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Product category: Industrial Drives/Controls
News Release from: Lenze | Subject: Servo PLC model 9323 rated at 3.9A
Edited by the Engineeringtalk Editorial Team on 05 March 2007

Servo drives machine created in five
months

Europack set about designing a high-speed servo drives machine to handle up to 40 cartons per minute.

Smart Karton owns the patents on a cardboard carton that incorporates a film to wrap the product, saving on packaging material and reducing waste To meet urgent demand for a new design of production machine, Smart Karton turned to packaging specialist Europack, a division of the Bradman Lake Group

Europack was able to draw on extensive experience on carton forming and film handling.

In a partnership with drives specialist Lenze, a high-speed servo drives machine was designed and built in only five months from the concept stage.

The Smart Karton concept is based on a special plastic film that is glued firmly to the base of the box and glue-tacked lightly to the closing flaps.

In fact there are two versions, both using boxes that are erected using locking tabs.

The Commercial Karton has a single layer of film that is folded over the product by hand and then tightened by a heat shrink process.

The Retail Karton has a special two-part film with adhesive between the two layers.

Intended for either commercial or domestic use, heat shrinking is not needed.

The film layers are peeled open and then the inner layer is pressed by hand onto the product.

The adhesive hardens to fix the film in position and firmly hold the product.

Smart Karton are ideal for shipping goods in boxes with base dimensions between 150 and 500mm, for example books, small electrical items, or decorative gifts.

Apart from the product and the layer of film, there is nothing but fresh air in the box.

So use of packaging material is cut and waste disposal problems reduced.

The glued film is so effective that transit damage is minimised.

Field tests have shown that smaller box sizes can be used, in one case reducing warehouse shipments from 7 to 4 vehicles per day.

These advantages have already triggered a strong demand, particularly in the United States.

The Bradman Lake Group's brand Europack set about designing a machine to handle up to 40 cartons per minute.

A stack of pre-cut boards is conveyed to the in-feed de-stacker.

Here a servo driven pusher mechanism presents individual boards to the in-feed conveyor, correctly gapped to the preceding board.

The servo-driven in-feed conveyor transports the board under the glue guns and on to the compression rollers which are also servo-driven and at that point the film is applied to the board under tension.

A fourth servo drive controls the rotary knife which cuts the film between the boards in such a way that there is a film overlap to make it easy for users to apply.

The finished boards with glued film are stacked and removed by an out-feed conveyor.

The machine design process began with creation of a 20-page specification, developed between the Technical Director of Europack, David Burlingham, and the Engineering Director of Smart Karton, Al Moore.

This specification defined the process, the required performance, main controls and safety functions.

At this early concept stage the packaging specialist involved Lenze, who it knew from previous experience were capable of putting together a package of drives, servo geared motors and motion control software.

It was clear from the outset that the servo technology was critical to achieving the performance targets.

After a collective design review, a team was established of three mechanical and two electrical designers at Europack with two control and automation specialists from Lenze.

Whilst the the Bradman Lake Group's engineers worked on the machine structure, glue process, film handling and external controls, the Lenze engineers established a detailed specification for the drives, wrote the software, gave drive training and helped with commissioning.

The successful result of this teamwork was a machine running after just five months from the concept stage and approaching target performance one month later.

With board speeds of up to 50m/min, precise and smooth handling from servo drives was required.

Lenze specified the Servo PLC model 9323 rated at 3.9A.

This is a drive with a built-in powerful PLC running programs to the standard IEC61131-3.

The control concept requires each drive to handle its own motion control whilst a central PLC looks after safety functions, the glue patterns and the conveyors.

The four servo drives communicate between themselves with an integrated CAN system bus, and each drive is fitted with a DeviceNet module to communicate with the central PLC.

The system can be considered a hybrid, with a mix of centralised and decentralised control.

All four servo axes are driving Lenze synchronous geared motors of frame sizes 56 and 71 with type GKS helical bevel gearboxes.

The high efficiency of the gearboxes at 96% and low backlash at about 10 minutes of arc make them well suited for servo motors operation.

The pusher axis is a good illustration of decentralised motion control.

As each new board is entered by the operator on the HMI, a new profile is created within the drive based on the board length and the required gap between boards, which can be set between 20 and 100mm.

The drive then directly controls the vacuum heads to pick up a new board from the stack before beginning the calculated profile.

The pusher drive fine tunes the motion profile to allow for small variations in timing in the operation of the vacuum heads.

The drive accelerates the board smoothly to a speed above the line speed to catch up with the preceding board.

As the required gap is achieved the drive slows the board down to line speed and then runs in gearlock.

Once the board is taken into the in-feed rollers, the pusher drive returns at high speed to the start position.

The in-feed is the master drive on the Bradman Lake Group's machine.

It is programmed to stop so that the board is always under the compression rollers in order to maintain the film tension.

The compression roller drive follows the in-feed except during start-up when it waits for an edge of the next board and ensures the gap between the boards is maintained.

The knife axis is another example of effective decentralised drive control.

The synchronous helical bevel geared motor drives a single-blade rotary knife of diameter 160mm.

The knife speed profile is calculated for each new board.

The drive accelerates the knife into position and then cuts at a speed synchronous to the line speed.

This method ensures high accuracy and means that a single knife can handle all sizes of board.

There are six glue heads on the machine.

Four are high-capacity twin nozzles that apply a carton-specific glue pattern on the base with different adhesives according to customer specifications.

The remaining two single heads apply a light tack of glue to the carton flaps.

Lenze did not only supply the servo system.

All the other ac geared motors were supplied too, including worm and helical models for the out-feed, stackers and conveyors.

The in-feed destacker and out-feed stacker are specified to handle up to 500kg.

Lenze supplied 1.5kW helical bevel geared motors, chosen to withstand high starting torques and to run efficiently.

These geared motors inch the stack up and down with position feedback from an incremental encoder mounted on the output shaft and speed control from Lenze 8200 vector inverters.

The machine, designed and built by the Bradman Lake Group's brand Europack, reads bar codes from the boxes and records a detailed profile of the output.

An onboard wireless modem allows this data to be transmitted to the machine owner.

In addition the modem can interrogate the drives, allowing diagnosis of faults and potentially correction without travel to site.

The software for new box formats can be downloaded remotely.

Europack Technical Director David Burlingham sums up the development process "All the servo sizing and programming worked from day one so our partnership with Lenze was a great success".

"The machine is up to specification inside six months and we are already looking at the next generation that will run faster".

"For us as part of the Bradman Lake Group, this machine is unusual as it is a process machine, not our normal packaging".

"But it is a good fit to our expertise available in the wider group, for example film handling, board handling and carton erecting". Request a free brochure from Lenze ...

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