Technical field

This invention relates to a method of manufacturing a product formed in a pressing tool according to the pre-characterising part of claim 1. The invention also relates to the use of the method according to the invention.

Background of the invention

E.g. in what are referred to as press-hardened sheet-metal products, subsequent cutting or subsequent punching is sometimes necessary in order to meet prescribed contour requirements and/or in order to achieve desired hole configurations, etc., sometimes in combination with high tolerance requirements. A significant problem encountered with cutting/punching in, e.g. a press-hardening tool is how to remove cutting/punching waste from the tool in a reliable and efficient manner.

One problem encountered when punching/cutting operations of this kind are carried out in the pressing tool is therefore the removing of the resulting cutting/punching waste from the pressing tool before a new initial blank is supplied to the pressing tool. This therefore has an adverse effect on the rate of production.

In order to solve the abovementioned problem, the cutting operations/punching operations are generally carried out in a separate machining station arranged downstream of the pressing tool.

By virtue of this invention, the required edge cutting/edge punching operations, hole cutting/hole punching operations, etc. can be carried out in the pressing tool without encountering the abovementioned problems. According to the invention, the cutting/ punching waste is/are taken along with the formed sheet-metal product when it is removed from the pressing tool for further transport in a processing line where the cutting/punching waste can be removed in a simple manner from the formed sheet-metal product without the risk of lost tolerance, etc. In press hardening where a pre-heated sheet-metal blank is form-pressed in the pressing tool and then cooled in the pressing tool, subsequent punching/cutting is particularly problematical on account of, inter alia, increased tool wear as a result of the hardening. This invention is particularly advantageous in this connection.

Aim of the invention

One aim of this invention is to provide a method that minimizes the need for subsequent working of, e.g. press-hardened products after they leave the pressing tool.

Another aim is to achieve an increase in quality and efficiency compared to the prior art.

The aim of the invention is achieved in that the method and the use have the features specified in the claims.

Brief description of the drawings

Figure 1a is a perspective view of a press-hardened sheet-metal product in the form of what is referred to as a B-pillar for a passenger car after forming, hardening and cutting/punching according to the invention.

Figures 1b-1d are partial enlarged views illustrating cutting/punching bridges according to the invention.

Figure 2 is a diagrammatic cross section showing a first method of weakening a bridge according to the invention.

Figure 3 is a diagrammatic cross section showing another method of weakening a bridge according to the invention.

Detailed description of the illustrated embodiment

Figure 1a shows what is referred to as a B-pillar 10 for a passenger car, the said pillar/product/component being formed by press hardening.

The product 10 is manufactured from a flat sheet-metal blank which is heated, then formed in a forming tool and cooled while being held in the pressing tool/forming tool so as to obtain the desired hardness. The aforementioned method of manufacture is referred to as press hardening and results in dimensionally accurate sheet-metal products of high strength since the sheet-metal component is pressed during the hardening process.

The product 10 shown has a central part in the form of a hat-shaped section with a central flange 15, two web parts 16, 17 and side flanges 18, 19. The product 10 is provided at its upper and lower ends with parts 25, 26 for connection to a vehicle chassis.

The press-hardening tool (not shown) comprises an upper and a lower tool half shape-cooperating to give the desired final product configuration.

In connection with the forming operation carried out, it is necessary to cut/punch the outer contour of the product or portions of the said outer contour, as well as to cut/punch holes or hole patterns in the relevant product. In order to achieve combined forming, and possibly hardening and cutting/punching, the forming tool is designed as a combination tool with the desired properties.

The sheet-metal waste or sheet-metal scrap produced during the cutting/punching operation causes problems in that, inter alia, it is difficult to remove the waste/scrap from the tool at the same rate at which the product is removed.

According to this invention, connecting bridges or land parts are produced between the waste/scrap and the product so that the waste/scrap is taken along with the product as it is removed from the tool. The waste/scrap can thus be removed from the product in a simple manner in a subsequent step.

Figures 1a and 1b show a cut/punched hole 30, wherein, according to the invention, a relatively narrow bridge/land 31 is left behind around the circumference of the punched/cut cut 32. The centre part 33 of the hole, now in the form of scrap, thus remains with the product 10 via the bridge/land 31. Figures 1a, 1c and 1d show a punched/cut cut 40 for removing an outer contour part

41 for trimming the product 10. The outer contour part 41 remains with the product 10 via at least one bridge/land 42. The outer contour part 41 , now in the form of scrap, thus remains with the product 10 via the bridges 42.

The presence of the abovementioned lands thus ensures that the waste/scrap is taken along with the product 10 when it is removed from the tool. The width of the land may of course be selected so as to obtain the desired retention properties.

According to the invention, the land can also be weakened as desired in order to further facilitate the removal of scrap.

Figure 2 shows an example of weakening of the land 50 of this kind in which a transition region (bridge) 51 according to the invention is weakened by partial shearing, e.g. by cutting or punching in such a manner that a part 52 of the scrap can be removed, e.g. broken off, from the relevant product 10 when the product has left the tool. The figure shows two tool components 101 , 102 effecting the said weakening of the land 50 in the form of a breaking notch or fracture notch.

Figure 3 shows an example of alternative weakening of the land 60 in which a transition region (bridge) 61 according to the invention is weakened by a V-shaped indentation 62 resulting in a narrow part facilitating the subsequent removal of a scrap part 64 from the product 10. The figure shows a tool component 200 with a V-shaped edge 201 which weakens the land 60.

It will be clear from the above that the lands/bridges according to the invention can, if necessary, be weakened in many different ways other than those shown in order to facilitate the subsequent removal of scrap.

It should furthermore be noted that the invention is suitable for both hot forming and cold forming. Press hardening is an example of an application for which the invention is particularly advantageous. Both hot punching/hot cutting and cold punching/cold cutting may be appropriate in connection with the invention. The invention may of course also be applied to the subsequent separation of what are referred to as multi-component couplings, i.e. when two or more products are manufactured simultaneously in one tool.

In summary, it can be stated that the invention eliminates or simplifies subsequent finishing, such as contour cutting and the making of holes in association with press hardening by providing complete cutting/complete punching in association with the press-hardening process, wherein lands/bridges are left behind, as a result of which waste/scrap is taken along with a press-hardened product when it leaves the press- hardening tool. The subsequent removal of waste/scrap from the product can be further simplified by providing the lands/bridges with weakened areas in the form of fracture notches or breaking notches. This allows for both manual and mechanised removal of scrap. The waste/scrap can thus be removed from the product in a simple manner in a subsequent operation by, e.g. cutting, punching or shearing or by breaking the lands/bridges.

It will thus be clear that the invention can be applied to components/products of any desired configuration. The invention is thus not limited to what is illustrated and described here, and amendments and modifications are possible within the scope of the following claims.