Applications Dictate the Optimal Solution
Robot speeds are determined by the reach of the arm and the speed at which it can move. Servo motors, gearboxes, inertia balancing, and counter weights are the factors used by robot OEMs to optimize speed.
The pallet pattern determines the number of placements needed per layer, and thus the speed capacity of a Robotic Palletizer. The lower the number of robot cycles per layer, the higher the speed capacity. Grippers designed for placing multiple products at a time increase speed. Row or layer forming that pre-orients multiple products to the pallet pattern further increase speed.
Picking a large array of product to run faster requires a larger gripper, which weighs more and requires a larger robot to move it. Larger robots inherently move slower. Larger robots, larger grippers, plus complex row and pattern forming infeeds all contribute to finding the optimal solution but cost additional money. For every robotic application, there is a point of inflection where no amount of money can return more speed. Prior to this point, there is generally a ‘sweet spot’ where the optimal solution is an effective combination of robot, gripper, and infeed design. Different speeds, sizes, and applications dictate this combination, and define the optimal solution.
When an optimal robotic solution is not reasonable or cost-effective, a Conventional Palletizer may offer an alternative solution. Generally, basic robot designs are effective at speeds up to 30 products per minute. Complex robot designs can reach or exceed 40/min. When that is not enough, Conventional Palletizer can achieve 50-60/min utilizing standard designs, and these higher speed applications are where they are best applied.
The cost of robots continues to come down, while their performance and usability have gone up. Further, due to the rising cost of labor and healthcare, the cost of building and maintaining a conventional palletizer has gone up. These effects have blurred the line between which palletizer is better suited, and the merits of each application often dictate the optimal solution.
Actual Cost Comparisons
Machine shop hours for conventional palletizer-approx. 750 hours
Machine shop hours for robotic palletizer- approx. 230 hours
Approximate number of parts on the BOM (Bill of Material) for a conventional palletizer is 1100 items.
Approximate number of parts on the BOM for a robotic palletizer is 300
Almost a 4:1 Ratio
Arpac/Duravant is a leading integrator of palletizing robots in North America. We can supply either style of machine but when we recommend robotic palletizing, the benefits are:
a.) Floor Space – A Conventional Palletizer generally takes up more space that a robot, especially high speed models that have a buffer table for layer sheets or pallet changes, a high-level infeed (9 feet above floor level), and require an inclined infeed conveyor that is 20 feet in length, or a large spiral elevator.
b.) Mechanical Failure – The periodic adjustment of a robot is almost zero. A conventional machine requires regular chain tightening and photo eye adjustments.
c.) Maintenance – The preventative maintenance on a robot is a fraction of what is required with a conventional machine. However, many maintenance personnel prefer to troubleshoot the PLC programming in a conventional machine. Robotic programming is done using structure text coding that is similar across robot platforms, but slightly different with each robot OEM. Training is required if the end user is not already operating robots. However, as robots gain further acceptance and implementation, this barrier to entry is diminished. Students and workers in each new generation of workforce have more robot experience than each previous generation.
d.) Flexibility – Our customers require a higher rate of flexibility over the life of a palletizer. Robots can handle pallet height changes, product changes, and the addition of sheets. Conventional machines do not often have as much flexibility unless it is designed in at the onset of the project.
Real world examples of a & b and the pitfalls of a tradition machine, from the perspective of a customer:
The Robot Advantage
The benefits of robotic automation are numerous. The number of applications and new industries is expanding. Below are the most important attributes of implementing robots in their production:
a.) Robots work 24 hours per day, 7 days per week, 365 days per year, and perform at the same efficient level, every day
b.) Installed cost is approximately $ 2.40 per hour. Calculated over a 15-year life with no vacations, holidays, or sick time
c.) No lost time due to injuries or lawsuits
d.) Let Robots do the ‘heavy lifting’. Palletizing robots available up to 800 KG. (1,764 LBS.).
e.) Consistent, predictable, and generally perform at a higher rate than a human
f.) Robots improve quality because there is no variance
g.) Robots reduce rework because there are no mistakes
h.) Showcase your facility to your customers with world-class robotic automation
By Brian Ormanic – Sr. Robotics & Integration Engineer