Steam Pressing Equipment in Commercial Laundry: Hoffman Presses, Bucks, and Vacuum Tables

Flatwork ironing handles sheets, pillowcases, and tablecloths in continuous flow; but shaped garments — shirts, trousers, uniforms, and dresses — require pressing equipment that can conform to three-dimensional form. Commercial laundries handling garments alongside flatwork maintain a pressing section equipped with steam presses designed for specific garment types, vacuum pressing tables for hand-finishing, and in some cases automated tunnel finishers for high-volume garments. The engineering of pressing equipment — steam supply, vacuum extraction, head pressure, and cycle timing — directly determines the quality and throughput of the garment finishing operation.

The Hoffman-type steam press

The Hoffman press — named after its original inventor and now a generic term for the clamshell garment press design — consists of a lower padded buck (the stationary pressing surface) and an upper heated head that descends under pneumatic or mechanical pressure to clamp the garment against the buck. Steam is injected through the buck surface into the garment from below during the press cycle to relax fabric fibres and set the pressed finish, and vacuum is then applied through the same buck surface to extract the steam moisture and cool the garment, setting the finish in position before the head lifts.

The sequence of a Hoffman press cycle is therefore: position garment on buck, close head under pressure, apply steam for a set duration (typically 3 to 8 seconds depending on fabric weight and moisture content), close steam and apply vacuum for a set duration (typically 4 to 10 seconds to extract moisture and cool the fabric), open head, remove garment. A skilled operator can complete this cycle for a shirt body or trouser leg in 15 to 25 seconds, achieving press rates of 120 to 200 units per hour per press on straightforward uniform garments. The quality of the pressed finish depends on steam pressure, head pressure, steam duration, and vacuum duration being correctly set for the fabric type.

Buck configurations for different garment types

The shape of the lower buck must match the garment zone being pressed. A Hoffman press configured for general utility work uses a flat rectangular buck suitable for trouser fronts, jacket backs, and flat garment panels. Specialised configurations include:

• Sleeve board: A narrow, tapered buck shaped to accept a garment sleeve without the seam rolling over the edge. Essential for shirt sleeves and jacket sleeves where a sharp crease at the sleeve seam is a defect rather than a finish feature.
• Trouser leg buck: A flat narrow buck with a tapered end, designed to press one trouser leg at a time with controlled crease placement. May include a crease guide bar to align the crease position before the head closes.
• Trouser top press: A shaped buck that accepts the waistband, hip, and seat of trousers in a single press stroke, with a shaped head contoured to match the three-dimensional form of the trouser top. Achieves in one cycle what a flat press would require multiple repositionings to accomplish.
• Form finisher or doll: An inflatable body form that fills to the shape of a jacket or shirt when pressurised with steam, simultaneously steaming and tensioning the garment to a finished shape without physical pressing contact. Produces a soft, rounded finish rather than the sharp pressed finish of a flat buck, which is appropriate for knitwear and casual garments where a flat pressed appearance would be a defect.

Vacuum pressing tables

A vacuum pressing table is a flat perforated work surface connected to a vacuum pump, with a steam iron or steam hand press used in conjunction with the vacuum. The operator places the garment on the table surface, applies steam and pressure with the hand iron, and the vacuum simultaneously extracts steam through the table surface, drying and setting the pressed finish immediately. Without the vacuum extraction function, steam applied by a hand iron exits through the garment's upper surface and takes minutes to cool and dry under ambient conditions; the garment cannot be moved or hung until fully dry or it will re-crease. With vacuum extraction, the operator can move to the next pressing step or hang the garment immediately after the iron stroke.

Vacuum pressing tables are used in commercial laundries for garment types that require detail hand-finishing — lapels, collars, pocket flaps — after machine pressing on a Hoffman press, or for low-volume speciality garment work where the production rate does not justify a dedicated shaped machine press. The vacuum pump for a pressing table section must be sized for the total number of simultaneously open table valves and the table surface area, typically requiring 2 to 4 kW of vacuum pump capacity per table in continuous use.

Steam and utility requirements for a pressing section

A pressing section comprising six Hoffman presses and two vacuum tables has a steam demand that is intermittent but can be significant: each Hoffman press injects steam for 3 to 8 seconds per cycle at a rate of 0.5 to 2 kg of steam per hour average consumption depending on cycle frequency and fabric type. Total steam demand for a six-press section is approximately 3 to 12 kg of steam per hour, modest compared to the main wash plant but requiring a regulated steam supply at 2.5 to 4 bar (lower than the main plant pressure, requiring a pressure reduction station with steam trap on the outlet).

Compressed air is required to actuate the Hoffman press head closure mechanism — typically at 4 to 6 bar, with each press head consuming a burst of air at head closure and opening. A single pressing section is a minor compressed air load. However, the pressing section should be served from the main plant compressed air ring main rather than from a dedicated small compressor, since a small dedicated compressor serving only the pressing section will short-cycle continuously (head demand is intermittent and low average flow) and will fail from short-cycling within months without a correctly sized receiver.

Steam iron supply for vacuum tables should be filtered steam at 3 to 4 bar fed through dry steam separators immediately upstream of the iron connections, since wet steam reaching the iron causes water marks on the pressed garments. A steam iron section with multiple irons must be vented from the steam supply header at a high point to purge air and condensate at the start of each shift before production begins.