VRC – Vertical Reciprocating Conveyor
Lenze 8400 Highline application
Machine: VRC (Vertical Reciprocating Conveyor)
Description of operation: Car lifts 4000 lb payload to any of 4 levels. Car must be positioned accurately enough to roll loaded pallet jack from floor onto or off of the car. At each level there is gate with a safety latch, a pneumatically released mechanical lock, and a 5 button control station with pushbuttons for each level plus e-stop. At any level an operator can send the car from any level to any level. Here’s what happens:
- Before the car can move all gates must be latched – verified by the safety latch & prox sensor
- Pneumatic cylinders retract the mechanical lock and the retraction is verified with prox sensors.
- Light indicating target floor illuminated at all levels
- The 8400 drive generates torque in the drive motor before releasing the brake so the load does not drop
- Brake releases and car accelerates to full speed and then decelerates and stops in position
- Motor brake engages
- Pneumatic cylinders exhaust and mechanical locks extend – verified by prox switch
- Gate safety latch at target level only is energized to allow gate to be opened
Lenze 8400 Highline drive: Using a VFD rated motor & motor mounted encoder the 8400 controls the position of the car. All logic controlling gates and the mechanical locks is programmed into the drive via Lenze Engineer software. 14 inputs and 10 outputs are required for this application. In order to accommodate this much I/O the drive controls external I/O – Lenze I/O1000 – connected via CAN bus. There is a homing routine for initializing the location and the drive is programmed to remember its position through a power cycle. Programmable user units allow for the positions and homing offset to be set in inches. Programmable user menu allows for easy access to both the homing offset and the individual positions of each level that can be quickly adjusted via keypad. The amount of adjustment required is easily determined with a ruler. The brake control relay is an integral part of the 8400 drive.
8400 Highline; variable frequency drive
- 7 digital inputs – 2 used for encoder feedback
- 4 digital outputs
- 1 programmable relay – used in this case to control brake
- CAN bus is standard on drive (additional communication bus modules available)
I/O1000; remote I/O
- Compact, DIN rail mount
- CAN bus shown – many communication bus modules available
- 8 DI PNP and 8 DO PNP modules used – many different modules available
L-force Engineer; programming software
- Used to program 8400 drive
- Full version allows access to program function blocks, network set-up, establish communication interconnection
- Free version available to program all parameters
- Hot swappable design
- User menu set up to make any required adjustments to individual target positions or adjust the homing offset if the lifting chain stretches due to wear.
Adaptability: This application required external I/O to control several external devices and is a stand-alone system. The 8400 can easily be integrated into a more complex system. It can be triggered to move to pre-programmed targets (like this application) using either the digital inputs or via communication bus. Alternately the target can be written to drive parameters on the fly by logic controller via communications bus.
The positioning & homing applications are written into the drive so a move can be programmed using a few parameters. Acceleration and deceleration are programmed separately and don’t need to be adjusted if the target changes – they automatically adapt the profile to stop at the target position. This reduces the workload of the PLC controlling the overall machine operations. It also allows for a conveyor to be a easily added piece to a system. This same basic setup used in the VRC can be applied to any type of conveyor or machine that needs to move to from 2 to 15 positions. The basic program can be written and then quickly modified with a few parameters to fit the new application.
For more information please contact: Nick Young – [email protected], A R Young Company, Inc. PO Box 111135, Indianapolis, IN 46201 – Phone: 317-263-3800