SMC Vacuum Generator Selection: ZP vs ZH vs ZU — A Field Engineer’s Guide

Last month, a customer doing electronics packaging called me. Vacuum cups weren’t gripping reliably. I asked which vacuum generator he was using — “one of those small ones, you plug compressed air into it.” Model number? No idea. He sent a photo. ZP3, single-stage, 0.5mm nozzle.

The problem was staring at us: he was using a 0.5mm nozzle ZP3 to grip a 200g PCB, with 3 meters of vacuum tubing between the generator and the cup. It’s not that the ZP3 is a bad product. It’s that the selection was completely wrong for the application.

SMC’s vacuum generator lineup has three core series: ZP, ZH, and ZU. Each has a distinct operating window. Confuse them, and your pick-and-place performance tanks.

ZP Series. SMC’s foundational vacuum generator, single-stage Laval nozzle design. Key models: ZP3, ZP3-B, ZP3E. Nozzle diameters from 0.3mm to 3.0mm, maximum vacuum -84 kPa. Use ZP when you need a cheap, reliable, low-maintenance vacuum source and vacuum requirements don’t exceed -80 kPa. Electronics assembly, small packaging, label application — ZP likely owns half the single-stage vacuum generator market. Worth noting: ZP3-B has a built-in silencer cutting noise 5-8 dB versus standard ZP3. In a cleanroom or near operator stations, that difference matters.

ZH Series — High Vacuum. Two or three-stage ejector structure pulling vacuum to -93 kPa and beyond. Models: ZH07, ZH10, ZH13, ZH18 (number = nozzle diameter x 10). Trade-off: air consumption 20-30% higher than equivalent ZP. Applications: precision gripping, semiconductor wafer handling, micro-component placement — processes demanding above -85 kPa. My first ZH deployment was LED die sorting: spec called for -88 kPa within 50ms. ZP stuck at -82 kPa. ZH07 hit -91 kPa in 40ms with same supply pressure.

This ties to solenoid valve selection (see our SY series article) — the vacuum generator supply side needs a fast 2-position 3-port valve. SY3000 VQ series works well with pilot response under 5ms.

ZU Series — High Flow. Multi-stage generators with 2-3x the suction flow of equivalent ZP models. Models: ZU07, ZU10, ZU18. Why flow matters: porous workpieces like corrugated cardboard, breathable textiles, foam leak air. ZU maintains working vacuum despite leakage where ZP falls off. Packaging automation engineers know this series well — case erecting, fabric handling, foam pick-and-place are ZU territory.

Selection sequence. Don’t start with nozzle size. Characterize the workpiece (weight, material density), size the cups, match generator type to porosity (ZP/ZH for dense, ZU for porous), check vacuum level requirements, then select nozzle size and supply pressure.

Supply pressure matters more than people think. ZP specs rated at 0.5 MPa. At 0.4 MPa actual supply, maximum vacuum drops 8-12%, suction flow drops further. This connects to air preparation (see our AF/AR/AL article) — FRL pressure drop directly impacts vacuum performance.

Vacuum tubing: if length exceeds 2 meters, tube ID should be at least 4x nozzle diameter. 1.0mm nozzle needs 6mm ID minimum. Undersized tubing multiplies vacuum build time.

Maintenance: vacuum generators are reliable but sensitive to air quality. Moisture and oil mist deposit on the nozzle throat over time. Install a 0.01um precision filter (AF series -U element) on the supply side.

Spec the right generator and the vacuum system is the most forgettable part of your machine. Spec wrong and you’ll spend a full day chasing intermittent grip failures. Check SMC’s global vacuum product page at smcworld.com for complete ZP3E and ZU-S series data.