MINISTAGES (Top)

Mini motion stages consist of three elements: the stage, the screw, and the motor. Stages can be 2 styles: external or internal screw. Either the screw is part of the motor or is part of the stage. The motor can be a " linear actuator" with the screw as the motor's shaft or a standard NEMA frame motor which bolts onto the internal screw stage's mounting face and shaft coupler. Linear stages (tables) are an off-the-shelf solution.

From more custom requirements and a cost savings, a linear slide or micrometer slide can be converted to motion control by using a stepper motor linear actuator. See the attached drawing. Standard linear tables cost more and tend to be longer because of the motor mount bracket and shaft coupler. Linear actuator conversions are simpler but have the disadvantage of the screw sticking out of the back of the motor. However, the screw can be shortened for just the maximum amount of travel.

The choice of screw sets the resolution and speed of the system; this is typically a trade-off. High resolution screw slows the overall speed of the system. Speed and resolution are also selected by the choice of motor and motor driver. Typical machine screw pitches for step motor linear actuators are: 2-56, 4-40, 6-80, 10-32, 1/4-16 (one or two start acme), and 1/2-10. Step motor resolutions are 200, 400, 800 (size 23 only). The motor drivers can be in full, half, quad, or microstep. Note that microstep, in theory, would be an overall solution to resolution except for the problem that microsteppers do not give equally spaced steps (microstep spacing error).

For example:

(1) 6-80 pitch screw x 800 spr motor x 1/4 step driver (3200 spr) = 256000 step/inch or 0.0000039 inch/step. Therefore, with a top speed of 20000 pulses/sec from the motion controller (CY545 @ 11 Mhz), the max speed is 12.8 sec/inch.

(2) 10-32 pitch screw x 200 spr motor x 1/1 step driver (200 spr) = 6400 step/inch or 0.000156 inch/step. Therefore, with a top speed of 20000 pulses/sec from the motion controller (CY545 @ 11 Mhz), the max speed is 0.32 sec/inch.

Note: 800 spr Size 23 motor with 6-80 screw is $363.00 in 1-9 each; 4 weeks.

400 spr Size 17 motor with 6-80 screw is $231.00 in 1-9 each; 4 weeks.

200 spr Size 17 motor with 10-32 screw is $136.00 in 1-9 each; 2 weeks.

STEPPER MOTOR DRIVEN PERISTALTIC PUMPS (Top)

VIEW PICTURES OF THE PUMP HERE

Step motor driven peristaltic pumps are intended for scientific and industrial applications requiring precision metered dispensing either at constant flow/volume or one-shot operation. The step motor pump operates under positional control rather than timed interval. Resolution is typically 1/200 (fast dispensing) to 1/3200 (minimum pulsation) of a pump revolution per step . Speed control is in steps per second and normally ranges from 0 to 8000 sps (10 revs/sec). Available in NEMA 23 or 34 frame sizes and multiple stack lengths, steppers offer torques from 40 to 1000 oz. in. Step motors feature permanently lubricated oversize ball bearing suspension. The mean time-to-failure of a stepper is infinite.

Steppers are synchronous DC brushless devices and offer distinct advantages over traditional pump motors including: no brush contamination, unlimited stall, adjustable torque (over-pressure protection), safe low-voltage operation, and direct connection to computer control. Steppers are bi-directional. This feature enables programmable suckback, purging, and mixing during liquid dispensing. In vacuum pickup applications, blow-off capability eliminates the requirement for bleed valves. Step motor amplifiers feature reduced current during standstill (minimum product heating), built-in braking (no back pressure creep), or no torque (free mode) as required.

Step motion pump systems typically include an onboard microprocessor referred to as the "motion controller." Motion controller features include ramped acceleration-deacceleration (no foaming), on-the-fly velocity control (pressure regulation), and general purpose input/output (I/O) functions. The outputs control solenoids, valves, relays, and indicators; the inputs read switches and sensors for temperature, pressure, flow, or product. Motion controllers support stand-alone execution of preprogrammed routines which can be triggered by power-on, external switches, or PLC relays.

Step motion controllers connect peristaltic pumps to any computer, laptop, smart panel, industrial network or even the WEB. Networked controllers support multiple pump stations either as groups or individual stations throughout a process line. Multiplexed controllers support ganged applications such as paint mixing, chemical prescriptions, food recipes, or solution preparation.