Larger frame Exlar K90 actuator offers inline or parallel motor coupling

Ideal for low cost food packaging applications where users may want to use their own servo motors like Siemens, Rockwell, Baldor or similar, Exlar’s K series provides long life and is available as standard in an IP65-rated ingress protected enclosure. Roller screw linear actuators provide an efficient modern alternative to hydraulic or pneumatic units in a much more compact, low maintenance format, without the contamination or noise problems. The K series offers the option of two grades of planetary roller screws 'rolled satellite M and X grades' along with an option for an ACME screw.

A roller screw is a mechanism for converting rotary torque into linear motion, in a similar manner to acme screws or ball screws, but the differentiating factor is that roller screws can carry heavy loads for thousands of hours in the most arduous conditions. This makes roller screws the ideal choice for demanding, continuous-duty applications, or giving extremely long life in general purpose applications. Olsen Engineering has already won a large OEM customer for the newly launched K90 who realised the advantage a dynamic load rating of 51kN, with low capital investment.

“The K90 drive motor can either be coupled inline or in parallel mount using a 1:1, 1.5:1, or 2:1 ratio belt or any custom ratio belts,” said Piers Olsen, sales and marketing director for industrial automation at Olsen Engineering UK. “We request a drawing of the drive motor to be used and then we design and manufacture the adaptor plate and housing to suit the motor, coupling and belt to be used.”

A recent technical release from Exlar states that since their belts are designed for four times the peak rating of the actuator they are extremely reliable and more efficient than a gear drive system.

Olsen adds: “The K90 has internal anti-rotate sliders in the form of a precision nylon coupling running on linear guides inside the frame designed to protect the roller screw mechanism in the event of 1.25 times the peak recommended input torque. It has a comprehensive choice of coating options including a smooth food-grade extrusion, white epoxy FDA approved, electroless nickel salt water rated and Type III hard coat outdoor use, and comes as standard with black anodised aluminium end caps.”

The main rod material is stainless steel tipped with electroless nickel-plating suitable for food industry and washdown locations, with full stainless steel option available. While the K60 handles a maximum force of 6kN at a speed of 420mm per second or 3kN at 833mm per second based on a 5,000 rpm input speed, it is possible to over-speed at 7,500 rpm up to 400mm travel, and also comes in a 950mm travel version. A non back-driving acme screw option provides a low cost solution for low-duty applications, without the need for fail safe braked motor option in high load vertical installations.

The newly released K90 handles force to 15.6kN at 250mm per second based on a 3,000 rpm input, and 7.8kN at 500mm per second, and again it is possible to over-speed to 5,200 rpm up to 800mm.

“You have to be mindful of over-speeding at longer travel lengths, because this can result in a torsional whipping effect as the actuator accelerates and decelerates,” continues Olsen. “It is possible to use a 2:1 belt to reduce the motor size. Also the maximum radial loading reduces at longer actuator travel lengths (up to 2m option available).

“If the inline coupling option is selected, we have designed a bellows compression coupling to connect the drive motor to the actuator. These low-friction units incorporate a G9-rated 0.2mm backlash in the M series and 0.1mm in the X series and 200µm/1000mm lead accuracy, operating at a temperature of up to 80 degrees centigrade.”

Mounting options include rear-clevis mount, front or rear flange mount, front or rear angle mount, foot mount and trunnion mount. Because the aluminium extrusion has grooves in all four sides of the frame, it is possible to slide the trunnion and foot mounts to any position as needed for the application. It is also possible to mount it directly on the front face plate of the actuator including ISO63 and other pneumatic cylinder standard dimensions for ease of retrofitting.

“You can have limit switch options, and we supply the clevis pins and the front spherical rod eyes,” concludes Olsen. “We can supply Exlar SLM rotary servo motors with connectors to match the drive manufacturer’s standard cables and with rear clevis for inline mounting for inline filling applications, which is quite unique. Also a front protective bellows option is useful in dirty environment to offer additional protection to the front seal assembly.

“The whole philosophy of the K series is to design and produce a low cost actuator to compete with ball screw mechanisms while still providing two to three times the travel life, together with advantages such as a preloaded angular zero-backlash bearing which is heat-shrunk rather than glued, IP65 as a standard, also Food Grade, Cleanroom and low temperature grease options for -40◦C operation, lower noise, faster accelerations and reduced risk of Brunnelling on pressing & sealing applications.”

Exlar carry stocks of all common travel lengths so standard production times are 3 weeks. For OEMs, Olsen also can carry local stocks of preconfigured part numbers - all part of the service.