GRAPHITE MOLD DIE CASTING (GMDC)

 

 

ALUMINUM GRAPHITE DIE CAST (GDC) PARTS IN A380 & A356

 

What is Graphite Mold Die Casting?

 

Casting molds are machined from graphite blocks into which molten Zinc is gravity die cast.   Armstrong Mold is the first and only U.S. producer pouring Aluminum in graphite molds.  Armstrong is now moving ahead in the development of pouring Magnesium in graphite molds.

 

      

 

 

Tooling for Graphite Mold Die Casting

 

 Graphite tooling is produced at a fraction of the cost and lead-time of high-pressure die-casting tools, thus reducing capital risk during the product design and performance confirmation phases of a new program. Graphite Die Cast parts can have the same properties as those made by high-pressure die casting and can be used not only for the prototype and development process, but for low-volume production parts as well.  Graphite Die Cast parts can have thin walls, tight tolerances, and an excellent surface finish for aesthetic applications (see specs below). 

 

 

  • GMDC utilizes an alternative mold material, produced on CNC machines directly from CAD data, providing a new level of casting performance
  • Graphite is easy and fast to machine, resulting in short lead times, low cost and readily modifiable tooling
  • CNC cavity detail delivers production high-pressure die cast tolerances and repeatability at a fraction of the cost
  • The excellent thermal properties of Graphite facilitate rapid solidification ensuring excellent mechanical and physical properties and cell structure
  • Enables processing of 380 – 390 Die Cast Aluminum alloys, with production rates in excess of 50 to 100 castings per day
  • Tooling is produced in days to weeks – not months
  • Provides the capability of supporting bridge to production needs and “back-up” tooling
  • Process Controls in place for fully automated molds,  with pneumatic slides and ejection systems,  mold temp, cycle time, and metal temp
  • A rule of thumb for Graphite tooling cost is 25%-30% that of high-pressure die cast tools, while the piece price is about five times that of high-pressure die cast parts, when run in much higher minimum volumes
  • The life of the GMDC mold is shorter than that of pressure die-casting

 

 

            

 

               GDC mold is polished after machining     GDC Aluminum Chassis – Medical Device

     

 

What materials are used in GMDC?

 

Alloys:  Aluminum and zinc alloys common to die-casting

 

  •  Aluminum: 356, 380 and 390

  •  Zinc (Zamac): ZA-3, ZA-8, ZA-12

  •  Coming Soon: Magnesium AZ9ID-F

 

Graphite Mold Die Casting Design & Technical Information Overview

 

       

 

 

 

Size Envelope:  36 x 36 x 6 inches

Surface finish:  63 to 90 RMS

Wall thickness:  Depending upon geometry, a .120” nominal wall is standard with walls as thin as .090” possible in some areas

General tolerances:  +/- 0.005 inch plus 0.0015 in./inch.  Across parting line, add +/- 0.005”

Slide Areas: Additional tolerances are required on slide pulls, based on projected areas of slide.  Up to 5 square inches add +/- 0.005 inch, up to 20 square inches add an additional +/- 0.007

Flatness and Straightness:  As cast +/- 0.005 inch first square inch.  Add

+/- 0.003 inch for each inch thereafter

Radii Min Requirement:  .015”

Holes:  Min hole size “as cast” is .125”

Draft: Typical requirement is 1 degree, same as die cast parts

Angles:  Standard is +/- .5 degrees

Delivery: Typically, 3 - 5 weeks for tooling, 30 to 100 pieces cast per day

ADVANTAGES OF Graphite Mold Die Casting:

 

 

  • Good economics for low-volume Aluminum, Zinc and Magnesium castings

 

  • Much lower up-front capital investment for tooling

 

  • Excellent for aesthetic applications where appearance is very importang

 

  • Significantly reduced "time to market" on new programs

 

  • Engineering changes easily and quickly implemented

 

  • Small lots allowing market potential evaluation with minimum capital risk

 

  • Low volume parts with production tolerances

 

  • Low volume parts with the intended production mechanical properties

 

 

      

 

 Reduced RM waste & Machining             Complex Shapes           “Raw” GDC Casting - Heat-Sink      

 

 

  • Same properties as high-pressure die castings

 

  • Where thin walls are necessary or where weight is critical

 

  • Reduced time for machining and secondary operations necessary with many other low-volume casting processes

 

  • Larger volume of parts in shorter time frame (faster cycle time)

 

  • Graphite tools can be used as production back-up insurance to fill the supply gap in the event hard dies are lost, damaged or delayed

 

 

  • Process Control: fully automated molds with pneumatic slides and ejection system, mold temp, cycle time, and metal temperature

 

  • Early fixture development for assembly & further processing operations, ahead of tools for aggressive product launch schedules

 

  • Reduced time for U.L. approval

                                                                   

 

Contact me for additional information about GDC or a budgetary quote for your low-volume custom-engineered, Aluminum, Zinc or Magnesium mechanical component parts.

 

Ron Humphrey 425.450.0099

rhumphrey@humphrey-associates.com