Kohler Company - MCV3016 Oil Pan

Kohler wanted to produce a more cost competitive 15-20 Hp engine for the lawn and garden market segment. To produce a high-quality engine while reducing costs, Kohler Company gave Ellison Technologies a list of criteria they felt would help accomplish this goal.

Single Operation – Simplify part flow and minimize the chance of missing features
Cycle Time – 4.5 minutes or less including part load/unload
Load/Unload – Not More Than 6 Seconds/Part
Common Platform of Fixturing between Cylinder Heads and Oil Pans (Quick Change)
Quality Requirement – 1.67 Ppk on all critical features

Assessment
The part required machining on (4) sides which meant that a rotary table with window fixture would be needed to machine all features in a single clamping. Ellison Technologies had implemented (4) Vertical Machining Centers at Kohler Company the year before to manufacture cylinder heads for the Courage Engine project. It was determined that this technology could also be applied for oil pans. This also would solve one of the criteria Kohler Company desired, common fixture platform. Ball locks on the trunion table would allow quick change capability between fixtures both oil pans and cylinder heads.

We would utilize the following technologies:

Machine: Vertical Machining Center (32 ATC & 15,000 RPM)
Rotary Table: Nikken NSZV300
Coolant: Turbo Systems 1000PSI High Pressure Coolant
Tooling: Kennametal Hydraulic Tool Holders with PCD Inserts
Unload Assist: Royal Part Puller (Through-The-Spindle Air Activated)

Solution

Ellison Technologies implemented the Nikken 4th Axis Trunion Style fixture to an vertical machining center. The part was clamped utilizing a live hydraulics with air seat sense to confirm part present before the cycle started. The aluminum casting for this part was not very rigid so we also used hi/lo switchable clamp force when machining. This limited the amount of casting flex while machining critical features.

During the cycle we were able to achieve very fast cuts. The cuts were optimized by the use of PCD tooling, hydraulic holder rigidity, machine rigidity and high pressure coolant.

Cutting Speeds Achieved:

• Face Mill (2”) -> 12,100 RPM / Feed Rate 145 IPM (6250 SFM)
• 6mm Drill for Governor Hole -> 10,000 RPM / Feed Rate 60 IPM (615 SFM)
• Boring of Crank Bore -> 4500 RPM / Feed Rate 11 IPM (1900 SFM)
• Back Bore Oil Seal Bore -> 3000 RPM / Feed Rate 18 IPM (1865 SFM)

Finally at the end of the cycle prior to the auto door open, we used a spindle mounted 3-finger gripper which was actuated by through the spindle air blow. This allowed us to unclamp the part, remove it from locators and place it on top of the rotary table housing. When the door opened the customer was able to load the raw part directly on the fixture and remove the finished part from the unload position. This greatly minimized the load/unload time. The unload position also had a proximity switch so the machine could not go into cycle until the finished part was removed from the machine.

End Result

We were able to reach all of the criteria outlined by the customer in the proposal.

Single operation completed a part. (No WIP and eliminated the chance for missed features)
Cycle time was 4 minutes 18 seconds (with load/unload)
Load/Unload time was under 5 seconds
The fixtures had ball lock base plates which will allow for quick change out to cylinder heads

Minimum Quality standard of 1.67 PpK was achieved on critical features

Flatness Tolerance: .1mm (Statistical Capability Result: 12.896 PpK)
True Position F Hole: .07mm (Statistical Capability Result: 3.876 PpK)
Distance –E- to –F- Hole Tolerance: .07mm (Statistical Capability Result: 2.699 PpK)
True Position of Crank Bore Tolerance: .07mm (Statistical Capability Result: 7.3664 PpK)
Perpendicularity of Crank Bore: .025mm (Statistical Capability Result: 6.305 PpK)

This installation was so successful, that Kohler Company ordered total of (9) systems over a 1.5 year period to produce oil pans at their Hattiesburg, MS and Kohler, WI facilities.