COMPETING GLOBALLY: IN THE MOLD MARKET
Using Manufacturing as a Competitive Weapon
Many manufacturers—large and small—are facing multiple challenges to stay profitable and competitive. Some of these include price, delivery and intense competition. There are also challenges of off-shoring, escalating raw material costs that squeeze margins, a shrinking skilled labor pool and constant technology advances.
Mold makers know that inefficiencies in the mold building process can cause poor lead-times and inflated overhead. Pressure to decrease bench work and lead-times, while making molds that produce superior parts, is pushing many mold makers to investigate more effective methods and new technology.
Makino’s team of application engineers is helping mold makers deal with these pressures by utilizing some of the most advanced machines and techniques in the world. They are helping North American companies use manufacturing as their competitive weapon.
"Making changes to the mold manufacturing process can cut lead-times in half or more," says Bill Howard, vertical machining center product manager for Makino. "This can help you win business you may not normally get, generating more revenue. In addition, you can significantly reduce manufacturing times, reduce inventories, slash manufacturing costs, minimize direct and indirect labor by eliminating or avoiding associated expenses, and – best of all – improve quality."
A More Efficient Process
Typically, a mold maker will first process a mold on a machine tool, cutting a mold that is pretty rough. After hours of cleaning up the cuts by hand, hand-fitting the two mold halves together, and running several test pieces, a mold is produced. Once the final test pieces are run, the molds often have to be hand-polished to meet final fit and finish requirements.
"With the machinery and techniques of the past it is nearly impossible to get a perfect mold straight from the machine, so a lot of bench-time goes into making them right," says Howard.
"Time demands and competition have changed, but the process that some mold makers use has not. Many spend too much time on bench work and testing. We can change that with the latest generation equipment, advanced tooling, and modern techniques such as hard milling and high-speed machining."
Makino recently helped a sunglasses manufacturer develop a new mold making process, reducing their costs and lead-time to market, while improving quality.
The sunglasses being manufactured required extremely precise molds due to their unique design. The design has no metal – no hinges, screws or other metal parts to hold everything together. Everything necessary to assemble the finished sunglasses is integrated into the plastic injection molded frame made of anti-glare, UV insulated, scratch resistant prescription quality polycarbonate.
The sunglass mold represented a typical mold that might benefit from the new moldmaking process. The mold features complex 3D parting surfaces that require clean blend and parting lines for a stylish look, while the optical characteristics of the glasses require a precise surface finish and exacting tolerances. In addition, the cam action, which closes the mold, occurs in the critical no-hinge area at the side of the glasses, demanding a finish with no flash or trim.
There are three main parts being produced, the core and cavity blocks, the lens inserts, and the cams. The main objective was to create all three parts with no hand fitting required, so they could go straight from machining to the mold process.
This required machining down to a zero stock on the cavity, the core to a negative stock of 10 micron or 0.0004 inches, the lens pocket to 0.0003 inches oversize, and the lens machined to zero stock. In addition, the parting surfaces are not relieved from the edges, so the entire parting surface has to match to improve alignment and reduce flashing potential.
Core and Cavity Blocks
The first pieces of the mold to be produced are the core and cavity blocks. The mold manufacturer, using a traditional mold making approach, drilled all holes and rough machined with the steel soft, and then sent the blocks out for heat treating.
When they came back the blocks were ground to size, the lens pocket and cam clearance were wire EDMed, and then the finish machining was done. Finally, the pieces were benched and polished to meet the final requirements.
This traditional process took the manufacturer 30 hours to complete, 10 hours of which was benching and polishing.
The new approach Makino implemented drills all the holes soft and then the blocks are sent to heat treating. Once they come back, they are ground in the hardened state, the lens pocket and cam clearance is wire EDMed, and then the block is roughed with a Z-Level, offset type climb cut, using a balanced collet-type (G2.5) tool, and then the block is finish machined.
An especially challenging portion was the critical area where the cams match up to shut off the mold, producing the no-hinge area. For this cut, a Z-Level offset climb-cut is used with stock model recognition.
Shrink-fit, balanced (G2.5) tooling is used with some tools at a 12:1 length-to-diameter ratio (1 mm x 12 mm ballnose endmill) and a TIR of 0.001 mm. The core and cavity parts are ready for mold assembly directly from the machine, without the need for hand polishing or benching.
The new approach takes 12 hours, a 40 percent reduction over the manufacturer’s original process.
Producing the Cams
The second piece produced was the cams. The sunglasses manufacturer used to rough machine the geometry of the blocks while soft, then send them out for heat treating. When they came back, the blocks were ground to size, the actuator pocket was wire EDMed, and finishing machine was done.
The cams were then benched and hand polished to meet final cam requirements. The process took 11 hours, including four hours of hand polishing.
Makino’s new approach has the blocks heat treated first, then the hardened blocks are ground to size, the actuator pockets are wire EDMed, and finally the cams roughed and finish machined. Again, no hand polishing or bench time is required.
The new approach takes six hours, a 46 percent reduction over the manufacturer’s previous process.
The final pieces of the mold were the lens inserts. The manufacturer’s previous process would again drill all holes in the soft state, rough machine geometry soft, and then send the inserts out for heat treating. Once the pieces came back they were EDM profiled, finish machined, and benched and polished to meet the required finish.
The manufacturer’s original process took 28 hours. Twenty hours (71 percent) was dedicated to benching and polishing to meet the strict fit and finish requirements needed to create the delicate optical surfaces.
Because the lens inserts are critical to the overall quality of the glasses, Makino decided to take a radically different approach to the lens inserts, including nickel plating and diamond turning.
Makino’s new approach drills all holes soft and then sends the inserts out for heat treating. Once the parts are back, they are rough and qualify machined. The qualifying machining is critical to ensure that the next step, nickel plating, can be done effectively.
Prior to nickel plating, the geometry of the lens surface must accurately reflect the optical characteristics of the lenses, and the surface finish must be consistent (20 RMS) so that the nickel plating will consistently adhere to the lens surface.
After nickel plating is complete, the profiles and lens surfaces are re-machined using a parallel, climb and conventional cutting technique and shrink-fit, balanced tools with a TIR of 0.001 mm. This creates a highly qualified optical geometry and a 20 RMS surface finish to facilitate the last process, diamond turning. The lens surfaces are diamond turned to meet the final optical and surface finish requirements.
Makino’s new process takes four hours, an 86 percent reduction over the manufacturer’s previous process.
Straight From the Machine
Beyond just cycle times being reduced, the manufacturer has also seen a dramatic reduction in mold start-up times.
With their traditional process, the in-house spotting press took 20 hours to complete, many times requiring additional hand-work and adjustment of the mold. This, combined with sampling press time at the molder, is a 24 hour process.
Makino’s new process doesn’t require spotting or adjustment and reduces the sampling press time at the molder to two hours (including mounting, heat-up and tear down), with the first part a good part, every time.
Total savings in the mold start-up is 22 hours with the new process, a 92 percent reduction.
Additional Benefits Additional Benefits
This new process also allowed for cleaner seams, a more stylish appearance and polycarbonate savings over a traditional moldmaking process. "The seams are cleaner because the molds fit together more precisely," says Howard. This is especially apparent under the rims of the glasses, where a noticeable seam-line appears on the glasses made from a traditional mold."
The new glasses are also slightly thinner with a more consistent cross-section, because the glasses aren’t over-molded to compensate for the hand polishing necessary with a traditional mold. The ability to make the sunglasses thinner saves polycarbonate material and makes the product weigh less – an added bonus for the manufacturer.
The sunglass manufacturer has realized a 59 percent reduction in component processing time, from 69 hours to 28 hours, using the new molding approach with Makino. This 59 percent reduction includes a 40 percent reduction on core and cavity blocks, a 46 percent reduction on cams, and an 86 percent reduction on the lens inserts.
The lead time for the prior sunglasses mold had been 10 weeks. With Makino’s new approach, the lead time to manufacture the new sunglasses mold is four weeks. This represents a 60 percent reduction in mold lead-time.
Overall, the new molding approach has seen a 68 percent reduction in the entire process time, from 93 hours to 30 hours. In addition, the cost to produce the mold has decreased 46 percent.
In addition to the cycle time and quality improvements, the manufacturer is experiencing six weeks more sales and revenue than they would have seen in the past. Their inventory turns also occur more often – they now see 13 turns per year, versus the 5.2 turns in the past – an increase of 250 percent.
The Right Tools and Techniques
"The right tools and techniques are the keys to producing the most competitive mold," says Howard. "The machine tool needs to have highly precise alignment and exacting surface contact with lubrication pockets. It should be extremely accurate over the entire travel, tightly controlled over alignment and should minimize lost motion. The machine needs to be exceptionally stiff and rigid, providing an outstanding cutting platform and high-speed spindle with three point thermal control.
"In other words, the key to producing a more efficient mold is high-performance machining – using the proper combination of machine tool, cutters, tool-holders and programming techniques.
SUMMARY FOR SUNGLASS MOLD
59% reduction in component processing time
From 69.0 hours to 28.0 hours
40% on Core and Cavity
46% on Cams
86% on Lens Inserts
60% reduction in mold lead-time
92% reduction in mold "start-up" time
From 24.0 hours to 2.0 hours
68% reduction in entire process time
From 93.0 hours to 30.0 hours
46% reduction in mold cost
"When we’re asked to make someone’s mold better, the first thing we do is look at the machine the molds are being cut on," says Howard. "Features such as heavy cast construction, core-cooled spindles, spindle lubricant temperature control, axis configuration with no overhangs, squareness, alignments and accuracies all influence the precision of a cut.
"Once we make sure the machine tool is up to the task, we focus on the cutters and holders," Howard continues. "We work with a shop’s vendors to ensure that the cutters are doing exactly what they’re designed to, and working in perfect coordination with the machine tool. A balance must be found between speed and precision, without sacrificing the cut quality. Shrink-fit tooling, collet-type holders, new technology, coatings and geometries all can be helpful in this process."
"The right training for specific techniques, such as high-speed machining and hard milling, is also key to this new approach to mold manufacturing," says Howard. "Learning by doing is one way to figure it out—an easier way is through advanced application assistance, seminars, or by talking to someone who’s already doing it, like Makino."
The Right Software
The Right SoftwareAccording to Howard, once a good machine tool is in place and the proper tooling and holders are selected, the next step is dealing with the software and the programming to cut the part.
One key machine tool software control enhancement that comes into play is geometric intelligence. The most recent edition of geometric intelligence is SGI.4 (Super Geometric Intelligence version 4), which enables the processing of long, complex, 3D mold programs at high feedrates, high spindle speeds and high accuracies. The machine tool, control and servo motors are tuned for optimum performance and to enhance final part accuracies.
"It is important that a machine tool not only have software technologies like SGI.4, but that the programmer also knows how to use these technologies to his advantage," says Howard.
"Experience also identifies the right partners," says Howard. "Look for high performance CAD/CAM systems – an addition to balanced tool holders and high performance cutters.
"Out-of-date software and programming systems or techniques can go a long way to making a theoretically good cut far less accurate than anticipated," says Howard. "Makino’s application engineers work with various CAD/CAM providers to ensure the software used, as well as the programming, will perform as anticipated when the machine actually starts cutting.
"There are certain programming techniques and capabilities that are critical to support high-speed machining and hard milling in complex, three-dimensional mold surfaces."
For Your Shop
"According to the most recent Industrial Manufacturing Economic Census, a typical mold shop does approximately $2.1 million in business a year, has 19 employees and works on about a 30 percent profit margin, leaving around $630,000 in profits on that level of business," says Howard.
"If we apply this information to the reductions in the mold process Makino has found using the example of the sunglasses mold, a typical shop would realize a 207 percent increase in margins (from 30 percent to 62.2 percent), and an increase from $630,000 in profits to $1.3 million in profits if it applied the new moldmaking techniques."
"Beyond this, if a 60 percent lead time reduction is applied, as was the case in the sunglasses mold, inventory turns would increase from 5.2 per year to 13, a 250 percent jump," Howard continues.
"If this new found capacity was utilized, the $2.1 million a typical mold shop brings in per year would increase to $5.25 million, resulting in $3.27 million in profits.
"So a choice has to be made. Will your shop stick with the traditional processes or move to a newer process, potentially increasing profits and revenues dramatically? If you could cut your lead times by 60 percent while dramatically cutting your costs, you should be able to compete with any shop, anywhere, on both price and delivery, with unsurpassed quality."
Keeping Business in North America
"The simple fact is competition is tougher today, but that doesn’t mean North American shops have to lose business," says Howard. "In fact, with a few changes most shops can increase their profitability, decrease their lead-times and reduce their prices, all at the same time. By doing these things you can not only compete with the shop down the street, but also with any mold builder in the world.
"The proper combination of the machine tool, cutters, tool holders and programming techniques can allow any mold maker to produce molds that require little or no bench work or testing, greatly reducing lead-times and overhead while increasing profitability."
"A mold-maker can experience the same sort of results out of nearly any traditionally made mold," says Howard. "You need the technology available in modern machine tools and the knowledge of experienced application engineers that know those machines."
Vertical Machining Center
Product Manager, Makino