Operation Overview
This section provides an overview of the operations of the Part Feeding option.
Part Feeding process
The Part Feeding process is a sequence of operations which involves automatically controlling the vision system and feeder.
You can start the Part Feeding process by executing the PF_Start command from your program.
The Part Feeding process is as shown below.
- Identify parts in the feeder
Use the vision system to check the quantity and distribution of parts on the platform. - Process parts
The feeder is controlled and parts are moved in order to make it easier for them to be grasped by the robot. When the parts are low in quantity or there are none remaining, the PF_Control callback function is invoked to supply parts from the hopper. - Move the robot
The parts coordinates queue (a list of coordinates of parts in the feeder) is generated. The PF_Robot callback function is invoked to perform pick/place of parts.
The Part Feeding process can be stopped by invoking the PF_Stop command from your program.
Supplying Parts to the Feeder
The following methods are used for supplying parts to the feeder.
- Using the hopper
- Manually supply
Quantity of Parts Supplied to the Feeder
The quantity of parts supplied to the platform is an important element in determining operation cycle time.
- If there are too many parts:
An excessively large quantity of parts negatively affects the cycle time due to parts overlapping and the need to vibrate the feeder numerous times. - If there are too few parts:
An excessively small quantity of parts also negatively affects the cycle time because you have to supply parts to the platform numerous times. The cycle time is negatively affected.
Accordingly, there is an ideal quantity of parts to be supplied (quantity of parts on the platform after feeder operation). This quantity can be calculated during feeder calibration.
The three methods (timing-related) described below can be used for supplying parts to the feeder.
Run-Out Feeding
Parts are supplied from the hopper to the feeder only after all the parts in the feeder have been fed.
We recommend using this method for parts that are sensitive to vibration (easily affected by vibration) because retention time of parts in the feeder maintains fairly uniform. However, this method increases the cycle time because it reduces the average quantity of parts that can be retrieved by a robot during one feeder operation.
Add-In Feeding
Parts are additionally supplied from the hopper when all the parts in the feeder that can be retrieved are depleted.
Cycle time is shortened because the average quantity of parts that can be retrieved by a robot during one feeder operation is relatively large, thereby improving efficiency. However, this method cannot be used for parts that are sensitive to vibration because the parts retention time can be long.
Parallel Feeding
This method is used together with a function for specifying the pick locations of parts.
While the robot is picking parts, parts are added to the region on the opposite side of the parts picking position. This method decreases the cycle time because the average quantity of parts that can be retrieved by a robot during one feeder operation is increased. Cycle time is further reduced because both the hopper and robot can operate in parallel (simultaneously). However, this method cannot be used for parts that are sensitive to vibration because some parts remain in the feeder for a long period of time. It is necessary to write your own program so that the hopper and robot can operate in parallel.
Feeder Control
The Part Feeding option is executed by selecting feeder operation automatically depending on the conditions of the parts in the feeder. This makes it easier for the robot to grasp parts.
Feeder operations are described below. Explanatory drawing shows the outline. It might be different from actual movement.
Flip and Separation
Space parts out evenly on the platform. Keep an appropriate amount of space between the parts so they can be easily grasped by the robot.
There may be an operation to move parts to the center before flip and separation. This is called centering.
Shift
Moves all parts in one direction while maintaining the spacing (distribution) of the parts.
Moving parts closer to the place position reduces the robot movement distance and improves the cycle time.
Shift can be performed either forwards (closer to the pick position) or backwards (further from the pick position).
Positions for Picking Parts on the Platform
The robot can pick parts from two positions: "Pick from Anywhere" and "Pick from Region".
The most efficient position for your system depends on your equipment configuration, including the parts, end effector, and hopper you are using. Have the machine perform some actual operations, retrieve the logs, and check to see which position is more efficient.
Pick from Anywhere
Picking is performed for all parts on the entire surface of the platform.
Select this if parts are large for the size of the platform (e.g. approx. 2 cm^2 or more for the IF-240).
Pick from Region
Picking is performed in a region near the place position.
Using this method, shifting of parts to the picking region is performed automatically according to the distribution of parts. Also, parts can be supplied simultaneously with the robot’s operations in any area where picking is not performed. (It is necessary to write your own program.) Use of this function generally reduces the robot cycle time in comparison with the pick all method.
Preventing End Effector and Platform Interference
To prevent physical interference of the end effector by the platform, it is necessary to specify the region where it is possible to pick parts in the feeder so that it falls within the outer circumference of the platform. That distance can be easily specified using the Part Feeding option. Parts that are detected to be too close to the feeder tray are not added to the part queue for pick up.