Keeping to the straight and narrow
02 August 2012
Whether you need a linear guide or stage for precision positioning in a laboratory, a heavy load bearing system for industrial assembly or even a positioning system that is certified for use in a hazardous environment, there may be something here for you. Les Hunt reports.
Looking for a system that provides precision positioning in a laboratory or industrial test and inspection or assembly application? Then Aerotech's versatile MPS75SL series miniature linear positioning stages, at just 75 mm wide and with travel ranges from 25mm to 100mm, are well worth investigating. This small footprint, low-profile stage uses the latest generation of miniature 1mm pitch precision ball screws, high resolution encoders and anti-creep crossed roller bearings for ultra smooth, reduced error motion.
The MPS75SL is available in a choice of standard precision (+/- 4 micron) or with Aerotech's HALAR linear error-corrected certified precision (+/-1.5 micron) for the 100 mm travel version. There’s a choice of brushed dc motor or open loop stepper motor drive, both offering a linear positioning resolution of 0.1 micron.
Despite its small size, the MPS75SL has a 15kg direct load rating, which allows a practical offset load factor thanks to the choice of crossed roller bearings - particularly important for maintaining high stiffness in multi-axis configurations. Direct carriage to stage body mounting is provided for X-Y configurations, and optional right-angle L-brackets are available for vertical Z-axis mounting. All multi-axis configurations provide XY, XZ or YZ orthogonal precision to 5 or 10 arc-sec.
Another recent addition to Aerotech’s MPS linear stage family is the MPS50SL, which is just 50mm wide and comes with travel ranges of 25mm or 50mm. MPS stages can also be supplied with modified materials, surface preparation, hardware venting, lubrication and other features that render these systems suitable for use in high-vacuum applications (down to 10-6 torr).
For larger scale, heavier duty assembly operations, MiniTec can now supply a new range of linear positioning actuators that is compatible with its ProfileSystem range of machine framing and building components. The precision ball screw driven Linearmodul LMS provides up to 1,400mm of travel and is housed in a 90 x 90mm extruded aluminium profile with standard T-slots on 45mm centres. As well as facilitating rapid frame configurations, these lateral slots also provide fixing points for datum sensors and limit switches.
Linearmodul LMS is aimed at those applications that require accuracy coupled with durability, plus the capability for installation in a tight space. The system is suitable for large area gantry, pick-and-place and robotic handling duties, either as part of a complete MiniTec machine frame system, or as separate components, complete with motors, drives and motion controls – all of which are available from MiniTec’s portfolio.
The standard LMS product comes with lubricated-for-life dual linear rail ball bearings with matched carriages that support loads in all directions for speeds of up to 1.6m/s (16mm diameter x 16mm pitch ball screw option). Other ball screw pitch options include 4, 5 and 10mm variants, while a T7 accuracy grade option features a preloaded nut system for 0.04mm axial play and repeatability to 52 microns per 300mm of travel.
Another offering for those OEMs seeking linear positioning components for restricted space applications is Parker’s MX45S, a 45mm wide miniature screw-driven positioner based on the award winning MX80 family. Available from Parker’s motion partner, Micromech, the MX45S features anti-cage creep cross roller-bearings and a choice of high-efficiency lead screw or high-precision ball screw, both of which are capable of producing 40N of thrust at linear velocities of 20mm/s and 30mm/s respectively. The MX45S will position up to 7kg of normal load on currently available standard travel lengths (5mm, 15mm and 25mm).
Suitable for biomedical imaging, fibre optic alignment, semiconductor inspection and laser diode research, the MX45S is best deployed on applications requiring small incremental movements, micron repeatability, smooth motion and high stiffness - all in an ultra-compact package.
Japanese manufacturer, Misumi is also endeavouring to reduce the size of its components in order to meet the current trend towards miniaturisation in automation technology. The company’s latest linear unit, the LX15, is just 20.2mm tall, only 44mm wide and in lengths of between 75 and 200mm. This makes it considerably smaller than Misumi’s previous smallest linear guide, the LX20 (27 mm tall, 52 mm wide and between 80 and 300 mm long).
The LX15 can be supplied as an open or closed model, and in two precision classes, with a positioning accuracy of ±20 micron and a repeatability of ±3 micron. You can choose whether or not to have Misumi’s MX lubrication unit and standard or low-particulate lubricant included as part of the package. MX comprises a special type of polyurethane saturated with lubricant, and can extend periods between planned maintenance operations.
Misumi claims the most basic model (ie no cover, standard lubricant, no lubrication unit) can be supplied within eight days of making an online order. Units with optional extras such as the low-particulate lubricant, superior accuracy and a lubrication unit included, can be with the customer within 13 days of receipt of the order.
Contrary to what one might expect from a parts ordering operation, Misumi’s catalogue ordering service neither imposes a minimum order quantity nor applies a small-volume surcharge. And if you happen to be located in Germany, delivery is free - even for orders of just one item. The new LX15 linear guide can be ordered directly from www.misumi-europe.com/lx15.
Hazardous area installations
Using its IEF Werner linear motion product programme as a basis, R A Rodriguez is able to engineer linear motion systems that provide a variety of characteristics – rigidity, high accuracy and precision, high load bearing and high speed – not just for designers of standard industrial applications, but now also for those designing and specifying systems for use in explosive atmospheres.
Individual components through to fully assembled single- and multi-axis positioning systems can now be configured for use in Zone 2 (gas) and Zone 22 (dust) environments. For this purpose, R A Rodriguez takes elements from its standard IEF Werner product range and combines them with components such as planetary gears, servomotors and power chains that have appropriate certification.
A typical job undertaken recently involved installation of an IEF Werner Module 105 for safe parts handling during a painting process. Suitable for space restricted applications, this positioning system was fitted with a special electrically conducting toothed belt to prevent electrostatic charge accumulation.
A special IEF Werner Module 80/15 was also specified for a diesel injection pump testing station. This versatile linear product was designed to provide high dynamics and good running characteristics, and for this application it formed the basis of a system that also included appropriate certified planetary gears, a servomotor with absolute encoder, servo amplifier and cable set.
And in yet another special application, an IEF Werner two-axis positioning system is used to transport components above a basin filled with inflammable liquid. It was similarly equipped with ATEX compliant driveline components, with control systems supplied for use outside the hazardous area.