Shop Solutions: Vision System Boosts Inspection Throughput, Reliability
When UltraSource Inc. (Hollis, NH) experienced a significant increase in parts production, the company knew it needed faster and more reliable inspection. After looking into various optical inspection options, engineers discovered a way to increase both inspection productivity and their ability to gage fine tolerances.
The company, a 50-person supplier of thin-film circuit devices and related services, produces components for the commercial and military markets using precision sputtering, photolithography, and dicing technologies. From prototype to high-volume production, UltraSource's parts are used in products such as cellular and wireless communications, microwave components, fiber-optic, infrared, and laser systems.
The company was using two manual toolmaker's microscopes with electronic readouts for quality inspection, and engineers initially assumed its needs could be met by purchasing additional measuring microscopes. After soliciting quotes for new systems, however, managers discovered they could purchase an automated video measuring system for about $12,000 more.
Ultrasource engineers looked at automated vision systems in an attempt to solve their two main QC problems: the need to improve inspection throughput of two high-volume parts, and the need to collect data to optimize manufacturing processes. The system needed to meet five primary requirements:
- Increase final inspection throughput and reduce overall inspection time;
- Improve gage repeatability and reproducibility (R & R), which ran as high as 0.000343" (8.7 µm);
- Automate data collection to support efforts to improve process capability (Cpk);
- Be easy to use and program;
- Be flexible enough to allow skilled operators to perform more complex tasks and data analysis.
Quality Assurance Manager Daniel Tessier evaluated several vision systems, and found four that seemed to match expectations. But demonstrations of each unit showed two of the systems didn't have the accuracy or precision needed for tolerances of ±0.0005" (0.013 mm) or less. Another was far too expensive--nearly twice the cost of the system UltraSource eventually selected, the Galileo 5000 from L.S. Starrett (Athol, MA).
UltraSource purchased the system in August 2003, and soon experienced improved gage R&R and other benefits, according to Tessier. "With the Starrett system, total gage R&R error was reduced from 0.000343" to less than 0.000050" [1.3 µm], an improvement of over 85%," he says. "Independent studies done by our largest customer confirmed that our measurements were now correlating with their high-end vision system. They concluded that our combined gage R&R errors are less than 0.5 µm."
The vision system also allows statistical data collection, reducing the time needed for process capability studies and allowing fast downloading of measurement data to a spreadsheet. And, the system software was easy to understand and program, Tessier reports. "Within days, my lead mechanical inspector and I were able to write and design complex programs for our highest-volume customers," he says. "But the software is also flexible enough that our lower-volume, semi-repeat jobs can be programmed in a few hours."
After training with the software, UltraSource further improved measuring throughput by developing a modified glass plate and a pallet system for two of their high-volume customers' products. "I bought several precut glass laminated pieces and designed some triangular points to be used as positioning stops," Tessier explains. "Each measured device would need three points to act as an inspection datum. I glued down the points and used a piece of graph paper as a reference to ensure the points were in approximately the right locations.
"Since the Starrett tabletop comes pre-drilled with tapped holes, I purchased four long thumbscrews to hold down the glass and guarantee accurate repositioning when removed. For under $200 and in a few hours, I developed a simple pallet system that helps speed up part inspection."
With the combined productivity features of Galileo and the palletized inspection method, UltraSource was able to implement 100% inspection of product dimensions in 50% less time, and collect data on all features measured by the machine. In-process inspection of more complex devices that once took three to four hours is now done in less than 90 minutes, Tessier reports.
Waterjet Slices Cutting Time
In 1983, David Buck founded Superior Mfg. & Hydraulics Inc. (Broussard, LA) to provide parts and service to users of hydraulic systems. Over time, the company, which serves customers in the oilfield, marine, mining, forestry, fishing, and construction industries, evolved to include full system design, fabrication, and service capabilities.
Buck also launched the Clincher Products Div., which manufactures equipment designed to provide reliable handling and connection of premium oil and gas field tubulars. A key component of the clincher product is the jaws, which Superior produced by milling from a solid, 6" (152-mm) block of 4140 steel.To speed flat-part production, the company purchased an Integrated Flying Bridge Abrasive waterjet cutting system from Flow International Corp. (Kent, WA). The system uses water pressurized to 60,000 psi (414 MPa) and a garnet abrasive entrained in the jet stream. The water is forced through a precision orifice 0.013" (0.33 mm) in diameter to quickly and precisely cut materials with accuracies of ±0.005" (0.13 mm).
Superior realized immediate time and cost savings using the waterjet. For their first waterjet job, the company cut parts from 6" (152-mm) thick 4340 alloy steel plate. Parts with minimal taper and no HAZ saved 2 1/2 hours of finish milling, and reduced total turnaround time for the parts from three days to one day.
That success prompted a fresh look at the clincher jaw design. In the new design, jaws are assembled from waterjet-cut pieces of 3/4" (19-mm) steel plate. The taper-free accuracy of the Flow machine and excellent edge quality of the parts result in jaw pieces that fit perfectly flush without further manipulation. The material is also much less expensive than the 6" plate previously used, and is easier to store and move. Use of the waterjet cutting system to make the redesigned jaws resulted in time and material savings of 66% for the parts.
Shrink-Fit's a Good Fit for Automaker
Shrink-fit toolholding systems, which use induction heating to quickly heat the toolholder and allow the tool shank to slip into the holder before it cools, are finding their way into high-volume production applications, including automotive powertrain machining.
In one case, engineers tooling up a new line for machining six-cylinder engine components at a major automaker were searching for a toolholding solution. After investigating tapered-shank, ABS, FL, HSK, hydraulic, collet, and other types of systems, they chose shrink-fit.
The plant had been using shrink-fit systems since 1998 with good results. But, until recently, the lack of a good tool-presetting capability was a drawback of shrink-fit systems in production applications. Wider adoption would require the capability to preset shrink-fit tooling in the quantities required to support large-scale production.
Enter Briney Tooling Systems (Bad Axe, MI). The company developed a heat-shrink device concept that was adaptable to tool presetting, then worked with presetter suppliers KPT/Speroni to develop equipment and software for a shrink-fit tool presetter capable of accurately presetting quantities shrink-fit tooling.
The patent-pending presetting device provides a practical method of accurately presetting shrink-fit tooling within 0.0005" (0.013 mm). It consists of a KPT/Speroni presetter, PC interface, a clamping and presetting assembly, the induction heating unit, and a cooling system.
Engineers at one engine plant used the system to try to solve a persistent tool breakage problem in a core drilling operation. In the process, a 0.826" (20.98-mm) diam drill is run at spindle speed of more than 900 rpm, surface speed of 195 sfm (5 m/min), and feed of nearly 14 ipm (355 mm/min). On the two engine sizes produced on the line, this tappet bore drilling operation--considered a roughing pass--had a persistent tool breakage problem that cost the plant thousands of dollars in machine downtime and tooling.
For one of the engines, core drill tool life increased from 5100 to 75,000 pieces, and the number of tools used for 1000 engines went from 2.35 to less than 1. Tool cost per 1000 engines decreased from nearly $600 to less than $40, and annual cost of downtime from tool changes went from more than $34,000 to less than $10,000. Production on the other engine showed similar improvements in costs and tool-related downtime.
"The Shrink-fit holder's rigidity and concentricity were key to big improvements in tool life, a reduction in chatter, and elimination of tool slippage [pull-out]," the plant tooling engineer reports.
Vertical Storage Fits Lean Concept
Managers at Rogan Corp. (Northbrook, IL) took advantage of their building's ceiling height to develop a storage system that fit into their lean manufacturing initiative and freed up 5000 ft2 (465 m2) of valuable floor space.
With more than 4000 customers, Rogan manufactures and distributes 13,000 different types of hardware products such as instrument knobs, clamping knobs, and dials. The company's markets were very fluid; some were cooling off while others skyrocketed. To meet changing market conditions, Rogan set out to create a more flexible manufacturing process.
Engineers targeted three storage areas for improvement: two 1000 ft2 (93 m2) areas containing 6' (1.8-m) high racks and a 4000 ft2 (372 m2) area in the center of the plant supporting a 25" (7.6-m) high pallet rack used to store semi-finished inventory.
Shuttle Vertical Lift Module (VLM) systems from Remstar International (Westbrook, ME) met Rogan's storage requirements and supported managers' long-term plan to provide customers with shorter lead times and lower costs while increasing current manufacturing capacity. Replacing the pallet rack are two 21' (6.4-m) high Remstar units for mold bases, two additional units for semi-finished inventory, and a fifth unit for sample parts.
"We gained a net 5000 ft2 of floor space by going up," says plant manager Jim Ritzema. "With the space freed up from the elimination of the pallet racking, we were able to set up manufacturing cells using both existing and new equipment. This has given us greater control over in-process inspection and greater throughput without increased labor costs."
The plant's 150 mold bases, used in plastic injection molding machines, weigh up to 500 lb (225 kg) each and are difficult to move and store. Previously, molds not in use were stored in heavy-duty racks. They were lifted on and off the shelves and moved to the assembly table with a powered lift walker.
"All mold bases are now assigned to two 21' tall Remstar Shuttle VLMs, with two bases on each shelf," Ritzema explains. "Assembly technicians store and retrieve bases by simply pushing a button." He says Remstar was the only VLM supplier that could handle the weight of the mold bases, which totals 31,500 lb (14,175 kg).
The new setup also improves ergonomics and safety for workers, according to Ritzema. "We realized that we needed an ergonomic solution so assemblers no longer had to slide the mold bases around," he says. "In the new system, a counterbalanced pneumatic manipulator grips and lifts the bases and swings them between the shuttles' extraction tables and the assembly table."
Similarly, totes containing semi-finished parts are no longer picked using forklifts or by hand via portable stairs. Instead, the parts are protected on trays within two enclosed shuttle VLMs, and are retrieved simply by entering a shelf location via a keypad. The selected shelf is automatically brought down, delivered onto an extraction table, and presented to the operator at waist height. Having all semi-finished inventory brought to the worker reduces forklift costs as well as walk and search time.
"The storage of semi-finished inventory is common with clamping knobs, because these products don't tend to be as customized as instrument knobs," Ritzema explains. "We generally can make longer molding runs, place the parts in stock, and then pull and finish them as orders are received."
Sample stock--Rogan has 13,000 sample and prototype knobs on hand--has been transferred to a 25' high VLM, which requires only 70 ft2 (6.5 m2) of floor space and allowed expansion of Rogan's toolroom and assembly area.
The shuttle system protects the samples from dust, dirt, and light exposure, and allows access at the touch of a button. Located in front of the shuttle unit is an assembly table with hand-operated machines for producing prototype knobs for customer review and test. "Building samples is more art than science, and depends on the knowledge, memory, and skills of the assembler," Ritzema says. New knob designs are often created by mixing and matching parts from different samples, he adds.
This article was first published in the February 2004 edition of Manufacturing Engineering magazine.