Methods for processing and shaping metallic and other materials

Abstract

Method for machining and shaping metallic and other materials in a machine tool with a drive system (42) arranged in the area of ​​the machine table (12) for the process-oriented force flow and movement sequence of the functional elements for the purpose of realizing the methods, characterized in that the upper tool (1) is designed as a clamping and clamping device and is connected to the upper tool holder (9) by means of machine elements operatively connected to it, consisting of at least two tension elements (7), at least two connecting rods (10) and at least two eccentric shafts (11) as well as a controllable balancing mechanism consisting of the pistons (29) for weight compensation,the unlockable check valves (30 and 31) and the compressed air reservoirs (45 and 46) allow the workpiece to be moved quickly and quietly from the workpiece removal position (43) to the stationary workpiece clamping position (44) and is connected to the lower tool holder (15) guided in the machine table (12) with the lower tool (5) and the drive system (42), consisting of the hydraulic pump (20), the accumulator (25), the unlockable check valves (21, 22, 23 and 24), which is operatively connected to the working cylinders (13) and the piston rods (14) and performs the machining of the stationary clamped workpiece (2).

Description

[0001] The invention relates to a method for machining and shaping metallic and other materials in a machine tool with a drive system arranged in the area of ​​the machine table. State of the art

[0002] The constant pressure to increase output while ensuring part quality and the constant cost pressure on both the operator and the manufacturer of forming machine tools require continued consideration in global competition.

[0003] It is well known that high-quality drawn parts can be produced with double-acting drawing presses. Such drawing presses with stationary sheet holding are also suitable for higher stroke rates if short-stroke working cylinders are used to ensure reproducible sheet holder forces and reduce impact in the sheet holder, as proposed in DE 40 06 101 A1. Unfortunately, the output of a press system with a double-acting drawing press as the lead press is limited because the workpiece formed with a double-acting drawing press must be turned before further processing in the downstream presses. When using a single-acting head press, turning the drawn part between the head press and the first downstream press can be omitted.However, profound changes are required not only to the drive and the drawing ram as the upper tool holder, but also to the cushion in the table as the lower tool holder, particularly for the synchronization of the moving upper and the stationary lower tool part before the drawing process.

[0004] To mitigate the quality-reducing impact of impact during the alignment of the upper and lower tools with the workpiece inserted, crank presses were initially replaced with more complex articulated presses. However, further modifications were necessary to ensure a moderate alignment process while continuously increasing the number of strokes.

[0005] In DE 41 12 942 A1, EP 0 716 916 A1, and DE 39 35 011 A1, it was proposed to temporarily significantly change the movement characteristics of the upper tool holder during the alignment phase with the lower tool holder. The design impact on the ram area and, above all, the control engineering effort required to ensure reproducible and stable clamping of the workpiece before the forming process across the entire drawing depth and stroke rate range are considerable.

[0006] EP 00 74 421 A1, DE 38 07 683 A1, DE 196 39 220 A1, DE 196 39 222 A1, and others have introduced solutions that actively accelerate the stationary lower tool, designed as a cushion, before the drawing process. These designs also require highly sensitive control requirements, particularly regarding the synchronization of the pre-accelerated cushion and the moving ram across the entire drawing depth and stroke rate range, as well as the variable cushion force.

[0007] Single-acting head presses in press systems are often equipped with hydraulic displacement cushions, which also have the task of implementing a moderate adjustment process between the upper and lower tool with the inserted sheet metal part in all drawing depth, cushion force and stroke rate ranges before the actual drawing process according to the principles of control and regulation technology, as proposed in EP 0 330 718 A1, DE 195 41 693 A1, DE 42 18 914 A1, among others.

[0008] Cushions in the table that operate according to the servo-hydraulic displacement principle require the use of highly sensitive electronic and hydraulic equipment to ensure process reliability, as the required sheet holding force curve must be guaranteed independent of the stroke rate, the drawing depth and the drawing speed, as well as problem-free restart after short-term disruptions.

[0009] Single-acting presses, which work against the cushion in the table during drawing, require increased drive motor power when using hydraulic displacement cushions or controlled pneumatic cushions, since the ram with the upper tool must apply not only the forming force but also the force required to clamp the workpiece throughout the entire drawing process. This clamping force, which acts along the entire drawing path, increases energy consumption and is irreversibly converted into heat. Cooling systems are required, which further increase the system's connected load.

[0010] Several proposals have been made to avoid unused clamping work during passive drawing. DE 40 28 921 A1, DE 41 00 716 A1, DE 41 01 606 A1, DE 41 21 869 A1, and WO 2012 / 139566 A2 propose solutions for synchronizing and clamping the workpiece between the upper and lower sections of the transient sheet support before drawing begins, and then forming it. These known solutions not only require considerable effort in production, assembly, equipment, and control, but also tie up significant effort until the first good part is produced, especially when dealing with a wide range of parts with small batch sizes. The additional space required reduces accessibility to the system.

[0011] The bottom-up forming process commonly used in stationary sheet metal clamping is well known from specialist literature (e.g., Handbook of Forming Technology, ISBN 3-540-61099-5). It is not only the most energy-efficient but also the most cost-effective method for forming metallic and non-metallic materials, because the energy required for forming can be supplied with minimal effort and via the shortest route.

[0012] DE 41 22 128 proposes a mechanical solution for bottom-up drawing using a hydraulic press. The bottom-up forming process is performed by hydraulic cylinders and a hydraulic drive of the lower tool located in the machine table area. The bottom-up drawing solution, which is implemented in a technically feasible manner in DE 41 22 128, is not suitable for use in highly productive press systems due to the low drawing speed and low drive power, especially since clamping the workpiece using a complex locking technique is time-consuming.

[0013] In DE 10 2010 037 950, the workpiece is formed from bottom to top using the well-known mechanical crank drive, which is mounted on the machine table and driven by an electric motor or servo motor in direct drive without an energy storage device such as a flywheel. For each drawn part, the enormous masses of the tool change table and the masses of the clamping plate with the lower tool attached to it must be raised and lowered, resulting in enormous energy losses. Clamping the unmachined workpiece is time-consuming, and the force flow is not clearly represented. Task and advantage of the invention

[0014] The invention is based on the object of further increasing the output and process reliability while ensuring part quality by means of a modified manufacturing process and by redesigning the press structure, reducing investment and operating costs, reducing energy consumption and expanding the field of application to include non-metallic parts.

[0015] According to the invention, the object is achieved by a method having the features of patent claim 1. Further detailed embodiments are described in claims 2 to 5.

[0016] The core idea of ​​the invention is to clamp the unmachined workpiece in a stationary manner and to establish the stationary clamping by means of a drive system arranged in the machine table area, in that the upper ram is designed as a sheet holder ram for holding the sheet and can be brought to a standstill and into the clamping position quickly by a drive arranged in the underfloor during the closing stroke without load and, supported by a controllable balancing, and that after the stationary and stable clamping of the unmachined workpiece, the active drawing tool designed as a lower tool carries out the deformation

[0017] The solution according to the invention provides the operator with the following advantages: The inventive modification of the operating principle and process steps for parts production increases process reliability because the number and duration of short-term disruptions are reduced due to the simplified manufacturing process, thereby increasing utilization and thus profitability. Furthermore, the modified process flow and the simpler machine structure enable a significant increase in the usual output. The change in the force and energy flow proposed by the invention no longer requires the drive from the headpiece with its drive elements, such as the clutch, brake, flywheel, gear drive, and lever system, thereby significantly reducing the overall height of the system. The total drive power of the system can be reduced because only the forming work for part production needs to be applied.The effort required for the transient sheet clamping required for the alignment process, which is common in the state of the art, is eliminated. The effort required to implement low-energy sheet clamping during passive drawing is also eliminated. The requirement for solid guidance of the blank holder ram is secondary.

[0018] The changed production process creates opportunities to efficiently form both metallic and other workpieces, as well as tailored blanks. Examples of implementation

[0019] Embodiments of the invention are illustrated in the drawing and are described in more detail below.

[0020] They show: Fig. 1a Path-time diagram of the blank holder ram and the drawing ram with stationary workpiece clamping of an unmachined sheet metal part Fig. 1b Path-time diagram of the blank holder ram and the drawing ram during unsteady workpiece clamping of a sheet metal part in the state of the art. Fig. 2 Mechanism of action when drawing from bottom to top for metallic sheet metal forming. Fig. 3 Mechanism of action when drawing from bottom to top for metallic sheet metal forming with 2nd forming stage to stiffen a sheet metal base. Fig. 4 Action mechanism for drawing from bottom to top for metallic sheet metal forming with sheet clamping by synchronized servo drives and active pneumatic cushion as drawing ram. Fig. 5 Mechanism of action when drawing from bottom to top for metallic sheet metal forming with mechanically synchronized and servo motor driven sheet clamping of a multi-ram press with drawing ram according to Fig. 2.

[0021] In the embodiment according to Fig. 2 is the mechanism of action according to the path-time curve according to Fig. 1a.

[0022] The upper tool 1 is designed as a sheet metal holder and is attached to the sheet metal holder ram 9. The sheet metal holder ram 9 is operatively connected to drive elements of the machine table 12 via guide elements 7.

[0023] In the machine table 12, for the rapid lifting and lowering of the sheet metal holder ram 9 and for the stationary clamping of the sheet metal part 2 inserted for forming, supported by the controllable balancing (29, 30, 31, 45, 46), preferably several crank drive pairs are arranged, consisting of at least two connecting rods 10 and at least two eccentric shafts 11, which are driven via worm gears 16 and via a central gear 18, preferably by a hydraulic motor 19.

[0024] The drawing tool 5 required for forming the workpiece 2 is mounted on the drawing ram 15. The drawing ram 15, which is guided in the machine table 12 for forming, is driven by piston rods 14 of the working cylinders 13 attached to it.

[0025] The required drive unit 42, consisting of a hydraulic pump 20, a hydraulic accumulator 25 with oil tank 26 and the releasable check valves 21, 22, 23, 24 for operating the drawing ram 15 on the one hand and the hydraulic motor 19 for driving the upper tool holder 9 on the other hand, are arranged below ground.

[0026] For complex drawn parts and for stretch forming, short-stroke cylinders 27 and 28 can be used in the machine table 12 and / or the drawing ram 15. They are active both individually and in groups during the forming process and can be controlled and regulated with minimal effort.

[0027] After the unmachined workpiece 2 has been placed on the stationary sheet metal holding ring 3, the hydraulic motor 19 is activated. At high speed, the eccentrics pull the underbalanced and unloaded upper tool holder 9 with the upper tool 1 onto the tool 2 by means of the eccentric shafts 11, which are rotatably or pivotably mounted on the machine table 12, and by means of the connecting rod 10. They clamp it stationary to the machine table 12 via the drawing ring 3. The active forming process is initiated by opening the valves 21 and 23. The pressure pistons 14 of the hydraulic cylinders 13 act on the drawing ram 15, which, driven by the accumulator 25, moves upwards with the drawing tool 6, thereby pressing the clamped and unmachined workpiece 2 into the upper tool 1 and deforming it into the workpiece 2. After closing the valves 21 and 23 and opening the valves 22 and 24, the drawing ram 16 quickly reaches its starting position.At the same time, the upper tool holder 9 also lifts off the workpiece 2 and rushes into its workpiece removal position 44. The finished workpiece 2 can be removed for further processing.

[0028] The embodiment according to Fig. 3 shows the closed tool according to the operating principle of Fig. 2 with a workpiece 2 formed in a second stage while maintaining the stationary clamping in the workpiece clamping position 43. The second forming stage begins after the drawing tool 5 has pressed the workpiece 2 into the upper tool 1. The punch 32, driven by the working cylinder 33, acts on the workpiece 2 via control elements not shown.

[0029] The embodiment according to Fig. Figure 4 shows, while maintaining the stationary workpiece clamping, the possibility of quickly raising and lowering the blank holder ram 9 by means of the drive unit arranged on the machine table 12 and supported by the controllable balancing system, via an adjustment drive 36 with a servo motor drive 37. Its drive power is optimized by the controllable balancing system, consisting of the piston 29, the releasable check valves 30, 31, and the compressed air reservoirs 45 and 46. After the blank holder ram 9 is closed by the servo motor drive 37, the workpiece 2 is clamped, and the forming process is initiated by opening the valve 24. The compressed air stored in the pneumatic piston 39 acts on the pneumatic cylinder 38 and this on the drawing ram 15. The pressure bolts 35 guided in the tool change table 34 push the drawing tool 5 guided in the lower tool 6 into the upper tool 1 and deform the clamped workpiece 2.

[0030] A further increase in the return speed of the drawing tool 5 is possible if, instead of the pressure accumulator 25, the alternative use of a pneumo-hydraulic pressure intensifier 40 becomes effective.

[0031] The embodiment according to Fig. Figure 5 shows one possible drive for the blank holder ram 9 of the head press and for the subsequent presses for finishing in a multi-ram press according to the invention. In the illustrated variant, the upper tool holders 9 are positively connected in the machine table area 12 via gears 41 and shafts 17 and are opened and closed synchronously by a servo drive 37. List of reference symbols 1 upper tool 2 Workpiece 3 sheet metal holder ring 4 clamping bolts 5 pulling tool 6 Lower tool 7 Tension and guide elements 8 Guide upper tool holder 9 upper tool holder 10 connecting rods 11 Eccentric shaft 12 Machine table 13 Working cylinder for the drawing ram 14 Piston rod for drawing ram 15 drawing rams 16 Worm gear 17 Connecting shaft 18 mid-gearbox 19 Hydraulic motor 20 Hydraulic pump 21 Pilot operated check valve 22 Pilot operated check valve 23 Pilot operated check valve 24 Pilot operated check valve 25 storage 26 Oil pan 27 short-stroke cylinders in the drawing ram 28 short-stroke cylinders 29 pistons for weight compensation 30 Pilot operated check valve 31 Pilot operated check valve 32 2. Drawing ram 33 working cylinders 34 tool changing table 35 pressure bolts 36 Adjustment drive 37 Servo motor 38 pneumatic cylinders 39 pneumatic pistons 40 Pneumo-hydraulic pressure intensifier 41 gearboxes 42 Drive system 43 Workpiece clamping position 44 Workpiece removal position 45 compressed air tanks 46 compressed air tanks

Claims

[1] Method for machining and shaping metallic and other materials in a machine tool with a drive system (42) arranged in the area of ​​the machine table (12) for the process-oriented flow of force and movement of the functional elements for the purpose of realising the methods, characterized bythat the upper tool (1) is designed as a clamping and tensioning device and can be moved quickly and quietly from the workpiece removal position (43) into the stationary workpiece clamping position (44) by the upper tool holder (9) by means of machine elements operatively connected to it, consisting of at least two tension elements (7), at least two connecting rods (10) and at least two eccentric shafts (11) as well as a controllable balancing system consisting of the pistons (29) for weight compensation, the releasable check valves (30 and 31) and the compressed air tanks (45 and 46), and with a lower tool holder (15) guided in the machine table (12) with the lower tool (5) and the drive system (42), consisting of the hydraulic pump (20), the accumulator (25), the releasable check valves (21, 22, 23 and 24), which is connected to the working cylinders (13) and the piston rods (14) is operatively connected and carries out the machining of the stationary clamped workpiece (2). [2] Method according to claim 1, characterized by that further processing steps can be carried out in the closed tool. [3] Method according to claim 1, characterized by that the time offset between clamping the workpiece and the start of pulling as well as the end of pulling and the workpiece unclamping is programmable. [4] Method according to claim 1 characterized by that the material-specific properties and influencing factors during the forming of metallic and other materials (e.g. plastic) can be taken into account by programmability of the time-variant pressure, speed and path curves of the drawing tool (5) and by variability of the pressure curve during stationary sheet holding. [5] Method according to claim 1, characterized by that in multi-ram presses the upper tool holder (9) of the head press can be used for stationary sheet holding and the upper tool holders of the follow-on presses can be operated with active tools for finishing the workpieces.

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