# Machine Retrofit & Connectivity Checklist > What to verify before you change a running machine's controls, or connect it to anything. Source page: https://mnpsystems.ca/resources/machine-retrofit-checklist/ PDF: https://mnpsystems.ca/downloads/machine-retrofit-checklist.pdf (free, no email required) MNP Systems is an engineering consultancy based in Brampton, Ontario, Canada, that takes work from anywhere: remotely, or on site where a job needs hands on the equipment. Contact: https://mnpsystems.ca/contact/ or contact@mnpsystems.ca. This checklist is for a machine that already runs and earns its keep: a press, a filler, a conveyor line, a test stand. Nothing here is about choosing a new PLC brand or designing a line from scratch. It is about the gap between "the machine works" and "we can safely change it". Most retrofits that go wrong do not fail on the new hardware. They fail on something nobody wrote down about the old. Work through it before you ask anyone for a quote, and again before the cutover. The first pass tells you what the job is; the second tells you whether you are ready to do it. ## 1. What the machine does today - [ ] Someone has watched a full cycle, start to stop, and written down each step the machine takes and the condition that moves it to the next - [ ] Every operator mode is listed, including the ones used once a month: setup, jog, manual override, cleaning, recovery after a jam - [ ] Every fault the machine raises today is listed with what the operator does about it, because the new controls have to handle the same faults - [ ] The electrical drawings exist and have been checked against the panel, not assumed to match it - [ ] Cycle time, throughput and scrap rate are measured now, so the retrofit can be judged against numbers rather than memory ## 2. The controller and its program - [ ] The PLC, its firmware version and every module in the rack are identified by part number, and each part's availability is known - [ ] A copy of the running program has been uploaded from the controller and stored off the machine, with the date it was taken - [ ] The uploaded program has been opened in the programming software and confirmed complete, with any missing comments or tag names noted - [ ] Drives, servo amplifiers, HMIs and smart sensors have their parameters backed up too, since a replacement drive with factory settings will not run the machine - [ ] Licences, passwords and the programming cable or software version needed to connect are known and in the hands of the plant, not one technician ## 3. Safety - [ ] Every emergency stop, guard interlock, light curtain and two-hand control has been tested and its wiring traced to the device that acts on it - [ ] It is written down which safety functions are hardwired and which pass through the PLC or a safety relay, so nobody changes one by accident - [ ] The retrofit plan says plainly whether any safety function changes. If one does, it gets a risk assessment of its own - [ ] In Ontario, someone has checked whether the change needs a Pre-Start Health and Safety Review under Regulation 851, section 7 - [ ] Lockout points and energy sources, including air, hydraulics and stored mechanical energy, are documented for the people who will work on it ## 4. Connecting it - [ ] The protocols the controller can already speak are known (Modbus RTU or TCP, Ethernet/IP, Profinet, OPC UA), before anyone buys a gateway - [ ] The machine network is separated from the office network, with only the connections it needs allowed between them - [ ] Nothing outside the plant can reach the controller directly. Remote access, if there is any, goes through one controlled, logged path - [ ] The first connection reads data only. Writing to the controller from outside comes later, if at all, and on purpose - [ ] Every address, tag and register being read is documented with its units and scaling, so a value of 2,350 means something to the next person ## 5. The data you want - [ ] The questions the data must answer are written down first (why did the line stop, how many good parts per shift) rather than "collect everything" - [ ] Each signal has a defined sample rate and a reason for it; a temperature does not need reading ten times a second - [ ] Machine states are defined (running, idle, blocked, starved, faulted) and agreed with the people who will read the reports - [ ] Someone owns the screen or report the data feeds, and it has been shown to an operator before it is called finished ## 6. The cutover - [ ] The new program has been tested before it reaches the machine, in a simulator or on a bench rig with the real I/O map - [ ] Every input and output has been checked point by point on the machine, with the result recorded - [ ] There is a written way back to the old controls, and the old program and parts are kept until the new setup has run a full production week - [ ] The cutover is booked into a production window with the people who run the line, not squeezed into a weekend nobody planned for - [ ] Operators and maintenance have been shown the new screens and fault messages before the first production shift, not during it ## Where this usually goes wrong **The program on the machine is not the program in the file.** The only copy is on a laptop from years ago, and the machine has been edited online since. Retrofits built on that file reproduce a machine that no longer exists. Upload from the controller first, every time. **Safety rides along unnoticed.** A guard switch wired through the old PLC moves to the new one, nobody reviews it, and a safety function changes without a risk assessment. Decide on paper which safety functions the job touches before any wire moves. **Connected before it is understood.** A gateway goes in, a dashboard appears, and nobody can say what the numbers mean or who acts on them. Data with no question behind it is noise that costs money to keep. ## When this needs outside help Most plants can work through this list with their own maintenance team, and should. It is worth bringing in help when: - The program cannot be read, the drawings do not match the panel, and nobody left on site knows how the machine actually decides what to do - Parts are obsolete and the line cannot stop for longer than a planned shutdown, so the migration has to be staged around production - Machine data has to reach an MES, an ERP or a cloud system securely, and the controls and IT sides of the plant have never had to work together If any of those describe where you are, this is work we do: **contact@mnpsystems.ca**.