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Product category: Control systems, DROs, etc, for machine tools
News Release from: Mitsubishi Electric Automation Systems | Subject: Control systems
Edited by the Manufacturingtalk Editorial Team on 11 January 2002

Control system copes with difficult
woodsawing

Stenner have revolutionised the cutting process, utilising new technologies from Mitsubishi Electric, to give their new third order cutter (called PK) the edge in the wood cutting industry.

Founded in 1875, Stenner are to wood saws what Hoover are to vacuum cleaners; "People do not buy a wood saw they buy a Stenner" Stenner prides itself in being a top of the range wood sawing equipment supplier and are confident they offer their customers the best in quality products with the highest possible performance

Wood cutting is divided into three main disciplines.

The first is taking trees and turning them into planks of wood or rough sawn timber.

The second processes the rough sawn timber and makes it into smaller sawn timber elements and the final cutting stage is where timber is accurately or fine sawn (down to +/- 0.15mm) to produce items such as Parquet flooring.

It is in this third order cutting marketplace that accurate cutting and repeatability has always been hard to achieve.

However, now that Stenner have revolutionised the cutting process, utilising new technologies from Mitsubishi Electric, to give their new third order cutter (called PK) the edge in the wood cutting industry of the 21st century.

The new PK saw is twice as fast as previous machines while still reducing cut waste by up to 70%.

The saw can vary the waste removal (or Kerf) by automatically altering the saw blades positions.

The significance of reducing cut waste is considerable.

Less waste means more wood available for making product, which translates in to extra hard cash.

Additionally, it should not be under estimated the effect this potentially has on the environment.

By better utilisation of the sawn wood less trees less trees are required to be felled in the first place.

Saws made by Stenner are now used in more factories than timber mills.

The factories are clean, efficient and demand more sophisticated control.

The infeed of the new saw is a continuous driven chain feed conveyor.

The speed of sawing is 50m/s for softwoods and 20m/s for hardwoods.

The speed is adjusted automatically with precise control by a Mitsubishi A500 Variable Speed Drive (VSD).

Cutting speeds have been increased dramatically due to new advances in blade technology.

The PK machine keeps the blade bands under very high tension which is controlled and monitored by a Mitsubishi FX2N PLC.

Additionally, four Mitsubishi A500 VSDs control the blade speeds.

Two drives are allocated per blade band; one for each of the two wheels the band loops around.

The design utilises the A500's speed matching function to synchronise band speed.

Different woods need different cut speeds, so the use of a Variable Speed Drive allows the operators to change wood types and hence cutting speed without having to stop the machine.

The operator selects the wood type on the machine's E910 touch key HMI and the saw automatically sets itself for the next wood type and cutting thickness.

The saw uses a floating datum point when it is started and then calculates and adjusts itself to the required sawing conditions.

The position of the saw blade height is controlled using screw jacks driven by another A500 VSD.

The local position is then fed back to the PLC via a pulse generator connected to the FX2N's integral high speed counter input.

Feedback from the VSDs is also fed into the FX2N PLC using analogue inputs.

The FX2N monitors each drive's frequency and current consumption, aiding in the detection of any problems, errors or inaccuracies that may occur.

Set up, starting and stopping controls (including saw speeds and width cutting of sawn material) are performed on the Mitsubishi E910 HMI.

The large 10.4 inch display area and good viewing angles permits the operator to see the status of the machine from a distance.

Stenner take full advantage of the RS422 connection between HMI and PLC, which allows them to mount the control HMI remotely from the control cabinet, giving them greater flexibility in the overall machine design.

Using the PLC to control all aspects of 'start' and 'stop' ensures the PK saw follows mandatory regulations pertaining to starting and stopping procedures.

This guarantees a safe start up and shut down of the machine, preventing damage to the saw or to operators.

Martin Kolaszynski, Stenner's senior design engineer for the PK machine, says "Stenner delight in offering their customers the latest technology in saws and need to constantly offer the latest technology in control equipment.

We recognised Mitsubishi as a major developer of new automation techniques and partnering with them offered us a cost saving solution over previous control solutions. Request a free brochure from Mitsubishi Electric Automation Systems ...

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