How To Choose Your Vacuum Cups – EUROTECH
The advancement of manufacturing processes into automated systems has elevated efficiency and reliability. This shift towards automation equipped with vacuum cups in handling relies heavily on sophisticated computer-controlled systems, often employing robots for tasks once handled by human workers.
Vacuum cups play a crucial role in these automated workholding systems, serving as the components that come into direct contact with the sheets or parts being manipulated. Despite often being an afterthought in system design, understanding the significance of vacuum cups is essential. In this discussion, we will emphasize their importance in manufacturing automation and explore the specific operational characteristics and parameters to consider when choosing the most suitable cup for your application.
Not Suction Cups, but Vacuum Cups
It’s important to note that vacuum cups are distinct from suction cups. While suction cups operate by applying downward pressure to create a seal, vacuum cups utilize pneumatic vacuum generators with venturis. This process involves creating compressed air to establish a vacuum, where the lower pressure inside the cup lifts the object, guided by the higher atmospheric pressure.
The selection of a vacuum cup depends on the material characteristics, specifically whether it is porous or nonporous, dry or oily, and flat or contoured. Understanding these factors is crucial for optimal performance in automated systems.
Vacuum Cup Varieties and Applications
Users typically choose from round, oval, or bell-shaped vacuum cups, each designed for specific applications. The bell-shaped vacuum cup, with its internal friction pattern, excels in adhering to convex or concave surfaces, offering advantages in various scenarios.
Vacuum cups come in two general design types: flat or bellows-style. The former requires less air volume but is less flexible, while the latter, resembling an accordion, provides flexibility for grasping irregularly shaped items.
The hardness of the vacuum cup, measured on the durometer scale, indicates its suitability for different applications. A softer durometer is ideal for contoured surfaces, while a harder durometer is more effective on flat surfaces.
Selection of Vacuum Cup Depends on Material Characteristics
Materials can be broadly categorized into two types: porous and nonporous. Porous materials, such as cardboard, wood, and Styrofoam, generally necessitate a higher vacuum flow for effective lifting. However, they do not always require high-level vacuum generation. On the other hand, nonporous materials like steel, aluminum, and hard plastic can be lifted using a lower vacuum flow.
Surface types are further classified into dry or oily. While most objects have a dry surface, some materials may exhibit a fine oil layer. For instance, sheet metal treated with rust inhibitors before stamping can leave an oily sheen.
The contour of the material is another critical factor in cup selection. The choice depends on whether the material is flat or possesses curves and rounded edges. In instances where an object has numerous curves or undulations, a vacuum cup may not be suitable. Similarly, objects with too many closely spaced holes are not compatible with vacuum cups. Understanding these material characteristics is essential for making informed decisions when selecting the appropriate vacuum cup for a given application.
Considerations in Mounting Types
Various mounting types, such as male/female, imperial NPT, metric-G threads, square T-mount, and quick-disconnect, cater to different automation systems. It’s crucial to match the mounting type with the automation system for seamless integration.
Understanding Vacuum Cup Hardness and Its Applications
The hardness of a material is measured using a durometer, a common practice for materials like polymers, elastomers, and rubbers. Vacuum-cup suppliers typically employ the Shore A hardness scale for testing, which specifically assesses the hardness of flexible molded rubbers. This scale encompasses a spectrum, ranging from very soft and flexible to medium with some flexibility, and finally, hard with minimal flexibility. Higher numerical values on the durometer scale indicate greater hardness.
The durometer scale provides meaningful insights for selecting vacuum cups, and here are some key values and their implications.
- 30 Shore A hardness: Represents a soft cup, ideal for contoured panels. However, cups with this measurement may have a shorter lifecycle compared to harder alternatives.
- 45 Shore A hardness: Signifies a medium-hard rubber, effective in sealing and adapting to various contours.
- 60 Shore A hardness: Indicates the harder durometer measure, suitable for extremely oily, flat surfaces.
- 75+ Shore A hardness: Standout as the hardest solution for highest stability but lacks the flexibility of bending.
Some vacuum-cup suppliers simplify identification, maintenance, and replacement by color-coding their products based on durometer. When selecting a durometer for a specific application, it’s crucial to consider the shape of the parts involved. Softer durometers are suitable for contoured parts with sharp corners or edges, facilitating easy grip on the contours. Conversely, harder durometers are more fitting for flat surfaces due to their stronger holding properties.
Similar to tire manufacturers, vacuum-cup suppliers have developed unique tread patterns for their products. The design of these patterns directly influences the holding power or grip of the vacuum cup on different surfaces. What proves effective in one application might not be suitable for another, especially when dealing with dry or oily material surfaces. Some vacuum cups integrate their distinctive treads with a range of durometers to enhance grip strength, offering a versatile solution for various scenarios.
Conducting Tests for Optimal Vacuum Cup Selection
When faced with selecting the right vacuum cup for your application, it is advisable to perform tests to ensure the most suitable choice. Initial assumptions, such as employing two large vacuum cups, might be reconsidered after testing reveals that six smaller vacuum cups provide more satisfactory performance.
In addition to considering the type of material, factors like the weight and size of the object to be lifted play a crucial role. For instance, a lightweight sheet metal automotive hood with an easily gripped flat surface might initially seem compatible with a single vacuum cup. However, the sheer size of the object can lead to imbalance during movement, potentially causing a drop. To address this, employing four or more vacuum cups can distribute the load evenly, ensuring a secure transfer.
Emphasizing the significance of vacuum cup size, tread pattern, and durometer becomes paramount in high-speed pick-and-place transfer applications. The vacuum cup must effectively grip the panel during the acceleration and deceleration phases of automation, ensuring reliability in each cycle.
In specialized applications, additional operational characteristics come into play. Take, for example, the hot-forming steel-stamping process, which involves lifting and transferring steel sheets with temperatures exceeding 450°F. While some standard vacuum cups may tolerate such high heat, certain instances may necessitate the use of specialized high-temperature vacuum cups to ensure optimal performance and durability. Therefore, a comprehensive understanding of the specific operational requirements is crucial for selecting the right vacuum cup for any given application.
Specialized applications, such as hot-forming steel stamping, may require vacuum cups designed to withstand high temperatures. Consulting experts to discuss application goals and technical specifications is advisable for optimal vacuum cup selection.