Product Overview

The Siemens 6AG1688-3XY38-2AX0 SIPLUS HMI Blank Front Panel is an industrial operator-panel component designed for building customized human-machine interface stations. It uses the KP8 format and provides a mounting surface for standard 22.5 mm operator controls, allowing machine builders to configure control panels around their specific operational requirements.

Manufactured by Siemens under the SIPLUS product family, this component is designed for industrial environments where modular operator interfaces, flexible panel layouts, and enhanced environmental resistance are important. Its blank-front design allows engineers to install compatible pushbuttons, selector switches, indicator lights, and other suitable operator devices instead of using a fixed, preconfigured keypad.

Unlike a complete HMI terminal, the 6AG1688-3XY38-2AX0 does not provide a display, processor, programmable interface, or integrated communication functions. Its primary purpose is mechanical integration and front-panel mounting. The electrical functions depend on the individual control devices installed in the panel and the wider automation system.

The component is based on the Siemens 6AV3688-3XY38-3AX0 design and incorporates conformal coating. Its specified operating temperature range is -40°C to +60°C, with a minimum startup temperature of -25°C. The front has an IP65 protection rating, while the rear is rated IP20, making correct installation and enclosure design essential.

The panel can accommodate up to five compatible command or signaling devices. This makes it useful for modular operator stations in industrial machinery, production equipment, and certain SIMATIC HMI PRO extension-unit installations.

For maintenance teams, machine builders, and industrial spare-parts suppliers, the exact Siemens article number should be verified before ordering. Mechanical dimensions, mounting compatibility, environmental requirements, and the type of operator devices used in the assembly all affect successful integration.

Technical Specifications

Dimensions and weight above follow the supplied product listing. Confirm the physical unit and packaging details before using these values for enclosure design or shipping. Published component data gives different body dimensions and net weight.

Function and Working Principle

The Siemens 6AG1688-3XY38-2AX0 serves as the mechanical front section of a customized operator interface. Rather than performing control processing itself, it provides a structured mounting area for individual operator devices that can be wired into a machine’s electrical control system.

1. Mounting Standard Operator Controls

The blank front is designed to accommodate standard 22.5 mm operator controls. Depending on the selected components and their mounting requirements, these may include pushbuttons, selector switches, illuminated controls, or indicator lights.

This standardized mounting approach gives panel designers flexibility when developing machine interfaces. Instead of purchasing a complete operator station with fixed controls, engineers can select the individual devices required by the application.

The physical compatibility of each component should be checked against its cutout, mounting depth, terminal arrangement, and the available rear clearance.

2. Supporting Modular Panel Design

The KP8-format design is intended for modular operator-panel construction. It provides a defined interface area that can be incorporated into a larger control arrangement.

A machine builder may use this blank front for local start and stop commands, mode selection, status indication, or other machine-specific functions. The exact configuration depends on the devices installed and the control logic implemented in the PLC or other controller.

3. Providing an Operator Interface Surface

The front panel creates a physical interface between operators and machinery. Operators can interact with installed controls without requiring every function to be accessed through a software-based touchscreen.

For example, an industrial machine may use a selector switch to choose between automatic and manual operation, pushbuttons to request a start or stop, and indicator lights to display operating status.

The blank front itself does not generate these signals. The installed operator devices and their wiring provide the electrical interface.

4. Environmental Protection

The SIPLUS design incorporates conformal coating and supports an extended operating temperature range. These characteristics can be valuable in industrial environments where standard components may face more demanding ambient conditions.

The front protection rating is IP65, while the rear is IP20. The complete assembly’s protection therefore depends on correct mounting, compatible operator devices, seals, cable routing, and the surrounding enclosure.

The component should not be treated as fully sealed on both sides simply because its front has an IP65 rating.

Role in Industrial Control Systems

The 6AG1688-3XY38-2AX0 is typically used as part of a larger industrial operator station. Its role is to provide a configurable mounting surface for the controls that connect operators to the automation system.

PLC-Based Control

A programmable logic controller can process signals from the installed pushbuttons and selector switches and then execute the corresponding control logic.

For example, pressing a start button may provide a digital input to the PLC. The PLC checks the relevant permissives and interlocks before issuing a command to a motor drive, contactor, or other actuator.

The blank front panel does not perform this logic. It supports the mechanical arrangement of the operator controls used by the PLC system.

Machine Status Indication

Indicator lights can be installed to communicate machine status, operating modes, alarms, or maintenance requirements. Their signals may be controlled by PLC outputs or other suitable control circuitry.

When designing the operator station, the color, labeling, electrical rating, and intended meaning of each indicator should be defined consistently with the machine’s operating procedures.

Manual and Automatic Operating Modes

Selector switches mounted on the panel can provide a physical method of selecting operating modes. The PLC or control system then interprets the resulting electrical signals.

Mode-selection circuits must be designed carefully, particularly where maintenance, manual movement, or safety-related functions are involved. The blank front is only a mounting component and does not independently provide safety logic or machine interlocking.

Integration with SIMATIC HMI PRO Equipment

The product is suitable for installation in certain extension units of SIMATIC HMI PRO devices. This makes it relevant to modular industrial operator stations where physical controls are combined with other operator-interface equipment.

Before installation, verify the dimensions and mounting provisions of the specific extension unit and confirm that the selected controls fit the available space.

Industrial Applications

The Siemens 6AG1688-3XY38-2AX0 can be used wherever a modular operator panel is required and the installed devices are compatible with its mounting format.

1. Manufacturing Machinery

Production machinery often requires local controls for starting, stopping, mode selection, and status indication. The blank front provides a way to arrange these controls in a consistent and accessible format.

Machine builders can select controls according to the production process, operator workflow, and electrical requirements.

2. Packaging Equipment

Packaging systems may require buttons and switches for machine operation, setup, fault acknowledgment, and manual intervention. A customized operator station can place frequently used controls where operators can reach them conveniently.

The installed devices and PLC logic determine the actual functions. Emergency-stop devices, where required, must be selected and integrated according to the machine’s risk assessment and applicable safety standards.

3. Assembly Lines

Assembly stations may use local controls for cycle initiation, mode selection, part handling, and status indication. A modular blank front allows the operator interface to be adapted to each station’s workflow.

Standardized panel layouts can also help maintenance personnel identify control functions more quickly.

4. Material-Handling Systems

Conveyors, transfer systems, and other material-handling equipment may use local pushbuttons and selector switches to support normal operation and maintenance procedures.

The control arrangement should clearly distinguish ordinary operational commands from safety-related functions and ensure that all signals are correctly connected to the control system.

5. Industrial Equipment with Extended Environmental Requirements

The SIPLUS version’s specified temperature range and conformal coating may make it appropriate for selected installations exposed to challenging ambient conditions.

However, suitability depends on the actual environmental hazards. The component’s temperature rating and conformal coating do not automatically establish resistance to every chemical, liquid, contaminant, or installation condition.

6. Modular Operator Stations

Equipment manufacturers may need different control arrangements for different machines or production lines. A blank front makes it possible to customize the physical interface without changing the entire operator-panel platform.

This approach can simplify panel standardization when multiple machine variants use the same general mounting format.

Installation and System Integration

Correct mounting and wiring are essential to ensure that the blank front and its installed controls function reliably.

1. Verify Mechanical Compatibility

Before installation, confirm that the 6AG1688-3XY38-2AX0 matches the intended KP8-format mounting arrangement.

Check the manufacturer’s mechanical drawing, mounting cutout, panel thickness, mounting hardware, and available rear clearance. Do not rely exclusively on shipping dimensions or approximate product-listing measurements.

If the component is being installed in a SIMATIC HMI PRO extension unit, verify compatibility with the exact extension-unit model.

2. Select Suitable Operator Devices

Choose buttons, selector switches, and indicator devices that meet the mounting requirements and the electrical needs of the application.

Confirm the following:

• Mounting diameter and required cutout.
• Front-panel thickness limits.
• Rear depth and terminal clearance.
• Voltage and current ratings.
• Contact configuration and switching function.
• Environmental rating and sealing requirements.
• Required labels and operator identification.

The maximum number of devices is five, but the practical number may be lower depending on the physical dimensions of the selected controls and the required spacing.

3. Maintain the Correct Protection Rating

The front has an IP65 rating, while the rear has an IP20 rating. Maintaining the intended front protection depends on correctly installed and suitably rated operator devices, seals, and mounting arrangements.

Avoid assuming that the panel assembly will retain its specified protection if incompatible controls are installed or the mounting surface is damaged.

The rear area should be protected from conditions outside its specified rating.

4. Plan Electrical Wiring

The installed controls must be wired according to their individual documentation and the machine’s electrical design.

Pushbuttons and selector switches may connect to PLC inputs or suitable interface circuits. Indicator lights may be driven by PLC outputs or other appropriately rated circuits.

Use correctly rated conductors, terminal blocks, and protective devices. Clearly label wires and terminals to support troubleshooting and future maintenance.

5. Integrate with the Control Program

Confirm that the installed controls correspond to the intended PLC input and output assignments. Update electrical drawings and software documentation whenever the panel configuration changes.

For example, if a selector switch is added to select an operating mode, the PLC program must interpret the switch position correctly and enforce the required permissives.

The blank front itself does not contain a programmable controller or communication interface.

6. Test the Completed Assembly

After installation, inspect the mechanical mounting, verify wiring, and test every installed operator device.

Confirm that buttons, selector switches, and indicator lights operate as expected. Test relevant interlocks and safety functions using the procedures specified for the complete machine.

Record the final device layout and electrical connections for maintenance and future replacement.

Compatible System Components

The 6AG1688-3XY38-2AX0 is a mechanical mounting component. The following equipment may be used with it as part of a complete operator station, subject to individual compatibility checks.

These are examples of system components, not items automatically included with the blank front panel.

Alternative Models and Replacement Considerations

When replacing the 6AG1688-3XY38-2AX0, the most important considerations are mounting compatibility, environmental requirements, and the specific operator devices used in the assembly.

Before selecting a substitute, compare the complete article number, mounting dimensions, number and type of operator positions, environmental ratings, and compatibility with the target enclosure.

A standard blank front should not be assumed to offer the same environmental resistance as a SIPLUS variant. Similarly, a powered key panel is not a direct functional replacement for an empty front unless the control architecture and mounting requirements support the change.

Key Advantages

Flexible Operator Configuration

The blank-front design allows engineers to choose the individual operator controls needed for a particular machine rather than accepting a fixed control layout.

Standardized 22.5 mm Mounting

Compatibility with standard 22.5 mm operator controls supports the use of a broad range of suitable pushbuttons, switches, and indicator devices.

Modular Panel Construction

The KP8 format supports customized operator-panel layouts and selected SIMATIC HMI PRO extension-unit installations.

Extended Operating Temperature Range

The specified operating range of -40°C to +60°C provides flexibility for suitable installations exposed to a wider ambient temperature range than many standard indoor control-panel components.

Conformal Coating

The SIPLUS configuration includes conformal coating, which provides additional protection to applicable surfaces against certain environmental influences. It does not replace correct enclosure design or establish universal chemical or moisture resistance.

Front-Face Protection

The front IP65 rating supports protection against dust and water jets under the conditions defined by the IP standard, provided that the complete front assembly is installed correctly. The rear remains IP20.

Straightforward Maintenance

Because the panel uses separate operator devices, maintenance teams can often inspect or replace an individual button, switch, or indicator without redesigning the entire operator station, provided the replacement is compatible.

Technical FAQs

1. What is the Siemens 6AG1688-3XY38-2AX0?

It is a SIPLUS HMI blank front panel in KP8 format. It provides a mounting surface for standard 22.5 mm operator controls and is intended for customized industrial operator panels.

2. Is it a complete HMI terminal?

No. It does not have an integrated display, processor, or built-in control application. Its purpose is to accommodate separate operator devices that connect to the machine’s control system.

3. How many operator controls can it accommodate?

The documented design allows up to five command or signaling devices. The actual number depends on the selected components, their dimensions, and the mounting arrangement.

4. What is the front protection rating?

The front is rated IP65, while the rear is rated IP20. Correct installation and the use of compatible operator devices are necessary to maintain the intended front protection.

5. What is the operating temperature range?

The specified operating range is -40°C to +60°C, with a minimum startup temperature of -25°C. Confirm the complete assembly’s environmental limitations before using it in extreme conditions.

6. Does the product include pushbuttons or indicator lights?

The product is a blank front design. Pushbuttons, selector switches, indicator lights, and other operator devices must be sourced separately unless a supplier explicitly states otherwise.

7. Can it be integrated with a Siemens PLC?

Yes, as a mounting component in an operator station. The installed controls can be wired to compatible PLC inputs and outputs or suitable interface circuits. The blank front itself does not communicate with the PLC.

8. Is it compatible with SIMATIC HMI PRO extension units?

It is designed for installation in compatible extension units of SIMATIC HMI PRO devices. The exact mechanical fit should be checked against the target extension-unit model.

9. What should be checked before purchasing?

Verify the full article number, mounting format, environmental ratings, actual dimensions, weight basis, condition, and whether any operator devices are included. For replacement projects, compare the original panel layout and mounting provisions.

10. Why do the supplied dimensions differ from published component dimensions?

The supplied 180 × 109 × 66 mm values may reflect a listing or packaging measurement rather than the published component body dimensions. Verify the physical unit and the manufacturer’s drawing before using the figures for cabinet design.

Procurement and Maintenance Recommendations

When sourcing the Siemens 6AG1688-3XY38-2AX0, begin by verifying the full article number and confirming that the component matches the required KP8-format mounting arrangement.

For replacement projects, inspect the existing panel and document the dimensions, mounting orientation, number of controls, and rear clearance. Confirm whether the target installation requires the SIPLUS environmental specification or whether a standard-design blank front is suitable.

Before purchasing, establish whether the item is supplied as a blank front only or as part of a larger assembly. Verify the included accessories, physical condition, and supplier’s warranty and return terms. Distinguish product net weight from shipping weight when preparing logistics documentation.

During maintenance, inspect the front surface, seals, mounting hardware, operator devices, and rear wiring. Replace damaged or incompatible controls with components that meet the original mechanical and electrical requirements. After any modification, test all operator functions and update the wiring documentation.

For installations exposed to low temperatures, moisture, dust, or other environmental challenges, evaluate the entire assembled operator station rather than relying solely on the SIPLUS designation. The mounting arrangement, installed devices, cabinet, and wiring all affect overall reliability and protection.

Conclusion

The Siemens 6AG1688-3XY38-2AX0 SIPLUS HMI Blank Front Panel is designed for customized industrial operator stations using standard 22.5 mm controls. Its KP8 format, support for up to five operator devices, conformal coating, and extended operating temperature range make it a useful component for modular panel construction.

The product is a mounting component rather than a complete HMI, and its front IP65 and rear IP20 ratings must be considered when designing the installation. Accurate article-number verification, mechanical compatibility checks, and correct selection of the installed operator devices are essential for reliable integration into industrial automation systems.