainstream and appropriate manufacturing methods and materials enables us to get you to market quickly and cost effectively.

Our many years of experience in design and manufacture of all kinds of electronic enclosures is one of your best benefits as we’ve likely done what you need many times before.  There’s no lengthy discussion or analysis to decide should it be done this way or that. Having our roots in manufacturing, a strong background in thermal dissipation methods and regulatory compliance, these decisions are clear practical common sense for us. We push through the design very quickly and then right into manufacturing.