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Product category: Stepper and Servo Drives, Motors, Controls
News Release from: Lenze | Subject: Servomotors
Edited by the Engineeringtalk Editorial Team on 26 August 2002

Driving forward drug discovery

A sophisticated new machine that dramatically speeds the testing process for new drugs makes extensive use of servomotors to automate the process.

TTP Labtech supplies a wide range of products to the healthcare and pharmaceutical sectors With the help of drive specialist Lenze, the company has developed two new machines that allow drug companies to significantly raise efficiency levels

As controls for the introduction of new drugs become more rigorous, pharmaceutical companies increasingly require more extensive and thorough drug development and testing.

In light of these demands, Cambridgeshire-based TTP Labtech (part of The Technology Partnership Group) has developed a sophisticated new machine that dramatically speeds the testing process.

The TTP machine consists of two parts: 'comPound', a storage and retrieval unit, and 'comPiler', a modular unit that prepares chemicals for test.

Both machines have been developed with the help of Lenze - providing TTP Labtech with motion control expertise.

The comPound machine is a library of chemical compounds held in small phials known as 'tubes'.

Up to 100,000 tubes can be stored in one machine, with a positive pressure nitrogen environment and at a constant temperature of -20C.

The design requirements were to achieve retrieval of any tube inside a target time of four seconds, although with the help of software that optimises the retrieval sequence, faster times can be achieved.

The Design and Development Engineer on the comPound project, Simon Tullett, comments: "We identified a market requirement for a fast storage and retrieval machine, and set out to achieve a design that will meet customer requirements even in five and 10 years time.

The development process required us to innovate in areas such as the drives, which had to be optimised for speed, accuracy, space and low weight.

Lenze worked with us as a partner for over 18 months, bringing in both new products and new ideas".

The heart of the comPound machine is a stack of 26 carousels, each a precision plastic casting holding over 3800 of the tubes.

Two Lenze servo motors are used to rotate the carousels into the required position, each motor driving 13 carousels.

The carousels are free to turn on the central axis, driven on their outside diameter by a double-sided tooth belt.

Requirements for positional accuracy meant the backlash in the drive had to be minimised.

Lenze also supplied bevel gearboxes with a reduced backlash of five arc minutes fitted to each of the servomotors, and connection from the drive shaft to each of the carousels is achieved through Lenze pole face clutches.

In addition, a Lenze spring-applied brake provides a holding torque to keep the carousel in its driven position.

While Lenze supplied all the comPound drive equipment, there was no single source deal; instead products were selected on their own merits.

For example, Lenze addressed the problem of mounting 13 clutches onto a 2m long shaft driven by each servomotor.

Shaft rigidity was important for accuracy as was compact dimensions and weight, to keep down the floor loading.

The solution was a 20mm plain shaft with keyless connection to the clutch using ETP locking bushes.

The result is backlash free and avoids high shaft stresses, allowing the shaft diameter to be kept to a minimum.

Lenze produced a special clutch to suit the friction connection of the ETP bush.

The two servomotors are driven by Lenze 9321 drives with built-in positioning software.

These were chosen because of integrated CAN fieldbus and the accuracy of positioning.

The comPound machine is controlled from a PC and CAN is used to communicate with the drives, with I/O and control cards developed by TTP Labtech.

Having the positioning software in the drive allows decentralised control, offering the benefits of reduced communication traffic, reduced PC processing, and less programming time.

Support provided by Lenze included a three-day training course on the software, supplied as a free option to servo customers.

Finally, the drives were supplied without heat sinks to save panel space, with the cooling requirements being met by the thermal mass of the mounting surface.

During operation, tubes are identified from a database and addressed as if on a computer hard disk.

The clutch on the corresponding carousel is engaged and the brake released, followed by the servo system indexing it round to exactly the position where the tube can be unloaded.

By driving the edge of the carousel, accuracy better than 2arc-min is achieved.

The tube is then picked out and delivered automatically to an x-y table on the comPiler machine.

After a tiny quantity of chemical has been taken from the tube, the process is reversed and the tube is returned to its position in the comPound carousel.

Up to 12 comPound machines can be networked to form a library of 1.2 million chemical compounds.

TTP Labtech is leading the world with this machinery, allowing pharmaceutical companies to automate and vastly increase the speed of drug development.

The machines have recently been exhibited in Vancouver and New Jersey, and six comPounds have already been delivered to the US.

The success of comPound and comPiler can be attributed to the high level of co-operation between the machine maker, TTP Labtech, and the drive supplier, Lenze. Request a free brochure from Lenze ...

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