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Deep Drawing Process

Deep Drawing Process
Deep Drawing Process

We manufacture hydraulic press with a deep drawing process. Deep drawing process & Deep drawing press & Double action deep drawing press & Triple action deep drawing press

Sheet metal forming is one of the most important production methods used in different industries such as producing industrial parts, office, and home appliances, automobile bodies, airplane parts, etc. Deep drawing is one of the frequently applied methods in sheet metal forming.

Deep Drawing Operation

Deep Drawing Operation
Deep Drawing Operation

Deep drawing operation is based on producing engineering parts with specific shapes through major plastic deformation of flat metal sheets. An external force on a metal sheet does this plastic deformation. This external force has to be large enough to place the material in the plastic zone and
to ensure that after displacing the external force, the metal part doesn’t spring back or elastically deform again.

The final quality of the parts produced through this operation is based on the final wall thickness and being wrinkle-free and fracture-free

The flat blank for use in the analysis of deep drawing may be divided into three zones, X, Y, and Z [13], as shown in Fig. 1.1 As the punch is lowered
into the die opening, several distinct phenomena occur. X, the outer annular zone consists of material in contact with the die. Y, the inner
annular zone is not initially in contact with either the punch or the die, and Z, the circular zone is only in contact with the flat bottom of the punch.

As the deep-drawing operation proceeds, the outer flange portion of the blank, zone X will be subjected to a radial drawing tensile stress as it is drawn progressively inwards towards the die profile and the effect of continuously decreasing the radius in this zone is to induce compressive hoop stress, resulting in an increase in material thickness [3]. Then when the magnitude of these stresses exceeds a certain critical value, wrinkling and buckling of the flange may occur if the blank holder pressure is not high enough.

The material in the inner parts of zone X is thinned by plastic bending under tensile stress as it passes over the die profile. The inner parts of zone X are thinned further by the tension between the punch and die, resulting in an increase in thickness for the outer parts of zone X. Zone Y is subject to bending and sliding over the die profile, stretching in tension between the punch and die and finally to bending and sliding over the punch profile. Zone Z is subject to stretching and sliding over the punch head

Deep Drawing Process Steps

In summary, five processes take place during the course of deep drawing.

  • Pure radial drawing between the die and blank holder in zone X, causing the blank to thicken due to the resultant hoop stress.
  • Bending and sliding over the die profile, r2, will cause some thinning of the metal.
  • Initial stretching in zone Y. This will cause thinning of the material at the intersection of the bottom of the cup and its side wall. If a cup fails to form it is invariably due to tensile failure in zone Y.

Bending and sliding over the punch profile radius, r1, thinning to some degree occurs here. Stretching and sliding over the punch nose in zone

Defects in Deep Drawing Progress

A number of defects may occur in deep-drawn parts. Figure 1.2 shows the type of defects that may be found after drawing cups. The description of
such defects is discussed below:

Earing:
It occurs in deep-drawn parts made from anisotropic materials. Because of planar anisotropy, the sheet metal may be stronger in one direction than in other directions in the plane of the sheet. This causes the formation of ears in the upper edge of a deep-drawn cup even when a circular blank is
used. In practice, enough extra metal is left on the drawn cup so that the ears can be trimmed.

Wrinkling in the flange
Wrinkling in deep drawn parts consists of a series of ridges that form radially in the flange due to compressive forces. Wrinkling in the wall occurs when ridges in the flange are drawn into the vertical wall of the cup.

Wrinkling in the wall
It occurs when ridges in the flange are drawn into the vertical wall of the cup.

Tearing

It occurs near the base of the drawn cup and results from high stresses in the vertical wall that cause thinning and failure of the metal at that location.

Surface scratches
It occurs in a drawn part if the punch and die surfaces are not smooth or if lubrication is not enough.

Parts of a Hydraulic Press with the Deep Drawing Process

Top Plate of a Deep Drawing Press

It is the plate that is situated at the top of the machine. It will be made up of MS material. This plate will support the

one cylinder which is used for punching the workpiece. This plate will also support two small cylinders which are situated beside the punching cylinder. It will hold four pillars which will be fixed with the help of bolts. It will support the whole weight of three cylinders which are used for different purposes in the machine. It also will help to correct the alignment of the base plate and pressure plate with four rods at its end.

Base Plate

It is a plate that is situated on the frame. It will take all load off the machine. It is connected to the top plate with the help of four pillars. The pillars are situated at their ends. It has a T slot cut into it. This T slot helps for mounting the die set on it. It is the plate on which the workpiece is actually placed and then the punching operation takes place. An ejection system will be provided below it to eject the workpiece from the die set.

Pressure Plate

The pressure plate is a little less in dimension than the base plate or top plate as it has to move up and down in the machine. This plate will move up and down with the help of two piston rods which will hold it at the two ends. This plate will hold the metal sheet and then the punch will come down and punch the metal sheet. It has a center hole through which the punch moves up and down. This is an important part of the system as it has to hold the metal sheet. Due to this plate, there are fewer chances of wrinkles on the workpiece.

Pillars

There is a total of four pillars in this machine. These pillars are mounted between the top plate and the bottom plate. They are fixed with top and bottom plates with bolt arrangement. They support the whole weight of cylinders and the top plate. They reduce vibrations of the machine to transfer to the base plate and ultimately to the die set. This avoids any variation in the workpiece.

Frame

This is the component of the system that takes all load of the machine. This takes a load of hydraulic cylinders, base plate, top plate, and pillars. It also holds an ejection system which helps in the ejection of the workpiece from the die set.

C-Clamp

This component of the system helps in the ejection of the workpiece from the die. It also limits the movement of the pressure plate. This C- clamp is connected to the piston rod of the punching cylinder. It also has one limiting movement mechanism. With this mechanism the armature of C-clamp is made contact with a pressure switch is used to stop the Clamp.

Double Action Deep Drawing Hydraulic Press Machine Automation plane uses a hydraulic cylinder for both direction movement and stroke, a hydraulic motor is used to drive the hydraulic cylinder, and a pleasure switch to control the movement of the press pad and punch. Solenoid valves are widely used on compressed air or hydraulic fluid for powering actuators on mechanical components.

While motors are used to supply continuous rotary motion, actuators are typically a better choice for intermittently creating a limited range of movement for a mechanical component, such as moving various mechanical arms, opening or closing valves, raising heavy press rolls, and applying pressure to presses.

Control circuits are often drawn using ladder logic, so named because the wiring diagram resembles a ladder. First of all base plate is mounted on the frame. The base plate is welded to the frame. Then take four pillars and they were situated vertically on the base plate and in they are fitted to the base plate with help of a bolt and lock nut.

Over that pillar, the top plate is situated and it is fixed with the nut and bolt. After that, the round plate is welded to the top plate at its center. Over that round plate cylinder of 20 tones is fixed with nut and bolt. Which are situated in the holes on the circumference of the round plate. After this situation of the center cylinder is used for the punching operation. Then and edges of the top plate square blocks are welded and over that block cylinder of 2.5 tones is fixed. With the same process that of the center cylinder.

After that piston of the cylinder which is of 2.5 tones brought down and the pressure plate is fixed with it at the edges and with help of a square block. In that Allen bolts and nuts. After that clamp is situated in the center cylinder piston by cutting and milling it into that shape. Another part of the c-clamp is assembling the top of the ejection system. Which is situated below the base plate Pressure switch is situated on the top plate to limit the movement of the c-clamp in the upward and downward direction.

The hydraulic system is brought near the machine and its pipes and ports are connected to the vales of the cylinder. There is a system of switches. The white switch is for the downward movement of the center piston which acts as the punch.

And the black switch is for the downward movement of the pressure plate with the help of the downward movement of side pistons. The red switch is for the upward movement center piston which acts as a punch. The blue switch is for the upward movement side piston which acts to move the pressure plate.

Sequential Control

Sequential control may be either a fixed sequence or a logical one that will perform different actions depending on various system states. An example of an adjustable but otherwise fixed sequence is a timer on a pressure switch. In a typical hard-wired motor start and stop circuit (called
a control circuit) a motor is started by pushing a “Start” or “Run” button that activates a pair of electrical relays.

The “lock-in” relay locks in contacts that keep the control circuit energized when the push button is released. (The start button is a normally open contact and the stop button is normally closed contact.) Another relay energizes a switch that powers the device that throws the motor starter switch (three sets of contacts for three-phase industrial power) in the main power circuit.

All contacts are held engaged by their respective electromagnets until a “stop” or “off” button is pressed that de-energizes the lock-in relay. (Note- Large motors use high voltage and experience high in-rush current, making speed important in making and breaking contact. This can be dangerous for personnel and property with manual switches.

Conventional deep drawing can be achieved without a blank holder as indicated in Figure 1, or with a blank holder as shown in Figure 2 (Malinin 1975; Popov 1977). Normally, the first method employs conventional drawing punches which consist of matrix 1 and punch 2. It is used for manufacturing shallow vessels or thin-walled articles with no folds or corrugation. Figure 1-b presents the second stage of deep drawing without a blank holder.

Blank holder 3 is used in the second method of the deep drawing shown on Figure 2. The collar section of the workpiece is pressed against the matrix by the blank holder in order to prevent corrugation from forming on the material, as the material is forced downwards through the matrix hole under the punch pressure. Figure 2-a shows the first stage of deep drawing by punching a flat workpiece whereas Figure 2-b shows the second stage of drawing the hollow workpiece.

Drawing dies 1 in Figure 3, whose chamber is filled with oil beforehand, overcomes the opposing compression of the hydraulic clamp 2 and initiates drawing of the blank part over punch 3. Due to the progressively growing pressure within chamber 1 oil starts flowing along channel 5 and then into channel 4 thus exerting radial pressure along the periphery of the blank part. Upon the consequent downward stroke of puncheon 6, the blank part is inserted into its receptive aperture

This causes oil pressure to increase thus exerting pressure against the lower base of punch 3 which is pushed upward and impacts this section of the blank that is inserted between puncheon 6 and mold 1. The opposing motion of punch 3, mold 1 and clamp 2 which is in permanent contact in relation to puncheon 6 is adjusted and synchronized electro-hydraulically. A general view of the test unit with its attachments and instrumentation is shown in Figure 5.

EMS Metalworking Machinery

We design, manufacture and assembly metalworking machinery such as:

  • Hydraulic transfer press
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  • Hydraulic deep drawing press
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  • Bandsaw for metal
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as a complete line as well as an individual machine such as:

  • Edge cutting trimming beading machines
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You can check our machinery at work at: EMS Metalworking Machinery – YouTube

Applications:

  • Beading and ribbing
  • Flanging
  • Trimming
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  • Lock-seaming
  • Ribbing
  • Flange-punching