Knowledge · Maintenance
How do I connect older machines that have no interface?
By Gerd Bart, Founder and Managing Director · Updated
The short answer
Usually by one of three routes: through an interface the control does have, which a gateway translates into OPC UA or MQTT; through the control's OPC UA option once it is licensed or enabled; or through retrofit sensors on the signal tower and the power supply when the machine truly offers nothing. Sensors deliver status, run time and downtime, while programs, alarms and process values only come from the control. On Transaction-Network, machine records, maintenance and ordering sit in your account without any connection, and the IoT Hub reads controls through open interfaces such as OPC UA, Modbus TCP, REST or MQTT.
First decide what you want to know
Connecting means something different for every question. If you want to know whether a machine is running and how long it stood still, a status signal is enough. If you want to know why it stopped, you need alarms and messages from the control. If you want to analyze the process, you need process values such as spindle load or feed rate.
Much of the work needs no connection at all. A machine's manual, spare parts list, maintenance plan and service history can be kept without any interface.
What older machines usually do have
No interface often means no open standard interface. Before you buy sensors, check what the control can already do.
A network port with its own protocol.
Many controls talk over Ethernet in their maker's own language, such as S7 communication on Siemens, LSV2 on Heidenhain or FOCAS on Fanuc. A gateway translates that into OPC UA or MQTT.
OPC UA as an option.
Some controls have an OPC UA server on board that has to be enabled by license or by the machine builder first. Ask about it before you retrofit anything.
MTConnect on machine tools.
Many machine tools have adapters for the open MTConnect standard.
A serial port.
On older machines, NC programs often travel over RS-232. It is of limited use for status data.
Four routes compared
| Route | What you get | Work on the machine |
|---|---|---|
| Existing interface through a gateway | status, counters, alarms, the running program, often process values too | none on the PLC; the gateway connects to the control by network cable |
| The control's OPC UA option | the same data, straight from the control in an open standard | a license or activation by the control maker or the machine builder |
| Retrofit sensors | status, run time, downtime, cycles, current draw, vibration and temperature | sensors on the outside of the machine; any electrical tap belongs in the hands of a qualified electrician |
| New control | everything a modern control delivers | a major rebuild that usually only pays off when the old control has to be replaced anyway |
Retrofit sensors: what they deliver and where they stop
If a machine truly offers nothing, sensors measure from the outside. For many maintenance questions that is enough.
Signal tower.
Optical sensors on the tower or a tap on its wires show whether the machine is running, waiting or in fault.
Power supply.
A current transformer around the supply line tells whether the machine is producing, idling or off, and shows how much current it draws.
Vibration and temperature.
Sensors on the spindle, bearings or pumps show wear before a part fails.
Spare contacts.
Existing contacts, for cycle start or the safety door for example, count cycles and parts.
What sensors do not deliver is the running program, the alarm number and the reason for a stop. You find those in the control, in the manual and in the machine's service history.
How to proceed
Make a machine list.
For each machine: manufacturer, year built, control and model, existing interfaces and location. The control's nameplate and the wiring diagram answer most of it.
Choose the route per machine.
First the existing interface, then the control's option. Sensors are for the machines that truly offer nothing.
Prepare the network.
The machines stay in their own network segment. A secured connection leads out through a gateway with a firewall, following the zone model of the IEC 62443 series.
Start with a few machines.
Two or three machines of different kinds show which signals arrive and what they are worth day to day. The rest of the fleet follows.
Talk to the manufacturer.
Before anyone works inside the control cabinet, check with the machine's manufacturer whether the warranty or a service contract is affected.
How Transaction-Network handles older machines
On Transaction-Network every machine sits in your account, even without a connection: with its machine record, maintenance plans, Service Requests and ordering from the manufacturer. For live data in the Visibility module, the IoT Hub reads the control through the interface it already has, such as OPC UA, Modbus TCP, REST or MQTT. Nothing changes on the PLC, and no additional software runs on the control.
The machines stay in their own network on the shop floor, behind the hub. For your IT the hub is one device with one connection to secure. Before connecting, we go through your machine list, check each machine's control and interface and tell you which can be connected as they are and which need more.
Questions
Frequently asked questions
Can I connect a machine that has no interface at all?
Yes, with retrofit sensors. Sensors on the signal tower, the power supply or the spindle deliver status, run time, downtime and wear values. Why a machine stopped is something only the control or the service history can tell you.
What is the difference between a gateway and retrofit sensors?
A gateway reads the data the control already has and translates it into an open standard such as OPC UA or MQTT. Retrofit sensors measure from the outside what the control does not give out.
Do I have to modify the control?
Usually not for a gateway or sensors. Anyone tapping signals electrically inside the control cabinet should clear it with the machine's manufacturer first and leave the work to a qualified electrician.
Do I need a connection to use Transaction-Network?
No. Machine records, maintenance, Service Requests and ordering from the manufacturer work without a connection. Live data comes through the IoT Hub if you want it.
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