Note: This is the third of a three-part article series covering plastics manufacturing automation (1)trends, (2) material/process advances and (3) applications.

Production cell applications that increase manufacturing efficiency are central to modern plastics manufacturing automation. To respond effectively to the challenges of global competition, plastics processors are increasingly realizing that lean manufacturing is a necessary component, and manufacturing cells are an important strategic tool.

Lean manufacturing is directed toward eliminating waste in all areas of production, using less human effort, inventory, time and space to develop products, and become highly responsive to customer demand while producing top quality products efficiently and economically. Lean manufacturing, a coordinated response to today's highly competitive environment, is strongly influenced by the manufacturing principles originally developed at Toyota.

LeanBlitz Consulting/Toyota
14 management principles of the Toyota way.

Manufacturing cells are a basic approach at the heart of lean manufacturing. The manufacturing cell — an efficient grouping of all resources, including people, supplies, machines, tools and other production equipment required to manufacture a product reduces product costs, while improving lead times and quality.

Defining the advantages of manufacturing cells is the best starting point for lean plastics manufacturing. One reason manufacturing cells are so successful is they eliminate many of the wastes inherent in a typical manufacturing operation.

Waste elimination is one of the most effective ways to increase profitability in a manufacturing business. While products differ in each manufacturing operation, the typical wastes found in production environments are quite similar.

1. Overproduction: Overproduction is one of the biggest wastes in manufacturing operations. More is made upstream than the next operation can immediately use. Organizing manufacturing into manufacturing cells helps eliminate this overproduction waste as all operations in a cellular arrangement are in close proximity so that balancing the production process steps is simplified.

2. Waiting time: Unbalanced workload is one of the most common causes of waiting. Manufacturing cells can reduce waiting by supporting more synchronized flow. Synchronized product flow is enhanced when all the required resources are closely grouped together as in manufacturing cells.

3. Excess transportation: The transportation and multiple handling of raw material, goods in process, and finished goods are commonly observed manufacturing facility wastes, often caused by a poor layout of the factory floor and storage area, which creates long distance transportation and material overhandling. A manufacturing cell reduces material/part transportation as the close proximity of the cell’s resources makes such transportation almost nonexistent allowing material handling equipment to be greatly reduced or eliminated.

4. Overprocessing: Reprocessing a part to make it function properly is another form of waste. The close proximity of all processes in the cell and the strategy of only making what can be used avoid over-processing or over-handling. Unnecessary processes such as packing and unpacking with the inherent risks of damage are eliminated.

5. Excess inventory: Excess inventory from overproduction is one of the costliest of all manufacturing wastes. Manufacturing cells address the issue of inventory waste by balancing the work and not exceeding what can be handled downstream so that work-in-process inventory is greatly reduced.

6. Motion: There is significant wasted motion in a typical manufacturing process, often resulting from a poorly organized work area. By putting everything together in a manufacturing cell, wasted motion can be reduced, if not eliminated. While eliminating travel to other areas to get parts is an obvious improvement, the reduction of motion within an individual process in a well-designed cellular operation, shifts motion from non-value added to value added with much wasted motion eliminated.

7. Product defects: While cells may not completely eliminate defects, they will allow those that do occur to be identified faster, and corrective action expedited thereby minimizing production of defective parts.

A manufacturing cell also simplifies scheduling. Because all operations are grouped together, the order can be fed to the cell on a first-in, first-out basis, and tracking of the status of orders is greatly simplified, eliminating the need for complex computerized order tracking systems.

Continuing, when Campbell's Soup saw its popular "Red & White" Campbell’s soups as a natural extension of its highly successful microwaveable bowls for Chunky and Select soups, it turned to Stull Technologies for a new improved overcap. The company wanted a cost-effective solution to lock the lid onto the container, while maintaining consumer convenience.

Stull Technologies
Campbell's Soup's proprietary soup container lid.

The easy-to-use, yet tight-locking lid developed by the company has tabs that fasten securely over the container's bead to prevent it from popping off during microwave heating. Stull designed both the patent pending soup container lid and the fully automated manufacturing cell that produces them. A fully integrated company, Stull Technologies is a global leader in developing and manufacturing innovative, value-added closures and food packaging components.

The cell designed to produce the microwaveable soup caps consists of twin 550-ton, all-electric Cincinnati Milacron Powerline presses with Xtreem ST controls. They each run 2+16 StackTeck stack molds with Moldflow Altanium hot runner controls and produce several thousand parts/min/press/day.

The clamp decompression capabilities of the Milacron Powerline presses improve manufacturing efficiencies. The machine's clamp decompression can be customized by molders, saving critical cycle seconds without adversely affecting part quality, according to Milacron.

The manufacturing cell was fully automated by CBW Automation. The lids are ejected onto a turntable, where a photoelectric eye identifies upside-down lids and activates an air blast to turn them right side up, to facilitate further downstream automated handling.

CBW Automation systems nests the caps, positions and packages the cap "logs," ejects the cartons, then closes and seals them for subsequent labeling, stretch wrapping and palletization. The production cell is equipped with five robots (two horizontals, two verticals and one punch arm).

All the cell's systems are controlled by CBW's Lumerics control, which features fiber-optic communication capabilities for quick remote troubleshooting. The automated gravimetric blender and material handling system is supplied by Maguire Products.

Stull Technologies' lean thinking helps to eliminate waste, which drives cost out of their production systems. In this way, we can bring in newer technologies and maximize automation to better compete and get the company to the next level.

In conclusion, every modern plastics processing line is characterized by numerous sensors and actuators, each requiring wiring and cabling to handle power and data. This wiring and cabling is not only costly to install, but must be maintained and also can be a source of failure.

ABB manufacturing cell with wireless sensors.

Additionally, wireless systems are more flexible than their wired equivalents in terms of mobility and simple reconfiguration. Automation supplier ABB Ltd.'s wireless sensor technology, was intended to address these issues. The wireless proximity switches developed by ABB make restrictions from cabling on movable machine parts in manufacturing cells a thing of the past.

Instead of requiring power cables, wireless sensors draw their power from an electromagnetic field installed in the manufacturing cell. Wireless proximity switches in the cell draw energy from the AC (alternating current) field inductively using small coils.

The sensors are also equipped with small radio transceivers for communicating with a special input module. This module, serving as a traditional input module, can handle up to 60 wireless proximity switches simultaneously. A maximum of five input modules can coexist in the same area to handle up to 300 sensors in one manufacturing cell.

One of the keys to the future success of wireless operations will be the ability to integrate multiple wireless networks together. In a typical plant, in addition to one or two well-managed sensor networks, there are island networks for plant security's radio, executive cellphones and maintenance people probably using push-to-talk. These island networks are becoming a growing operational problem.

San Francisco-based PowerTouch Technology Inc. is working to develop a system that deals with wireless congestion, bringing together multiple forms of wireless communications including radio frequency (RF) sensors, push-to-talk radio, 800 MHz radio, cellphones and text messaging.