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Company
Recreation & Racing Boat Industry
Process: Drive Shaft Turning
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Company Background
Mercury Marine and Ellison Technologies a longstanding relationship together. Mercury Marine has made a commitment to lean manufacturing processes and has been implementing automation on all new capital equipment purchases. The automation has taken many forms. Ellison Technologies has implemented barfeeds, bar loader/unloaders, gantry's, robots, etc… , all with the intent of lowering production costs while increasing throughput.
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Challenge
Mercury Marine needed a solution for turning the ends on their Verado 4-Stroke Outboard 200-275HP engines. The solution needed to meet the following criteria:
- Automated or semi-automated solution
- Capable of handling parts between 24"-37" long
- Capable of turning through a friction weld between 4140 and SS sections of the part
- Capable of holding length and diameter tolerances to a 1.33 Cpk or better.
- Capable of holding the friction weld turn diameter to a 1.33 Cpk or better.
- Capable of producing a part in 60 seconds or less
- Capable of change over in less than 30 minutes part-to-part
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Assessment
The major challenges with this project were holding the overall length of the part to a .010 tolerance. Handling the long shafts in an automated method and finally turning through a healthly chunk of friction weld that had varying depth and hardness but still be capable to 1.33 Cpk on a .002" tolerance.
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Solution
The choice for turning the part was a 2-axis lathe. This machine's design and 10 HP spindle offered more than enough rigidity to cut through the friction weld. Concerning a semi-automated process. We wanted to use a Maranco Flexsys LE-51 Loader/Unloader similar to one we had implemented on a different drive shaft operation at Mercury 18 months earlier. The problem was that the shafts were not dimesioned from the face of the part we were cutting but instead the back side. The way the loader works is that it loads a part in a collet through the main spindle to a turret bump stop. The collet remains on the part during machine cycle. At the end of the machine cycle the part is unloaded through the main spindle and ejected down a ramp to a stop. Another part is then loaded from a "queing rack" and the process repeats. Because a turret stop didn't guarantee the OAL of the part we needed a different method of operation. We worked with the engineer at Maranco and we were able to design a backstop method of locating the part with the loader. They were doing something similar at another company and were currently holding .005".
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End Result
The process is capable of producing drive shafts in less than one minute each. The process is holding OAL to a 1.33 Cpk statistical window for both the OAL and turning of the weld.. In addition the tool life appears to be predictable despite turning through an inconsistent friction weld. The customer is happy with the end result and because of the semi-automated nature, they only need an operator to load and unload the trays nad change inserts a couple times per hour.
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