Building robots and tool reception in CAD correctly

Basics #

In RoboDK – similar to numerous CAD systems – a hierarchical structure is used. This means that the individual components, which are arranged one below the other in the structure tree, reference each other.

Best practice

Especially at the beginning, it is recommended to build the machining station (cell) and tool reception in RoboDK step by step.

User interface #

On the left side, you can see the structure tree, and in the center, there is the origin coordinate system. By double-clicking on the individual elements in the structure tree, the properties’ window opens on the right side.

Save the station! #

Save your cell and tool reception first! Otherwise, several hours of work can be lost. The RobPathRec app also only works with saved RoboDK stations!

Creating a Reference Frame #

It is recommended to create a reference frame for the global coordinate system, which can later serve as the origin for the entire cell. It is advisable to include not only the robot, but also a “tool holder”, such as a tabletop, in the base arrangement. This simplifies visualization. At least for the beginning.

In this example, the coordinate system of the table is shifted by -350 mm in the X direction relative to the global reference frame.

IMPORTANT! The coordinate system of the table MUST be determined in the external CAD system. This means that during the creation of the design drawing / assembly drawing, the coordinate system MUST be correctly assigned to the OBJECT WITH THE CORRECT ORIENTATION.

Any frame can be a reference frame #

Any frame can be converted into a reference frame:

  • Select frame
  • Right-click to call up options
  • Select Active Reference Frame

Start with the robot. When a robot is loaded into RoboDK, a reference frame is automatically created for it. The preferred order for RobPathRec is:

  1. Robot
  2. Tool
  3. Other objects in the cell This way, the structure tree can be logically and correctly constructed.
The MUST tree structure for the RobPathRec app!

IMPORTANT! The RobPathRec app requires a reference frame in the tree under the robot’s frame! If this condition is not met, the RobPathRec app will not work!

Importing a robot #

The easiest way to do this is to open the library directly from RoboDK, filter for the appropriate robot, and then download or open it.

Each robot is automatically opened with a reference frame (base frame).

Pay attention to the position and orientation of the robot’s reference frame relative to the global coordinate system. Accidental rotations and displacements must be avoided!

In the examples above, simple arrangements were shown (which in most cases can serve as a good starting point). Please note the orientation of the coordinate systems: the axes are always parallel to the global coordinate system.

Don't move the hardware only!

If the 3D model has been built identically to reality, the components (robot, table, tool, etc.) must not be physically moved or rotated. A typical mistake is to shift the robot by a few centimeters or “simply” rotate it by 90° because it offers more space. In such a case, the coordinate systems (model vs. reality) will no longer match, and the robot movements will be directed in the wrong direction or to the wrong coordinates. It is crucial that the reference points and orientations remain unchanged!

Avoiding Errors #

A typical mistake is to build the robot and other objects in CAD systems, “assemble” them in the CAD system by overlapping surfaces/edges/points, and then import them into RoboDK.

Here is an example: The robot is twisted, both on its own base plate in the drawing and relative to the coordinate system. Such a drawing is NOT suitable for creating a setup with which you can work quickly and effectively with the RobPathRec tool.

For comparison (just for illustration), the same robot was imported directly from the RoboDK library. Coordinate systems and orientation are correct. There is no random twist to be found in the individual axes.

Importing external CAD robot drawings

For comparison (just for illustration), the same robot was imported directly from the RoboDK library. Coordinate systems and orientation are correct. There is no random twist to be found in the individual axes.

Checking the model construction #

Suppose this arrangement corresponds to your setup. The following directional descriptions refer to the robot’s base coordinate system.

Now move the real robot with the Teach Pendant in X+ direction. The robot should move in the X direction as shown in the figure. Repeat the same with Y and Z directions. The real robot should always move in the correct direction.

If this is not the case, you need to improve your CAD component arrangement / robot arrangement in RoboDK. Drive slowly, safety comes first! The size of the coordinate system can be changed with the “+” and “-” keys.

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