Design News for Mechanical and Design Engineers

Consistency is the name of the game in most packaging operations. In some industries such as pharmaceuticals, regulations require extensive testing to validate consistency. An open-architecture design using Allen-Bradley (AB) Programmable Logic Controllers (PLC) and Sercos Interface for the automation portion and alpha gear gearboxes provides a standards approach to consistency.

"The pharmaceutical people are standardizing very strongly on Allen-Bradley and alpha," says Kevin Biffert, president of AFAST Robotics Inc. "The reason they are doing that is because the FDA is mandating that for the life of that machine you have to have support." With traditional computer software, the Federal Drug Administration (FDA) mandate means any transition from one level of software to the next requires updating the robot using the newest software and re-qualifying it. While companies are recommended to implement the mandate now, the effective date is sometime in 2009.

The FDA requirements cover both production and packaging. The goal is to avoid a problem where support is minimal, such as a second or third shift. The FDA wants manufacturers to avoid changing to another PC with different software or different controls or a different PLC just to make a production schedule and avoid the inconsistencies that could result. Once a machine is validated and started with a given set of controls, the FDA does not want process changes. They require a very lengthy re-validation procedure unless a standard component is replaced that is within the defined parameters of the initial validation.

AFAST Robotics addressed the compliance issue by using an open-architecture approach with a design using standard components for the development of a Scara (Selective Compliant Articulate/ Assembly Robot Arm) robot. "What we did is make a Scara robot based on alpha and Allen-Bradley's standards," says Biffert. "As far as the physical mechanics of the system, the difference is we are using standard off-the-shelf components that the customer can buy themselves."

The Scara robot standardization allows the customer to easily buy spare parts. With alpha gear's five-year guarantee on the gearbox, a robot owner can expect long, uninterrupted service. However, when a failure occurs, the standard parts minimize maintenance/replacement issues that can cause downtime and inconsistencies.

Another aspect of the standards-based approach to the Scara robot is Allen-Bradley's Kinetix 6000. "Our controls are based on the Allen-Bradley control and you don't need additional training," says Biffert. "There is no black box." The robot is controlled by the PLC in the Kinetix 6000. Robots that perform the same operation with a black box typically require learning a special language. With the off-the-shelf programming language in A-B's Kinetix, this training is avoided.

Pharmaceutical applications include solid dose, liquid dose and medical devices. Besides the pharmaceutical industry, where this approach is both critical and mandated, there are other industries with similar "no surprises" requirements. One industry that is closely following suit is food processing and packaging.

The robot's role in the pharmaceutical environment includes pick-and-place manipulation of the product to get it into the carton. "It's really a fast, high-speed manipulator," says Biffert. A lot of products that AFAST's Integral Series Robots deal with are syringe handling, package handling or syringes in a package-handling situation. This requires performing intricate movements to make sure the product is nested right and passes final inspection.

In one pharmaceutical application involving a medical device, a company wanted to load safety needles into a thermal former with complex end-of-arm tooling, and then put the products into the packaging. Fast cycle time for the payload was the deciding factor in AFAST's favor. By specifying the right type of gear box to handle the situation, alpha gear's cantilever moment allowed AFAST to put more payload on the arm. The TP+ and SP+ were chosen based on bearing capacities, bearing life calculations, tilting moment and finite element analysis, which basically identified the strengths and weaknesses of the gearboxes in the application. Alpha gear's Cymex simulation tool for sizing gearboxes was used for many of the calculations.

"The TP Pluses are the two main pivot points to the robot," according to Ray Hamilton, national sales manager for alpha gear. "The SP+ gear box is used in a vertical ball screw, which is the vertical movement of the tooling going up and down and grabbing the part."

"Using the alpha gears, they have a much higher bending moment on their gear set," says Biffert. "We can hang more weight on there and move at a faster speed and still stay within the boundaries of the specification of the alpha gear drives." The end-of-arm tooling for this application weighs about 20 lb.

"We were about a half a second faster than the nearest competitor," proclaims Biffert. The full cycle time from one side of the pick area to the other side and back occurs in about two seconds on an 800 mm reach robot. This meant a 40 to 50-inch swing in one second over and one second back.

		AFAST Robotics Scara robot uses two of alpha gear’s TP+ gearboxes for articulation and an SP+ gearbox for vertical movement and picking up units.
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