by Laura Dietrich, Ergonomist
As an ergonomic consultant, I often start the visit by taking a tour of the manufacturing facility requesting the ergonomic evaluation. Over the years, I have noticed several ergonomic mistakes that are present during many of my walk-throughs. The following are the Top 5 Ergonomic Mistakes I see and ideas for low cost resolutions.
#5 – Pallets of Parts Lying on the Floor
Anytime a pallet of parts is on the floor, someone will eventually have to bend forward greater than 90 degrees to pick up the last layer of parts. Surprisingly, the main concern may not be the weight of the part but the weight of the employee’s torso; 70% of the total body weight is located above the hips. A 200 lb. male picking up a 5 lb. part is actually lifting around 145 lbs. This type of lifting can easily lead to a back injury.
The solution may be as simple as putting the pallet on a stationary table that is built in-house. If the pallet has a starting height above 5 feet, the first 50% of the material can be unloaded while the pallet is on the floor and then be placed on the stationary table with a fork truck. There are other more costly improvements, but the focus of this article is low-cost resolutions.
#4 – Location of Small Parts Bins
Engineering often spends a great deal of effort to assure that equipment is debugged so the line will run efficiently. But when it comes to locating the small parts for the employee to assemble, containers are placed in any area that is open after everything else is in place. The main concern with this is the repetitive, extended reaches required by the employees to pull parts from the bins. This type of movement often leads to shoulder injuries.
One solution is to locate the small parts bins under the work table, as long as this does not require the employee to bend to get the parts. An alternative option would be to put the parts in small bins that are to the side of the work table within a 20” reach.
#3 – Placement of Hanging Tools
I often notice that air tools will be hung overhead to get them off of the work table, in an effort to implement lean manufacturing. In general, this is a good idea. However, a concern exists if the tools are hung too high or too far forward, causing an extended reach.
The solution would be to have the hanging tools slightly to the side, at a height of 5 feet. Many times, the tools are hung at a higher height because there is concern employees will hit their heads on the tools while working. If the tools are hung around five feet high, within a 20” reach, and slightly to the side, the employee will not be required to repetitively reach overhead to access the tools.
#2 – Excessive Push/Pull Forces on Carts
When purchasing a stock cart, often the only requirements are that it will fit through the aisles and be large enough for the material being transport. Unfortunately, that is only half of the equation. The second area to consider is what forces will be required by the employee to get the cart moving and to keep it rolling. Push/pull forces greater than 30 lbs. should be evaluated for improvement.
The solution is often preventive maintenance on the cart’s wheels. Having your maintenance department evaluate the carts to determine if the wheels need to be replaced is your first step. Sometimes the wheels are too small for the weight being loaded and simply changing the wheels will decrease push force. Alternatively, loading smaller quantities of boxes or parts onto the carts will decrease the weight and thereby decrease the push force. Finally, looking into a lighter weight cart will also decrease the push force.
#1 – Performing Work in a Non-Neutral Posture
The ability to generate force decreases whenever the employee is performing work in a non-neutral posture. In addition, the chance of injury increases significantly with non-neutral work postures. The chance of injury increases even further if the employee is lifting, using a tool, pushing or pulling parts.
This final solution involves looking at the posture of the employee while performing the work and determining if the posture is neutral, i.e., the position in which muscles are neither contracted nor stretched. If the worker is not in the optimum posture, the next question is why? If you can answer this question, you are on your way to determining what can be changed to bring the employee into a neutral posture and preventing potential injury.