A Look Inside: The PGM Parallel Gripper Explained in Detail

Why is the PGM parallel gripper so durable, precise, and always self-centering? To answer this question, we need to look beneath the surface. In the blog post "PGM Gripper Design," we analyze the cross-section of our compact powerhouse and explain why its mechanical design makes all the difference in your production.

The Heart of the Matter: The Cam

Inside the PGM, a cam is at work. This mechanism converts the vertical movement of the piston into the synchronous, horizontal movement of the gripper jaws.

The PGM Design in Cross-Section

The cross-section on the right clearly illustrates the quality features of Wagner grippers:

• Robust Housing: Made of high-strength aluminum with a hard-anodized finish for minimal friction and maximum protection against wear.
• Precision Piston: Provides the necessary driving force—even at low operating pressure (operating pressure: 2–8 bar).
• Mechanical Guidance: In addition to the cam and the guide rods, the jaw guide ensures stable movement and helps absorb moments.
• Sensing Option: The housing features holes for direct sensor installation, allowing the "open" or "closed" position to be reliably detected. From size PGM-60 onward, C-slots are incorporated (depending on size).

💡Technical Details for Engineering Enthusiasts

The pneumatically driven piston (1) is mounted in the guide element (2) and transmits its movement directly to a guide track via a hard-chromed piston rod (3), which is the so-called cam (4) (material: X45NiCrMo4).
The clamping jaws (5), onto which the customer later mounts their fingers, are force-guided in the central guide track (6): a ramp converts the movement of the pneumatic piston into a gripping or spreading motion. At the same time, the guide track is guided in turn by a slot (7) in the respective jaw. To absorb tilting moments, both jaws run on ground and hardened, stainless steel guide rods (8).
This design principle is highly compact, easy to maintain, and inevitably results in a self-centering gripping system!

It is true: dirt can enter the open PGM gripper, but it can also escape just as easily! As a result, dust does not accumulate in the guides or cause them to stick or become clogged. Of course, the piston rod runs in a wiper seal built into the guide cover (9).
For subsequent operation, an open system means that the parallel gripper can be blown out and lubricated while installed.
In addition to the component material selection already described above, the housing and jaws are made of high-strength, hard-anodized aluminum for enhanced durability!

All variants feature mounts for inductive sensors (11). Through blind holes incorporated in the jaws, the sensing sensitivity can be adjusted so that the "up", "closed", and "gripped" positions can be detected.

Sensing Options for the PGM

💡Expert Tip: Mounting the Gripper and Fingers

All grippers are supplied with six centering rings. These h6 fits are used in pairs (diagonally) with the corresponding holes (13) to mount the fingers and the gripper housing.

Technical Details

• PGM variants are available with a stroke of 2 mm to 15 mm per jaw.
• The repeatability is +/-0.02 mm.
• The maximum recommended workpiece weight across the different sizes is 0.13 kg to 7.2 kg (piston diameter 10–63 mm).
• The length across both closed jaws is 29 mm for the smallest gripper (PGM-29) and therefore 140 mm for the PGM-140.

💡Expert Tip: For Small Workpieces

The technical data applies at a pressure of 6 bar, although the PGM can be operated at 2 to 8 bar. The PGM-29, in particular, can be operated with less force for very small workpieces. As usual, gripping speeds can be adjusted using external throttle valves.

Why Engineers Love the PGM

In automation, reliability is the most important currency. The PGM impresses with:

• Compact Design: Ideal for use in automation and assembly cells.
• Easy to Maintain: The open design allows the gripper to be blown out and lubricated while installed.
• Robust: No matter what the gripping task entails, the hard-anodized housing made of high-strength aluminum is durable and resistant to wear.
• Self-Centering: With its centrally designed principle, the PGM parallel gripper offers a repeatability of +/-0.02 mm. 
• Design Details: Simple solutions such as gripping force safety devices or an integrated slot help in everyday use.

Slot on the PGM Mounting Surface

Conclusion: Quality is Visible from the Inside

A gripper is only as good as its mechanics. The cross-section of the PGM shows that we make no compromises at Friedemann Wagner. Every detail is optimized for durability, repeatability, and reliability.

🎥 See the PGM's Inner Workings in Motion: