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Development of Safe Combination Dial for the Safe Manufacturing Industry

Converting components manufactured from metal to plastic can present significant cost savings over metal fabrication, and offer a great deal of design flexibility. An example of this is an OEM manufacturer of safes, who approached Port Erie to convert a steel combination dial to plastic.

Their current steel dial was made in China; manufacturing required milling to size and polished to a mirror finish. Once these two processes were completed, numbers and tick marks had to be etched into the outer surface. Then the dial was hand-painted black. The benefits of converting this four-step labor intensive process into a much simpler insert molding and decorating operation was obvious.

To take full advantage of the benefits of molding required planning and an understanding of the processes’ strengths. Port Erie’s engineering team helped determine that there would be design issues to overcome in order to keep the part geometrically similar to the metal dial. The new plastic part had to meet minimum torque requirements while maintaining the design characteristics of the original dial; material selection would be critical. The design also had to accommodate a secondary operation of pad printing. In addition, the ink used had to bond to the selected dial material; this would require scratch and chemical resistance testing.

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Highlights of this Product Development Project

Product Name
Safe Combination Dial
Product Description
These parts are used in a Safe Combination Lock System
Industry for Use
Safe Manufacturing
Product Development Capabilities Applied/Processes
  • Process Design/Product Development
  • Tooling Design
  • Mold Build
  • Component Sourcing
Insert Molding
Tooling Material Used
P20 Steel / Hot Manifold – 2 drops
Equipment Used to Make Tooling
High Speed CNC Machining Centers
Precision EDM
Equipment Used to Manufacture Parts
Molding Machine: Nissei with High Speed Wittmann Robot
Overall Part Dimensions
Part Size: 3.5” x 5"
Part Weight: Original part, almost 300 grams; Redesigned plastic part, less than 100 grams
Tightest Tolerances
± 0.003” for CTF Features
0.015” Maximum Perpendicularity Base to Spindle
Molded Spindle Length: ± 0.007”
Spindle Pullout Force: 175 lb Minimum
Artwork Alignment True Position: 0.025”
Material Used
High Impact Polystyrene Black
Two Part Epoxy Based Ink
In Process Testing/Inspection Performed
Dimensional Inspection, Scratch Resistance Testing, Visual Inspection
EAUs: 300,000+
Standards Met
Customer Specifications, 2D CAD Drawing
Secondary Operations
Pad Printing
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