Inside an HMI Screen: How It’s Made & What It's Made Of

Inside an HMI Screen: How It’s Made & What It's Made Of

An HMI screen may look like a simple touch display, but it’s built with precision engineering and layered technology to handle the demands of industrial environments. Understanding the internal layers of an HMI screen helps you appreciate why it’s so reliable, responsive, and durable.

How an HMI Screen Is Made

The manufacturing process of an HMI screen involves assembling multiple layers that work together to provide a clear display, responsive touch, and long-term durability. These screens are usually made in clean-room environments to prevent dust or contaminants from affecting performance.

Layers of an HMI Screen

1. Protective Cover Layer (Top Layer)

This is the outermost layer, often made of tempered glass or durable polycarbonate. It resists scratches, moisture, dust, and chemicals commonly found in industrial settings.

2. Touch Layer (Touch Sensor)

Below the cover is the touch-sensitive layer, typically based on either resistive or capacitive technology.

3. Air Gap or Optical Bonding Layer

Some HMI screens have an air gap, while higher-end models use optical bonding, where adhesive is applied between the touch layer and the display. This reduces reflection, improves contrast, and enhances visibility in bright environments.

4. Display Layer (LCD/TFT Panel)

This is the actual visual display unit—often an LCD (Liquid Crystal Display) or TFT (Thin-Film Transistor) screen that shows system data, alarms, and graphics. It determines the screen’s resolution, brightness, and viewing angle.

5. Backlight Layer

Located behind the LCD, the LED backlight illuminates the display. It’s engineered to be energy-efficient and long-lasting, especially for 24/7 industrial use.

6. Controller Board / Touch IC

This layer interprets input from the touch sensor and translates it into commands. It connects the screen to the main controller or HMI software, making the system interactive.

7. Rear Housing & Shielding

The rear of the HMI screen includes EMI shielding, heat dissipation elements, and a durable metal or industrial plastic enclosure that protects internal electronics.

Durability Is Built Into Every Layer

Each layer of the HMI screen is chosen not just for functionality, but also for durability and safety:

1. Shock and vibration resistant materials
2. Anti-glare or anti-reflective coatings
3. Moisture-sealed edges and corrosion-resistant parts

Industrial HMI screens are also tested to meet standards like IP65/IP66 for water and dust protection and IK ratings for impact resistance.

Types of HMI Screens

Choosing the right type of HMI depends on your application. Here are the main categories:

1. Basic Text-Based HMIs

1. Monochrome display
   
2. Suitable for simple monitoring
3. Low cost, limited features
   

2. Graphical HMI Screens

1. Color LCD/LED touchscreen
   
2. Rich visualization (graphs, trends)
3. Used in advanced automation setups
   

3. Industrial PC-Based HMIs

1. Windows or Linux OS
2. High-end SCADA integration
3. Ideal for complex systems and analytics

Final Word

The next time you tap an HMI screen, remember—it’s more than just a glass surface. It’s a layered, engineered solution built for accuracy, durability, and real-time control in harsh conditions. Each layer works behind the scenes to ensure you get fast, reliable performance every time.