Precision Stamping Progressive molds

A progressive die is a multi-tasking die. Here we take a closer look at progressive molds.

The working principle of a progressive mold

A progressive die (also called a continuous die) consists of several stations, each associated with a different process in sequence, completing a series of different stamping processes in one stroke of the press. After one stroke, the press feeder moves the material forward in a fixed step so that several processes can be completed on one die, generally punching, drop feed, bending, trimming, deep drawing, etc.

Requirements for progressive molds

1.Smaller parts;

2.Large batches;

3.Thin material(0.08~2.5mm);

4.Soft material;

5.Complex shape;

6.Precious metals are not suitable (low utilization rate);

7.Not suitable for high precision (below IT10 level).

Features of progressive mold

1) Improve labor productivity and equipment utilization. Some complex small parts are almost impossible to produce without progressive molds.

2) Increased productivity and reduced costs. It also has the distinctive feature of being safe to operate.

3) The use of progressive die is also subject to certain restrictions: the size of the workpiece, too large workpiece, more king bits, large die, at this time to consider the die and punching machine worktable matching. As the progressive die has to use strip material, more scrap is generated for complex-shaped workpieces, so attention should be paid to the material utilization rate when choosing a progressive die. In general, the utilization rate of material for progressive molds is low. The accuracy of workpieces produced by progressive molds is generally low.

Materials for progressive molds

They are all long sheets. When the material is thick and the production batch is small, it can be cut into strips; rolls should be selected when the production batch is large. The rolls can be fed and collected automatically but stamped automatically with a high-speed press. The 11-step die has strict requirements on the thickness and width of the material. If the width is too large, the material will not be able to enter the guide plate of the die or will not pass smoothly; if the width is too small, it will affect the positioning accuracy and will easily damage the side edges, the convex die, and other parts.

The design of the progression diagram strip layout

1) The number of kings of the die spacing and the process content of each king.

2) The arrangement and sequence of the processes of the workpiece to be stamped.

3) The arrangement of the workpiece.

4) The die’s step, the strip’s width, and the material utilization rate.

5) The way of guiding the material, the setting of the pop-top, and the arrangement of the guide pins.

6) Basically, the mold structure is determined.

Notes on the design of the progressive molds

(1) When punching more holes, the length of the small convex die should not be too large. For multi-convex die medium-pressure die, the size of the convex die can be made into different heights according to the size of the convex die, forming a stepped type, which can avoid the maximum value of pressure in each convex die to be generated at the same time, which can effectively reduce the punching pressure of the die and reduce the load of the punching machine. (However, it should be noted that for the stepped die, to ensure sufficient rigidity of the die, the smaller die should be made shorter and the larger one longer, with a difference of one height between the two is the thickness of the sheet). This way, the larger holes are punched, then the smaller ones. Otherwise, the material will be squeezed by the small die when the medium and large holes are punched, and the small die will be broken due to insufficient rigidity.

(2) Continuous molds should try to add blocking, side edges, and other step positioning devices to ensure the accurate positioning of the workpiece in the continuous mold and to ensure that the step of the continuous mold is the same so that it is possible to punch out qualified parts.

In continuous molds, common positioning devices are fixed stopper pins, guide pins, side edges, and other forms. When stamping, the fixed stopper pin is used for initial positioning, and the guide pin installed in the die is used to ensure the correct positioning of the strip when the material is dropped. The side edge controls the distance the strip is fed in each step. The length of the side edge should be equal to the step length plus 0.05-0.5mm, depending on the thickness of the material.

(3) The guide pin of the continuous mold should not be too long. The continuous mold must have a good positioning device to control the feeding distance. The commonly used positioning devices are guide pins, initial stop pins, side edges, guide pins, etc. Among them, the guide pin is a precision positioning method widely used in continuous molds, and it can also be used with the misfeed detection sensor to stop the alarm and protect the die. In high-precision continuous die stamping, it is common to punch a pre-center hole and then use a guide pin to guide the roll in each step. In this case, the diameter of the guide pin is usually 1.2-6 mm, and care must be taken that the length of the pin is not too large, nor is the length of the hole into which it enters. Otherwise, it will cause poor die feeding, with material, etc. For this reason, the length of the straight body of the guide pin of the continuous medium-pressing die should be the thickness of the fixed template of the guide pin + 1 material thickness.

(4) In the continuous die and another automatic punching die should not be used to unload the components of Urethane or polyurethane rubber; for continuous die, this kind of high-efficiency production dies, its life is often in 500-5 million strokes above, punching speed in 40 times/min above if the use of Urethane and polyurethane such elastic components unloading, on the one hand, unloading force may be insufficient, unloading unreliable, on the other hand, their life is also limited, to To ensure that the continuous die works reliably and normally and to reduce maintenance, a spring with a healthy life should be used as the unloading element.

 

(5) Complex or slender shapes in continuous stamping molds should not be sub-struck

Complex and slender shapes in continuous molds should not be punched out at one time but should be split into several center heads and punched in parallel if the process allows. Improving production efficiency

 

 

(6) Designing empty steps to facilitate commissioning and mold change

The design of continuous deep drawing parts or the forming size of unsafe products can not ignore the design of an empty station. For this kind of mold, in the sample drawing design, often the first human pulls tea into will D after leaving an empty station; leaving some room to make the mold after the trial can also be appropriate changes and adjustments. The cover part is left empty between the third and second drawings. In addition, the die is protected when the die’s opening is too close to the die. For the construction of concave die inserts, small die holders, carbide inserts, etc., it is also necessary to leave empty spaces on the sample drawing. Leave an empty space between the shaping step and the final drop step to facilitate the installation of the concave die and the unloading plate and improve the concave die’s strength.

(7) Anti-chip jumping design

The die is a continuous stamping process, especially when there are many punching holes and cutting edges. To avoid crushing the product and the stability of the die, it is usually necessary to do an anti-scrap jumping structure. Mainly from the starting points: 1. punch made of shaped, can increase the adhesion of the waste in the moon day; 2. punch plus blow hole; 3. edge to do V or dovetail card form; 4 reasonable put punching gap, reduce jump 5. die suction waste device

(8) The carrier of the continuous die should not be deformed

The lap side of the material transfers the workpiece of each process in the continuous die, and the part is usually separated from the material in the last drop process. This lap is called the carrier of the continuous mold. In continuous molds, the common forms of carriers are edge carriers, intermediate carriers, double-sided carriers, single-sided carriers, and so on. The edge carrier is used to punch a guide hole in the workpiece’s edge stock to position it for deep drawing, bending, and other forming processes. This type of carrier is simple, reliable, and material-saving in design and is therefore widely used. The intermediate carrier is a carrier that cuts away most of the material around the workpiece along the strip, leaving only a small amount of connecting material in the middle of the strip width. This carrier is not rigid and is often used for continuous stamping thin workpieces with a large feed. This carrier is less rigid and can only be used for continuous stamping of workpieces with a large material thickness and a small infeed. As continuous molds require high step accuracy, the carrier must not be deformed to ensure the step’s dimensional accuracy and improve the stability of the continuous die operation. To ensure that the carrier has sufficient strength and rigidity, often use an appropriate increase in the size of the lap; if single-sided carrier strength is not enough, you can design a double-sided carrier and intermediate carrier; punch out the process cut between the carrier and the workpiece, so that the carrier and the workpiece are separated, the deformation of the workpiece will not affect the deformation of the carrier and other measures.

(9) Quick release and part dummy prevention

In the design of continuous molds, quick release of parts and anti-dulling of parts/standard parts are particularly important. Because of the need to achieve rapid mold repair, the complete mold is rarely removed from the machine for continuous mold maintenance, but rather the parts and templates are removed individually for repair in the event of a stoppage, so a quick release structure is required. While removing the parts and formwork to replace them with new parts, it is often easy to misload the parts and misdirect the formwork, resulting in broken molds, so attention needs to be paid to parts and formwork dummy proofing.

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