If your production line is in the process of transitioning from a human-based workforce to something involving more automation, you’re going to need to choose a human-machine interface (HMI) that will allow the remaining human workers to oversee the manufacture of your products. With automation technology quickly gaining popularity in the manufacturing sector at an unprecedented pace, there are literally hundreds of HMI solutions available from which to choose. The question then is, how do you go about choosing the right one?
What’s the operating environment?
Like many tools, you need to consider the conditions under which the HMI will operate. Even the HMI’s proximity to other devices or equipment can help you narrow down the field. For example, if the HMI is to be installed somewhere along a food production line, it’d likely need to have a significant ingress protection (IP) rating as these types of environments tend to be scrubbed down regularly. HMIs that will be exposed to extreme temperatures, both hot and cold, will need to be insulated against them so that they can operate properly and reliably. HMIs that operate outdoors will need to include screens that can be easily readable in daylight. Once you’ve taken a step back to examine the external conditions that will impact the HMI, the field of available options will narrow considerably.
What’s the application and what else may the user want it to do?
This question can be difficult to answer because knowing everything that will be required from the HMI isn’t always apparent from the get-go. While it is certainly beneficial to leave a bit of wiggle room for enhancements down the line, it might help to know that HMIs can be qualified into three pretty broad categories, each of which is described below.
- The pushbutton replacer. Simply speaking, this type of HMI is used to replace the physical buttons/toggle switches controlled by hardwired inputs and outputs. The HMI emulates these controls via a touchscreen mounted directly on the device or in close proximity to it. Bear in mind that if the associated machine has a number of controls, you’ll want to make sure that you choose a system that includes an adequate screen size to accommodate them. You’ll also want to note that HMIs in this category tend to be limited in their functionality (e.g. the lack of colour will hinder adding on-screen colour-coded status indications).
- The data handler. This type of HMI is ideal for more complex manufacturing processes, where it will beneficial to storing alarm information, analyze trends, and logging data. If the intended use of this type of HMI is to oversee the manufacture of many different products, the ease in which you can add and remove data from the HMI will be worth considering. If the data or alarm information collected will be disseminated and analyzed elsewhere, an adequate network connection and additional software tools will also need to be considered.
- The overseer. For sophisticated systems, like those that include a manufacturing execution system (MES), require data warehousing, and record database transactions, the overseer HMI is typically an industrial PC that runs a robust operating system.
What will the HMI be connected to?
A simple question that can become more complex the more it’s considered. Will the machine be connected to one PLC, or several? Will it simply connect to a motor that will drive a conveyor and therefore only need to provide speed instructions? The HMI will also need to support the connection types of the connected devices (i.e. USB, Ethernet, etc.). For the sake of simplicity, and when dealing with complex systems like automatic robots you may want to consider an HMI and PLC that comes from the same manufacturer. Similarly sourced components can help to expedite troubleshooting when there is a problem.
Having said that, most systems are capable of accommodating equipment produced by other vendors; just be sure that things like drivers, end-user documentation, and configuration direction are readily available.
What data entry tool best meets your needs?
Most HMIs are controlled using one of two methods: touchscreen or keypad. Which type you choose could simply come down to preference, but there’s at least one thing to consider here. Touchscreens have come a long way and are incredibly responsive, but a physical keypad is generally faster to enter a long string of characters and is easier to use in environments where manufacturing employees are required to wear gloves.
What are your programming software preferences?
Like pretty much all of the preceding considerations, the application of the HMI will determine the type of software needed to drive it. The three main categories include:
- Proprietary software: This type of software is created by the HMI vendor and is generally simple to use for the task required. The downside to this type of software is that if another HMI (produced by a different vendor) is required for a process that will be rolled out in the future, the application will need to be re-developed.
- Hardware independent (pre-built) software: Better known as third-party software, this type is developed specifically to accommodate HMI hardware from various sources. One benefit is that this type of software can be run on any open platform. Because of its wide-spectrum compatibility, this software tends to be less user-friendly than other solutions.
- Open software: This type of software offers qualified personnel complete freedom to build the application to meet their exact criteria. Though it will allow for the creation of a completely customized system, the development and implementation time is of course much longer than an out of the box solution.
Moving to an automated process will undoubtedly mean fewer manufacturing employees, but the automation technicians that will remain on-site will still need to have access to the right tool to complete their jobs. For that reason, choosing the right HMI for your facility is crucial. By carefully examining the considerations listed above, identifying the right product should be just a little bit easier. More than ever is it important for current and aspiring PLC technicians to understand this, and George Brown College’s PLC Technician Certificate Program is a great way to supplement your knowledge and kickstart your career in this emerging field.