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ROBOTIC RESOURCES

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Vertical Injection Molding Industry Turns to Robotics

by Jay Hallberg
Robotic Industries Association


Horizontal injection molding machines with automatic unload systems are a common sight.  Walking through the plant floor of any number of custom molding companies will provide a good illustration of gantry systems that unload finished molded product directly from horizontal molding presses.  The term "robotic unloaders" is the common phrase used to describe unload equipment in the molding industry.  However, horizontal molding machine unload systems should not be confused with robotic insert load systems in the vertical injection molding industry, which utilize sophisticated SCARA robots. 

Indeed, the vertical injection molding industry would seem to be a natural fit for robotics - labor costs for three shifts, repetitious manual motion, and dedicated presses to meet customer production demands are common in the molding industry.  A robotic terminal load system, which could reduce labor, eliminate potential Carpal Tunnel Syndrome, and increase overall production would seem to be a wise investment.  Until recently, however, the vertical molding industry as a whole has shied away from using  robots as an integral component for insert loading applications.

The industry has embraced semi-automatic vertical molding machines.  These presses are usually equipped with a rotary dial which presents the mold tooling (and inserts) directly to the molding machine.  But the loading of inserts in this process is still performed by operators.  The typical process is the following:  An operator(s) load inserts into mold tooling, which is mounted on a rotary dial.  The dial indexes, presenting the terminals to the molding machine.  When the cycle is complete, the operator unloads the molded parts, the runner, and repeats the process. 

Manual loading can result in an inconsistent process.  Don Santucci, President and CEO of DEK, Inc., a custom molding company in West Chicago, IL, asserts, "The cycle rates will vary from operator to operator.  Breaks and lunches must be considered for all production runs."  Downtime caused by incorrect loading of inserts is also a concern.  "Improper loading of an insert can result in a mold crash, which can take hours or even days to repair."

To improve upon the manual process, a robotic load system would be required to keep up with the molding machine cycle rate and be precise enough to load inserts directly in mold tooling. 

"Insert loading applications require both high speed and precision," explains Santucci. "Until recently, the general feeling was that robotics couldn't meet the clearance tolerances associated with insert loading applications.  Now, the robots are built to meet the stringent demands of the industry."

ROBOTS MEET THE INDUSTRY DEMANDS

"High Speed" and "Precision."  Two buzz words which are used frequently in the world of robotics.  Two words which now accurately define where the Robot Industry has arrived.

Competition in the SCARA robot industry has led to rapid advances in robot technology. 
Seiko Instruments, along with other robot manufacturers, are continually introducing "new and improved" robot technology at a dizzying pace.  The race for speed and accuracy has direct benefits for industries previously hesitant to purchase robots.  Industries like vertical injection molding can now take advantage of these new products and technology.

Seiko SCARA robots boast of high speed and accuracy.  Seiko's SCARA robots, for either the 850 mm or 550 mm reach SCARA robot, have a cycle rate of less than .50 seconds (based upon the industry standard move, 1" x 12" x 1").  This is standard speed, with no additional speed kits needed.  The accuracy of their SCARA robotics is specified at approximately .0008' for both sizes of SCARA arms.  Machine vision guidance, where applicable, can aid in improving accuracy.  Yet, only recently, has injection molding become a target industry for robot manufacturers.

VERTICAL MOLDING MACHINES READY-BUILT FOR AUTOMATION

Turn-key systems include the insert presentation, the part molding and the part removal.    Robotics is the key component to providing the insert loading and part removal.  However, it is also important that injection molding machine manufacturers design machines with the flexibility for automation. 

Glenn Frohring, Product Manager of Van Dorn Mag, Newbury Products, agrees with the industry trend:  "We are supplying more 'automation friendly' features on the machine to give customers the flexibility to automate in the future.  Many of our customers who would like the automation integrated immediately request turn-key systems."

Newbury's vertical molding machines now are designed with features which lend themselves for automation.  Having robotic integration as a standard option allows the customer to purchase a C-Frame rotary table machine complete with the necessary features required for tie-in of a robot.  The rotary table can present mold tooling directly to the molding press.  This option is targeted towards customers who do not intend on running the machine initially with operators.  The customer can send the machine directly to an automation source for immediate integration of the robotics and other devices.  The automation source can then provide the customer with a turn-key system which includes insert presentation, molding, and part removal.

Newbury offers a second option, which is ideal for customers who desire a semi-automatic machine initially, with the intent of adding automation in the future.  Customers who intend on using the machine with operator(s) for an undisclosed period of time can purchase a semi-automatic enhanced system with light curtains.  The robotic integration, including guarding, can be added at any time in the future.

Frohring estimates that "30-40% of the rotary table machines that Newbury sells (this year) will be automated at some point; and the number is growing."

PROVIDING THE ROBOTIC SOLUTION

Forte Automation Systems, Inc., has taken a leading role in developing robotic systems for the injection molding industry.  "We see a real opportunity in becoming a leader in an industry which is moving more and more towards robotic automation," points out Toby Henderson, President of Forte Automation.  "We believe that we can now offer the injection molding industry a standard solution for terminal insertion applications."

Forte Automation specializes in small parts handling and assembly applications in several industries.  Henderson maintains that establishing a niche in the injection molding industry was "just taking a proven product (robot) and adapting the technology to a different application.  Many systems we have built for companies in different industries have similar requirements, as far as speed and accuracy are concerned."
   
SMT Limited Liability Company, based out of suburban Chicago, specializes in very high volume, precision insert molding.  SMT's dedication to providing its customers with quality parts and service is evident from the various quality awards they have received. 

For almost ten years SMT has used gantry type robots to load and unload its high volume production cells, which use horizontal molding machines.  'We had the vertical automation cells concept in mind for years, but the accuracy and repeatability required to make it a viable option was not available to us,' states Reinhard Buchmann, General Manager of SMT.

SMT made the decision two years ago to turn to Forte Automation to provide the systems integration for a new concept in robotic load systems on a new high volume project.  Two production cells would be required to handle the total product demand.  The task at hand was challenging.

Forte Automation's system design centered around the Seiko TT8550 SCARA robot to perform the loading of inserts into the mold tooling.  A total of 16 inserts would need to be loaded into the mold tooling for each cycle.  Two inserts at a time are fed to the robot with the correct spacing and orientation.  The robot then picks the two inserts and places them into the mold tooling.  While inserts are loaded into one set of tooling, the other set of tooling is loaded into the molding machine.

Forte designed a rotary dial into the system to rotate each mold tool into a load position and a servo slide system, which automatically inserts the mold tooling into the press.   When each cycle is complete, the mold tooling slides out of the press and the dial rotates.  This process is repeated for all cycles.  To maximize cycle rate, an independent unload system was designed.  When the mold cycle is complete, a linear slide enters the molding press, removes the parts and runners, and places them into separate bins.

The overall success of the automation equipment is striking.  The new vertical machine production cells exceed the efficiencies of the horizontal machine cells by 40%.  One-quarter of the improvement is solely due to cycle time reductions.

In addition, the overall product quality has increased.  This can be attributed with the consistency of the robotic load and unload systems.  A key element in producing quality parts in the injection molding industry is to have consistent cycle times.  Manual loading leads to varying cycle rates; however, the robot's cycle rate remains the same.  "Insert molding cycle time variation with an operator is measured in seconds; cycle time variation for the automated cells is under .1 seconds," reports Mr. Buchmann.

These robotic terminal insertion system have another significant advantage, one that will become useful for future projects.  By providing a robot as the main handling component in the system, the system design lends itself to flexibility.  Part design modifications will not require that an entire new piece of equipment be added; rather, minor software and robot end of arm tooling changes can enable a new product to be introduced in quick order.    

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