Mold shop gets boost from software

Mold shop gets boost from software

When Cadmold Group Inc. started in 1990 it had three employees and recorded a first-year revenue of about $200K. Since introducing Pro/ENGINEER Production Solutions from Parametric Technology Corp., Waltham, Mass., five years ago, the company has grown to

Cadmold owner Harry Britt stands over the Stanley Bostitch screw-gun mold. The Stanley contract was won with the time-saving capabilities of Pro/ENGINEER production solutions.

Drastically reduced cycle times for mold design and NC part programs helped make the mold for a screw gun in 10-weeks.

The high-speed IBM IntelliStation runs toolpaths 50 to 75% faster than previous hardware.

Pro/ENGINEER lets users go directly from the solid model to the CNC machine. The mold was constructed directly from the Pro/ENGINEER model without having to recreate geometry.

When Cadmold Group Inc. started in 1990 it had three employees and recorded a first-year revenue of about $200K. Since introducing Pro/ENGINEER Production Solutions from Parametric Technology Corp., Waltham, Mass., five years ago, the company has grown to 70 employees and $10 million worth of business. The catalyst for this growth, according to owner Harry Britt, has been the comprehensive, integrated manufacturing environment created by Pro/ENGINEER and the IBM IntelliStation TM.

Cadmold can start designing a mold in the earliest stages of product development, knowing that all the manufacturing deliverables, including mold geometry, NC toolpaths, and mold drawings will update automatically if the design changes. By working with customers to address issues up-front like moldability, Cadmold has increased customer satisfaction-and saved thousands of dollars in tooling costs. Cycle times for mold design and NC part programs have been reduced 50% or more, cutting delivery time by an average of eight to ten weeks.

Pro/ENGINEER gave Cadmold the edge over foreign competitors for a contract with tool producer Stanley Bostitch. Because Stanley wanted its screw gun manufactured quickly and inexpensively, the company initially considered a Czech moldmaker, but was apprehensive about the company's ability to handle Pro/ENGINEER data. Stanley found Cadmold on a referral list from Parametric Technology.

By simply reviewing Stanley's Pro/ENGINEER files, Cadmold was able to identify moldability issues and offer design suggestions even before delivering a quote. They won the contract by proposing a ten-week turnaround at an attractive price for the complex, four-cavity mold.

The tight schedule was possible because of the software's integrated environment and unique features. The entire mold was constructed directly from Stan-ley's Pro/ENGINEER model, without recreating geometry. Cadmold also saved time when adding intricate detail to the mold. EDMing fine details would have once required several electrodes—each with its own setup and matching—but with Pro/ENGINEER, toolmakers could include all the detail on a single electrode.

"Because Pro/ENGINEER references a single product model throughout the entire design-through-manufacturing process, it ensures accuracy," says Britt. "We go directly from the Pro/ENGINEER solid model to the CNC machines."

Another time saver was the high-speed IBM IntelliStation running Windows NT. The Intellistation ran toolpaths 50% to 75% faster than Cadmold's previous hardware. Stanley's engineer was able to assemble a screw-gun prototype from the first run off the press and then test it on the spot—it worked. This was a first for Stanley.

Approximately 70% of Cadmold's customers use Pro/ENGINEER, many of whom became customers after Cadmold started using the software. According to Britt, Pro/ENGINEER enhances communication even when customers use other software. His company has never experienced a compatibility problem—Pro/ENGINEER has always been able to read IGES files from other systems like Unigraphics and CATIA.

Manual machines weren't cutting it

EDM operators inspect a cavity for a print developer case and notice the improvement in surface finish.

An operator uses the ESPER input system which prompts him to select parameters and then determines the machining sequence.

Precise Mold uses the Mitsubishi EX30 to burn molds unattended.

The personnel at Precise Mold in Columbus, Ind., were a little apprehensive when they bought their first CNC diesinking machine, a Mitsubishi EX30 EDM. The company already had 6 manually operated EDM diesinkers. "It scared me to bring in a CNC machine," explained Shorty Murphy, the firm's purchasing agent. "I was convinced beforehand that we would spend a lot of time writing and debugging computer programs, but we wanted unattended machining."

Apprehension about computer control evaporated when the EX30 was used for the first time. "The input consists simply of keyboarding answers to questions that specify the finish you want, burn locations, and depths— the same information you would have to know anyhow for a manual machine," notes Max Mensendick, EDM department head.

The input system — called ESPER, for Easy and Simple Programming by Expert System — asks the operator to select, among other parameters, the number of roughing and finishing electrodes. ESPER determines the machining sequence. For example, if there are multiple rough burns and finish burns, ESPER will arrange these in the most efficient order, keeping electrode changes to a minimum. Typing in all the parameters, Mensendick has found, takes five minutes or less for a mold requiring a single burn, and about 20 minutes for a very complex mold.

"I could see that it was faster, and we were using fewer electrodes," says Mensendick. "But the biggest surprise was the surface finish, which was much smoother than what we are used to with manual machines."

"On the manual machines," notes Murphy, "a surface finish of 15 to 20 is normal. But the EX30 delivers a surface finish between 5 and 7."

Improved performance is due to the EX30's fuzzy logic. With it, the machine makes adjustments, formulated from the input data, to conditions from moment to moment during machining.

A sensor sends feedback to the control system as the fuzzy logic works in conjunction with the fine-pulse power supply in the EX30. According to the manufacturer, this supply virtually eliminates secondary discharge and the electrode wear it creates. This wear can result in a low-quality surface, and the machining waste that causes the secondary discharge can reduce operating speed. Low discharge/waste also helps the electrodes last longer.

Recently Mensendick used the EX30 to burn a complex part having 11 ribs and a depth of 2.5 in. The part took a total of 43 hr to finish; Mensendick estimates that a manual machine would have required 60 to 70 hr for the same part. The EX30 used 7 electrodes for this part; a manual machine would have used about 15.

Another part—the mold for an automotive taillight lens—is large and has a contoured shape. Precise Mold, with the EX30, can sink this mold in a single extended burn. Manually, the same mold would require 30 to 40 burns. "The more burns, the more chance of errors," Murphy explains. "When there are that many manual adjustments to make, even the best machinist can get lost in the details and make a mistake.

"The new machine pretty much removes the element of human error. If your input is right from the start—and it's easy to check that it is—you can just let it run without worrying about it."

Murphy was particularly impressed at the ability of the fuzzy logic to control small detailed cuts without arcing or blowing the electrode. He's found that they can do ribs without any initial machining and still achieve tolerances within 0.001 in.

CNC contour machining pays off

Monroe Custom Mold's first CNC machine, the Arrow 750 VMC from Cincinnati Milacron does double shifts to speed processing of die sets and plastic injection molds.

Monroe Custom Molds (MCM), Monroe N.C., hit the mark with an Arrow 750 VMC for machining a new archery bow that required CNC contourcutting. The Arrow, a Vertical CNC Machining Center from Cincinnati Milacron, Cincinnati, made 3D processing of the free-form part economically viable, and proved an ideal choice in upgrading the business from manual to CNC production, says owner David McAteer.

For starters, he notes, the new VMC enabled the shop to: process die sets and injection molds faster by reducing setups and bench work; introduce lights out, unattended finishing; bring outsourced work in house; and respond aggressively to growth opportunities, such as the bow project.

When area resident and nationallyranked archer Dave Tetrick first approached MCM with his bow idea, McA-teer had to turn him down. "With our manual equipment, I couldn't get the part cost down enough for his target market price," he says. The core element of the bow, the riser, is contour-machined from aluminum plate. After buying the Arrow, it was no problem.

"We start out with 13 lb. of 6061-T6 solid bar and finish it down to two pounds," says McAteer. " The Arrow runs these parts in 25% of the time and with half the setups required for manual equipment."

McAteer did not rush into CNC and decided on the Arrow after much re-search. "We looked at everything in this machine size — low end to the top of the price range," he says. "Cincinnati wasn't the cheapest, nor the most expensive, but it offered the most for the dollar."

For example, Cincinnati was one of the few machine makers that included and guaranteed a metal removal rate in its literature. Most only specify torque and horsepower, but with nothing to judge how well the machine applies that power.

In fact, notes McAteer, his machine operator says he's able to take 25%-30% heavier cuts on the Arrow than on other VMCs he has run.

According to McAteer, the Arrow provided four to five times more tool reten tion force than any other machines in its price and size range. Strength, rigidity, and accuracy of the Arrow pays off for machining of demanding mold and die steels. Progressive stamping dies are typically machined from A2, D2 and 4140 pre hardened steels, he notes, while injection molds and vacuum-form tooling utilize S7, H13 and A6.

"We're able to cut all the holes and features into a progressive die set in one setup on the Arrow," says McAteer. " We draw everything on the CAD system and finish the die shoes on the Arrow, including the dowel pin holes. Before, we would transfer all the locations to the blocks and line everything piece by piece. The Arrow saves us a lot of assembly and mounting time on these dies." For 3D contour machining molds, the Arrow's precision results in an accurate match-up of mating parts and parting lines. "This saves lots of bench work and makes for smooth production flow," says McAteer.

Stretch form dies using Ren shape TM boards

To save time, cut costs, and improve dimensional accuracy and stability on its stretch form dies, Rohr, Inc., Chula Vista, California, recently began using Ren Shape TM 5168 boards. The material, supplied by Ciba Specialty Chemicals, Performance Polymers, East Lansing, Michigan, is for large 8 X 6-ft polyurethane dies durable enough to withstand 400,000 psi pressures used to stretch 071 gauge, 2024 clad aluminum. The formed sheets are used in the production of wing-engine nacelles for the MD 11 commercial aircraft.

Rohr began with a plastic board stock to CNC machine stretch dies years ago. However, a price increase in the tooling material prompted department engineers to initiate a search for a lower-cost product with improved handling and performance qualities.

The decision was ultimately made to switch to Ciba Specialty Chemicals' Ren Shape TM 5168 board. The material exhibits the combination of physical properties required for the tough application, including a compressive strength of 8,800 psi, notched Izod impact strength of 0.90 ft-lb./ in. And outstanding resistance to abrasion. Rohr toolmakers also found that the Ren Shape boards offer improved dimensional stability and resistance to warping.

In addition to these numerous performance benefits, the board is priced nearly 40% below the previously used plastic material. According to Steve Di Stefano, systems and procedures analyst at Rohr, "With the easy-to-cut Ren Shape TM 5168 boards, we've reduced machining time by about 50% and significantly cut overall manufacturing. We've also lowered tool weight and cost by incorporating filler board in the die cavity.

Toolmakers begin building a die by bonding Ren Shape TM boards together to form a block large enough for the required die tool. The block is cut on a milling machine with T-ball, two-flute carbide cutters. Roughing passes are made on the Ren Shape TM 5168 block at 1,000 rpm and 25 ipm. Finishing passes run at 1,800 to 2,000 rpm and 35 to 40 ipm. Previously used board stock had to be cut at significantly slower rates of 500 rpm and 20 ipm.

"The Ren Shape TM boards provide us with the speed and stability to hold tolerances to ±0.0020 in," reports Di Stefano.

After milling the exterior die shape, toolmakers fill the cavity inside the tool with Ren Shape TM 350 filler blocks. The goal, as the company continues working with the boards, is to use 50% filler boards to reduce die weight and costs. Weight reduction is critical because large, solid stretch form dies can weigh as much as 70,000 lb, making tool movement to and from the stretch form difficult. By contrast, a die with lowdensity board and mounted on a steel support plate weighs about 10,500 lb.

When each die is completed, it is run through a coordinate measuring machine for application of a series of dots over the surface of the tool. These dots are then connected to obtain the dimensions for trim and chemical-milling tools that will be produced from plaster castings taken from the die.

To form aluminum engine nacelle sections, the die is mounted in the press and a light lubricant is rolled over its surface. Aluminum sheets are then pulled across the tool to shape and stretch it by about 15 inches on either end. Before taking the stretched aluminum off the die, machinists hammer dimples in the sheet. The marks are locators to help ensure that the nacelle section is in the correct position on the trim tool before it is cut.

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