TUNDAL ULF (NO)
DE19633619A1 | 1998-02-19 | |||
EP0672473A1 | 1995-09-20 | |||
AT389655B | 1990-01-10 | |||
GB767472A | 1957-02-06 | |||
EP0425869A2 | 1991-05-08 | |||
US4817411A | 1989-04-04 |
1. | Method for calibrating extruded aluminium profiles (3) including an extrusion press (1) and, after the extrusion press, a runout table (2) along which is provided (1) a cooling means (6), a puller means (7) and a cutting means (6), characterized in that the profiles (3) are calibrated inline after cooling by a calibrating means (13). |
2. | Method according to claim 1, characterized in that the calibrating means (13) includes an inline roll forming or cold drawing operation or a combination of these. |
3. | Method according to claims 12, characterized in that the extruded aluminium profile is drawn to a second puller (8) on a second runout table (14) before being cut to predetermined lengths. |
4. | Equipment for calibrating extruded aluminium profiles (3) including an extrusion press (1) and, after the extrusion press, a runout table (2) along which is provided (1) a cooling means (6), a puller means (7) and a cutting means (6), characterized in that a calibration means (13) for calibrating the profiles (3) is provided after the cooling means (6). |
5. | Equipment according to claim 4, characterized in that the calibrating means (13) includes an inline roll forming or cold drawing unit. |
6. | Equipment according to claim 45, characterized in that the runout table has room for two full extruded lengths, whereby the extruded profiles (3,4) are cut in predetermined lengths by the cutter means (9). |
In the past extruders have improved the geometrical tolerances of the extruded sections by better die designs, better equipment for profile cooling and better control of the process parameters. This has to a large extent eliminated the need for any extra calibration operation for standard extrusions. However, for automotive applications where the parts go into assem- blies the requirement on geometrical tolerances are much higher, and normal extrusion toler- ances are normally not good enough without any secondary operation.
At the extrusion presses it is common to use carbon blocks or similar close to the press opening to control gap openings of extruded sections. This is, however, only a method for coarse adjustments of the dimensions. Since this calibration occurs when the profile is hot the geometry will not be very accurate because the dimension may change during cooling. Except for this method, no other in-line calibration methods are known to exist for normal extruded sections.
With the present invention is provided a method and equipment for calibrating extruded aluminium profiles that is more rational and efficient and much cheaper than the known solutions. The invention further improves the quality of the extrusion process by providing extruded profiles with much more narrow and consistent geometrical tolerances.
The method and means according to the invention are characterized by the features as defined in the accompanying claims 1 and 6 respectively.
Claims 2--5 and 7-10 define preferred embodiments of the invention.
The invention will now be further described by means of examples and with reference to the drawings where: Fig. 1 shows schematically an extrusion press according to the invention, Fig. 2 shows an example of a profile cross section that may be calibrated by an in-line roll forming or a cold drawing operation according to the invention.
Fig. 1 shows schematically, as stated above, an extrusion press 1 with a double length runout table 2 with profiles 3,4,5, a profile quench box 6, a first puller 7, a second puller 8, a saw 9, extruded profile stretchers 10,11 and cooling table 12. In a position right in front of the saw 9 and first puller 7 is provided a calibration unit 13 which either can be a roll forming unit or a cold drawing bench, or a combination of these. Fig. 1 further shows three extruded profiles, one 3 just emerging from the extrusion press 1, another 4 is provided at the end of the runout table and a third 5 is moved sideways an is provided on the cooling table 12.
The main feature in this setup is the double runout table 2 for the extruded profiles, i. e. obtain- ing sufficient space for two extruded lengths 3 and 4, one after the other, on the table. The first profile 3 in the order is extruded to its full length and reaches approximately out to the position of the saw 9 and first puller 7. The first profile 3 will not be cut at this stage. When a new billet is inserted in the extrusion press 1 and is extruded the profiles will weld together in the extrusion die (not shown per se). The two full lengths will then reach out to the second puller 8 when the said new billet has been extruded. In the dead cycle between the previous billet that has just been extruded and the new one to be extruded, the profiles are cut at the stop-mark between the two extruded lengths (the stop-mark is a mark originating from the extrusion die when the profile stops). After cutting, the profile 4 is moved sideways on to the cooling table 12 to the position of profile 5. This implies that there is always at least one full length of a profile at the runout table under the whole extrusion process (whole order). Having arrived the cooling table 12 the profiles 5 will be successively stretched by the stretchers 10, 11, typically 0.5-1.0%, in order to remove the residual stresses and to straighten the profile.
A double runout system as described above is possible to combine with a setup for in-line calibration of the extruded profiles. The profile 3 emerging from the extrusion press is fed through the calibration unit 13, but all further handling of the profiles takes place behind the calibration unit.
Since the profiles are being cooled down to room temperature by the profile quench box 6, there will be no problems due to variable temperatures of the profiles and no problems with profiles being so hot that they for instance would stick to the rollers. By doing the calibration in-line like this, the mechanical properties of the aluminium alloy will be very consistent. If the calibration is done at a later stage, off-line, the mechanical properties of the extruded profiles will vary with the time between extrusion and the calibration operation if the profile is produced from an age hardening alloy AA6000 or a AA7000. Since the spring back after cold forming varies with the mechanical properties of the profiles, an off-line calibration operation will not produce as good geometrical tolerances as an in-line calibration will do.
One of the challenges with the in-line calibration operation will be to ensure that the forces on the profile (s) at the die opening are fairly constant during the press cycle. With a normal puller system the forces applied on the profile (s) are typically between 25 and 200 kg depending on the alloy and the cross section of the profile. In a normal off-line roll forming operation the rollers are self-driven, and the profile will be pulled through by the rollers. When the roll forming operation is in-line with the extrusion operation, the pulling forces from the rollers should not exceed the forces that normally are applied on the extruded profiles. This is solved by having force control on the rollers. Another possibility would be to use a self-driven roller when feeding the first profile through, but then use the puller behind the roll forming unit to pull the profile through the roll forming unit for the rest of the order. If the roll forming unit is arranged at a slide where it is possible to measure the forces applied on the roll forming unit, the puller can be made to adjust for this and apply the correct forces on the profile.
Fig. 2 shows an example in cross section of a profile which may be calibrated by an in-line calibration operation according to the present invention. A profile with a cross section as here shown is difficult to extrude with very tight tolerances, especially on the gap opening of 39.0 mm between the vertical legs. This will be amplified if the profile needs to be water quenched in order to obtain a high strength of the material. With the present invention the profile will be extruded with a larger gap opening than the end product will have. The first profile 3 in the order will be fed through the calibration unit 13 that will force the legs inwards, probably by means of a mandrel between the legs. The calibration unit can either be a roll forming line or some kind of a cold drawing die that will correct the dimensions of the profile by some plastic deformation of the section. A relatively large variation in the gap opening prior to the calibra- tion unit will be reduced to a smaller variation after the calibration operation.
As compared to an off-line calibration operation, this setup will make the operation continu- ous without need for any extra floor space and probably also without extra persons for handling the profiles. Any marks or variations in the dimensions of the profiles, created by the calibration unit due to the stop and start of the extrusion, will be in the front end of the profile which has to be scrapped anyway due to weld zone between two billets, which is a weak region in the material.