Shirt Pressing Unit

Overview

The shirt-pressing unit is an automated flat-pressing station used in commercial laundries and on-site laundry services in hotels, hospitals, and office buildings. The machine presses standard dress shirts, blouses, and lightweight garments flat-on between a heated upper pressing platen and an inflatable lower air form, using a combination of heat, steam, vacuum, and controlled pressure to remove wrinkles and create crisp creases in 10–20 seconds per garment.

The key innovation is the integration of vacuum suction and steam injection: vacuum holds the garment flat against the form, preventing bunching, while steam softens fibers and allows heat transfer. This combination produces professional results faster and with less fabric stress than manual pressing or traditional hot-platen-only presses.

The machine is operator-friendly: an operator places a shirt on the air form, positions it under the platen, and steps on a foot pedal to trigger the cycle. The PLC automatically sequences heat, steam, vacuum, and press force; the platen descends automatically, pressing the shirt for 8–12 seconds, then retracts. The finished, wrinkle-free shirt is removed and hung for cooling.

Typical throughput is 120–180 shirts per 8-hour shift per machine, making the unit economical for high-volume operations. The machine is particularly popular in on-premise laundries where quick turnaround (same-day or next-day service) is critical.

How It Works

An operator retrieves a damp or slightly damp (conditioned) shirt from the wash/dry line and lays it flat on the inflatable air form. The shirt is smoothed to align the front panels and sleeves on the form.

The operator steps on the foot pedal, which signals the PLC to begin the pressing cycle. The PLC simultaneously initiates four actions:

1. Air form inflation: The solenoid air valve energizes, sending 0.5–1.0 bar compressed air to the air form. The cushion expands gently, providing a contoured support surface that conforms to the shirt body.

2. Vacuum application: The vacuum solenoid energizes, drawing air from a perforated work surface through the shirt fibers. Vacuum suction (approximately 70 kPa below atmospheric, created by the vacuum pump) holds the garment flat and immobile, preventing bunching or shifting during pressing.

3. Steam injection: The steam solenoid opens, admitting 100°C steam from the boiler into the pressing chamber (the space beneath the platen). Steam saturates the shirt fibers, softening cellulose molecules and allowing plastic deformation (wrinkle removal).

4. Head descent and pressing: The pneumatic cylinder beneath the pressing head energizes at 3–8 bar pressure (operator-selectable), creating a controlled downward force. The heated platen (150–180°C, also operator-selectable) descends toward the shirt at approximately 0.1 m/s, making contact with the shirt surface.

For 8–12 seconds (depending on fabric type), the platen maintains pressure on the damp, steam-saturated shirt. Heat from the platen (150–180°C) transfers through the fabric, evaporating moisture and setting the wrinkle-free shape. The vacuum continues, removing moisture vapor from the pressing chamber and assisting drying.

At the end of the press cycle, the cylinder retracts, raising the platen away from the shirt. The steam valve closes, stopping steam flow. The vacuum valve de-energizes, venting the vacuum to atmosphere (allowing air to re-enter). The air form valve de-energizes, deflating the form.

The operator removes the hot, freshly-pressed shirt (typically 60–80°C) and hangs it on a rail to cool. The shirt is now wrinkle-free, with creases set (or absent, depending on the operator's front-panel positioning before pressing). The machine is ready for the next shirt within 5 seconds.

Temperature and Pressure Control

The pressing platen is continuously heated to maintain the operator-set temperature (typically 160°C for cotton, 140°C for synthetics, 120°C for delicates). The 12 kW heating element (either immersion or infrared) provides rapid heat. The proportional thermostat with a thermocouple sensor embedded in the platen maintains ±5°C setpoint by modulating heater power.

The 8 kW steam boiler is maintained at 2.0–2.5 bar absolute pressure, generating steam at approximately 120°C. The pressure relief valve (set 3.0 bar) protects against overpressure. Steam is released into the pressing chamber via the adjustable nozzle only during the steam phase of the cycle; a check valve prevents backflow when steam is not being injected.

Pressing force is set via the pressure adjustment valve, which modulates air supply to the head cylinder. Typical settings are 3 bar for delicate fabrics (light blouses), 5 bar for standard cotton shirts, and 8 bar for heavy fabrics (linen, thick weaves). Excessive pressure causes wrinkles in the fabric (reverse creasing), so operator training emphasizes appropriate pressure selection.

The vacuum system operates at 0.3 bar absolute (approximately 70 kPa below atmospheric) during the press cycle. The rotary vane pump (1.5 kW) creates this vacuum continuously; the solenoid valve connects or disconnects the vacuum to the pressing chamber as programmed. A lint trap protects the pump from fiber contamination, requiring weekly cleaning.

Pressing Cycle Variations

The PLC firmware stores preset cycles selectable via the preset buttons or HMI touchscreen:

• Sport Cycle (10 sec, 140°C, 4 bar): Designed for lightweight casual shirts and delicate fabrics. Lower temperature and pressure prevent shine marks.
• Business Cycle (12 sec, 160°C, 5 bar): Standard cycle for dress shirts, blouses, and everyday garments. Balanced for durability and appearance.
• Formal Cycle (15 sec, 170°C, 6 bar): Extended time and higher temperature ensure deep wrinkle removal for suits and formal wear.
• Custom Mode: Operator selects cycle time (8–20 sec), temperature (120–180°C), and pressure (3–8 bar) via touchscreen.

Advanced versions include a moisture sensor on the platen that detects residual moisture; the cycle automatically extends if moisture is detected, ensuring complete drying before platen retraction.

Fabric Considerations and Operator Skill

The machine is designed for medium-weight fabrics: standard cotton dress shirts, cotton-polyester blends, blouses, and lightweight dresses. Heavy fabrics (linen, wool suits) require extended cycle times and higher temperatures; delicate synthetics require lower temperatures to prevent heat damage.

Proper shirt positioning is critical. The operator must:

1. Align the front panels symmetrically on the form.
2. Smooth the collar and lay it flat on the form surface.
3. Ensure sleeves do not fold or bunch under the platen.
4. Select the appropriate cycle for the fabric type.

Most laundries provide 1–2 days of training for new operators. Experienced operators can achieve 180+ shirts per shift with minimal defects (shine marks, incomplete wrinkle removal < 5%).

Construction and Durability

The platen is typically aluminum (lightweight, good heat transfer) or steel (durability). Aluminum platens require occasional resurfacing (every 2–3 years) to smooth worn areas. Steel platens are more durable but heavier.

The air form is constructed from a flexible elastomer (silicone or polyurethane) over a frame, creating a contoured but compressible surface. Forms are replaced every 5–10 years (cost 800–1500 EUR) due to gradual loss of elasticity and pinhole development.

The welded steel frame is powder-coated for durability. The perforated work surface is stainless steel, allowing easy cleaning and preventing rust.

The pneumatic head cylinder is rated for approximately 500,000 cycles (10–15 years in typical operation). The boiler requires descaling every 6 months to prevent mineral buildup; proper water treatment extends boiler life to 10+ years.

Safety and Ergonomics

The foot pedal provides intuitive cycle initiation. Continuous-press foot controls (requires constant pedal pressure to maintain press) and hold-pedal controls (press once to start, again to stop) are available per operator preference.

The platen descends slowly (approximately 0.1 m/s) to allow operator reaction if a hand or object is detected under the platen. Most machines include a safety pull-cord above the work surface; pulling the cord immediately retracts the platen and vents all vacuum/air/steam, stopping the press within 1 second.

The machine is compliant with European CE safety standards and OSHA requirements in the US. Guard rails or interlocks prevent access to the pressing chamber during operation.

Energy Consumption and Operating Cost

Typical consumption per shirt:

• Electricity: 0.5–0.8 kWh (heater, motors)
• Steam: 0.3 kg (equivalent to 1.8 MJ thermal energy)
• Compressed air: 0.01 m³ at 6 bar
• Total energy cost: approximately 0.30–0.50 EUR per shirt

Labor cost (operator at 15 EUR/hour, 150 shirts per shift): 0.10 EUR per shirt.

Total operating cost per shirt: 0.40–0.60 EUR, making the machine suitable for service laundries, hotels, and on-premise laundries servicing businesses or institutional campuses.

On-premise machines pay back investment (approximately 15,000 EUR) within 3–5 years through reduced outsourcing cost.