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Sheet metal working

Deep draw­ing, spin­ning & rounding

Besides bend­ing, deep draw­ing, spin­ning & round­ing are other non-cut­ting form­ing processes. These highly pro­duc­tive processes are also among the core com­pe­ten­cies of the SwissFactory.Group.

 

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hydromechanical press Dieffenbacher

Hydro­me­chan­i­cal deep draw­ing of sheet metal (up to 900 t press­ing force)

Con­ven­tional deep draw­ing of sheets
(63–230 t press­ing force)

Auto­matic metal spin­ning
(cen­tre height: ‑750; cen­tre width: ‑1450 mm)

Man­ual metal spin­ning
(cen­tre height: ‑500; cen­tre width: ‑900 mm)

Round
(L 1040 x D 100 or max. width 1020 mm)

Deep Draw­ing

Deep draw­ing is the ten­sion-com­pres­sion form­ing of a sheet metal blank into a hol­low body open on one side, or of a pre-drawn hol­low body into one with a smaller cross-sec­tion with­out delib­er­ately chang­ing the sheet metal thick­ness. In many cases, the part geom­e­try is rota­tion­ally sym­met­ri­cal, but it can also have almost any shape — with gradations.

As a rule, a deep-draw­ing con­sists of three com­po­nents, deep-draw­ing punch, deep-draw­ing, and blank holder (also called sheet holder). The pur­pose of the hold-down is to pre­vent the unde­sir­able for­ma­tion of wrin­kles due to tan­gen­tial com­pres­sive stresses in the flange. An impor­tant char­ac­ter­is­tic value (mate­r­ial con­di­tional), which describes the extent of a form­ing, is the deep draw­ing ratio ß, which is defined as the quo­tient of round diam­e­ter d0 and inner diam­e­ter d1 of the cup (punch diam­e­ter) at the ini­tial draw­ing. For the onward pull, the deep-draw­ing ratio is deter­mined from the decrease in the inter­nal diam­e­ter of the cup.

There are many pos­si­ble areas of appli­ca­tion for deep draw­ing. One rea­son for this is that very many met­als can be formed using this process, start­ing with alu­minium, brass, cop­per, sheet steel, rust and acid-resis­tant alloys, but also heat-resis­tant and var­i­ous other metal alloys.

Deep-drawn parts can be found in vehi­cle con­struc­tion, mechan­i­cal engi­neer­ing, space tech­nol­ogy, solar tech­nol­ogy, house­hold, energy tech­nol­ogy, chem­istry, and many other places.

Pic­ture: Can (slot­ted pipe) for pump motor

approx. 12 form­ing steps

Can for pump motor

Press

Gen­eral

Besides deep draw­ing, metal spin­ning is also a very eco­nom­i­cal process. Metal spin­ning is a very old craft. Thin sheet metal was used to make every­day objects at an early stage. In recent decades, thanks to Improve­ment of tech­nol­ogy (automa­tion) from it an effi­cient man­u­fac­tur­ing method. Espe­cially for the pro­duc­tion of rota­tion­ally sym­met­ri­cal parts — small and medium quan­ti­ties — metal spin­ning is supe­rior to other processes. In metal spin­ning, a sheet metal round plate is pressed cen­trally — with the pre-set­ter — against the spin­ning die and set in rotary motion. The spin­ning roller reshapes the rotat­ing round blank step by step until the mate­r­ial is in con­tact with the spin­ning form. The form­ing process is con­trolled by means of two axes. With per­fect con­trol of the process, the wall thick­ness of the mate­r­ial remains almost con­stant. Since the parts have a good shape and dimen­sional accu­racy, there is usu­ally no need for machin­ing. In addi­tion to the form­ing of cir­cu­lar blanks, com­po­nents that have already been pre­formed, such as deep-drawn blanks, can also be fur­ther reduced in diam­e­ter by spin­ning. The form­ing takes place very locally due to the process, there­fore only low forces are required, in con­trast to deep drawing.

In addi­tion to auto­matic spin­ning, hand spin­ning is still indis­pens­able today for prototypes/sample parts and small series for the most diverse areas, such as tech­ni­cal prod­ucts, lights/reflectors, house­hold arti­cles, but also high-qual­ity design products.

Pro­jec­tion stretch spin­ning is a spe­cial form of spin­ning, it is a pre­cise process that uses a pro­jec­tion spin­ning roller to “project” the mol­e­cules of mate­r­ial on one plane into another. Con­i­cal work­pieces are pro­duced by mov­ing the pro­jec­tion roller (spin­ning roller) par­al­lel to the pro­jec­tion mould (spin­ning mould). Under its pres­sure, the mate­r­ial (cir­cu­lar blank) shifts axi­ally, whereby the wall becomes thin­ner (s0 times sin α) and the part of the cir­cu­lar blank that has not yet been machined is per­pen­dic­u­lar to the axis. The sur­face is very highly com­pressedby this process and also exhibits — on the pro­jec­tion mould side — a very good sur­face quality.

Graphic: Pro­jec­tion stretch press

Projection stretch press

Hydro­me­chan­i­cal deep drawing

Dief­fen­bacher

Hydro­me­chan­i­cal deep draw­ing with our Dief­fen­bacher allows higher draw­ing ratios to be achieved than with con­ven­tional draw­ing processes.

 

  • com­plex geometries
  • expanded tubes
  • Inter­sec­tions in the shaping
  • Parts with high sur­face quality
  • Parts made from mul­ti­layer sheets
  • Pro­to­typ­ing
  • Small and medium batch production

To hydro­me­chan­i­cal deep drawing

As one of the lead­ing sup­pli­ers of hydro­form­ing in Europe and Switzer­land, our part­ner com­pany Egro Indus­trial Sys­tems AG has a 900 ton press with 1’000 bar Hydromec pres­sure. With this press, the range of ser­vices can be cov­ered up to a part size of 1’400 mm x 1’600 mm. Con­i­cal and par­a­bolic drawn parts are pro­duced in one go with this process.

Pro­ce­dure

In the pro­duc­tion of demand­ing deep-drawn parts with larger draw­ing ratios, more com­plex shapes or increased demands on sur­face qual­ity, it is often advan­ta­geous to use the hydro­me­chan­i­cal deep-draw­ing process in — one — stage instead of the con­ven­tional deep-draw­ing process in — sev­eral — stages.

The prin­ci­ple of hydro­me­chan­i­cal deep draw­ing is based on the high hydraulic pres­sure in the draw­ing area (see graphic step 1 — 3). The sheet metal blank to be formed (blank) is pressed against the immers­ing draw­ing punch from the begin­ning with an appro­pri­ate, adjustable pres­sure in the water box, and thereby receives the exact shape of the punch. This hydraulic pres­sure, which also acts directly on the side­wall of the drawn part, causes addi­tional com­pres­sive stress there. With the help of this addi­tional com­pres­sive stress, the process is facil­i­tated in the draw­ing direc­tion. In con­crete terms, this means that the draw­ing ratio can be increased by up to 40% (depend­ing on the mate­r­ial) with­out dif­fi­culty. The lim­its of this method are the seal­ing pos­si­bil­i­ties between the sheet metal blank and the draw­ing ring.

As a cus­tomer, you can thus ben­e­fit from higher capac­i­ties, greater mechan­i­cal flex­i­bil­ity and more eco­nom­i­cally effi­cient solutions.

Graphic: Prin­ci­ple of hydro­me­chan­i­cal deep draw­ing in three steps

Principle of hydromechanical deep drawing with active medium

Advan­tages of hydro­me­chan­i­cal deep drawing

  • Higher lim­it­ing draw ratio, the achiev­able draw ratio is much more favourable (up to 40%).
  • Con­i­cal and par­a­bolic drawn parts are pro­duced in one go. In the clas­si­cal draw­ing process, depend­ing on the geom­e­try, it may require 5 to 6 draw­ing oper­a­tions and 1 to 2 anneal­ing operations.
  • Lower tool­ing costs thanks to the more direct path to the fin­ished part geometry.
  • Dif­fer­ent mate­ri­als and dif­fer­ent sheet thick­nesses can be processed in the same tool.
  • Bet­ter sur­face qual­ity due to the reduc­tion of fric­tion in the area of the die infeed radius (sheet metal blank is drawn over a “water bead”).
  • Less sheet thick­ness reduc­tion in the bot­tom radius and the pos­si­bil­ity of smaller bot­tom radii.
  • Less resid­ual stress in the component.

Image: Inverter hood

Solar sys­tem prin­ci­ple of hydro­me­chan­i­cal deep draw­ing with active medium in three steps.

Hydromechanical deep drawing hood inverter solar system
Pressing part particle filter, diaphragm plate. Shielding, pulling Reduction cone