Pneumatic vacuum generators (Venturi ejectors) and pneumatic actuators are both compressed-air devices, but they convert air into different outputs: an ejector produces a negative pressure (vacuum) at the suction port, while a pneumatic actuator produces a linear or rotary mechanical force on a load [S3].
On a typical pick-and-place station the two are used together — an ejector grips the part, an actuator moves it — so the engineer's first task is sizing each on its own metric: suction flow (l/min or m³/h) for the vacuum generator, and force/stroke (N, mm) for the actuator [S3][S7].
Two technologies, one air supply
Schmalz categorises vacuum generators into pneumatic (ejectors, vacuum units) and electrical (pumps, blowers), and gives all nominal suction rates referenced to 1,013 mbar ambient pressure and 20 °C ambient temperature [S3]. Ejectors work on the Venturi principle, are split into single-stage and multi-stage (eco-nozzle) types, and are chosen when short cycle times and direct-installation compactness matter [S3][S7].
Pneumatic actuators — cylinders, rotary vane, grippers — convert the same shop-air pressure (typically 0.4–0.8 MPa / 4–8 bar) into thrust or torque, and are specified by bore, stroke, and load. Suction capacity, not pressure level, is what differentiates a vacuum ejector from a cylinder on the same manifold.
Suction flow and ultimate vacuum: ejector class numbers
Gimatic's VN oil-free Venturi ejector family runs from 22 g to 183 g body weight and operates across 0 °C–60 °C, suiting it to be mounted directly at the gripping point [S1]. The OVEL lubricated series reaches an ultimate vacuum in the −1 mbar to 1 mbar band (essentially atmospheric reference), with a 0 °C–50 °C window and IO-Link for parameterisation [S1].
For deeper vacuum, multi-stage cartridge ejectors like the EJ-MEDIUM (2.4–19 g, ultimate −90,000 to −73,000 Pa) and EJ-LARGE (15–84 g, same ultimate band) are specified, and the EJ-BA pump version reaches −94,000 to −73,000 Pa in a 75–189 g anodised aluminium body [S1]. For higher continuous-duty flow, Becker VT 4.x rotary vane pumps deliver 1.9–9.1 m³/h at 150–400 mbar ultimate and 0.09–0.44 kW power, with integrated regulating valve and self-lubricating graphite composite vanes [S1].
Force, stroke, and cycle rate: actuator class numbers
Where the ejector is sized in l/min, a pneumatic actuator is sized in N. A 50 mm-bore double-acting cylinder at 6 bar develops roughly 1,180 N theoretical thrust; at 8 bar about 1,570 N — values that scale with bore² and supply pressure. The VOLUMEC RM01 manipulator demonstrates the actuator side at full system scale: 100 kg payload capacity, 0°–180° head rotation, pneumatic drive with integrated gripping tool, vacuum, clamping, or magnet end-effectors [S2].
Actuator cycle times drop as bore shrinks and stroke shortens: small grippers routinely hit 50–100 ms open/close, while a 100 kg manipulator arm on a column lift runs at deliberately slower, human-paced speeds for ergonomic loading [S2]. The Mindman VH/VS simple ejector line sits on the other end of the spectrum — push-in fitting, valve-direct mounting, sized to convey workpieces rather than position them [S8].
Decision matrix: when to spec which (and when to spec both)
Use the matrix below to route the requirement before opening a catalogue. If the task is "hold a smooth, flat, airtight part during a move", a pneumatic ejector is the right primary spec — pick VN/OVEL for light/medium suction or EJ-MEDIUM/J-LARGE for deeper vacuum at low mass [S1]. If the task is "push, lift, rotate, clamp" a part, the spec starts with a pneumatic actuator sized on force × stroke [S2].
On a single station that does both, the Pisco VY unitasking ejector integrates the ejector and the blow-off (vacuum-break) valve in one PBT resin body, RoHS2-compliant, simplifying wiring and reducing the pneumatic valve actuator count on the manifold [S4]. The trade-off is fixed function: a VY does one job, while separate ejector + 3/2 valve + silencer + filter lets you retune each. For high-cycle electronics or pharmaceutical lines the integrated path wins on footprint; for job-shop builds the discrete path wins on flexibility.
Compressed-air demand and energy budget
Ejector air consumption is governed by nozzle size and duty cycle: a typical single-stage Venturi pulling −60 kPa will consume 20–60 l/min of shop air per generator, and that figure roughly doubles when you add a vacuum-break pulse. Schmalz's eco-nozzle technology is explicitly designed to cut this air consumption while keeping suction rate up [S3].
Electrical vacuum generators (pumps, blowers) skip the compressed-air line entirely, which is decisive where no plant-air exists or where high suction capacity is needed beyond what ejectors deliver [S3][S7]. The Becker VT 4.x oil-free rotary vane pumps, at 0.09–0.44 kW, sit in that electric-vacuum zone and are rated for continuous duty in the rough-vacuum range [S1]. Actuator-side air cost is more linear: roughly 1 l/min per cm² of bore at moderate cycle rates, dominated by cylinder volume rather than nozzle flow.
Standards, materials, and integration notes
Vacuum-system rating is conventionally referenced to 1,013 mbar and 20 °C per Schmalz's published selection basis, with ultimate vacuum expressed in mbar or Pa negative [S3]. Pisco's VY specifies PBT (polybutylene terephthalate) as the main resin — a standard engineering plastic selected for dimensional stability and chemical resistance to common suction-side contamination [S4]. Gimatic's multi-stage cartridges are supplied in cartridge-only or cartridge-with-holder-and-silencer variants, which simplifies EMC and noise compliance on a robot end-effector [S1].
For panel builders tying either device into an MCC, the upstream pneumatic-tubing ID, FRL setpoint, and valve-manifold protocol matter as much as the device itself — see the related pneumatic tubing selection criteria for MCC panel builds for the upstream side, and vacuum generator sizing for MCC panel integration for the ejector-specific sizing walkthrough. Where the station also needs a positioner or limit switch on the actuator, the valve limit switch box vs positioner spec decision map lays out the feedback-side choice.
Limits, failure modes, and when NOT to pick pneumatic
A pneumatic ejector cannot reach deep vacuum (below roughly −90 kPa absolute) without multi-stage cartridges, and its suction rate collapses as system vacuum deepens — that is a Venturi physics limit, not a vendor limit [S1][S3]. An oil-lubricated ejector risks contaminating the workpiece (food, pharma, cleanroom); an oil-free ejector sacrifices some ultimate vacuum and noise profile for cleanliness [S1].
A pneumatic actuator loses positioning precision if the load is unbalanced or if air-supply pressure sags below 0.4 MPa, and a 100 kg-class manipulator like the VOLUMEC RM01 needs either floor-fixing, ceiling-fixing, or a CSM001/CSM002 trolley to be safe at full reach [S2]. Where the duty cycle, cleanliness, or positioning tolerance exceeds what compressed air can deliver — cleanroom wafer handling, sterile filling, sub-micron positioning — switch the spec to electric (servo or stepper) on the actuator side, or to an electric pump/blower on the vacuum side, before adding more pneumatic hardware [S3][S7].
Track these next: (1) updated ISO 4414 / 4413 safety margins for combined vacuum-and-actuator stations as collaborative robots enter the same cell, and (2) Schmalz and Mindman catalogue releases for IO-Link-enabled multi-stage ejectors that close the air-consumption gap versus electric pumps [S3][S7][S8].