You may find this list of answers to frequently asked questions both educational and specific. We are happy to add the answer to your question on this page.
- How many airboxes per network?
- Why use black cable
- Sensor Inputs
- How do I set the address code for an Airbox
- Can Airboxes be used for soft start applications
- Airbox flow rate is too low?
- Airbox seems expensive
- What do you mean by electrically bi-stable?
- What is the biggest operating problem for Airbox?
- Is Airbox 32 interchangeable with Airbox 1?
- Why use Airbox instead of a valve island?
- How quickly does an Airbox operate?
- What do I do about unused pneumatic outputs?
- How rugged is Airbox?
- Can Airbox switch low pressures?
- Which modules incorporate a 'watchdog' and how does this watchdog work?
- Can an AS-Interface surge protection module be used for electrostatic deflection? If not; is it possible to work with opto-decoupled inputs?
- Airbox K: What is the reaction of outputs in the event of power failure?
- Airbox: What are the address codes for the I/O bits?
- What quality compressed air is recommended?
- What is the current consumption of Airbox?
- Airboxes have black cable and yellow cable options. How are the inputs and outputs supplied in each case?
- Airbox General. What size of cylinder will an Airbox operate?
- How does Airbox achieve 5/3 function?
- Are Airboxes A/B addressable
- My Airbox seems to leak
- What is MTBF (Mean Time Between Failures)?
- Do A/B addressable Airboxes have enhanced fault/status indication?
- How many Airboxes per network?
- 31 or 62 depending on which level of AS-i and which Airboxes you are using. Each Airbox is one node on a network controlled by a "master" plc.
- An Airbox has two outputs. Either 2 off 3/2 valves (monostable), 1 off 4/2 or 2 off 4/2 (monostable or bistable). Each Airbox is designed to operate 1 or 2 single or double acting cylinders. The maximum number of actuators that can be controlled on one network is therefore 62 or 124. Standard Airboxes are not A/B addressable. An Airbox operating on a 2.1 or 3.0 network will occupy both A and B addresses. So the maximum number of standard Airboxes you can use on any AS-i level is 31. From 2007 onward some models of Airbox are available A/B addressable for use on AS-i 2.1 and/or 3.0. These Airboxes are branded EASi AirBoxes and are not directly interchangeable with standard Airboxes because the ID codes are different. You will be able to use 62 EASi Airboxes per version 2.1 or 3.0 network depending on the EASi Airbox model (see complete list of part numbers for guidance).
- Why use black cable?
- Unlike other pneumatic devices which have AS-Interface "bolted-on" as an after thought, the black cable is not needed for power. Additional savings can be made here.
- Black cable is a control option. Removal of black cable power with yellow cable as sensor feedback for status may be useful. Airbox is often used on a network configured with other AS-Interface devices, where black cable is required.
- Sensor Inputs
- Each airbox has either 2 or 4 PNP M12 sensor inputs.This makes the product very different from standard pneumatic valves with an AS-Interface interface. The concept is to make the airbox a true controller of an actuator (cylinder), not just a pneumatic direction device. 2 Outputs (pneumatic) and 2 or 4 inputs (from sensors) provide instruction and feedback to a single address code (the AS-Interface node).
- Use electronic sensors (not reed switches) as sensors. Old traditional reed type sensors can create a signal bounce which can be wrongly interpreted by the fast digital capacity of an AS-Interface network.
- How do I set the address code for an Airbox?
- Airbox 1, 32 and Powerbox use a standard hand held addressing device available from Siemens. The address code is set before the unit is installed onto its sub-base. All new Airboxes are supplied with an address code of 0 which will not be recognised by the AS-Interface master.
- Airbox K has an addressing port on the top of the unit. The addressing device now connects through a cable. Each Airbox K can be reassigned an address code up to 16 times. This can be done with the unit mounted onto its sub-base.
- Alternatively address can be set via software. When an Airbox is replaced in an existing system then the AS-Interface master can reassign the new box code 0 to the unit being replaced.
- Can Airboxes be used for soft start applications
- Yes. Use any Airbox K variant. A separate air supply is required to a 4mm pilot port on the top of the unit. With pilot air over 3 bar connected an Airbox K will switch from vacuum to 8 bar.
- A common installation error is to connect the pilot port (auxiliary air) using the same air line that is feeding the input to the Airbox. This has no effect at all, if the auxiliary line is then also subject to soft start.
- Soft start is the english term for slowly introducing compressed air through valves to actuators at low pressures, then steadily raising the pressure, to avoid sudden operation. There will be a period during a soft start process when the operating pressure is below 3 bar. If an Airbox (or any conventional pneumatic valve) is pulsed to change its condition during this period then the valve may not operate fully. Symptoms are a sticking valve which appears to leak. If this occurs re-pipe your installation correctly, or reconfigure your system so that no valve changes its condition during the soft start period.
- You may experience a soft start type condition when first pressurising the air line feeding your Airboxes. In some cases your system may take up to 5 seconds to pressurise sufficiently for an Airbox/any pneumatic valve to operate. If an instruction is sent to change an output status in this period you may experience erratic faults.
- Airbox flow rate is too low?
- Kuhnke Airbox outputs are 400Nl/min(Airbox 1 & 32), and 550Nl/min (Airbox K). First check that the Airbox with its 8mm ports performs better than a similar conventional pneumatic valve. With Airbox close to the actuator, signal and flow decays due to tube runs are minimised. Airboxes also operate quicker than conventional valves.
- If Airbox output is still insufficient (say for operating very large actuators 80mm diameter) then use it as a pilot valve. Significant cost savings can be made by using a pneumatic signal operated direction control valve, instead of a solenoid operated device. Airbox connected to a pilot/pilot main valve will require just interconnecting tubing.
- Electrical output connections from an I/O AS-Interface slave to a more expensive solenoid/solenoid main valve are costly, may need shortening, add expense and add failure possibilities. Additional power and IP protection make the non-Airbox solution expensive and a poor alternative.
- Airbox seems expensive?
- Compared with? The real benefits and cost saving are in AS-Interface itself. Mainly cabling, cable preparation and marking, programming, commisioning, fault finding and failure mode analysis of an entire system. Once AS-Interface is seen as a cost saving system, Airbox is the most efficient, lowest cost way of operating pneumatic devices.
- What do you mean by electrically bi-stable?
- Airbox K bi-stable versions operate in normal conditions like 2 conventional solenoid/solenoid 5/2 pneumatic valves. This is achieved internally using just one low power solenoid operated pneumatic pilot for each 5/2. The 5/2 outputs of an Airbox K are paired and operated by pulse. When one is high the other is low. Compressed air from the input port is used to make the changeover work.
- Outputs switch when electrically pulsed with air supply connected. During startup, particularly after E-Stop and air dump, this condition should be considered when programming. The valve will remain in the last electrically pulsed condition, (electically bi-stable) but will not changeover unless compressed air is available.
- What is the biggest operating problem for Airbox?
- The same as for any other pneumatic device - air quality. We recommend a 5 micron main line filter and non-lubricated air. But air contains water vapour which is not trapped by any filter element. Temperature drops down stream of main line filters (i.e. in unheated installations overnight) will cause water to condense and damage pneumatic devices. Ensure your installation has slopes to drain points and ensure your maintenance protocols include regular removal of condensate. Ideally use an air drier.
- Is Airbox 32 interchangeable with Airbox 1?
- Yes. Airbox 32 is effectively an upgrade enabling you to use 4 inputs instead of 2. Airbox 32 also comes with a black cable option.
- All Airbox 1 versions are yellow cable only. If replacing with Airbox 32 then use the yellow cable version of Airbox 32. Both Airboxes use the same base (coupling module).
- Why use Airbox instead of a valve island?
- There are many reasons. Airbox is the only fully integrated pneumatic device in today's market that has been designed for AS-Interface. It is decentralised, IP67, fast acting and very low power. It combines inputs with outputs at a single address slave node. Airbox combines the minimum of internal wireways and has integrated status indicators and diagnostics (Airbox K). Airbox is extremly easy to fit using standard bases and vampire pins. It is extremely easy to replace in the field.
- Compare this to valve islands, most of which have inputs as an after thought if at all, which require black cable simply to drive solenoid coils. Valve island solutions involve costly end plates and internal wireways. Replacement and even identification of valve islands in the field can be difficult. A valve island is really centralisation whereas Airbox is decentralisation. Airbox looks better on an installed process. Valve islands frequently do not offer simple vampire pin connectivity.
- Cost comparisions of hardware can be misleading. Remember that Airbox is a simple intergrated solution that does not even need black cable!
- How quickly does an Airbox operate?
- The time delay between an output instruction from the network and air output varies according to model and operating conditions, between 12 and 22ms. This is considerably faster than typical valve island outputs. The time taken to then operate your actuator depends on the tubing length and connections. Generally an Airbox located close to an actuator will enable the fastest overall operating time possible.
- What do I do about unused pneumatic outputs?
- We advise that any unused ports are protected with plugs. Compressed air will not pass unless the outputs are high.
- How rugged is Airbox?
- With all ports connected including exhaust, Airbox is IP67. We know of Airboxes in use in the food industry with daily wash down, in areas of high magnetic fields and covered in weld splatter, and many other demanding applications.
- Can Airbox switch low pressures?
- Yes. Use Airbox K. Connect a separate compressed air supply from a separate pressure regulator, to the 4mm input port on the top of the unit. With air pressure above 3bar applied to this port, the main valves will switch at low pressures, they will even switch vacuum. We refer to this supply as auxiliary or pilot air. Airbox K will operate normally (over 3 bar) using an internal pilot if the auxiliary line is not connected.
- Take care when programming your network, to allow sufficient time for air pressure to build, say 5 seconds, before instructing pneumatic outputs to change status. This advice applies at initialisation and restart.
- Which modules incorporate a 'watchdog' and how does this watchdog work?
- All Airboxes and the Powerbox incorporate a watchdog. Watchdogs monitor the message interchange between master and slave module. If data exchange is inhibited, the watchdog switches outputs into the safe OFF-status ("0"). Because these outputs are not changed in the processing image of the CPU their normal status will be restored after communication functions normally again. With watchdog function, emergency stop and isolation of external load power supplies, software must take care that after power restoration, outputs do not automatically switch the load ON again.
- Can an AS-Interface surge protection module be used for electrostatic deflection? If not; is it possible to work with opto-decoupled inputs?
- Overvoltages resulting from electrostatic charge can only be eliminated by equipotential bonding (e.g frequent earthing). An AS-Interface surge protection module is only effective directly within the AS-Interface cable. In most instances however, electrostatic surges are caused by flashover at sensors. Opto-decoupled inputs - that are designed for up to 500V only - would not solve the problem. Direct surge suppression in the inputs is not practical. Solution: Sensors must be protected against electrostatic discharges / flashover by means of brush type earthing to avoid electrostatic charges in the first place.
- Airbox K: What is the reaction of outputs in the event of power failure?
- Outputs of monostable pneumatic modules switch into safe condition (OFF-status) in the event of power failure. Valves are pulled back into initial position by spring returns. Outputs of electrically bistable modules switch off in the same way but the valves stay in the last position prior to power failure.
- Airbox: What are the address codes for the I/O bits?
- The addressing of AirBox 1 is the same as per 2 I / 2 O standard modules: D0 = IN1, D1 = IN2, D2 = OUT3, D3 = OUT4. The addressing of the monostable AirBox 32 and K is based on 4 I / 2 O modules: D0 = IN1, D1 = IN2, D2 = IN3, D3 = IN4, D0 = OUT1, D1 = OUT2. The addressing of the bistable AirBox K is based on 4 I / 4 O modules: D0 = IN1, D1 = IN2, D2 = IN3, D3 = IN4, D0 = OUT1 (Impulse ON), D1 = OUT1 (Impulse OFF), D2 = OUT2 (Impulse ON), D3 = OUT2 (Impulse OFF).
- What quality compressed air is recommended?
- We recommend air filtered to 5µm. Most standard filters are available with this element. You can use lubricated or non-lubricated compressed air, but if lubricated air is used then it must be always lubricated. Best advice is to use non-lubricated air. As with all pneumatic equipment in all operating conditions a pressure dew point below that which will be experienced on the application is recommended to avoid water condensing downstream of filter elements.
- What is the current consumption of Airbox?
- Airbox K: 85mA per output for 25ms then 35mA. For other Airboxes: 65mA per output for 25ms then 10mA. Kuhnke Airboxes use hit and drop technology to achieve these very low operating currents. Allow 10mA for the control circuits. Most Airboxes will therefore consume less than 200mA including sensor inputs, but total loads will vary according to the type of sensors. Technically 31 standard Airbox nodes can operate using a 7A supply on yellow cable only.
- Airboxes have black cable and yellow cable options. How are the inputs and outputs supplied in each case?
- Yellow cable Airboxes use the AS-Interface supply for both input and output. Airboxes with black cable supply (auxiliary voltage Uaux) use the yellow cable for input and status monitoring and black cable for outputs. Power consumption per box is about 100mA. Airboxes with black cable can be used to achieve E-Stop in category 1, using compressed air to reach a safe position but not to hold that position. Remember that in this instance primary energy including compressed air has to be positively switched off.
- Airbox General. What size of cylinder will an Airbox operate?
- There can be no clear answer because the amount of air used to operate a cylinder depends on bore size, stroke, frequency of operation and pressure. Experience shows that Airboxes will outperform conventional valves / valve islands. Airbox K has a higher flower rate (550l/s) than Airbox 1 or 32 (400l/s). All airways are maximised with 8mm fittings.
- Demonstrations show satisfactory operation of double acting cylinders up to 50mm bore, 100mm stroke, all popular size rotary actuators (say for large process valve operations) and all frequently used clamping devices, stops and balancing cylinders. Where speed is not critcal even the smallest Airbox will operate larger bore cylinders, 63mm & 80mm, at small stroke lengths.
- A good rough guide: look at the connection ports of the cylinder/actuator. If they are the same or smaller than the Airbox 8mm OD tube connectors then Airbox will do the job.
- Good tip: Really decentralise: site each Airbox next to the actuator and keep tube runs to a minimum.
- How does Airbox achieve 5/3 function?
- The answer is almost always yes, but "how" involves thinking automation not just pneumatics. The expression "5/3" is itself "old jargon" even if it is familiar. You combine two pairs of pneumatic outputs on any one Airbox. Block one of each pair and connect the other to the cylinder. By pulsing or setting one of each pair of outputs, or none or both, the Airbox becomes a "programmable 5/3 valve".
- Airbox 1 or 32 uses a pair of 3/2 valves which can be both low, both high or directional. In this case removal of power creates an "all ports open" function.
- Airbox K uses 2 off 4/2 valves, hence the blocking of one port of each. In the monostable version, we can achieve all ports exhaust, or all ports to pressure on electrical power off (depending on your choice of ports blocked).
- Airbox K bistable achieves 5/3 function in the same way as a monostable, but the valves remain in a stable condition when power is removed.
- It seems that one Airbox is needed to create one "5/3 valve" function, but this may not be the case. Consider certain stop conditions which require power, including compressed air, to be removed. In this case the system "dump" valve combines with one pair of Airbox outputs to create a "5/3" condition. In this case all ports exhaust because the pressure port is independently exhausted by the system. When this is practical then one Airbox can operate as two 5/3 valves. Chose mono or bi-stable according to the re-start requirement of your programming.
- Useful Tip: Airbox K has a seperate port for auxiliary air. Maintain pressure to this port in all conditions to ensure that the pneumatic port of Airbox can change position if an electrical pulse/reset/set command is made / could be received, with mains power off.
- Are Airboxes A/B addressable?
- Yes and No! July 2007 sees the introduction of new models of AirBox called EASi AirBox. New EASi AirBoxes are A/B addressable and suitable for use on v2.1 and 3.0. These are in addition to the standard AirBoxes which continue to be available. Although physically interchangeable standard AirBox and EASi AirBox have different ID codes and potential address codes.
- My Airbox seems to leak.
- If you do not have enough air pressure to switch the main internal valve when the slave output changes status, then the valve may only operate halfway. This has the effect of permanently exhausting pressure air. It can occur after e-stop sometimes. There are very easy ways to avoid this, call us for advice.
- What is MTBF (Mean Time Between Failures)?
- The answer to this question is almost impossible for a manufacturer of a pneumatic valve to define meaningfully. Laboratory tests confirm a life in excess of 100million cycles, but this is under controlled conditions. Actual MTBF will depend on ambient conditions, profile of operations (i.e. fast pulsing or intermittent), actual operating pressure, and most importantly air quality. Poor air quality can shorten life of any pneumatic component by, say, 75%. Contact us for help in determining a realistic MTBF for the Airboxes you are using.
How about Mean Time to Replace?
Airboxes are easy to replace. Disconnect all tubes and cables and unscrew the single fixing. Snap out and snap in the replacement, and reconnect. If replacing one unit on a network with a new one, the software will automatically apply the correct address code. Allowing for limited knowledge and "clean practice" an Airbox should be replaced in 3-7 minutes.
Unlike valve islands, Airboxes are standard components normally available off the shelf. Tip: When replacing ensure sure that no contamination from old tubing or local environment enters the replacement Airbox ports or vampire pin area. - Do A/B addressable Airboxes have enhanced fault/status indication?
- Yes. Yellow cable versions have a single AS-i indicator LED, which can show green, red, flash orange, or flash red/green. This can show communication failure, AS-i voltage failure, address code 0 or sensor overload. Combined with black cable versions LEDs these additional features can be particularly useful. Full details on instruction sheet packed with goods.
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