Overcoming the High Cost of HMI Development
A Practical Guide for Machine Builders
Imagine you are two weeks away from shipping a new machine. Your PLC code is solid, but you are still stuck manually mapping hundreds of tags between your controller and a third-party HMI. You are toggling between two different software environments, managing separate licensing fees, and realizing that every hour spent troubleshooting the communication link is directly draining your profit margin.
For OEMs and system integrators, this scenario is all too common. As engineering costs rise and time-to-market pressures intensify, the traditional “separate PLC and HMI” architecture is becoming a financial and technical bottleneck.
The Hidden Costs of Traditional PLC + HMI Architectures
While buying a separate PLC and HMI panel might seem flexible, the true cost of ownership is often buried in engineering hours and hardware complexity.
- Engineering Redundancy: Developing in two separate environments requires double the effort. You must program the logic, design the screens, and bridge the two with a manual tag database—a process prone to errors.
- Software Licensing Burdens: Complex HMI projects can require expensive SCADA or visualization licenses, with project budgets often ranging from $50,000 to over $600,000.
- Hardware and Installation Overhead: Two devices mean two sets of power supplies, two cutouts in the cabinet, and additional wiring for communication.
- Maintenance Complexity: Every time a PLC variable changes, the HMI must be updated and re-synchronized, increasing the risk of downtime and long-term support costs.
What OEM Customers Expect from Modern HMIs
OEM customers expect more than ever before—at a lower price point:
- Smartphone-Like Usability: Operators need intuitive navigation, high-resolution graphics, and responsive touchscreens.
- Industrial Ruggedness: The hardware must withstand heat, dust, and vibration while running 24/7.
- Actionable Data: Modern HMIs must provide real-time trends, color-coded indicators, and live alarm diagnostics to minimize downtime.
- Remote Access: Technicians expect to view machine status or adjust setpoints from a tablet or PC via VNC or web browser.
The All-in-One Solution: Integrated PLC + HMI
To combat rising costs, many machine builders are shifting toward integrated PLC + HMI controllers. This approach combines the logic controller and the operator interface into a single piece of hardware.
Why Integration Wins on the Bottom Line
- Unified Development: A single software environment handles both ladder logic and screen design using a common tag database—cutting programming time by roughly 50%.
- Reduced Physical Footprint: Integrated units typically take up half the cabinet space and require only one power supply.
- Zero Tag Mapping: Because the HMI and PLC share a processor, there is no need to manually link variables between systems.
- Faster Commissioning: Eliminating manual tag mapping means machines ship faster and with fewer integration errors.
Comparing PLC + HMI Architectures: At a Glance
When to Choose Which Architecture?
- Choose Separate Components if the machine requires the HMI to be mounted very far from the PLC, or if you are using a PC-based SCADA system that requires massive data processing across an entire facility.
- Choose Integrated Controllers for high-performance machines where space is limited, development speed is critical, or where you want to eliminate recurring software licensing costs. Ideal for packaging, water management, and conveyor systems.
Unitronics UniStream: A Flexible PLC + HMI Solution
For machine builders seeking to maximize these benefits, Unitronics offers the UniStream series—a flagship line of all-in-one controllers designed to eliminate the friction of traditional HMI design. Unitronics introduced the first all-in-one PLC+HMI over 25 years ago and has led the integrated market ever since.
Hardware Built for the Floor
UniStream controllers combine a built-in color touchscreen (5″ to 15.6″) with a powerful PLC and expandable I/O in one rugged, NEMA-rated unit—proven in heat, vibration, and dust.
- Integrated Touch HMI + PLC: Both run on the same processor and share memory.
- Virtual HMI / Headless Mode: Via the built-in VNC server or web server, operators can securely access HMI screens from a PC, tablet or smartphone anywhere—no special gateway required.
- No-Code IIoT (UniCloud): Cloud-inside models include free UniCloud connectivity with end-to-end IIoT and secure VPN tunneling for remote HMI access.
Cutting Costs: Free PLC + HMI Software
To avoid licensing fees, as well as the need to switch between different environments for PLC applications and HMI design, OEMs can select PLC+HMI controllers freely provided with All-in-One software. For example, Unitronics’ UniLogic is the all-in-one development environment for UniStream—covering PLC logic, HMI screen design, and communications setup in a single tool with a shared tag database.
- Zero Licensing Fees: UniLogic is forever-free, including all HMI/web design tools, widget libraries, and utilities. No per-seat or runtime costs, ever.
- Drag-and-Drop Screen Editor: Build screens by placing buttons, sliders, input fields and graphics—no scripting required.
- Comprehensive Widget Library: Includes ready-to-use gauges, bar graphs, alarm lists, data tables, media players and more.
- Built-In HTML5 Web Server: Publish HMI screens as browser-based dashboards—no HTML/CSS coding needed. Any PC, tablet or smartphone can view and control your machine via HTTP or VNC.
- Live Trends & Dashboards: Drag prebuilt Trend and Chart widgets onto screens to plot temperature, pressure or throughput in real time, with historical scroll-back and zoom.
- Custom Controls & Template Screens: Create reusable HMI templates or encapsulate complex UI elements into Custom Controls that can be dropped into any project.
- Online Debugging: Test logic and interface on your laptop, then connect via VNC for real-time, on-machine testing—without redeploying firmware.
Side-by-Side: Separate PLC + HMI vs. Unitronics UniStream
Frequently Asked Questions
Why does combining PLC and HMI reduce cost?
Integration removes duplicated hardware, eliminates communication wiring between devices, and allows development in a single environment—reducing both material costs and engineering time.
Are integrated PLC + HMI systems suitable for all applications?
They are well suited for many machine-building applications, particularly where repeatability, cost control, and development efficiency are priorities. In large, highly distributed systems, separate architectures may still be preferred.
How much time can integration realistically save?
Many teams see development and commissioning time cut by up to 50%, thanks to simplified workflows, a shared tag database, and fewer integration points between systems—including reduced wiring.
What screen sizes does UniStream support?
UniStream controllers are available with built-in color touchscreens ranging from 5″ to 15.6″, with expandable I/O via remote racks or motion modules to scale with your machine.
Final Takeaway
For machine builders, the challenge is no longer just delivering a functional HMI—it is doing so efficiently, repeatedly, and without eroding margins.
The most effective path forward is not optimizing individual components, but rethinking the system structure itself. Integrated PLC + HMI platforms directly target the root causes of cost and complexity—consolidating hardware, eliminating licensing fees, and cutting development time by up to 50%.
Unitronics UniStream with UniLogic is the clear choice for machine builders who need intuitive, flexible, and cost-effective HMIs—backed by world-class PLC performance.