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Articles from 2002 In June

Thermoforming: Keeping up with high-tech, competitive demands

Thermoforming is slowly defeating its perception as a black art and gaining rightful recognition as a high-tech process that can accommodate a wide variety of new applications in a cost-effective way. Continuous, incremental improvements have helped thermoformers attain greater efficiency and higher productivity in areas such as heating, trimming, line-speed, and the use of process controllers.
Battenfeld Gloucester and Battenfeld Extrusionstechnik combined efforts to produce the TSL thermoforming sheet line above. To the left are the post-cooling rolls integrated into the polishing stack. Line width is 1050 or 1650 mm. Output can be 1000 kg/hr for PS, with a 120-mm extruder.

Thermoforming machinery and equipment makers still tend to be small companies, and the thermoforming machines they make tend to be customized for the particular application the thermoforming company needs. Thus, there?s a lot of proprietary information that goes into the production of each machine, making it difficult for machinery makers to capitalize on those innovations they work with their customers to develop.

Heavy-gauge thermoforming equipment still needs better quick-change capability for reduced setup time between jobs. It also needs to reduce rejects, maintain better temperature control via thermocouples, and use thermal imaging systems to ensure the sheet is heated to the proper temperature for optimum forming. "The thin [gauge] guys have it down," notes Brian Ray, general manager of Ray Products Inc. (Ontario, CA). "We heavy-gauge guys are heading in that direction."

New Equipment, Old Technology
New adjustable clamp frames improve quick-change capabilities. An adjustment to the clamp frame can be made to accommodate a new mold instead of having separate clamp frames for each mold.

Ray notes that faster indexing is also something formers look for in new equipment technology. "We work closely with machinery companies to make sure they build what we need to make our jobs easier," he says.

Wynn Kintz of Kintz Plastics Inc. (Howes Cave, NY) also works closely with his machinery suppliers to obtain exact specifications to fit the company?s needs. "We can ask for certain parameters for the equipment," says Kintz. "We partner with them so there are no surprises."

Kintz, a heavy-gauge thermoformer, recently took delivery on a new 5-by-8-ft, three-station rotary thermoforming machine from Vector, and in July will take delivery on an even larger, 9-by-13-ft rotary machine. The company also operates a large, four-station rotary machine, and recently completed a new 30,000-sq-ft facility to house the new machines. "We?re bucking the trend a bit," notes Kintz. "But we?re seeing thermoformed parts getting larger and larger and thermoform tooling is still very reasonable, so we?ve opted for larger equipment."

Kintz recently won two awards in SPI?s TINA competition including best pressure-formed assembly for Eastman Kodak for that company?s Picture Maker Kiosk; and best twin-sheet part, a Tyco Inc. component, the Ultra Post Chassis.

Kintz says that when considering machinery, reducing cycle time is key. "We always look at the quality, but we also need a machine that can run good cycle times—can index quickly," he explains. "That?s been our mandate to Vector: Get us one that runs quicker and more productive than the old one. They?re working well with us to achieve that."

Thermoformers tend to hang on to old equipment. Ray Product?s Brian Ray notes that the company?s newest machine is a MAAC rotary, which is five years old, "but technically is still relevant to what we?re doing today," says Ray. "We can do upgrades to keep the machines current, and bring them up to date." Ray operates a total of seven machines, including a couple of Costers, the MAAC, a Golden, and a Comet. He specializes in pressure forming applications up to 6 by 9 ft. Ray Products was a winner in the TINA Awards for its pressure-formed cover housing for Orbit Pro.

This MAAC four-station, rotary twin-sheet pressure former features an Allen-Bradley (Milwaukee, WI) PLC, variable-speed motor-driven platens, and a Raytek (Santa Cruz, CA) infrared pyrometer. An adjustable lower oven is provided, along with air-assist pressure forming.
Retrofitting Heating Systems
Retrofitting older equipment with newer, advanced heating systems is the one key to realizing big gains in thermoforming. Equipment that can provide reduced energy consumption, faster line speed, and improved product quality is critical to thermoformers, for either cut-sheet or roll-fed applications.

When Maier (Grass Valley, CA), a medium-sized thermoforming operation specializing in replacement parts for motorcycles and all-terrain vehicles, needed to expand to keep up with increases in demand, it had several options: purchase a new machine at a cost of $100,000, change the operation to run a full second shift, or retrofit the existing machine to increase production.

After weighing its options, Maier chose to go the route of retrofitting the equipment. The retrofit consisted primarily of changing the heaters, controls, and power-switching devices.

Maier knew from past experience with a Heartland (Wichita, KS) thermoforming machine that production could be significantly increased by replacing its metal sheetbed tubular heaters with panel heaters. It found these panel heaters at Solar Products (Pompton Lakes, NJ), which supplies infrared electric heater products for thermoformer heating system retrofits.

Solar also installed a Cutler-Hammer/Eaton Corp. (Cleveland, OH) programmable-logic controller (PLC) with 32 outputs for individual zones. The power-switching devices were upgraded from mechanical contractors to mercury relays, which are common for sheet-fed equipment. The complete upgrade cost $15,000.

ABS and PE sheet heating time was reduced by an average of 84 percent. What used to take five days can now be done in 2.84 days. Although the available power more than doubled, the actual power usage was reduced by 10 percent. Improved consistency of heat over the sheet resulted in more uniform forming and stretching, eliminating product rejects due to uneven heating.

Productivity increased for both ABS and PE sheets, up to 80 sheets/hr from 45 for ABS (a 77.7 percent increase), and to 70 sheets/hr up from 40 for PE (a 75 percent increase). Maier also realized increased profit thanks to lower production costs and an increase in machine availability.

Retrofitting old equipment with Solar?s infrared heater products gave one manufacturer of plastic cups and plates a big advantage, even over gas catalytic heaters. The company, which has a fleet of old roll-fed thermoforming machines, saw the cost of operating the equipment dragging down profitability. In an effort to reduce energy costs, the company initially retrofitted several machines with gas catalytic heaters. While the company realized substantial energy savings over the previous calrod heaters, the resulting increased cycle times and loss of quality control ate up that savings.

The company then retrofitted one machine with Solar?s electric panel heaters, which reduced energy consumption by 35 percent and improved the quality of the product. Line speed was increased by 17 percent. A second machine retrofit realized an energy savings of 50 percent while maintaining the same line speed, and the reject rate has been lowered.

Mike Sirotnak, VP for Solar Products, notes that in the seven years he?s been affiliated with the industry, roll-fed thermoformers have gone almost exclusively to closed loop electric heating systems. "People were still using calrods seven years ago," says Sirotnak. "Now in roll-fed it?s all closed loop. They -wouldn?t think of using calrods for heaters. It?s amazing how the industry has come around."

Catalytic gas heating was making inroads into thermoforming a decade ago, but at this point, says Sirotnak, roll-fed thermoformers don?t use gas at all. "It?s very specific to cut sheet forming and also very regional," Sirotnak explains. "On the roll-fed side they were still talking about using gas up until a few years ago, but that went away."

Electric heating is preferred, he adds, because of the control issue. "The heat has to be extremely uniform and give the processor the ultimate amount of control," he says.

One supplier that aims to meet this need is Raytek (Santa Cruz, CA). It offers a line of noncontact infrared temperature measurement systems that reportedly offer thermoformers reduced setup time, control of temperature distribution, and detection of defects and failed heating elements.

The economical 2002 Comet C44S single-station thermoformer from MAAC, priced starting at $43,900, is designed for the low-cost market, where thermoformers have neither the application nor the budget to justify more.
New Machines Coming to Market
MAAC (Carol Stream, IL) has introduced a new Comet thermoforming machine that competes price-wise with used equipment. "We?ve designed this machine for the lower-cost market," says Paul Ryan, spokesman for MAAC.

Typically, MAAC has been known as the Cadillac line of equipment, notes Ryan. "We command the majority of the high-end marketplace. However, some customers don?t have the right application or the budget for this high-end equipment," he explains. "The new Comet machine is an ideal alternative to used equipment in that it?s a new machine with all new components, comes with a warranty, is priced similarly to used equipment, and they can get training on the equipment."

The machines are available as single-stations, rotaries, and double-enders ranging from 3 by 4 ft up to 5 by 9 ft. Deliveries are stocked to two weeks, and prices start at $43,900.

In May of 2000, Irwin Research & Development Inc. (Yakima, WA) and ISAP OMV Group SpA (Verona, Italy) formed a new joint venture called -Irwin OMV Technology Inc. The new company is about to introduce a large machine that can accommodate a 57-by-57-inch mold, moving the web about 10 to 60 inches—a larger system than previously available. Roger Underwood, sales and marketing director, says the new machine will be sold through ISAP group in Italy. Underwood explains that OMV was originally a product maker, then went into building thermoforming equipment, and now is an equipment maker as well as a product manufacturer. Irwin is best known for machines used in the production of PS foam and light-gauge solid sheet.

Trim Technology
Trimming is a critical—and unavoidable—component of the thermoforming process, but it adds to manufacturing costs. Because of this, trimming technology has become a target for improvements. Thermwood Corp. (Dale, IN) offers five-axis CNC routers that have true five-axis simultaneous motion and five-axis tool length compensation.

Irwin produces a line of trim presses to help reduce labor requirements. The company?s Model 50NT/VTS (Vertical Trim Stack ) can stack vertically up to 12 inches. The 50NT offers cycle speeds of up to 220 rpm. Irwin?s Underwood notes that its joint venture partner, OMV, is best known for its inmold trim technology and PP processing techniques.

The Progressive, one of Irwin?s high-tech pieces of equipment, is capable of forming, prepunching, and trimming, all on a single platen. It requires no trim press, but it doesn?t form and trim in place like many other inmold trimming machines. Instead, the product is trimmed as it passes further down the forming platen by the same platen stroke that forms the next sheet section. Maximum mold size on the Progressive is 20 by 20 inches.

A three-extruder, hot inline system from Welex processes 4000 lb/hr. The thermal losses that would be involved in cooling and reheating the sheet can be minimized or eliminated by feeding partially cooled sheet to the thermoformer.
What?s New in Roll-fed/Inline?
"I wish I could tell you that there are some enormous strides in technology for inline thermoforming, but there just aren?t," says Frank Nissel, president of Welex Inc. (Blue Bell, PA) Welex manufactures inline extrusion systems for producing thermoformed packaging. The current technology is already quite sophisticated, however. (See Words of Wisdom, July/August 2002)

Brian Crawford, VP of sales for Lyle Industries (Beaverton, MI), agrees. "There have been only incremental advances in roll-fed continuous thermoforming and trimming equipment." Lyle?s specialty is wide-bed, very heavy-duty, but thin-gauge roll-fed equipment that can accommodate thick materials and barrier-property materials including olefins, specifically APET, CPET, high-impact PE, and PP. "That is where our equipment is best," says Crawford.

Incremental improvements include servo controls for platen function and form valve function, servo drives on the sheet advance, independent servo control plug drives, and integration inline with extrusion. "We have several models that interface with extrusion for inline applications," says Crawford. "Also, we?re seeing greater use of servo controls to feed material into the trim press, and servo ejectors."

Lyle has an alliance with Gabler Machinery GmbH (Lübeck, Germany) for a line of a trim-in-place machinery to complement Lyle?s off-line trimming equipment. "Trim-in-place or cut-in-place technology is typically limited to 30 inches wide or less, but this alliance offers us the ability to take to the market both inmold trim and post-mold trim," says Crawford.

Lyle offers both vertical and horizontal trimming. The specific product usually dictates which method works better. Crawford notes that customers are looking for technology that provides greater control over the process, such as computer controls for consistency and repeatability, and recipe storage, "the kinds of things that enhance uptime on the machine," he adds. "These improvements all help reduce the variables and enhance the thermoforming process. The end result is greater product consistency, tighter tolerances, better throughput in terms of volume, and better parts."

Stiff Competition
Crawford believes that these and other advances in thermoforming are enabling the process to compete with blowmolding and injection molding. Kintz Plastics? Kodak Picture Maker Kiosk, seen in malls nationwide, is an example of how this can be done through design and engineering. "The pressure-formed parts had lots of undercuts and moving sections in the tools," Kintz explains. "There were square corners and not much draft to work with. Texturing was [also] critical. A lot of work went into the design of the tools to get this product."

Editor?s note: Clare Goldsberry is a contributing editor for PA&M and Injection Molding Magazine.

Robot line customized for molding

The RXplastics line of six-axis robots features three models (RX60, RX90, RX130) with load capacities up to 25 kg and a maximum reach at the wrist of 2185 mm. Coordination of robot movements with the molding cycle is aided by Euromap 12-compliant software. Since the RX line is prewired to Euromap 12 standards, the robots are ready as shipped for direct connection to molding machines and safety door systems.

A series of frequently used movements and scenarios comes loaded in the control software. Customizing is done with macros and modules that modify these preset movements to meet more specific parameters. The system?s control employs a graphical user interface that features common molding lingo to aid operator use. The RX line can be used in Class 100 cleanroom environments. High-speed, precision control allows the robots to follow complex trajectories at joint-speed ranges of up to 1125°/sec. The gearbox maneuvering the robot has zero backlash for smooth movements and consistent operation. Insert loading, demolding, inmold decorating, glue laying, powder coating, painting, assembly, inspection, and packaging are among the potential applications.

Staübli Corp., Duncan, SC
(846) 433-1980;

Compounding Extruders

The TEM series of corotating, intermeshing twin-screw extruders has high torque and high screw speed. It comes in 41- to 136-mm models. The increased torque of the redesigned gearbox is said to yield high-quality products at a low resin temperature.

The TEM Series reportedly provides 15 percent higher torque per free volume than similar-sized extruders of different design. The higher torque enables the extruder to produce more horsepower, which in turn creates higher throughput rates. Higher torque also allows greater filling of the screw flights, reducing the overall average shear rate and the final melt temperature.

The high torque per free volume yields a low melt temperature and the ability to run at higher speeds. The higher screw speed increases power input and production rates nearly linearly. Short residence times reduce the product?s heat history.

The TEM Series has unique vent ports and quick-clamp die-head design for reduced contamination and maintenance, while maintaining a smooth flow of material.

Standard TEM Series? barrels are made using a carbide lining (or alternate 10V liners) for wear resistance. The barrel design combined with the use of screws made from wear-resistant steel alloys is said to improve overall endurance of the machine compared to conventional-type models. The different configurations include feed barrels, vent barrels, closed barrels, and side-feed barrels.

NFM/Welding Engineers Inc.
Massillon, OH; (330) 837-3868;

Blow-through rotary valve increases throughputs

The ZXD blow-through rotary valve has an optimized design that is said to achieve up to 40 percent higher throughputs, for feeding of powders into pneumatic conveying systems, compared to previous powder rotary valves. The new valves are suitable for any kind of bulk material in powder form, such as polymers and their initial additives. Operating and maintenance costs are said to be decreased because of the reduced pressure drop in the ZXD rotary valve, which leads to lower energy consumption of the pneumatic conveying system. The valve has a maintenance-free drive and quick-clean design. ZXD rotary valves can be easily integrated and are redesigned to forego use of a venting device. The valves also are said to have an optimized housing and rotor geometry, an optimized rotor volume, tuned inlet, and blow-through cross sections. The housing has been reinforced with ribs. Extras such as nonstick coatings and chamfered rotor vanes or blades let it adapt to different bulk material characteristics.

Coperion Corp., Ramsey, NJ
(201) 327-6300;

Large mold-mounted hot runner temperature control

A 108-zone hot runner temperature control system is said to demonstrate robustness, scalability, and optimal space utilization. The Altanium 108 is reportedly the industry?s largest mold-mounted hot runner temperature control system. It uses 60 percent less space compared to previous products. The system controls 108 zones on both single-face or stack molds. It?s designed with a rail and latching mechanism, as well as an interface with standardized connectors to transition between the control system and the mold, easing mounting and removal for mold substitutions or service.

A hot runner temperature control system that is mold mounted adds a unique set of requirements. To meet these, the mold-mount design was combined with the latest Altanium hot runner hardware platform. Space on the mold is limited, requiring tight integration and service access for hard-to-reach areas. The mechanical design is also reportedly built to withstand the continuous stress generated by mold movement.

American MSI
Moorpark, CA
(805) 523-9593

Static melt blenders yield homogeneous mixes

Static KMB melt blenders support the extrusion of high-quality films, foils, sheets, profiles, and pipes, while reportedly increasing the flexibility of extrusion lines at a low cost. The blenders are compact, have no moving parts, require no maintenance, and are said to offer high mixing efficiency.

During the extrusion process, highly viscous melts develop a laminar flow profile in which flow lines are always parallel to the axis of the flow channel. The mixing elements of the melt blender split the melt flow into part streams, which are moved in a radial direction and recombined. Reportedly, even specially designed screws do not achieve the same mixing performance.

The static-melt blenders are installed just upstream of the die in the flow-melt channel. They typically use four mixing elements, reducing melt-homogeneity problems and temperature variations by a factor of five.

Koch-Glitsch Inc., Wichita, KS
(316) 828-5130

Hexagonal molded-in inserts

A new set of brass inserts is designed for placement in the mold prior to plastic injection. These molded-in inserts have a large hexagonal head on each end, as well as a large, center undercut. The heads are said to provide a high level of bidirectional torque resistance while the undercut is designed to provide high tensile strength for rigorous applications.

The Spirol Series 40 is a through-hole molded-in insert; and the Spirol Series 44 is a blind-end molded-in insert. Neither insert requires specialized insertion tools since they can both be placed directly into the mold prior to injection. These inserts have been designed to simplify orientation and placement. They?re targeted at applications where high torque and pull-out/through resistance are required, or where the molder would prefer to place the insert within the tool prior to molding.

Spirol Intl. Corp., Danielson, CT
(860) 774-8571;

Liquid coloring made easier

Many of the processing difficulties inherent in the use of liquid-color concentrates are reportedly eliminated by a new automated, liquid-color management system. The Pump-in-a-Drum liquid-color system uses a specialized metering system and pump fully enclosed in a drum to deliver color in a completely sealed environment. Siphoning the colorant through sealed tubes, Pump-in-a-Drum also features automatic shutoffs to prevent leakage in and out of the drum. The drum?s lid has a hydraulic quick-connect fitting with an internal shutoff valve that restricts liquid flow when the pump is operating. In addition, the system?s tubes reportedly aren?t susceptible to the wear and tear experienced with peristaltic pumps. Pump-in-a-Drum accommodates two drums and automatically switches over to the full drum once one is emptied. An alarm is also triggered to alert users that one drum is empty. Liquid colorant can cost more per pound than pellet concentrates, but Riverdale says liquid systems offer more value and long-term savings since they carry higher pigment loads and can be used in smaller amounts.

Riverdale Color Mfg. Inc.
Perth Amboy, NJ
(732) 376-9300

Software updates help improve mold design program?s usability

Two new wizards have been added to the PS-Moldmaker software. The software automates mold design, and the wizards are used for the design of slides and cooling channels. The slide wizard provides an automatic method for the design of slides that are needed when parts incorporate undercuts. The cooling wizard uses the dynamic sectioning command within PowerShape to create one or multiple planes within the mold core or cavity for layout of water channels and other design functions.

An upgrade to the PS-Electrode module allows the user to check the quality of the imported model and adjust the tolerances between the edges of various surfaces so that the final stages of the process will run smoothly. Now it?s also easier for the user to select the burn area in cases where the boundary doesn?t match the existing surface edges. Other additions include the ability to produce a combined electrode to burn two adjacent areas from a single blank, and automatic trimming of the blank to allow the electrode to move as close as possible to the surface of the mold without a collision.

A new version of the PowerInspect software supports inspection of models against STL files. This ability extends the usability of this program to all companies that provide rapid prototyping or manufacturing services.

Delcam Inc., Windsor, ON
(519) 974-8088;

Dark-colored stereo-lithography resins

A new series of stereolithography resins reportedly offers users high humidity resistance and toughness. The first in the series is called Raven 7620. It?s a photopolymer for solid-state laser equipment that comes as a clear, amber-colored material and turns dark during the polymerization process. The dark color achieved is especially suitable for both automotive and industrial applications.

Low product viscosity allows for easier cleaning and overall convenience in the build process, and parts made with Raven 7620 can also be used as patterns for investment casting. The series also includes transparent resins and a line with flexibility properties similar to polypropylene and polyethylene.

DSM Somos, New Castle, DE
(302) 326-8100