What Are The Core Technical Advantages of The Fixed Bridge Type CMM?

The UPM series of fixed bridge-type three-coordinate measuring machinesproduced by DIPSEC, as a measuring device, has its core technical advantages mainly reflected in aspects such as highly stable mechanical structure, independently controllable core measurement and control system, and high-precision motion control technology. This structure is recognized as the highest precision form among three-coordinate Measuring Machines (CMMs), and is usually used in measurement laboratories as the "reference" equipment.

Differences between Fixed Bridge Structure and Mobile Bridge Structure

From the perspectives of movement mode, precision stability, load-bearing capacity, and application scenarios, the main differences between the fixed bridge structure and the mobile bridge structure lie in the following points:

1. Differences in core structure and movement patterns

This is the most fundamental difference between the two:

• Mobile Bridge Type: The worktable remains stationary while the bridge moves. The bridge (including the X-axis and Z-axis) moves along the Y-axis direction on the base guide rails, and the Probe follows the movement of the bridge to cover the measurement range.
• Fixed bridge type: The bridge remains stationary while the worktable moves. The bridge is rigidly connected to the base to form a "closed frame". The workpiece is placed on the moving worktable, which moves along the Y-axis guide rail.

2. Differences in Accuracy and Dynamic Stability

The fixed bridge structure is generally regarded as having higher mechanical accuracy and stability:

(1) Eliminate Abbe error and deflection:

• Mobile gantry: Since the bridge is in motion and is usually driven by only one side (or driven by both sides but not in complete synchronization), it is prone to the phenomenon of walking, that is, the bridge undergoes minor deviations or distortions (swaying and pitching) while in motion, which affects the measurement accuracy.
• Fixed Bridge Type: Due to the fixed nature of the bridge, the deviation and pitch/roll errors caused by the movement of the bridge are fundamentally eliminated. This structure is considered an ideal framework for achieving ultra-high precision.

(2) Independence (decoupling) of axis movement:

• Fixed bridge type: The movement of the X-axis slider does not affect the force distribution of the Y-axis guide rail. The movements of each axis are independent and will not cause structural deformation.
• Mobile bridge type: As the X-axis slide plate moves along the bridge frame, the center of gravity of the bridge frame changes, causing uneven force distribution on the guide rails, which may lead to micro-scale structural deformation.

(3) Driving method:

The fixed bridge type is more conducive to achieving center-of-gravity-driven operation, that is, the driving force acts directly on the center of gravity of the moving component, further reducing the vibration and deformation caused by inertia, and achieving high dynamic accuracy.

3. Differences in carrying capacity and measurement range

The mobile bridge crane has greater advantages in terms of flexibility and load-bearing capacity:

• Mobile Bridge Type: Since the workpiece is directly placed on a fixed base (usually a huge granite block), its load-bearing capacity is extremely strong and it is almost not restricted by the movement system of the worktable. Moreover, it is easier to expand the measurement range, making it suitable for measuring medium-sized, heavy-duty components.
• Fixed Bridge Type: Since the workpiece needs to move along with the worktable, the weight of the measured object is limited by the driving system of the moving worktable and the bearing capacity of the air-bearing guide rails. If the workpiece is too heavy, it will affect the dynamic performance and accuracy of the Y-axis. Therefore, it is mainly used for measuring small-sized and moderately-weighted precision parts.

4. Differences in application scenarios

• Mobile bridge type (such as the KYUI series): This is the most widely used model on the market, balancing precision, speed and flexibility. It is widely applied in workshop production sites, general mechanical manufacturing, automotive parts, and other common inspection scenarios.
• Fixed bridge type (such as UPM series): Typically used in metrology laboratories, value transmission, and in fields requiring high precision (such as precision gears, aircraft blades, medical devices, optical molds, etc.).

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