Cold Forging a High Precision Automotive Output Shaft (Inner Spline) without Secondary Machining.

Meco was requested to produce a part with a MBP (measurement between pins) of 0.03 mm by cold forging. This tolerance requirement is highly precise and tight, as regular cold forging achieves a tolerance of 0.06 mm, thus presenting us with a challenge to overcome. Furthermore, the Jominy range of the steel material had to be strictly controlled, in addition to respecting critical parameters in stability/longevity. After our engineers performed the requisite analyses, we were satisfied that we could keep all factors under control and thus gained the confidence to produce this part. Through the experience and know-how of our various teams, we successfully satisfied customer needs where their previous supplier could not. To our knowledge, the cold forging of such a low-tolerance part has not yet been achieved by other manufacturers in the country.

1. Material Selection

Per the customer’s drawing, we were requested to use 20MnCr5 steel. Recognizing that the Jominy range of the steel material had to be controlled as low and as stable as possible, our engineer recommended the use of custom spec steel and subsequently requested the steel mill to control the chemical composition to achieve the desired Jominy values. We tested and validated the composition of the material upon arrival to ensure that customer specifications were met. 

2. Tooling and Process Design

Spline Punch Our engineering team tried various metals to achieve the best result, including tungsten-molybdenum HSS, cobalt super-hard HSS, powder sintered HSS, etc. Following repeated testing, we chose the most suitable material for the given application.