A global small engine manufacturer was dealing with an unacceptable scrap rate (3.03%) when drilling piston ring pin holes into pistons for the two-cycle engines that make up a large part of their product line. The parts are made out of high silicon aluminum castings. Upon placement of the pins, pistons were cracking due to excessive force. The root cause was identified as inconsistent diameters and surface finish of the cross pin drill hole. The target was 1.520mm (+/- 2 µm) using a rotary transfer machine. Without holding this tolerance, too much force was required to insert the pin, which resulted in the breakage of the finished part. The problem was aggravated by poor surface finish which made measuring and controlling such a small hole an additional challenge. After consulting with over a dozen well respected brands, they pursued what appeared to be a more costly solution from GWS.
GWS Action Plan
As with any application, the process with GWS started with our application specialists studying the operation and listening carefully as the customer outlined their problem and experiences with their test results. Taking these data points into consideration, GWS engineers were committed to finding a solution.
Their first conclusion was that an off-the-shelf drill just would not be able to deliver the solution needed. Tighter tolerances were required, as well as better finishes. Thus, the design team set out to create a drill design that would address the problems outlined by the customer, while delivering better tool life. Key design elements included a 2-micron diameter tolerance, a double margin for improved finish and custom cutting edge geometry suited for the abrasiveness of high silicon aluminum. The rest of the tool profile took shape as follows:
- Construction: Solid
- Material: Ultra-fine grain Carbide
- Coating: Uncoated, high polished flutes
- Geometry: 30 Degree Helix
- Tip: High-Performance S Type
As the prototype came together, it became obvious why the customer was having so much trouble finding the right tool for this job. Putting all of these features together in a double margin drill so small is beyond the capabilities of most cutting tool companies (see photo for proper scale). The final element in its successful production was the knowledge and skills of our manufacturing hole making division.
The customer’s manufacturing engineer stated that “The consistent diameter and phenomenal surface finish on the drilled hole now made it easy to consistently push the pin in with minimal force.”
The custom Micro Piston Pin Hole Drill from GWS:
- Dropped the scrap rate from 3.03% to .4% (including additional process improvements)
- Increased drill life from 10,000 to 22,000 parts per drill
- Created an estimated total cost savings well into 6 figures
Custom Comes Standard
Pennies still count, even when you’re a global manufacturing giant. But, as many of our other customers have discovered, paying a little more for a well designed and manufactured custom cutting tool can pay back big dividends in performance. The manufacturing engineer responsible for implementation noted that, while the cost savings from tool life alone justified the tool, the more significant savings was by far and away the elimination of the breakage problem. “Throwing away all of the costly machining work done prior to that drilling operation represented our biggest problem on that part, and GWS solved it.”
If you’re wasting time and money trying to find the right cutting tool for your application, contact us and put our expertise to work for you.