AN ASSEMBLY PERSPECTIVE
Assembly is everywhere in the manufacturing world. After parts are fabricated, welded, extruded, stamped, cast, machined, etc., they are generally put into an assembly; that assembly may be held together by screws, nuts, bolts, rivets, weld metal, and even glue. Because it is common for the assembly process to consume a great deal of time and resources, it often makes good (dollars and) sense to automate the assembly. Therein lies the question: “What is the best way to automate an assembly process?” While many in the industry are looking for a point of singularity on this issue, there is none to be found. Rather, there are a relentless amount of options to be had. The intent of this article is to provide principals for how to select an automation system for an assembly process.
The first principal asks the question, “Why?” This question must be asked and answered at the beginning of the selection process. Why are you doing this? What do you hope to gain by doing this? What is your goal? The CPA looks for ROI and the PE looks for 6σ. While the best of systems will be a mechanism for generating both value and quality, it hardly makes sense to build if the system cannot financially benefit the company. Most are seeking a one year ROI or less. In the final analysis, the system that can be fiscally justified and that meets the quality objectives will be the system of choice.
The second principal is directed toward the customer’s assembly, and should ask the question, “Can the assembly of these components actually be automated?“ (Caution: If you’re an integrator, don’t be the company that says that they can do anything. There are processes that cannot be automated!) To illustrate this principal, the example assembly will consist of two parts with (10) screws to hold the two parts together. If this example is designed for automation, it will have the following characteristics: reasonable torque requirements (+/- 10% accuracy is common), accessible screw locations (deep pockets are sometimes difficult to reach), screws that are driven vertically top-down (screws driven at an angle or horizontally require special attention), parts that can be held secure during the screw driving process), or more.
The third principal is one of type. What type of system best fits your needs, fits the space constraints, fits the existing power and pneumatic arrangement, and in terms of complexity, fits the personnel in your plant? It should be noted that more than one type of system might be a fit for the application. In selecting the right type of system it is helpful to move from the simple to the complex, from the inexpensive to the costly, from the more lightly automated to the more highly automated. Using the example above (2 parts, 10 screws), one might investigate the following systems:
• A Fixed table system can provide cost effective assembly including a significant boost in quality for a minimal price with typical ROI ranging from 18 to 24 months. One of the challenge with the fixed table system is that the operator has a significant amount of downtime. The operator is waiting for the system to drive in (10) screws before a new part can be inserted.
• A Turntable system can provide increased production while maintaining high quality. The system essentially doubles the throughput of the standard fixed table system by allowing the robot to complete its task while the operator is unloading and loading components on the other side of the table. Typical ROI: 12 - 18 months.
• A Conveyor system can further benefit the efficiency of the process by allowing more of the tasks to be automated. Instead of just automating the screw driving process, with the addition of the conveyor, front end and back end processing can now be automated. For example, a material handling robot with parts sorter can be added to the front end of the system. Also, a packaging robotic system can be added to the back end of the system. The result is that the customer has a complete automation process for the product from part placement to final packaging. While the cost of this system may be 3 times the cost of the standard turntable system, the system requires no operators, and is complete from part placement to assembly packaging. Based on increased production and reduced labor costs, the ROI for this system may fall within 12 months.
Getting the fit, function, and features right will provide for smooth installation and years of comfortable and profitable operation.
These principals are to serve as guides in directing the selection process. In any stage in the process, it is important to ask, “Where am I, and where am I headed?” If done properly, one will never be lost in the navigation of the automation machine selection process.