Industrial washing machine drum forming press

01

Define the drum and the operations the press performs

US patent 6,334,341 B1 (Cylinder washing machine) states that “Drums for automatic washers or washer-dryers usually consist of sheet metal structures” and that, with spin speeds of up to 1,600 rpm, must meet stringent strength, dimensional stability and rigidity requirements, which is why the drum sheet is textured with bulges. It describes how drum perforations of about 3.5 mm are made: holes of about 2.5 mm are first punched into a sheet coil, then deepened to a funnel and flared to 3.5 mm by an embossing process called drift punching; the cut coil section is then shaped and welded into a cylinder with the hole recesses facing outward, so that no burrs point into the drum. It adds that drift-punched holes of 2 mm would need punches no larger than about 1.2 mm, since "The gauge of the sheet metal customarily used for washing machine drums would quickly lead to breaking of the tools." [2]

US patent 8,011,210 B2 (BSH, Washing drum for a laundry treating machine) describes a drum shell formed from a finite sheet-metal strip bent into a cylinder whose ends are joined by a welded seam, with its long sides joined to the rear bottom disk and front bottom disk by an edge-formed seam carrying transverse embossments; carriers (lifters) drawn inward from the shell sheet are joined by a fold to openings in the bottom disks. [1]

Editorial note: list for the supplier every operation (perforating, texturing, cutting, rolling, welding, carrier drawing, seaming, embossing) and say which ones this press must do and which other machines it must match.

Give the supplier the drum drawings (diameter, depth, sheet grade and gauge), hole pattern and texturing, carrier design, seam design to the bottom disks, operations per press, cycle time and output, die change requirements for drum variants, how drums are loaded, located and indexed, press force and stroke if known, guarding and access, and the strength or spin tests the drums must pass.

02

Plan seam embossing, indexing and guarding

US 8,011,210 B2 explains that embossments spread evenly around the edge-formed seam resist opening but do not stabilise the carrier joints; it places embossments in close succession next to where each carrier joins the bottom disk, at least seven and preferably nine on each side, with centre spacing about twice the embossment width, and states a spacing of 13 to 22 mm suits strength and manufacture. It says a drum with the plain edge-formed seam suits washing machines with maximum spin speeds of around 1,000 rev/min and needs no embossments, while drums for faster spin speeds should be reinforced with embossments at least where the carriers join the bottom disks. In its tooling, dies on a tool table strike the seam, and the drum is turned on the table between strikes: with one die station it needs six turning positions, with one station per carrier join only two. [1]

Editorial calculation: the earlier patent's spin speeds of up to 1,600 rpm are 60% above the around 1,000 rev/min the BSH patent gives for a seam without embossments (1,600 ÷ 1,000 = 1.6), so state your spin speed and ask how the seam design covers it. [2] [1]

OSHA's general machine rule 29 CFR 1910.212 requires machine guarding to protect operators and others from point-of-operation, nip-point and rotating-part hazards, with guards affixed to the machine where possible. [3] Editorial note: ask how the die area and indexing table are guarded during loading and indexing.

03

Ask for joint stress results at your top spin speed and load

A 2022 open-access AHFE conference paper by Ying Liu and Yunfei Chen (Southeast University) analysed a cylinder washing machine inner drum joined by flanging riveting: the wall of a drawn hole in one sheet is turned over and pressed with a round punch against a countersunk hole in the other. For a 17 kg maximum load (clothes and water) at the 1420 rpm top speed, the authors applied 0.15569 MPa to the drum wall in an ANSYS model and checked it with strain rosettes on three machines run at 1420 rpm for 3 min. [4]

Stresses in the riveting area all stayed below the 280 MPa yield stress, peaking near the gaps (175 MPa) and around the rivets near the gaps (155 MPa); a single-row rivet carried more stress than the double-row rivets beside it. [4]

Editorial calculation: 175 ÷ 280 = 62.5% of yield. [4] Editorial note: tell the press supplier which joints its tooling forms (rivet rows, seams, gaps), and ask the drum designer for stress results at your own top spin speed and load; the paper's values apply to its 17 kg, 1420 rpm machine only.

04

Perforated shell, welded cylinder, carriers, bottom disks, edge-formed seam and embossing dies

The tooling follows the order of operations in the two patents: holes are punched and drift-punched in the coil before rolling and welding, and the seam to the bottom disks is embossed last, with the drum indexed between strikes. [2] [1]

05

Forming force, table size, stroke, indexing accuracy and layout for a drum press quotation

No row here has a published press figure; the drum-side values that drive them are in the patents and the AHFE paper — 3.5 mm holes, 13 to 22 mm embossment spacing and spin speeds of 1,420 to 1,600 rpm. [2] [1] [4]

06

Send the drum, operation and line data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Drum: [diameter; depth; sheet grade and gauge]
Holes: [size; pattern; texturing]
Carriers: [design]
Seam: [edge-formed; embossments]
Operations: [this press; other machines]
Output: [cycle time; variants; die change]
Handling: [loading; locating; indexing]
Safety: [guarding]
Tests: [spin speed; strength]

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