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