视觉点胶机的坐标系怎么理解？

Newcomers to dispensing machines are often confused by terms like 'coordinate system', 'origin' and 'offset'. Once you understand coordinates, the logic of machine programming and debugging falls into place. This article explains machine coordinates, workpiece coordinates and origin offsets in plain language.

1. Why a Dispensing Machine Needs a Coordinate System

To dispense adhesive precisely at specified positions on a plane or in 3D space, the machine must have an 'address system' describing every point — that is the coordinate system. Without it, the machine would not know where the needle is or where to go. Dispensing machines use Cartesian coordinates:X axis left-right, Y axis forward-back, Z axis up-down— three directions locate any point in space.

2. The Machine Coordinate System: The Machine's Own 'Home'

The machine coordinate system is fixed at the factory, with the origin usually at each axis's mechanical limit. The first thing done after power-on —homing— returns every axis to this mechanical origin to establish the coordinate datum.

Why home? Because after shutdown the machine does not know where the needle stopped. Homing drives each axis back to a physically fixed position, usually where it touches the limit switch; this position has fixed machine coordinates. With this datum, all subsequent motion coordinates become meaningful.

3. The Workpiece Coordinate System: Product-Based Coordinates

The workpiece coordinate system is built on the product or fixture.Its origin can be set at a corner of the product, at a locating hole or at a Mark point; axis directions match the machine system but the origin differs.

Example: suppose the product is a 50mm × 50mm square placed at the center of the worktable. In machine coordinates, its lower-left corner might be X=125, Y=100. But if you set up a workpiece coordinate system with the origin at that corner, all dispensing positions can be counted from 0 — lower-left is (0,0), upper-right is (50,50), which is far more intuitive for programming.

That is the value of the workpiece coordinate system: programming coordinates correspond to drawing dimensions, with no conversion to machine coordinates. When switching to a different product, simply reset the workpiece origin and the same program runs unchanged.

4. Z-Height Compensation and Vision Coordinate Mapping

Beyond the XY plane, the Z axis also matters. Products differ in thickness, so the distance from needle tip to product surface must be adjusted accordingly. Setting Z-height compensation in the software lets the needle adjust its Z position automatically for products of different heights, avoiding collisions or excessive distance.

For machines with vision, there is also a mapping between the camera coordinate system and the motion coordinate system. Image coordinates and motion coordinates are linked by a fixed transformation. During vision alignment, the camera images Mark points and computes the deviation; the software converts it into a motion-coordinate compensation and commands the axes to move the corresponding distance. That is why calibration matters — if calibration is off, the vision-computed deviation will not match the compensation actually required.5.

5. Summary

Previous: