Improving efficiencies for handling small parts: new technologies offer pharmaceutical manufacturers a better way of efficiently handling and orientating small parts.
OLD APPROACH TO CONVEYING
When engineers draw up plans for designing machinery and equipment, the supporting conveyor system isn't given much thought. The machine's functionality almost always takes precedence, and suffice to say that conveyors have generally been viewed as an afterthought in the in the design process. This backward thinking is at the root of the problem when it comes to conveying handling small parts and impedes the overall manufacturing process.
Machines that don't properly account for conveyors often leave little space for them. And since there haven't been many commercially built conveyors small enough to fit into tight places, a common practice is for end users to build their own. But this brings along its own set of problems.
For starters, the task is taking an employee away from their core competencies and asking them to build a conveyor. That's not their job and they don't have the expertise to properly build one. If a company is a manufacturer of fluid management devices, why would they be wasting their time building conveyors? And once is it built, what is the company going to do about spare parts? Who is the company going to call if it's not running properly? What happens if the employee who built it is on vacation, or no longer works for the company, then who's in charge of maintaining the conveyor?
The main problem with conveyors serving the pharmaceutical industries is their size. The locations of in-feed/out-feed applications within a machine that conveyors generally serve are extremely tight, and for years there haven't been many manufacturers that offer a viable small platform to fill this need. A reason for the dearth of availability is the low ROI manufacturers felt in comparison to the amount of research and development needed to develop material handling solutions for this industry. That left pharmaceutical companies scrambling to develop their own solution.
SMALL PART CHALLENGES
Anyone involved in the manufacturing or handling of small pharmaceutical parts knows the complexity of that task. Their small, lightweight and fragile design can make them difficult to handle, orientate and move on a conveyor from one processing area to the next. When designing a conveyor system to best work within a pharmaceutical application, the engineer has several challenges to consider in moving, orientating and transferring of parts.
Part end transfer -- Since the items are so small, the ability to transfer them from one conveyor to the next can be problematic. Parts are often less than 1" in size, therefore requiring a roller diameter much less than 1". Typical conveyors have rollers 1 1/4" or larger, a size that is simply too large to be practical as a viable transfer mechanism. Small parts attempting to transfer over a 1 1/4" or larger roller could fall between the two adjoining rollers of the conveyors and become damaged. Another transfer option can be the waterfall transfer, which is accomplished by placing the roller of one conveyor over the next and letting parts fall onto the lower conveyor. While this solves the transfer issue with the larger rollers, it does not maintain product orientation, and parts can become damaged due to the fall.
Part side transfer -- If a part cannot be transferred off the end of a conveyor, the alternative method is to transfer it off the side to an adjoining parallel conveyor. The problem with this type of transfer is that bearing housings typically are on the outside of the conveyor, preventing a flush meeting between the top conveyors. This causes a gap in which very small parts can fall through.
Conveyor belt flatness -- Typical operations performed in pharmaceutical applications include vision inspection, filling, robotic pickup, etc--all of which require the part be flat on the conveyor belt. Since the part itself is so lightweight, it does not have the weight to force the conveyor belt flat, and thus will simply follow the surface flatness of the belt. Belting used for small end rollers needs to be very thin, and these thin belts have a tendency to curl when placed under tension. Think of a rubber band expanded--it becomes thin and the edges curl--this same principle occurs with conveyor belts. This belt curl causes the light part to not lay flat, hence causing problems for the automation process.
Size of the conveyor -- The floor space an engineer is given for an assembly machine is relative to the product being assemble. Since the parts manufactured are small, the room and engineer is given to accomplish the tasks likely won't be very large. There is simply no room in the machine for oversized conveyors and the associated motors and drives that go with them. This compact size also creates a new challenge for an engineer. Because the machine isn't big, the distance between operations is short. Therefore, the conveyor transporting the product from one operation to the next is short, often less than 12" long.
So what is the best way to design a conveyor system to move and handle tiny pharmaceutical parts? Some of the design challenges include reduced bearing life due to small bearings, small component strength and durability, consistent short belt fabrication and effective use of product space. Additionally, conveyor manufacturers need to take into account the handling and orientation of parts during movement, as well as the overall environment they're operating in.
To build a miniature conveyor, end rollers have been reduced to 5/8". This profile enables it to fit into tight spaces within a machine, but also when positioned together end-to-end, can successful transfer products as small as 7/8" in diameter. The bearing housings are fully encapsulated within the conveyor frame. The advantage this affords an end user is that two conveyors can be positioned side-by-side and be nearly flush with one another with only a 1/4" gap from belt edge to belt edge.
Another challenge in building a miniature conveyor with a low profile was developing a mechanism to drive the belt--and that mechanism proved to be a pinch drive, a new engineering trend that allows the conveyor to run with almost no belt tension. Typical belt conveyors run under high tension, which is needed for the drive roller to have enough traction to drive the belt. However, it is this tension that causes bearings and conveyor rollers to be oversized--and that's something that wouldn't be feasible in a miniature conveyor.
The purpose of the pinch drive is to force the conveyor belt against the drive roller, giving it driving traction without the use of tension. Conveyors have two pinch drive mechanisms, each spring loaded against the drive roller. This design allows the belt to be run in either direction and only requires enough belt tension to lay the conveyor belt flat. Since over-tensioning the belt is not required, the belt lays flatter, which is needed for lightweight components.
Miniature conveyors give engineers more options in designing their applications, such as allowing them to integrate the right-sized conveyor into their machine. Miniature conveyors with new technologies are addressing product handling issues by expanding the available options to position and orientate parts as the move through production. Bottom line is that miniature conveyors provide added flexibility to design engineers in handling small parts for medical and pharmaceutical applications--a small design that's a big leap forward.
* By Mike Hosch, PE. Director of Product Development--Dorner Mfg. Corp.
ABOUT THE AUTHOR
Mike Hosch is the Director of Engineering at Darner Mfg. Corp. Since 7985, Hosch has held many titles at Domer, including mechanical engineer, chief engineer and manager of new product development. Hosch has a bachelor's degree in mechanical engineering from Milwaukee School
of Engineering, where he graduated on the Dean's List. Hosch holds multiple patents in conveyor design and is a licensed engineer in the state of Wisconsin. He can be reached at firstname.lastname@example.org.
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|Title Annotation:||MATERIAL HANDLING|
|Date:||Jul 1, 2013|
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