HMIs and touchscreen control panels are common on modern-day factory equipment, they are the interface between the machine and the operator. Hence Human Machine Interface – HMI.
But did you know they are constantly giving us feedback about their own health status? Well if you know the subtle signs to look for, HMIs in my opinion, give so much information about a failure that will happen. Remember that a failure of a HMI in operation means your plant will stop, you will have downtime and lost productivity.
So what signs should you be looking out for if you want to prevent a failure happening?
Well here are 5 sure-fire signs that your HMI will fail.
1 – The screen becoming dull or flickering. This is often seen as an annoyance to the operator, but in truth it’s the HMI telling you the backlights are about to fail. This can happen over a period of months before the backlights totally fail. Plenty of time to arrange a spare unit to be fitted or to remove the HMI for refurbishment.
2 – Lines appear across or down the screen. This means the LCD is failing, it will probably be just a few lines that appear at first and the operator can still continue to use the HMI, but a failure will happen.
3 – The HMI needs a few goes at powering-up. This is probably one of the most common signs of failure, if your HMI needs power-cycling to start then it’s indicative of an internal power supply failing.
4 – The touch screen becomes less responsive. touch screens are wearing parts; you may find that an area of a touch screen has stopped working or a soft-button needs several ‘presses’ to respond. This is a sign the touch screen element is failing. A big tip here, and pardon the pun but never use the tip of a screwdriver or pen to operate a touchscreen, it will scratch very easily or shatter the LCD glass. We see this all too often and is can lead to an instant failure of the HMI. You wouldn’t use a screwdriver or a pen to operate your smartphone would you?
5 – Key-presses don’t always work. Keys such as ‘process start’, ‘enter’ or ‘passcode keys’ can have the heaviest use on a HMI, they are very often seen as the keys with the legends worn away, but, ‘everyone knows that’s the start button’. Over time these will fail and the operator may just have to press a little harder than he did before. This is a sign the switch is failing and a new switch or a whole new membrane maybe needed.
These signs are often shown by HMIs months before they fail, so to prevent these failures and prevent plant downtime, it’s useful to speak with the machine operator. After all it’s they who have daily interaction with the HMI. Yet they are the ones who ‘put up’ with these problems. I’d suggest that maintenance teams ask the operators a few simple questions.
– Does the screen seem dull to you or does it flicker?
– Are there any lines appearing on the screen?
– Does the HMI power up each time?
– Are any of the membrane keys or touch-screen less responsive?
Acting on the operators answers will give you a good indication of whether the HMI should be changed. How many times have you heard, especially after a failure, the operator saying –
“It’s been getting worse for months that has!”?
Well now’s the opportunity to bring an element of preventative maintenance into HMIs to prevent downtime. Please remember that none of the conditions described above will get better on their own. Intervention is needed, and I’d suggest that intervention is a refurbishment, carried out by a competent repair company.
Fletcher Moorland has a workshop set-up for the diagnosis, repair and test of virtually all types of HMI. We see makes such as Allen Bradley, Siemens, Krones, Fanuc, B&R, Beckhoff, Midas, Proface, Mitsubishi, Beijer, Xycom plus many others.
Our repairs include replacement backlights and inverters, LED backlight upgrades, replacement membranes and keypads, replacement touch screens, replacement LCD screen, repairs to internal power supplies.
We also offer our ‘softwareVAULT’ service when refurbishing HMIs, we will take a copy of your software and store it in an off-site, password-protected data cent