Shop Solutions: Tangential Milling Secures Roughing Process
To solve a production problem in a high-volume setting, R.H. Sheppard Inc. (Hanover, PA) found that tangential milling improves process security for a difficult rough-milling operation. The lesson here is that you don’t have to settle for the first thing that works better. Dig deeper for what’s best.
That’s why manufacturing engineers at R.H. Sheppard spent almost a year working to fix a tool wreck problem in a rough-milling operation. Rather than settle on the first new tool that could marginally improve things, they dug deeper to uncover the single best solution from among more than eight tooling providers. The result: no more tool wrecks or their associated production stoppages—plus an unexpected 30–40% bump in throughput. Together, these gains helped the company contain costs and improve delivery performance for demanding customers. The annualized saving exceeds $100,000, offsetting higher energy and other indirect costs that are beyond the company’s control.
R.H. Sheppard is a leading first-tier supplier of OEM power steering components for transportation industries worldwide. The Hanover, PA, plant has 160 employees and runs 20 hours a day, four days a week, 50 weeks a year. Annual volume for the workpiece in question, a power steering housing made of ductile cast iron, is 100,000.
Key to the gain was the switch to tangential milling with an S-MAX face mill from Ingersoll Cutting Tools (Rockford, IL) that features a stronger cutting geometry. The previous cutter was a conventional mill, with inserts oriented radially. In tangential milling, the insert lies flat in the pitch circle, presenting its strongest cross section to the main cutting force. Size for size, the cutter body is stronger, and, according to Allen Smith, R.H. Sheppard manufacturing superintendent, “the selected inserts also are larger and more robust.”
The housing in question is essentially an 8 ½" (216-mm) long casting with a 3.937" (100-mm) bore diameter that is machined in a manually fed multipart setup on a horizontal CNC machine. The operator loads holemaking operations.
The operation that caused the problem, which occurs twice in an 18-step process, is rough-milling the mating surfaces on both ends. Since the parts are run four-up, it is by definition an interrupted cut. With the previous radial cutter, an insert edge would spontaneously rupture, starting the chain reaction leading to irreparable damage to the cutter itself. The damaged insert doesn’t take off its share of material, which overloads the next insert to failure—all in a split second. If the operator can’t shut down quickly enough, the excessive cutting forces overload the entire cutter body to the point where insert seats break out or the cutter gets bent out of shape.
“This is what was happening about twice a month,” said Smith. “Each time, we lost not only the cost of the cutter body, but also the value of the damaged parts and the lost production time and labor to swap out the damaged cutter. And the risk of such unpredictable failures is one reason why the operation must be attended.”
“Sheppard recognized the relationship between edge failure and destruction of the entire cutter right away,” explains Ingersoll’s Randy Bohn, field representative. “More often than not, a tool wreck begins with the sudden breakdown of one insert edge. It just happens so quickly that many production engineers miss the sequence and the cause-and-effect relationship.”
To find a solution, Smith’s team worked with their integrated supplies provider to examine eight tooling alternatives from all of the mainstream tooling companies. Meanwhile they ramped down the machining parameters with the incumbent tool to reduce the risk of future wrecks. From that original eight, Sheppard pared down to a short list of candidates for actual testing, including the incumbent. All were the same diameter as the incumbent: 6" (152 mm). Three of the four were conventional radial-insert face mills with more robust inserts than the incumbent; only the Ingersoll cutter was tangential.
“We had used tangential mills in past years with success, but wanted to be sure we were looking at the latest model’s time,” said Smith.
Over the course of several months, the comparative tests were run under identical conditions on both the “problem” cast iron housings and another part made of compacted graphite iron (CGI) that was posing the same problem. “We try to be brutally objective and strive to optimize each individual process,” said Smith. “We don’t have a preferred tool vendor, and we’re very cautious about general-purpose tools that provide convenience and tool count reductions at the expense of efficiency in each cut.”
Technical support representatives from the candidate companies were invited in to advise. At the end of the day, the tangential Ingersoll S-MAX face mill came out on top, not only for improved process security but also for higher throughput and lower annualized total cost. Following tool selection, Bohn worked machine-side with Smith’s team to optimize the parameters. This led to a final change to a tougher insert that extended edge life another 15%.
Test results achieved with a tougher 6" IN2015 grade tangential cutter with 10 inserts with four edges per insert increased parts per edge to 152 compared with 60 parts per edge for the incumbent 6" radial cutter and 132 parts per edge with the next best alternative, also an Ingersoll cutter. Cycle time for both Ingersoll tangential cutters (IN2005 and IN2015 grades) was reduced to 0.60 per part (min), and tooling cost per part was reduced from $1.33 per part for the radial cutter to $0.24 and $0.21, respectively with the two Ingersoll cutters.
“The most important result was the complete elimination of sudden edge failure, leading to a more secure process,” said Smith. “The throughput savings were of course welcome, but more as a dividend. You can’t easily put a price on improved process security and fewer interruptions, but they are invaluable.”
The tests demonstrated that the new tangential cutter could withstand the 40% greater power (10.9 kW vs. 7.8 kW for the radial cutter) requirement necessary to remove the material faster. “Sheppard now has an inherently stronger processing geometry plus a huskier cutter and a larger, more robust insert,” said Bohn. “Together they have completely removed the trigger to the chain reaction that led to their tool wrecks in the first place.”
“We’ve gone more than three years now without a single tool wreck or any production stoppage traceable to the tangential cutter,” said Smith. “That says it all.” ME
For more information on Ingersoll Cutting Tools, go to
www.ingersoll-imc.com, or phone 815-387-6600.
Cummins Engine Saves Time
with Presetting, Shrink Fit
The Cummins Engine Jamestown (NY) Plant with 1200 employees turns out approximately 500 heavy-duty diesel engines a day. MAG Mega 800 horizontal machining centers machine the cylinder heads and blocks for the 12-liter engines—eight for the cylinder head machining line and ten for the engine block line. Each machine has 30-40 tools, and 70% of the tools used in the critical machining processes use heat-shrink holders for extreme rigidity during heavy cutting.
Cummins engineers saw that valuable production time could be saved by investing in Zoller tool presetting and heat-shrinking technology. Avoiding tool setting on-machine saves about 5 min per tool, engineers estimated. Typically six tools a day are changed on each machine, which adds up to a half-hour production saved per machine per day. Cummins estimates it is achieving about 20% greater efficiency in production, thanks to the Zoller off-line presetting. The plant now changes its heat-shrink cutting tools and accurately sets key dimensions to within microns without interfering with production.
The Zoller redomatic 600, a universal presetting, measuring, and heat-shrink system, was the choice of the Cummins plant. Used by up to eight operators to exchange the mostly carbide cutters and preset those tools in their heat-shrink holders, the Zoller has dramatically changed the speed and accuracy of tool exchanges, presetting and accuracy. With a 13-kVA induction coil, tailstock and cooling system, the redomatic requires only 5 sec to heat-shrink and 30 sec to cool a tool in a single setup.
“A big advantage the Zoller brings us is the elimination of operator error, judging and entering offsets manually,” said David Malone, tool engineer at the plant. “We eliminate tool setting on the machine tools. Compared to the previous manual setting of our boring bars and milling cutters, such as for a chamfer width for example, the Zoller saves hours a day and is very consistent.”
“I love the thing. If you had any experience the old way, you would really appreciate this. No manual intervention,” said Joe Barto, Cummins machine technician.
Ideal for the large tools used to machine the heads and blocks at Cummins, the measuring range of the redomatic is 600 mm in Z and 175 mm in X with a swivel-mounted heating element diameter of 440 mm. The snap gage is 200 mm. The largest tool measured at Cummins is referred to as “Big Blue,” a crank boring tool.
A carrier system adjacent to the heat-shrink unit includes the heat-shrink control, cooling bodies, location holder, Zoller masterPiece heating element and tool length adjustment rods. These adjustment rods are used to automatically adjust tool length and position the cutters in the heat-shrink holders easily, quickly, and precisely to correct length within ±10 μm accuracy. “On tool regrinds, this helps us keep the cutting tool at the correct length, accounting for the material ground away,” Malone said.
Zoller image processing software pilot allows Cummins operators to measure and preset standard tools without data input or previous knowledge. Included in the software is a library of more than 200 cutter shapes the operator can use to select the type of tool to be measured. He is next prompted to confirm selection, and then start the automatic measuring sequence. The complex milling cutters used on the head and block lines are completely measured and inspected in very short cycles.
Measured tool data is printed on a label, which identifies the measured tool and its specifications. Afterwards the data can be read via scanner or stored on an RFID chip in the toolholder with the Zoller tool identification system and read by the machine control once the tool is replaced in the toolchanger. Tool data may also be directly transferred from the tool presetting and measuring machine to the machine control. Zoller offers the connection to more than 100 different machine-readable output formats.
The automatically generated inspection reports, detailing tool life and tool usage, and recording the number of parts a holder has cut, has been valuable information to Cummins, which has used the data to improve its efficiency and control tools costs.
Cummins uses the RFID chip to provide tool identification information to the machine tool, including how heavy the tool is which affects how quickly tool change can occur. There is also a read/write station for manual reading and writing the tool ID chip, so the tool life assigned to each tool can be changed, if necessary.
“The data we can get from the Zoller are having a big positive impact on our machining efficiency and tool cost,” Malone said.
“It not only allows us to closely inspect each cutting edge and precisely set them, but also tracks and reports tool life,” Malone said. “We put the data on each tool automatically into the chip so the machine tool can read the presets, targeted tool life between changes, and any offsets. These data are also stored in the presetter so we can review tool runouts and other details to get a good look at tool usage and relate that back to part quality and machine productivity.”
The Zoller can also automatically graph the runout of a tool, based on a program in the redomatic, Barto said. “Setting up the wipers on face milling cutters, which are generally 20 μm higher than the inserts, and then getting all the wipers adjusted to be the same height are extremely important. This is shown on the shadow display so you can see precisely the adjustment you are making.”
“I was really impressed at the many capabilities of the system, and we are still discovering additional ways the Zoller redomatic can help us save time, improve tool setting, and maximize tool life on the line,” Malone said.
The system has also been very helpful with accurately setting valve seat tooling before running production, eliminating a lot of potential rework. The Zoller has caught incorrectly sized tools which would not have been noticed with handsetting.
In the plant cutter grind department, Cummins uses a Zoller venturion for complete tool inspection after cutter regrinding. “We can input tolerancing for the tool and it can tell you if the tool is in spec and generate tool inspection data very quickly. All the reground tools are inspected and tracked. With the Zoller, we’ve reduced tool inspection time by at least 50%, and measurement is much more consistent. If there is ever an issue with a tool we will have the detail on its history,” Malone said.
The venturion combines outstanding flexibility and precision for checking a wide range of tools and is well-suited for every CNC production, and uses Zoller pilot image processing software. The machine generates measuring setting sheets/tool lists at the push of a button with direct transfer to the tool machine and storage in the presetter. The operators appreciate the adjustable LED lighting that displays cutting edges in sharp detail for careful inspection.
With its investment in Zoller tool presetting and measuring technology, Cummins is well on its way to further improvement of its production efficiency and product quality. ME
For more information on Zoller Inc., go to www.zoller-usa.com, or phone 734-332-4851.
for Vacuum Furnaces
Vacuum furnaces are expensive to purchase and operate. By using creative fixturing solutions, manufacturers and repair shops can safely increase the number of parts brazed or heat-treated per run, increasing productivity while lowering the cost per unit.
A shop can spend a million dollars purchasing a new vacuum furnace, and hundreds of dollars more on personnel, process gas and electricity each time a batch of parts is run through a brazing or heat-treatment cycle. To obtain more value from their capital expense, many companies add shifts so they can keep the furnace running. Often, however, there is a far simpler remedy: using a custom fixture that allows the maximum number of parts to be processed simultaneously.
“With a custom fixture, we can get more production out of our furnace,” said Kim Hutchinson, senior project manager for Hitchiner Manufacturing Company Inc. (Milford, NH). “The low mass of the plate heats up faster and we can pack the parts more densely so there are more pieces per load.”
Most vacuum furnace manufacturers are focused on one thing, building and servicing their furnaces. These are the high-ticket items that make or break the company. But, as with so many aspects of life, it’s the little things that can make the biggest difference. With furnaces, it’s easy to find a fixture that fits. What is harder, but can pay the biggest dividends in production and profitability, is a fixture with the right size, materials and design for both the furnace and the parts that are being processed. The trick is to maximize the work zone.
Furnace manufacturers will specify the useable work zone for their equipment—the exact dimensions of the space which they guarantee will reach a uniform temperature. The work zone is often cylindrical, but many fixtures are square or rectangular and so they don’t efficiently utilize the entire work zone. Switching to a round fixture allows more parts to be processed at a time.
“Many companies don’t realize that even such a simple design change to the fixture can allow them to process 25% more parts per load,” said Rob Kornfeld, president of Hi-Tech Furnace Systems Inc. (Shelby Township, MI).
Then there are times when the work zone can be utilized beyond what the manufacturer specifies. For example, an individual furnace can be resurveyed to verify that there is a larger work zone with uniform temperature within specification. Or there are certain types of parts that don’t require the precision heating obtained within the manufacturer’s specified work zone. If the parts can tolerate a wider temperature range and still meet their design purpose, then a larger fixture holding more parts can be designed, recognizing that some of the processed parts will be outside the manufacturer’s specified work zone.
Alternatively, there is the option of layering the parts. Instead of laying the parts out on a single level, a customized solution can be designed with multiple levels of the precise height needed to allow even heating of the parts, while utilizing the full height of the work zone.
Hitchiner is an investment casting company that manufactures parts for the commercial, automotive, aerospace and defense industries. It uses an Ipsen vacuum furnace with a 48 × 48 × 72" (1220 × 1220 × 1830-mm) work zone for solution annealing of turbine blades at 2250° F. A few years ago, it decided to go with a custom fixture from Hi-Tech Furnace Systems.
“I was familiar with the low lifespan of alloy fixturing at those kinds of temperatures,” Hutchinson said. “I studied switching to graphite and it seemed an ideal material to use.”
One of his company’s managers had experience with Hi-Tech’s customized fixtures and recommended that Hutchinson contact Kornfeld to look into a custom fixture. Hi-Tech Furnace designed a stackable graphite fixture that would hold 200 pieces per level. The fixture had five levels with 4" (101.6-mm) spaces in between, allowing 1000 blades to be processed at a time.
“The ease of stacking the plates and the configuration of Kornfeld’s modular design was really what sold me on it,” said Hutchinson. “Since you can lay out one plate at a time and stack the levels successively, you can minimize the distance between the plates without having to reach your hands into that small space.”
Kornfeld said that designing a creative, customized fixture doesn’t always make financial sense. For example, when repairing an expensive jet engine component, it is more important to get that engine back into service in the minimal time possible, rather than trying to process the largest number of parts possible. Even for production runs a standard, off-the-shelf grid, plate, or basket may do the job well enough and at a lower cost than a custom solution.
But either way, you won’t know which solution will be best unless you speak with someone who has the experience and expertise to analyze your business needs and show you which option offers the greatest business value. Kornfeld said that he frequently advises customers to purchase a standard fixture rather than ordering a custom one. In cases like Hitchiner, however, a creative solution is providing long-term benefits.
“We bought these fixtures in 2009 and they are still usable,” said Hutchinson. “We haven’t had to buy any since.” ME
For more information on Hi-Tech Furnace Systems, go to www.hi-techfurnace.com, or phone 586-566-0600.
This article was first published in the November 2012 edition of Manufacturing Engineering magazine. Click here for PDF.