Establishing the need for robotic systems in packaging lines is only the first step towards maximizing efficiency. First, the investment must be cost justified, and then the system itself must be modeled to make the most of its capabilities.
Robots are usually associated with handling repetitive tasks in a process - either in high volume production roles or where flexible handling systems are needed for frequent changes. In the packaging industry, robots generally fall into three main arenas: pick and place applications (where products are packed into trays or secondary packages), feed placement (where products are prearranged on a conveyor to ease future packaging procedures), and palletizing (pallet loading and unloading).
The most obvious benefits associated with the installation of robots in a packaging environment are those of labor savings, the overcoming of potential and existing labor shortages, better product quality and improved working conditions. Less obvious are savings linked to a reduced head count such as a reduction in cafeteria facilities, staff recruitment and training costs, National Insurance contributions and even the number of parking spaces required.
Configuring the system
As an example of configuration, consider the robotization of a picking line, since this area is more demanding than palletizing or feed placement. It is important to optimize the line by seeking to attain the highest line and robot performance; the minimum number of robots; the highest efficiency (minimum overflow); low robot load (for the highest acceleration and speed); high reliability; and high redundancy (i.e. the ability to keep the line running in the event of a robot stopping).
These objectives are easily defined, but less easy to fulfill because of boundary conditions and other external factors in most packaging processes. The first and most commonly encountered issue relates to product and tray flow. Variations and inconsistencies in the product's rate (high or low frequency), missing or damaged items and starting/stopping of the line all have a major impact on the efficiency of the line, irrespective of the capabilities of the robots. Other limiting factors include the specific placing order of the different product types and the placing of cushions between trays. Further factors in the selection and optimization of the robot packing line are the grippers required to handle delicate products and the potential for malfunctions in the equipment ancillary to the robotics themselves.
The number of products in the flow should be equal to the required number of products to fill all the trays. It seems quite simple but this correlation of product to packaging can actually be quite complex. On most lines, there is always the possibility of either having too few products to fill the trays (due to poorly located product on the conveyor) or an uneven product distribution which prevents the trays from moving constantly and consistently to the end of the line and causes frequent line stops and starts.
In such an arrangement, it is also important to model the actual scenario in relation to the real time of the robot operations. For example, a line may be designed to deliver a maximum product feed of 300 pieces per minute, but only intermittently peaks at this figure and, when measured in 60-second intervals actually has an average flow lower than this rate. However, shortening the time interval to 20 seconds, demonstrates that the peak flow of 300 pieces per minute is achieved about once in every minute. When the variation in product rate is investigated at time intervals of two seconds, it can be seen that the peaks are above 300 pieces per minute at any time. It is this variation which makes the configuration of the robot so important. For the robots to operate at peak efficiency, it is essential that they work at a realistically calculated nominal rate. In this example, that rate is 270 pieces per minute given that there is inconsistent product flow.
The line, running at a rate of 270 pieces per minute, also exhibits high product overflow of five percent, frequent stops of the tray belt and varying performance of individual robots from 65 to 95 pieces per minute. However, with careful line optimization it is possible to run the same line consistently at 300 pieces a minute, with no product overflow, no tray belt stoppages and an equal performance of all the robots at 100 pieces per minute.
The improvement in efficiency is brought about by adjusting the product belt speed to optimize it in line with the robot performance. It must be considered that efficiency is the name of the game and that the number of packed products should always be maximized.
Get in position
Apart from the product feed, line configuration and belt speeds, the positioning of the robots is critical to attain the highest efficiency. Commonly, robots are configured to pick from the shortest distance possible at their respective station position. While this is well and good at the start of the line, by time the fifth or sixth robot is reached, the product can be entirely centered within the belt. This can lead to catastrophic collisions at the end of the line, as the last two robots have to vie for the final picking of the products.
With optimal robot layout, programming, product placement, feed consistency and belt speed, it is perfectly feasible to have the robots picking consistently across the belt without the chance of collision and with minimal overflow. By defining the work area of each robot, there is no need for the reach of any robot to encroach into the picking area of another.
Once the case for the robot has been analyzed, it is important to address the economics of the process. Measured against human costs, this may be justified, but once line efficiency has been considered, payback may come not just from reduced costs, but also from increased productivity, efficiency and quality. To achieve this, it is essential to evaluate the packaging line, its layout, parameters, throughput and the potential robot configuration.