Product category:
Actuators, motion systems, etc
News Release from: Huco Dynatork | Subject: Kerk lead screws
Edited by the Manufacturingtalk Editorial
Team on 02 September 2004
Leadscrew design for stages saved
ballscrew costs
Microscope maker discovered that by comparison with a ball screw option, a leadscrew design brought significant cost savings with only a fractional increase in backlash.
Although price was the prime reason for Prior Scientific choosing Huco's Kerk lead screws for its OptiScan microscope stages, the company discovered that by comparison with a ball screw option, Kerk brought significant cost savings with only a fractional increase in backlash The automated OptiScan X-Y positioning stage is designed for routine imaging applications where accuracy is not the main operating criterion
This article was originally published on Manufacturingtalk on 25 Feb 2000 at 8.00am (UK)
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It was introduced to replace standard manual stages and its movement is either controlled by joystick or automatically using a pre-programmed sequence.
Whilst accuracy is not critical, minimal backlash is, as this movement is magnified under the microscope optics.
If the backlash is excessive, it makes it very difficult for the operator to position the sample using the joystick.
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Prior Scientific is unique in its field.
It is the UK's sole remaining manufacturer of microscopes whose headquarters are five miles south of Cambridge.
The company's commitment to offering optimal solutions has led to the development of a wide range of quality microscopes, motorised positioning stages and related accessories.
All products are manufactured within an ISO 9001:2000 environment.
Stuart Jarvis is the company's Project Planning and Resource Manager and responsible for the development of new products.
"Rack and pinion drives were used on our previous OptiScan stage," he explains.
"Although inexpensive to manufacture, they were difficult to set up to achieve minimal backlash.
They were also subject to a high degree of wear." Prior Scientific uses ground, grade 3 ballscrews on its ProScan high-end stages, but their high cost was not acceptable for the OptiScan stages.
Stuart Jarvis continues, "We are happy with the standard accuracy of the Kerk leadscrew.
If any of our customers require greater accuracy then we offer the ProScan range." Accuracy of the OptiScan stage may not be critical, but as Prior Scientific has a number of customers who build OptiScan stages into their OEM applications, the quoted accuracy must be true.
If there was a reduction in accuracy of the lead screw, this may compromise the quality of the resultant system.
The published positional repeatability with Kerk is to within 0.0013mm and standard lead accuracy is better than 0.0006mm/mm.
Lead accuracy is available to 0.001mm/mm with optional individual screw mapping verified by laser interferometer.
The special thread form of the Kerk lead screw has been developed for maximum life, quiet operation and compatibility with Kerk's patented anti-backlash nut, a crucial element for Prior Scientific.
This unique nut does not require high spring forces to maintain bi-directional, anti-backlash characteristics.
The Kerk assemblies therefore have a low drag torque, another factor in Prior Scientific's choice.
This is important as the stages are driven by small low torque motors to keep the overall dimensions of the mechanism to a minimum.
Huco can supply standard off-the-shelf Kerk configurations or as custom-machined assemblies. Request a free brochure from Huco Dynatork ...
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