Industrial Automation Equipment is a category of production equipment that is used to automatically perform some production operations.

The types of equipment used often include:

• industrial robots
• automation cells
• conveyors
• special devices like lifters and turn-over machines
• Test and measurement equipment
• Vision systems
• Powered workholding devices

Reconfigurable or adaptive tooling/fixturing is a concept that allows flexible manufacturing systems (FMS) to rapidly reconfigure fixtures, either automatically or manually. The current trend in manufacturing automation is to use flexible workholding techniques to enable reconfiguration of automated processes, allowing for multiple products, fluctuating build rates and variability in the supply of sub-component parts. This flexibility offers huge potential to increase the efficiency of assembly operations.

There are many benefits to using flexible fixtures and workholding systems including:

• Increasing cost efficiency through the re-use of fixture components on multiple projects
• Increasing production capacity
• Reduction of fixture design lead times using available dedicated design apps
• Removing limitations of traditional fixture design which requires component geometry and datums to be frozen months in advance of manufacture
• Reducing cutting fixture build lead times due to the use of off the shelf modular components
• Facilitating single piece flow on multi-product processes

With flexible fixturing and workholding, automated processes can perform changeovers automatically. This may sometimes limit equipment to running parts that share similar fixturing/tools or require additional devices to make automated changeovers possible.

The most popular powered workholding devices for automated manufacturing are hydraulic, pneumatic, and vacuum. These devices are typically machine-controlled and allow for unattended machine operation.

Hydraulic workholding is a good all-around choice to securely hold most parts but can cost more than the alternatives.

Pneumatic workholding is normally lighter duty and is typically considered when attempting to hold small or delicate parts.

Vacuum workholding, although much less popular, is a good choice when doing thin plate work when it is not clamping on the outside of the blank. Vacuum workholding can offer several different holding options on a single vacuum plate, allowing for little or no setup between several jobs.

Hydraulic Workholding

When considering hydraulic workholding, pressure requirements should be evaluated first. Typically, it makes sense to use the lowest pressure required. How much pressure to use is determined by the type of hydraulic workholding you are choosing, and the clamping pressures required.

There are several hydraulically actuated vises on the market that achieve full clamping pressure at less than 1,000psi. When using fixturing, small swing clamps regularly use pressures from 2,500psi up to 5,000psi to achieve the needed clamping forces.

Next, the number of hydraulic clamps required is evaluated. Is there one workholding position or two? If it is a fixture, is it a single, double, or even triple motion fixture? Each motion of your fixture, or each workholding position, will require separate hydraulic valves.

Pneumatic Workholding

When considering pneumatic workholding, the system will be based around the standard pressure range found in most manufacturing facilities. An air regulator feeding the workholding valves is used to lower this standard air pressure as needed. Just as with hydraulics, it is important to determine the number of pneumatic valves required to operate the system.

Caution - several workholding devices are on the market claiming similar clamping forces as hydraulic devices, but it is not normally made clear that these vises achieve that force at higher than standard shop air pressure. If higher pressure is required, a separate higher-pressure air system is needed to achieve such clamp pressures.

Typical choices for automatic workholding on a milling machine include vises, chucks, collets, expanding arbors, vacuum plates, and custom fixtures.

Vacuum Workholding

When considering vacuum workholding, the first decision is how to create the vacuum. Can a moderate-sized venturi-style vacuum generator give you what you need or is a full-fledged separate vacuum pump required? The flow of the vacuum system is what is important. On a perfectly smooth part where there is a nice seal, once the vacuum is created, it typically doesn’t leak, so there is no loss of holding power. Many times, the part is not perfectly flat or smooth and there is some loss. In this case, a larger pump may be used to overcome the leakage and maintain holding power. A vacuum pressure sensor should always be used to confirm there is a full vacuum and in turn, full holding power present during cutting.

The design of a workholding device and how it holds the part and how the automation will hold the part is critical. It is normally desirable for the workholding to hold as much of the part as possible, but sometimes a provision may be needed to allow a robot to grip the part also.

For example, when using a three-jaw chuck, a similar-looking three-jaw robot gripper could be used in a slightly different orientation, which allows both the workholding device and the robot grippers to hold the part at the same time. However, when using something such as custom fixtures or swing clamps – which work by starting in a position away from the part, rotate 90° or 180° into position, and then clamp down on the part – allows the automation full access to place the part with no interference from the clamping. Vise jaws may need to be made with slots or notches to allow room for a gripper jaw.

Another design point is to include a method to automatically clean the fixture as the part is removed. This can include air and/or coolant nozzles directed in key locations that will clean the fixture during the load/unload process. Some users may consider using the robot to clean the workholding devices, with its ability to articulate around. While this is certainly possible and has been done, it is usually done as a last resort. When using the robot in this manner, you increase the door open time, which increases your takt time, the rate at which you need to complete a product to meet customer demand. Strategically positioned nozzles, that do the job automatically during the load/unload sequence, don’t add to the takt time and are a good first choice.

Consideration should also be given to automation requirements for open communication between the Machine Tool, Fixture and Robot providers.

Many manufacturing plants prefer to go to the machine builder or dealer who has the personnel to provide a turnkey proposal. Since communication must pass through the machine control, it is recommended that machine personnel lead the project and do the integration.

In addition, the workholding device communicates through the machine control with the machine as well as the automation regarding actions such as:

• Clamp/ Unclamp confirmation
• Clamp Pressure monitoring
• Part seat confirmation
• Spindle On/ Off

These specific actions allow or prevent certain actions of the machine and the automation.

Challenged by non-traditional materials, generative design, and smaller production runs, manufacturers have a new appreciation of the importance of workholding. Good workholding makes machining easier and more profitable.

The increasing demand for components machined from conventional hard materials, including titanium, stainless steel, and customized alloys, as well as ceramics and glass, means more aggressive machining with higher speeds and feeds. This in turn has prompted the development of new workholding designs.

In automated manufacturing, workholding challenges occur on many levels, from basic size and strength considerations to problems of resonance and harmonics. As higher cutting forces are generated, higher holding capacities are needed without adding size to the workholding device.

Many new automated machining concepts are much easier on workholding devices and can use less workholding to achieve the desired results. For example, smaller, more compact chucks and vises may be used. Designers must ensure that the workholding is rigid and can support the increased speeds and feeds while providing clearance for access and optimum toolpaths.

Workholding suppliers note that the biggest factors affecting aggressive machining are rigidity, repeatability, and resonance. Harmonics can be a significant problem and frequently remains undetected in automated setups.

Still, other suppliers note that high-speed milling and drilling have changed the type and size of workholding solutions. To allow for a larger machining surface, more edge-clamping devices are being used. Automation and the need for quick-change capability prompted one supplier to develop a mechanical clamp that can be easily upgraded to hydraulic applications as automation is incorporated.

In addition, some application engineers believe that rigidity and repeatability have always been the most critical aspects of workholding. Advancements in machine and cutting tool design make poor workholding evident.

Automated manufacturing plants recognize, given shorter runs of more complex parts, that fast changeover is now crucial to making money in manufacturing.

Workholding is adapting to manufacturing automation. Increased use of automation and robotics is a key driver in the development of improved workholding methods.

Workholding in automated systems is moving beyond the mechanical aspects. When it comes to automation, there is a very real need for more sensing and feedback on the part of the workholding system. More sensors and systems that operate in real-time to record data are needed to ensure that the clamping force is constant.

Here is a list of some tasks and processes that use integrated workholding devices in classic and technically advanced factories:

• Arc welding
• Assembly
• CNC milling
• CNC motion control
• CNC turning
• Dispensing, painting, and sealing
• Laser cutting
• Machining
• Machine tending
• Material removal
• Part transfer
• Palletizing
• Picking and packing
• Spot welding

Many of these tasks and processes integrate workholding and fixturing into their automated manufacturing applications.

In manufacturing, robots with various end-of-arm fixtures and grippers are now regularly used in automated manufacturing to perform jobs that are hazardous to humans or beyond human endurance. These jobs typically include working multiple, consecutive shifts or performing at a higher quality and efficiency level than humans can. Robots often do the following: weld, including arc welding; spray paint; complete assembly work, such as pick-and-place for printed circuit boards; and package, palletize, and inspect products

Also known as lights-out manufacturing, fully automated manufacturing is an approach wherein factories are fully automated, and no human presence is required. As big data and IoT (internet of things) allow sophisticated, off-site real-time monitoring of production lines, lights-out manufacturing may take the lead.

Popularized in the 1980s at General Motors as “hands-off” manufacturing, the approach relies on dependable equipment and planned preventive maintenance to ensure the line stays in running. Examples of fully automated factories include a FANUC robot-making factory, which supervisors only visit monthly, and a Phillips electric razor factory, where humans only perform quality control. Currently, most factories run in limited lights-out mode, with partially “attended” machines.

Always key to accuracy and repeatability, workholding techniques, materials, and strategies continually evolve in response to more complex parts, improved machining capabilities, and emerging connectivity requirements to meet the needs of Industry 4.0.

Workholding paved the way for automated, high-speed, high-volume manufacturing processes.

If workholding is underestimated, it can lead to failure.

In this article, we gave you an overview of industrial manufacturing automation and workholding. We defined industrial automation equipment, discussed flexible workholding in flexible manufacturing systems, discussed the benefits of flexible fixtures and workholding systems and discussed things to consider when using powered workholding in automated manufacturing.

Then we discussed workholding design considerations for automated manufacturing, innovations in workholding, factory automation applications with integrated workholding, regular use of robots and end-of-arm fixtures and grippers in manufacturing automation and finally, what fully automated manufacturing is?

When done correctly, proper fixturing and workholding will enhance the capability of an automated manufacturing system and allow a machine to work at its full potential while efficiently and consistently producing quality parts. Modular workholding devices combined with automation systems increase process flexibility and capacity.