What do I look for in solving push/pull issues in the manufacturing environment?
The most popular push/pull issues arise on carts with capacities of 1000-2000 pounds. This is the first in a 3 part series on how to identify and solve ergonomics issues in the field. We will talk about wheels today.
The easiest solution, but rarely the best, is a hard wheel (steel or phenolic). The conventional thinking is the harder the wheel, the easier it is to push. This statement is true. A hard wheel will resolve your push and pull problem and pass your testing standards but at the same time will create many new problems.
First, will be the added noise. You will have carts that are easy to push and everyone in the plant will know when they are getting pushed. Loud, loud, loud!!
Second, a phenolic or plastic wheel will accumulate debris in the rolling surface of the wheel. Debris accumulation occurs in the cleanest of factory environments. Debris is a fact of life. It exists. This requires a regular time commitment to replace these wheels. We all know our maintenance people’s time is much better served somewhere besides swapping caster wheels.
Third, the steel wheel will damage the floor. Plant managers are never excited about grooves carved in their beautiful manufacturing floors. This should never happen.
So now that the hard wheel is no longer an option, where do we turn? Here is what I look for and most often suggest.
Am I restricted in the size of my wheel? Can I take a 4 inch wheel and go to a 6 or 8 inch? Increasing the diameter of a wheel results in much less effort to start and an increase in momentum to keep the wheel rolling. It is important to note that increasing the diameter of the wheel is a positive but increasing the width of the wheel is a negative. A wider wheel will create more surface pressure and make the wheel more resistant to switching directions.
Most importantly, I need to select a wheel material that will keep noise at minimum and not cause damage to the manufacturing floor. My suggestion is a polyurethane wheel with an A shore rating of 85-95. This wheel is hard enough to push and pull easily, soft enough to keep noise at a minimum, and resist debris. Any softer than 85A and the wheel creates too much surface pressure and becomes hard to move under load. Any harder and the wheel takes on the traits of its steel and phenolic equivalents resulting in more noise and destructive characteristics.
Next time we will discuss the caster rig/wheel housing and how we can modify it to achieve maximum push/pull results!