I was recently talking with a client who wants to improve productivity by increasing the efficiency of his facility’s picking operation. As we talked, I learned he was thinking about going to a pick to pack methodology, so I asked him how he was going to get the boxes to his operators.
He was leaning toward putting in a few carton erectors to build the various box sizes he needed for his orders, so I mentioned to him that carton erectors only built the boxes; they wouldn’t get them to the operators. He replied, “that’s the easy part: getting the empty boxes to the operators.” I knew right then that this guy had never before conveyed empty boxes.
Most people are just like him and think that because the boxes are empty, it should be easy. In my 23 years of experience, I have found empty boxes to be some of the most troublesome items to convey. I know they are empty, so they won’t stall out conveyor rollers; however, being empty and light creates its own set of problems.
The Problems with Conveying Empty Boxes
Problem 1: Once a box is erected it does not have a flat bottom. This uneven bottom will cause the box to track all over the roller conveyor and lean and possibly fall over on a belt conveyor. This uneven box bottom will also cause problems when you try to transfer off the main transportation line in the picking area. I know a lot of box erector companies say their machines make flat bottom boxes, however no companies will put that in writing with a money back guarantee either. The smaller the box and the narrower the box the worse the problem. Also, the bigger the variance from the largest box to the smallest box, the greater chance for problems. You can solve this by sizing the conveyor and guardrail so the box cannot fall over.
Problem 2: Friction between an empty box and a conveyor guard rail causes system jams. There can be a lot of friction between a box and the guard rail on a conveyor. When a box is empty, this friction often keeps it from being conveyed on either belting or conveyor rollers. This can lead to unwanted jams and backups in your conveyor system. You can solve this by using guard rail with the least amount of surface area touching the empty box. I recommend something that is round like a piece of light gauge metal tubing.
Problem 3: Empty boxes running on high-speed conveyor often tip over. Empty boxes on zero pressure accumulation conveyor can also be a problem if you run the conveyor with the empty boxes at a higher speed such as 120 fpm or higher. This higher speed with all the stopping and starting will cause a lot of the boxes to tip over or slide on the rollers and go past the accumulation zone sensor. When that happens, two boxes end up in the same accumulation zone.
The situations listed above are with boxes used for shipping; however, most distribution systems also have a trash conveyor system to move empty boxes as well. Most trash conveyors consist of a very wide belt conveyor with high guards to keep the empty boxes from falling out. If the trash conveyor consists of just one straight conveyor then you have very little to worry about. However, when you need to snake the conveyor through the building you will find out how tough conveying an empty box can be, especially when you have to make 90 degree turns with trash conveyors.
All of these situations will cause a conveyor system to jam or cause a problem in the picking areas, and again, the smaller and narrower the box, the bigger the problem. If you need to convey empty boxes, remember to:
- Size your conveyor and guard rail so boxes cannot fall over.
- Use guard rail with the least amount of surface area touching the box.
- Keep conveyor speeds a bit lower in areas transporting empty boxes.
I know my children never want to receive empty boxes for Christmas, but their dad knows how to handle them if Santa leaves any.