E-PAC ® - A Patented Chassis Concept





E-PAC ® , Electronic Packaging Assembly Concept is a world wide patented new chassis and housing concept for electronic devices. DMT as the exclusive licensee for E-PAC ® took over the responsibility for the global sub-licensing of selected foam molders. A current list of licensees is available on your request

Background

In 1990 a team of four is established in the Mechanical Technology Center of Hewlett-Packard in Boeblingen, Germany. The mission is set to let simultaneous engineering happen. The close team work of interdisciplinary specialists leads to a global sight on electronic products - the total cost of ownership for a product from the development to the end of use.

Soon the team realizes that often the pure material cost for mechanical parts of i.e. a workstation only plays a minor role. The secondary cost over the life cycle are becoming more and more dominating.


product lifecycle



E-PAC ® - the Concept



E-PAC ® stands for Electronic Packaging and Assembly Concept. E stands for the electronic industry sector however also for easy, economic and ecologic.

The aggressive goals and objectives for new computer products together with the results of market studies and functional analysis seem to be unachievable.

Soon the concentration is directed to form fit as a potential solution to hold the components in place. One of the main goals is to simplify the assembly. By drawing analogies from other products, industries and even from nature the team develops the technical solution.

Objective Analogy
  • Intuitive Assembly
  • wooden puzzle for toddlers
  • Protection
  • paper pulp box for eggs
  • Hold-In-Place
  • shipping box for a camera

  • foam-in-place of window frames

  • The idea of using foamed plastic for the chassis is fascinating and motivating the team. The next day a workstation Series 9000 model 710 is being disassembled and the redesign for an E-PAC ® feasibility study is started. Three weeks later the team is proud to present the same functionality with revolutionary results.


    conventional with E-PAC ®



    The Results



    The following comparisons and test results are based on the redigned HP workstation model 710. All required tests, HP internal qualification as well as all the product specific approvals like UL, CSA, TÜV, etc. were passed.


    Costs


  • The tooling cost could be reduced down to 40%. This reduction is achieved by less complex sheet metal enclosure parts, fewer and simplified plastic parts and in particular by the low-cost aluminum molding tools for the foam parts.

  • The number of parts went down and again the less complex designs reduced the material cost to 67% of the original. This could be achieved despite the addition of foamed plastic parts.

  • The assembly time is reduced by fewer parts. There is only a screw driver required to fix the grounding screw. The tolerance forgivingness eliminates adjusting and positioning.

  • The foam material improved the shock and vibration resistance significantly. This lead to reduced packaging requirements.

  • The disassembly of the components is as fast as shaking out the components after opening the top cover. The separation of recyclable and toxic materials is given without prohibitive cost.


  • Product Quality



    Besides the cost advantages there are numerous other advantages and improvements demonstrated.

    The excellent shock absorbing properties not only support the reduction of transportation packaging requirements. The product itself becomes more rugged. The foam material can act as a mechanical filter for shocks and jolts. It is expected that this dampening increases the MTBF of the most sensitive components, the disk drives.

    Besides the ruggedness the foam also dampens structural born noise which leads to quieter products.

    The ability of creating air channels into the foam supports the thermal management for the product. The average CPU temperature could be lowered from 54 down to 45C ( at 20C ambient).

    The part count went down from 36 to only 11. This reduces administration overhead in the area of sourcing, logistics, and material planning.

    The ease of assembly also improves upgrade and service of the product in the field. Last but not least the weight could be reduced. The chassis was reduced from 3840 to merely 287 grams.


    Introduction to Volume-Production



  • Ease of Assembly, no fixtures and special tools required.
  • Form Fit, intuitive assembly, hardly any instructions required.
  • Tolerances, resiliency of foamed plastic compensates for typical manufacturing tolerances.

  • Applications



    The application as a workstation chassis is only an example for the broad range of potential applications of E-PAC ®. High potentials have been seen in:

          • Office Equipment
          • Test & Measurement
          • Medical Instrumentation
          • Kitchen Ware
          • Hifi and Audio Equipment
          • Automotive Applications
          • Avionics and Aerospace


    As a rule of thumb you can say that the potential increases with following criteria:

          • Number of Components
          • Cooling Requirements
          • Noise emission
          • Ruggedness ( portable products)


    Future



    EPP foam is a relatively new material ( introduction late 80s) is offering high evolution potential. This is true for the raw material (PP) itself as well as the process and tooling technology.

    Some examples for ongoing developments:

  • Thinner wall sections achieved through smaller bead sizes
  • Flame retarding materials
  • Complete CAD CAM path for the tooling generation process
  • EPP Molding Presses with reduced Tool Change Cycles

  • The following pictures are demonstrating the principle of a typical E-PAC ® design.

    Example 1

    Example 2