Balancing Automation with the "Right" Assembly Technology
by Dan Zaborowski
In today’s world of automation, there are many wonderful assembly technologies from which to choose. This is, of course, a good thing and something that benefits us all... until it comes time to pick an assembly technology for the next application. Suddenly, having so many technologies at the disposal of assembly personnel can seem overwhelming. No single technology is right for every application, and many applications may be properly assembled with more than one technology. Making an arbitrary choice could lead to a failed project or, at the least, consume enormous amounts of unplanned capital and time. Getting involved, obtaining the facts and providing the right assembly solution for every application is a must.
Let’s start by discussing some examples of assembly systems available in today’s market.
Dedicated assembly systems
Dedicated systems are devoted to a single task or purpose; over the years, these have been the most widely accepted assembly systems. They are specifically designed and customized to service an individual part. Multiple dedicated machines can be used in sequence to complete an assembly of parts. Sonic welders that hit many weld points in a small area, hot plate welders and hot air cold stake machines are all examples of technologies that normally are defined in dedicated systems. Advances in machine control technology enable a single dedicated machine to utilize multiple assembly methods. A punch and weld system is a unique way to get the most of a dedicated machine, as it will first punch the part and then weld an accessory inside the punched hole.
Interchangeable assembly systems
Interchangeable systems involve a single machine that accepts alike parts, normally incorporating tool carts to load and unload tools. Tooling can be simplified to a single nest – in this instance, the assembly technology layout is dedicated to the machine. Before cycle start, the operator has the ability to choose which part has been loaded, via HMI. The control program then will fire the corresponding weld point. Complex tooling that has the assembly technology built into it provides more flexibility, and a wider range of parts will be accepted within the flexible machine frame.
Flexible (robotic) assembly systems
When chosen as the correct assembly technology, a flexible system that utilizes robots provides the user with many advantages. Robots are fast, efficient and reliable, allowing for short cycle times to satisfy large-volume production requirements. Automated insertion of plastic or metal clips provides a good example of a flexible system. Clip insertion is a tedious task for a laborer and, when many clips are necessary for the assembly of a part, robotics provide reliability. Incorporating a flexible robotic system into a plant provides unique value as the machine can be retooled and the robot reprogrammed for future jobs.
Flexible and interchangeable assembly systems
Flexible and interchangeable systems incorporate a combination of the two aforementioned assembly technologies. The flexible robots are programmed for each individual tool that will be loaded into the machine. These systems are popular in the automotive industry, especially for a car door program. A single machine can interchange tools for all four doors, significantly cutting down on capital and labor costs.
Manual assembly operations
A manual operation machine also is sometimes the correct choice, but normally is slow and could make meeting production requirements a challenge. These systems are inexpensive and are efficient in accommodating operators while they complete an assembly task. Additional automation options can be added to the machines to prevent operator error. A manual screw gun station provides an example. An operator will load a part into the nesting, a light will come on to indicate that the part has been properly loaded and pneumatic clamps will be activated to hold the part in place. When, and only when, a part is correctly loaded, the screw gun will be activated for operation. The operator then inserts the screws using the gun. Using sensors to detect the screws will trigger the pneumatic clamps to release, and the fully assembled part can be removed from the nesting.
The manufacturing world has changed
As discussed, each technology has its benefits, but the manufacturing world has changed. Globalization of product manufacturing to local facilities, higher complexity of products and the introduction of new engineered materials all create new challenges for manufacturers. Multiple part variations have led to each part being manufactured in a lower volume, creating more of a niche market. These factors force manufacturers to look at a wider range of technologies than they did just a few short years ago.
The more things change, the more they stay the same. Manufacturing still comes down to being able to compete globally. Manufacturers are required to make decisions that, among other things, maximize capital utilization, minimize piece price, reduce operating costs and provide return on investment. Improvements can be made to these items by making the correct decision or destroyed by making the wrong one. It goes without saying, but this hasn’t changed and never will change.
Factors that contribute to an assembly method decision
There are many critical success factors that should be considered when selecting an assembly method. It’s important to individually assess each factor to evaluate which assembly method is, indeed, correct.
Product designs have become more complex, creating obstacles that many assembly technologies don’t have the ability to hurdle. Product volumes and time-to-market demands require speedy evaluation of each technology. Product mix must be evaluated to decide if the project could be assembled using a flexible or interchangeable system. These are just some of the factors that contribute to a decision on the assembly method for each product.
When balancing flexible automation with assembly technology, it’s important to obtain the facts to make the right assembly choice for every application!
This article is based on a presentation given by Tim Gale, president of T.A. Systems, at the 2014 SPE Decorating & Assembly Division Topical Conference. T.A Systems brings over 35 years of expertise to the table. Specializing in the design and manufacture of automated and secondary equipment, the company offers quality systems for plastic welding, inspecting and assembly needs. Offering turnkey systems, T.A. Systems’ extensive support group works hand-in-hand with customers from initial quoting through machine shipping and beyond with exceptional service and support. The scope of equipment varies based upon the needs of the company’s customers as it recognizes and understands global needs of the industry. Strength in its business is a direct result of passion, adaptive program management and customer care. For more information, visit www.ta-systems.com or call 248.656.5150.
A Closer Look at Assembly System Selection
This closer look shows what will happen when all facts are not obtained before making a decision.
- A widget has a global volume of 240,000 units and is made in even volumes in three facilities on three different continents. The widget is planned to be in production for six years.
- The widget’s primary plastic substrate runs on a 3,000-ton press with a press cycle time of 28 seconds.
- The widget has 24 assembly locations, each of which has to hold a 40 N breakaway requirement for an assembled component that is purchased from a specialty molder.
Questions resulting from the facts: Should the manufacturer build dedicated systems or flexible? What assembly technology should be used?
- Many technologies would meet the stated product demands, including ultrasonic welding, hot air/cold staking, I/R welding, electromagnetic welding, adhesives, etc.
- A dedicated ultrasonic welding machine would run one-third of a shift to meet the volume requirements and would cost $125,000.
- A flexible ultrasonic solution could be located at the press and cost $200,000, but have the capacity to run two equal-volume parts with a tooling price of approximately $37,500 each. Therefore, assembly equipment for three parts would be $275,000 vs. $375,000, representing a savings of 26 percent.
The decision is made to utilize robotic ultrasonic welding with interchangeable tooling.
Issue 1. The part is Nylon.
- The robotic solution is not able to meet cycle time.
- The customer built a dedicated hot air/cold stake machine.
Issue 2. The part has a pull strength of 40 N per weld location, but it must have a hermetic seal with a burst strength of 800psi.
- The customer opted for electromagnetic welding.
Issue 3. The parts must be serviceable after installation.
- The customer chose automated screw driving in North America and manual screw driving in two LCC locations.