Shop Solutions: Partnering for Profits
Anderson Machining Service Inc. (Jefferson, WI) is the supplier of engine balance shafts for Harley-Davidson's Softail models. The company works closely with Harley to help the Milwaukee-based motorcycle builder achieve its price and quality goals.
For Anderson Machining, that meant revamping balance shaft machining processes that had been in use for four years. The company's main goal was to produce complete parts in a single setup on a just-in-time basis. VP of Manufacturing Erik Anderson sought his own partner to tackle the makeover, and after some research and a recommendation from another shop settled on Fuji Machine America (Vernon Hills, IL).
"Fuji didn't talk about machines or just try to sell us a machine, they talked about the application and how to process the part initially," explains Anderson. He also liked that Fuji would be supplying all major system components, including machine tools, robots, workholding, material handling, automated gaging, and cell control. "Single source responsibility in automation is almost a non-negotiable point in my book," says Anderson.
Anderson also felt Fuji's process-driven approach to automation and 25 years of experience using robot-integrated machine tools supported the company's take on lean manufacturing, which the company calls "Competitive Pricing Through Productivity." The method dictates that all operations are coordinated to produce a completed part, and that product is ready to be shipped as close as possible to when the costs of manufacturing are incurred, he explains.
Anderson Machining's setup for producing Harley balance shafts (clockwise from top): Overall view of five-machine cell; a look inside the machining envelope with part in place; and the forged steel workpiece before and after machining.
"We make just what we need to in order to replenish what's shipped on a given day. With batch processing, if there's a problem, everything in the pipeline between the first operation and everything that's running in all subsequent operations becomes a problem. But, when you start with a raw part and it comes out of the line a finished part, all the quality functions are done at one time. It's either a good quality product at the end of the line, or it's deviant and then there's one bad piece as opposed to an entire bad batch. We can monitor process capability all the time as well," he concludes.
Anderson Machining's previous batch process for the two-pound forged steel balance shafts consisted of two rough turning centers feeding a central finish grinding process, followed by manual deburring. The operation ran three shifts a day with three operators per shift.
The revamped process includes five Fuji machines--two horizontal machining centers and three two-axis turning machines--with automation and material handling to link all components of the cell. It begins with fixturing of a forging onto a workstocker. Each machine in the new cell contains its own robot; each set of machines share a transfer station. A Fuji HM-30 HMC center mills the ends and machines in centers for subsequent turning operations.
The part is then transferred to a Fuji ANS-31T two-axis lathe for rough turning. Custom workholding locates off the center and clamps on the forging OD. After transfer to a second ANS-31T machine, the two end-bearing journals are rough turned and the required thread is rolled.
After automatic reorientation, the part moves to a third ANS-31P, a precision two-axis lathe for hard turning and finishing that replaced two grinders from the previous process. Using a face driver for workholding, this machine turns and burnishes both journals for finish.
This machine also features automated gaging of both part and tooling to determine if process adjustments are necessary. If necessary, the line shuts down and the part is removed and isolated. The machine then automatically compensates for tool wear based on the gage data and continues operation.
After another transfer, the workpiece is completed when a second HM-30 HMC mills a flat, drills a hole, and deburrs 95% of the workpiece.
According to Anderson, the process can hold tolerances of 11 µm on diameter, 12 µm TIR runout, and 12 µm on surface finish. The line also had process capability (Cpk) better than 1.67 in runoffs in Japan and on Anderson Machining's shop floor.
The new setup produces 56 balance shafts per hour, a 33% increase from the 42 pieces/hr produced by the old process, allowing Anderson to eliminate a shift while gaining capacity. Scrap has decreased from 1.5% to <0.5%. Seven of the nine operators required for the prior machining method have been relocated to Anderson's Whitewater, WI plant, reducing the number of operators for this process to only one each for two shifts. Annual production costs for the component have been cut by $400,000.
According to Erik Anderson, changing from stand-alone machines to cellular production also requires changing thought processes. "In the 1990s when we were a job shop, we ran like gangbusters on our individual machines, so we know a lot about machining fast," he says. "Back then it was only about cycle time. But when you start pushing machines together, you have to start thinking about takt time and line balance.
"For example, one of our operations takes 55 sec--longer than the rest. Other operations could take only 30 sec, but why bother beating the machinery? That operation's going to take 55 sec, so we slowed certain things down to improve tool life. In fact, our tool life has increased by ten times.
"Americans tend to run the heck out of machines," he continues. "When you're balancing a line like this, it doesn't make sense to do that. Takt time--the time it takes from when one finished part is produced until the next finished part is done--is what we care about the most. The volume of this product line dictates a one-minute takt time."
Erik Anderson says flexibility was another reason Anderson Machining chose to partner with Fuji. "Harley-Davidson is aggressive on updates," he explains. "We rarely run a part for two years without significant changes, and it was cost-prohibitive to update with other machine tool builders concepts." Anderson considered everything from conventional turning to automated turning cells, automated grinding, and dedicated transfer machinery before selecting Fuji's self-contained automation.
"When you're looking at stuff like this for Harley-Davidson, they want to know what you're going to do if the volume doubles; they want to know what you're going to do if the volume drops," Anderson says. "With this, I can say if the volume goes up, I'll add machines, and your price will go down. If this project goes south, the machines are versatile enough that we could split them up for use on other applications," he concludes.
Opening the Door to Productivity
By equipping machining centers with automatic door openers, BorgWarner Emissions/Thermal Systems (Cadillac, MI) has improved productivity and controlled a source of repetitive motion injury among operators.
The plant manufactures cooling systems and other components for heavy-duty commercial vehicles. Many of its workpieces are castings that must be machined, and the company has many CNC machining centers to perform these operations. The plant routinely operates three shifts, five or six days a week.
Typically, machining centers have a sliding glass door that must be opened and closed manually to load and unload the machine between cycles. Some BorgWarner employees were experiencing problems with repetitive motion injuries. "Some of our machines are fairly large, and when the operators were moving the door open and closed all day long, they had some problems with shoulder pain," says Facilities/Maintenance Environmental and Safety Manager Chris Stanley.
In looking for a solution, Stanley found that the some of the machines were designed to use optional automatic door openers. "They were designed into the machine and hard to integrate once the machine was built," he says. "If it could be done, it would cost an extraordinary amount of money."
Instead, Stanley selected an automatic opener that was designed for field retrofit on existing machinery. The ATD automatic door opener, from A&A Mfg. Co. Inc. (New Berlin, WI) is easy to incorporate on a wide variety of machining centers for horizontal or vertical door orientations. The device protects operators from both crushing and repetitive motion injuries and includes built-in safety features that continuously monitor torque and speed.
"About two years ago, I bought four door openers to start with," Stanley recalls. "They worked out so well that we now have them on 14 machines. In the next few months, they will be on every machine."
The door openers reverse automatically when they encounter an obstacle, preventing both injuries and downtime. "We've done the pencil test, and it didn't break the pencil," Stanley notes.
The openers are self-calibrating and operate without adding limit switches, light curtains, pressure switches, or photoelectric eyes. Their internal braking system engages in any stopped position. They are fully electric and require no shop air. A preprogrammed control module is easy to use.
In operation, the machine cycles are automatic but controlled manually by the operator. "Once he loads the machine, the operator pushes a button to close the door and start the cycle," Stanley explains. When the machine reaches the end of a cycle and the operator needs to change a part, he simply pushes a button on the machine's control panel, and the door opens.
The primary benefit of the door openers has been a reduction in repetitive-motion injuries, Stanley reports. "We have reduced repetitive shoulder injuries by at least half, if not more," he says.
Opening the machine doors automatically also has helped speed up operations. "It's faster than opening the door manually," Stanley points out, "and the speed can be increased or decreased depending on your needs. It's very flexible." He says the units are easily programmed using a notebook computer.
The openers were simple to install, he adds. "We installed them ourselves. The brackets comes with the opener, and the only modification needed was to weld it to the machine."
While all the door openers at BorgWarner are now controlled manually, it's possible to integrate their operation into the machine CNC as well. According to Stanley, the company is looking into this option as a possibility on several machines.
Scanner Supports App Development
Determining dimensions and dimensional stability is key in the development of plastics applications. GE Plastics Advanced Application Technology Center (Pittsfield, MA) is well-equipped to characterize these properties in an accurate way using a coordinate measuring machine equipped with a 3-D laser scanning head.
Installed on a Wenzel CNC CMM, the LC50 line scanner from Metris (Leuven, Belgium; Metris USA is located in Rochester Hills, MI) can scan at rates of almost 20,000 points per second over a width of approximately 50 mm. The device also enables GE to rapidly capture an accurate 3-D digital copy of the object being scanned.
In developing processes to use GE's Noryl GTX plastic material for online painted fenders, the scanner was used to track shrinkage and expansion of parts at various stages of production.
Fender processing includes several stages that can affect the dimensions of the fender. The most important of these are injection molding, assembly, and paint baking. GE technicians gained an understanding of dimensional changes in each critical step by scanning the fender and comparing it to the closest theoretical model after each stage of the process.
The system can produce a digital copy of the car fender by scanning in 47 minutes. The fender is completely scanned in 43 subscans at different angles, which are qualified with an automatic procedure before the measurement. Although the unpainted fender has a dull, black surface, intensity of the laser light results in high-quality measurements.
Scanning results in a cloud of data consisting of more than 800,000 points. To speed up calculations, the point cloud is reduced using a curvature-based filter to approximately 50,000 points.
For comparison, data can be aligned with the CAD model or previously obtained point clouds in several ways. CADcompare software enables visualization of dimensional changes at all stages in the process, and n-point alignment--roughly aligning specific points in the cloud with corresponding areas in the CAD model--is also commonly used.
Once the best fit is achieved, deviations are visualized in a 3-D color map. Users can also compare sections sliced through the pointcloud and CAD model.
Another method is to align fixed points in the point cloud with corresponding fixed points in the CAD model, a technique called feature-based alignment. The fixed points can be part of the scanned application, but it is also possible to use references in the same coordinate system of the part. Overlaying these points with the CAD model allows immediate, direct comparison.
In this case, GE personnel used three metal spheres mounted on the body frame as reference points. Knowing the 3-D coordinates of those spheres allowed workers to add them to the CAD model. Overlaying the spheres from the point cloud with the spheres in the CAD model, allowed technicians to calculate absolute deviation.
The technique allows fast tracking of the root cause of any part defects, because users can analyze the 3-D scanning results at each step in the process to determine when errors were introduced. Final evaluations are reported in graphical color plots where part dimensions can be interpreted at a single glance.
This article was first published in the April 2005 edition of Manufacturing Engineering magazine.