We all know that the centrepiece of any vacuum system is the application and system layout, typically involving the method of vacuum generation, and thus whether you use ejectors or pumps to generate the negative pressure and transfer the workpieces. However, there are many more important system components which, if overlooked, could mean that your vacuum handling unit fails to perform at its optimum level.
By Irina Hermann, Product Manager, SMC Germany
Arguably top of the list are smart vacuum solutions thanks to the capabilities they bring. For instance, smart manifolds can leverage real-time distributed control via a fieldbus system, making it possible to control your components through integration with a PLC and facilitate the introduction of condition monitoring and predictive maintenance strategies. Further advantages include remote control of the vacuum ejector, vacuum generation on demand (depending on the pre-set vacuum level to be maintained) and vacuum break flow, which will increase the speed of your vacuum application.
A fitting solution
A vacuum handling system will also benefit from correctly specified fittings. In the first instance you should always check that any pneumatic fittings can work with negative pressure to avoid breakage and leaks and ensure the system runs perfectly. The selected fittings should also allow the necessary flow without introducing significant pressure drops. With these thoughts in mind, you should select fittings with a sealing contour that lies against the tube surface in such a way that it makes a seal regardless of whether you are using negative or positive pressure. Therefore the fitting’s sealing design is the influencing factor.
As a rule, keeping the pipework as simple as possible will reduce energy loss throughout your system, while another good tip is maintaining short tube runs to reduce cost, the risk of leakage and cycle time.
The filtration factor
Filtration is a further important system element relating to the reduction of maintenance time and cost as it helps to preserve the vacuum system. Installed in the ejector, it is also advisable to install filter units between your vacuum pad and ejector to prevent particles of dust or powder from entering the system during the adsorption process. Any penetration of contaminants can easily clog or damage your ejectors, compromising overall system life.
SMC´s In-line Air Filter – ZFC Series – One product to handle both positive and negative pressure
Picture on the right: Recreation of how SMC´s ZFC works
SMC´s Vacuum Filter – AFJ Series: Prevents vacuum equipment trouble
Picture on the right: Recreation of how SMC´s AFJ works
Centralised or decentralised?
As a further thought, engineers should give consideration to the centralised or decentralised system debate.
A centralised vacuum system consists of one ejector or vacuum pump for several pads, usually mounted on the robot arm and connected to the pads via tubing. This type of system is a common solution that is easy to integrate and install.
Decentralised systems see one ejector operating one vacuum pad, usually placed directly at the pad. The typical vacuum source is an ejector, which produces vacuum by routing compressed air through a venturi nozzle. An attractive option here is an integrated vacuum pad/ejector solution. A two-stage SMC ejector, for example, increases suction flow by up to 50% and reduces air consumption by up to 30%. Notably, the design features of these single compact units allow for daisy-chain piping, while mounting with lock rings makes for easier maintenance as it reduces the steps required for pad replacement.
Also easy to integrate and install, decentralised systems are often preferable in vacuum handling applications where you do not need to operate too many vacuum pads as they can boost productivity through quicker response times. Simultaneously, decentralised systems increase safety by using several vacuum circuits for the transfer of one workpiece, since one specific ejector operates every single pad. In case of operational failure of one vacuum circuit, the other vacuum systems that remain operational secure the workpiece.
This is an element often forgotten but one that can bring great optimisation to your vacuum systems. In applications where vacuum ejectors are operating multiple pads, some of which are not holding the workpiece, a vacuum-saving valve serves to restrict the reduction in vacuum pressure to ensure the workpiece remains held by the rest of pads.
Another benefit of using a vacuum-saving valve is eliminating the need for a tool-switching operation when changing workpieces, thus saving time and simplifying the control circuit.
SMC´s Vacuum Saving Valve – ZP2V Series – Automatically stops your air consumption
Picture on the right: Recreation of how SMC´s ZP2V works
If we are talking about optimisation, we need to talk about size. Small and light components will not only result in direct cycle time benefits, but also provide the possibility to build more compact machines with lower weight, which in turn reduces cost. Smaller components can fit into narrow spaces, which meets demand from a growing number of machine and robot manufacturers responding to customer requests for more compact solutions.
In all cases, SMC is a total solutions provider and we can advise and address all aspects of your vacuum handling system to optimise performance, cost, energy efficiency and reliability.