The Final Frontier

Since their introduction into the industrial workplace over 30 years ago, robots have been pigeonholed in the minds of many managers as expensive tools largely impractical for all but high volume production runs. With some exceptions, for example the widespread use of sprue pickers, this view has been especially common in the plastics industry, where tool changes can be frequent and labor costs have traditionally been below the threshold that would justify the cost of purchasing a robot. As a result, productivity has lagged: In 2000, the U.S. plastics industry’s productivity was 33% lower than the average for all other manufacturing, according to SPI statistics. In Canada, which trails the U.S. in productivity, the productivity gap between the plastics industry and other sectors is likely even greater.

In the past few years, however, China, improved robot flexibility and lower cost have changed managerial outlooks. Today, the attitude among plastics processors has switched from “prove to me why I should use robots” to “prove to me I can’t use robots”.

“Robot prices have declined or remained flat even though they do more,” says Joseph Portelli, plastics program manager at Fanuc Robotics. “Smaller shops can indeed afford robots and many processors are buying and installing them in their plants.”

Other benefits to robots include improved equipment uptime, faster cycle time, more predictable production flow, safety, reallocation of labor to value-added tasks and reduced employee turnover, according to Martin Pemberton, president of robotics integrator, Sierra Automation, based in Cambridge, ON. In one project, Sierra helped a customer automate two processes with robotics, resulting in a 17% reduction of cycle time and reduced labor content. Sierra will provide molders with an analysis of return on investment for a given automation project, at no cost or obligation, Pemberton reported.

In-mold automation applications expand

Advances in the design of end-of-arm tooling (EOAT) are playing an important role in the development of new and unique in-mold robotic applications for injection molders.

Sterltech Robotics, a division of Sterling, recently developed a complete turnkey robotic system for the in-mold application of applique labels for its customer, Plastics Products, of Greenville, KY. The labels had to be precisely positioned in the mold without any wrinkling or folding. Sterltech used its SRXII-400SLL series three-axis robot combined with custom end-of-arm-tooling and a two-station rotary table to accomplish the task.

The applique labels are picked up from a two-station rotary table nest and given a negative charge by a static wand generator mounted on the EOAT. The rotary table provides continuous feeding of labels. After molding, the finished part and sprue are removed from the B side of the mold, while a fresh label is inserted into the positively-charged A side. The finished part is placed onto a conveyor for inspection and packaging.

In another in-mold labeling application, Engel worked with Mar-Lee Companies to develop customized, automated work cells at Mar-Lee’s precision injection molding facility in Leominister, MA. Two of the work cells are used to manufacture Solo baby wipe dispenser lids. Each cell is equipped with an Engel high-speed Classic 450-ton toggle machine running in tandem with an Engel ERS (Speedy) robot and two Engel ERC, 3-axis servo robots. The cells produce eight parts with each shot in a nine-second cycle time.

The first ERC robot picks up eight foil inserts from a magazine mounted on a rotary table, swivels the C-axis 90 degrees, and hands off to the ERS robot’s end-of-arm-tooling. The ERS robot moves to the injection molding machine, waits for the mold to open, inserts the labels into the mold cavity, then removes finished parts from the other mold half. The molded parts are handed to a folding and condensing station, where the living hinge is flexed, the lid is latched, and the spacing is condensed for packaging. The parts are then placed on a servo-driven timing belt conveyor, then transferred to the second ERC robot, which deposits the parts into a box.

“This is Mar-Lee’s vision of how you compete with China,” said Mar-Lee president John Gravelle. “We are automating everything we do.”

Wittmann Inc. has partnered with Demag and moldmaker pgam advanced technologies, located in Auburn Hills, MI, to develop a robotic system capable of handling textile materials. The system consists of a Wittmann model W643 top entry servo robot with dual end-of-arm-tooling, a Demag ET 350/1250-2300 molding machine, an insert presentation table and a pgam single-cavity mold. The robot’s EOAT is equipped with needle grippers for gripping and lifting the textile, as well as a gripper style removal EOAT. The robot is designed with two separate C-axis cylinders for independent control and actuation of the offset mounted EOATs for textile insertion and part removal respectively.

The presentation table can hold up to two separate stacks of up to 50 textile inserts. Two opposing knife-shaped blades mounted on a rail work in coordination to separate the uppermost textile insert from the stack prior to gripping. The needle grippers on the insert EOAT are actuated to grip and lift only one textile insert from the stack. The robot moves the textile insert into the open mold and positions it onto alignment pins on the moving mold half. The needle grippers then release the textile insert, and the robot moves the removal EOAT to the fixed mold half. The molded part is gripped by pneumatically operated fingers and placed on an indexing conveyor for downstream finishing operations.

“The commercial availability of this fully integrated system package for in-mold textile insertion of automotive parts such as A-, B-, and C-columns, interior door panels, etc., will provide molders with a cost effective solution for mass production,” said Michael Wittmann, CEO, Wittmann Inc.

Speedier, more flexible systems

New programming technology, vision systems and fully articulated robots have combined to make robotics easier to implement and to push the envelope on new and unique robotic applications in plastics operations.

Robotic Production Technology (RPT) has recently introduced a new robot simulation software, TrimPro, for path intensive trimming applications, including water jet cutting, deflashing and router trimming. TrimPro is a PC-based offline robot simulation software which allows users to simulate and program a robot in 3D space. RPT jointly developed the product with Fanuc Robotics. TrimPro allows the operator to automatically create a cutting path without the time and costs associated with a prototype setup or a stop in production.

“TrimPro significantly cuts the amount of time needed to finalize a robot program while in production mode,” said Chuck Russo, CEO of RPT.

Six-axis articulated robots provide six degrees of freedom and the ability to reach any point in space from any direction. One of the main benefits to these robots, says Fanuc’s Portelli, is that they generally do not need any special part presentation equipment. This makes them ideal for machine extraction in combination with secondary operations such as deflashing and degating.

Fanuc installed five floor-mounted 6-axis robots and 11 machine-mounted 6-axis robots at a Delphi plant in Vandalia, OH. The robots are used to extract and trim a variety of interior automotive panels, replacing a system based on gantry robots for extraction and manual trimming/cutting. The robots remove the panels from the mold, then rotate the parts over heat guns to melt away excess flash in critical areas. The robots then place the panels on outbound conveyors. The new system has reduced the original 13 sec. extraction cycle time to 5.5 sec.

ABB Robot Automation has become a leader in supplying flexible robotic plastic fuel tank assembly systems. In 1998, fuel system supplier TI Automotive became the first company to adopt the system in a production setting, and the technology is now rapidly spreading through the auto
motive industry. The technology uses robots to carry out all secondary operations, such as assembly, cutting and welding, after the fuel tank has been blow molded and cooled; thus eliminating the need for hard automation. The major benefits afforded by robotics-based assembly are a huge increase in flexibility and a long-term investment savings.

“If there is an engineering change to move a component on a fuel tank by a few millimeters, our robots can accommodate the change at no cost,” said Slawomir Smolec, business unit manager, robot automation. “With hard automation making such a change would be very costly.”

The key components of the flexible automation system are an ABB 6-axis IRB 4400 robot with a 60 kg capacity, a patented end-of-arm combination tool, and a unique 2D vision system supplied by ABB’s strategic partners Braintech, Siemens and Cognex. The L-shaped combination tool is one of the system’s most critical elements, Smolec reported, facilitating both part handling and highly accurate assembly and welding operation, all with a single robot.

“The tool is a breakthrough, because it allowed us to master robotic hot plate welding with a greater accuracy and lower cost than ever done before,” said Smolec.

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LOW-COST PART REMOVAL

These days, smaller processors can obtain all the benefits of automated part extraction without a large capital outlay.

Nucon Wittmann’s W602 sprue picker can be used for either sprue removal or for extraction of small parts. The W602 is capable of removal times as short as 0.6 seconds. The fast removal time also permits shorter mold open times, resulting in increased machine throughput. The W602 sprue picker axes were optimized with vibration dampening features to prevent vibration in the vertical arm and maximize speed of all axes in motion. The pivot axis is freely adjustable between 45 and 95 degree, accommodating a simple change-over of the vertical arm from rear-side to operator-side placement.

Two high-performance Ventax Viper AS 206 SE robots are used for part retrieval from a stack mold at a high-speed packaging operation. The robots feature 2000 mm of horizontal stroke and a 100 mm of strip stroke. The robot’s Synchro-link arm design and integrated X-axis allows for a real-time intrusion time of 0.8 sec. with 75 mm of strip stroke. The parts are then passed to dual servo transfer arms that interface with corresponding servo down-stacking conveyors ensuring smooth stacking.

Conair’s new BE-950 pick-and-place robot performs like a beam robot but is priced in a range between sprue pickers and conventional beam robots. The robot provides processors with a higher degree of control over part release than a traditional sprue picker can deliver, at about half the cost of a beam robot. The unit can handle payloads up to 6.6 lb. The 90 degree wrist rotation allows parts to be placed under control onto a belt conveyor or table.