Thanks to all who have posted their comments to my short article.
Obviously, the subject of ergonomics, as it relates to tools or manual assembly functions, can get very complicated and a bit confusing. It's complicated because there is rarely a perfect solution to any hand assembly function, and confusing because the end user is frequently getting opposing opinions from various "expert" sources. The solution to any given ergonomic issue is usually found by considering opinions and experiences from multiple sources. As is too often the case, the "perfect solution" to the problem usually ends up breaking the budget, or requires too many other procedural changes with long lead times to implement. The goal is to find relatively simple solutions that will allow the end user to get 1 or 2 steps closer to that magic place we effectionatly call "ergonomic compliance".
The use of pneumatic or electric tools is a good example of moving 1 or 2 steps closer to the perfect solution. Often times, power tools provide a vast improvement in production and technician comfort by simply reducing repetative motion and allowing the tool to produce a more consistent end result. This is not to say that power tools don't have their own ergonomic issues. I can honestly say that I have NEVER seen the perfect "ergonomically designed" tool, yet many manufacturers play that marketing card to let the end user know they are trying to improve design and functionality. So, until the assembly operation in question can be fully automated, we will likely spend many more decades trying to develope the perfect screwdriver, hammer, crimper, etc. Who knows... maybe someone may actually ring that bell someday. In the meantime, we are left with the option of utilizing the tools and equipment readily available, or allow your vendor to help develop a more "custom" solution to meet those more demanding applications. Some of us welcome the challenge, while others would prefer to stick with the status quo.
I can relate to problems with repetitive motion disorder(s) (RMD(s)), specifically carpal tunnel syndrome (CTS). Despite a love of computers and having use them since gradeschool through years into college studying Physics and, later, engineering, problem free, I developed CTS one summer working for the university washing windows. Toward the end of the summer, at night my hands, starting at the wrists, would get tingley, then numb, like they had 'fallen asleep'. After it became more frequent and acute, it was mentioned it to my supervisor who took me to the hospital where I was given a wrist support and a prescription to help with the problem. I attribute it primarily to washing the windows on the outside where we used a brush and hose attached to a telescoping aluminum rod that reached nearly twenty feet, then using this to scrub second story windows clean from the ground. It is still occasionally a problem, so often I use light wrist supports, although I know both my weight (fat can further constrict the nerves in the carpal tunnel) and use of the computer aggrevate things.
Having been a manufacturing engineer supporting aircraft component fabrication and (sub)assembly, I've helped support manual operations (as well as special processes and equipment). While powered hand tools (typically we used pneumatic and electric) offer vast improvements over manual tools, and some operations cannot be done without powered hand tools, but they often have their own ergonomic problems, often causing issues such as RMDs. While part and assembly design can help with some problems, often DFMA (Design for Manufacturing and Assembly) can only do so much...
Three of the biggest problems with powered tools include weight, vibration, and orientation.
We have powered hand tools that can be heavy to hold, even with two hands, for hours a day, especially those that require pneumatic hoses. While tool balancers would be ideal, with the small runs and wide variety of components / assemblies, it's not always practical to employ tool balancers, which are designed to provide counterweights to tools. Overhead hose reels, especially with 3/8" and 1/2" pneumatic hoses, can help support some of the weight of the hose and help keep them out from under foot.
Most power tools are used for material removal, turning/torquing, or compression (e.g. riveting), and these, in turn, through their constant vibration and/or impact can cause numbness as often the vibration is dampened by the operator's own body.
Even choosing the right tool for the job can cause problems as often there are issues with orientations of the part/assembly, fixture/jig, and operator. Is it better to use a straight/in-line drill, a pistol grip drill, or a small clearance 90 degree head drill?
There's also the trade-offs between electric and pneumatic power. There's nothing like using a heavy duty hand router then having it jerk badly because water accumulated in the line, pressure drop from bad line balancing, or inadequate lubrication causes the normally fast-spinning router bit to suddenly slow down/stop and grab the part, having the power go out while using an electric tool, or having the trigger, air motor, brushes, etc. cause the powered tool to stop because it's clogged up with chips.
Powered tools aren't bad, but just seem to have their own set of ergonomic issues, too.
In many ways, this is akin to carpal tunnel syndrome, the pain from repetitive motion that many of us relying on keyboards to do our jobs deal with on a regular basis. Paying attention to the ergnomic factors involved in factory work is very important to pushing manufacturing to the next level. Many simulation tools are incorporating ergonomic type functionality into their footprints so plant operators can test out equipment and processes to gauge the impact on workers. While much of that focus is on automated equipment, it can likely help mitigate problems for manual processes as well.
Sometimes it is also good as a designer to spend some time with your completed design to work out the ergonomics before deploying it to the production floor. If you work on it for an hour and you are tired out, imagine an operator working 8 hours on it.
Also, as designers, we can consider designing for ergonomic assembly when we are creating the product designs. We need to avoid awkward assembly motions during product assembly (that could cause these types of motion injuries) and try not to design individual parts that are too heavy for one person to manipulate.
In addition to creating tools, fixtures and jigs that reduce repetitive motion injuries, manufacturing supervisors and management can rotate workers to different cells regularly. Since each cell typically has different motion sets, this gives the body a little more time to heal itself from the previous motion set and helps reduce injuries. This strategy can also has the additional benefit of further cross-training the workforce to keep production lines going when key-employees are out.
This article reminds me of a part-time summer job I had working in a factory where for hours I would turn and sit upright deodorant packages coming down a line. The repetitive motion was killing me. I certainly understand how a person could be injured from repetitive work.
Jim, once while judging senior projects at a local university I saw an automated wire cutter. I wondered about the utility of the project, but your article makes clear how useful it would be. This device measured the length and was microprocessor controlled. It could be made quite economically, and would help avoid the problems you mention.
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