Monitoring the workspace limit in the opposite conveying direction

Attention

This function may not be used to implement safety-related functions.

As soon as the synchronisation process is completed, the function for automatically maintaining the workspace limit in the opposite conveying direction is activated. This reduces the conveying velocity to prevent crossing the workspace limit in the opposite conveying direction. However, this type of intervention by reducing path velocity can only take place if the movement of the X axis (parallel to the conveyor) in the co-moving coordinate system PCS₁ takes place in the opposite conveying direction. The contour is checked for intersections with the workspace limit.

If an intersection is detected in an NC block, the path velocity in this NC block is reduced in the co-moving coordinate system PCS₁ to the velocity v_conv of the linear conveyor. As a result, the TCP is stationary in the stationary coordinate system PCS₀. Therefore, in this case, the movement of the X component along the contour of this NC block is solely implemented by the movement of the conveyor. The behaviour of this function is shown in the figure below.

The time taken to traverse the contour is increased by reducing the feed rate for the colliding NC segment. However, the increase in machining time can be optimised, as described in the next section.

Operating principle of the end position monitoring function

Optimised workspace limit monitoring in the opposite conveying direction

Optimised end position monitoring can be activated in the master axis by the axis parameter P-AXIS-00555 (conv_sync_optim).

Here too, the programmed contour is monitored in the path preparation function for intersections with the configured workspace limit (P-CHAN-00374).

If an intersection is detected, the optimum braking instant and the corresponding braking profile are calculated so that path velocity reaches the exact conveyor velocity v_conv when the workspace limit is reached.

With linear blocks, this means that the tool comes to a standstill exactly at the workspace limit and remains there.

With circular blocks, the tool is pushed away from the workspace limit due to the tangential velocity on the circle.

Optimised end position monitoring reduces the time required to move along the colliding NC segment since the segment is traversed at the programmed feed rate until the workspace limit is reached.

The behaviour of optimised workspace limit monitoring is shown in the figure below. The star shows the calculated optimum point on the contour at which the conveyor velocity is reached exactly at the workspace limit.

Operating principle of optimised end position monitoring

Notice

Compared to simplified end position monitoring, optimised end position monitoring requires greater computing power and therefore calls for more powerful control hardware.

Fluctuations in conveyor velocities with optimised workspace limit monitoring

It is normal for the conveyor velocity to fluctuate. NC blocks with reduced feed rate due to workspace limit monitoring may cause the configured workspace limits to be crossed.

The parameter P-CHAN-00374 (pos_limit) can be used to configure a position offset of the workspace limit to ensure that the workspace limit is reliably maintained even if fluctuations in conveyor velocity occur. This shifts the monitored workspace limit.

In addition, a safety factor (P-CHAN-00366) can be defined to reduce the velocity and acts directly on the velocity that reduces the feed rate of the colliding segments. The following applies:

v_path= P-CHAN-00366 * v_conv

The value range of the factor is between 0 and 1. A setting of 0.95 has proven to be most effective in practice.