“A common goal throughout the business world is to increase productivity while reducing costs. This certainly applies to machine design, which means achieving the fastest possible cycle times. For pneumatic systems, this often requires running actuators as fast as possible without introducing excessive shock loads to the system.” This is the fourth and final post in series of blogs from Michael Guelker, product manager – pneumatic actuators, with Festo USA. This week Mr. Guelker will finish his discussion and summarize the advantages and disadvantages of using air cushions.
Self-adjusting cushion (pictured above):
This graph shows relatively constant deceleration, and thus gentle travel into the end position, resulting from the constant pressure curve.
The advantages of self-adjusting end-position cushioning are considerable. Manually adjusting the end-position damping of linear actuators is time- consuming and can only be done effectively once the actuator is installed and under operating load conditions. By then the automation supplier is invariably under pressure to complete the task as quickly as possible.
It also frequently involves two people – one to operate the appropriate pneumatic valve, the other to adjust the actuator’s damping characteristics. As with all moving parts, access can be potentially hazardous, which means that safety considerations dictate that only experienced personnel should perform these adjustments. Actuators are often less than perfectly adjusted, with under-damping resulting in higher end-position impacts, higher noise levels and increased wear, or with over-damping resulting in increased machine cycle times. We can estimate that, on average, the self-adjustingend-position cushioning system will help users save five minutes from a cylinder’s installation and set-up time. For a typical application, such as a package sorting system with 60 cylinder-driven routing stations, this would result in savings of five man- hours. Self-adjusting end-position cushioning is a ‘fit and forget’ product feature. Since it has no settings to change, it is completely tamper-proof and it offers a long, maintenance-free service life.
Without any need for manual interventions, self-adjusting cushioning now ensures an optimum cushioning action every time, even if parameters such as friction and pressure change. It also reduces the acceleration forces acting on components and work-pieces. This reduces wear and minimizes time- consuming vibration.
Advantages: no manual adjustment is required, responds automatically to load and speed changes.
Customers enjoy the following advantages:
• Time saving (economy)
No need for manual adjustment of the cushioning.
• Accessibility (convenience, economy)
Once cylinders have been installed, carrying out cushion adjustments in a confined area is often a problem.
• Consistent cushioning quality (safety)
Self-adjusting cushioning always deliver the same optimum performance.
There are none of the variations that can occur with PPV when these are adjusted by different people.
Other arguments in favor of self-adjusting air cushioning
- Cannot be varied by machine operator, which means no possible
- Long service life, thanks to optimum cushioning setting, not only for cylinders but for entire
- Optimum cushioning even with varying mass/pressure within permissible range.
Disadvantages: cannot be used when the cylinder is operated at its limits (heavy loads, very high or low speeds).
If you would like to see more articles like the ones appearing in this series please email me at email@example.com.
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