Aluminum Extrusion: Die Adjustment

Almost every new extrusion die for extrusion of aluminum requires adjustments:

• to eliminate deviations from the specified cross-sectional dimensions;
• to eliminate deviations of the profiles in straightness and twist angle.

Correction of the matrix consists in accelerating or slowing down the outflow of metal in certain parts of its working belt.

Matrix Adjustment Reasons

There may be several reasons for the adjustment., including:

• errors in the design of the matrix;
• inaccuracy in the manufacture of the matrix;
• deviations from perfect press alignment;
• uneven heating of the workpiece;
• inhomogeneity of the container temperature;
• heterogeneous temperature of the die and other pressing tool.

A die corrector

A key figure in every aluminum profile production is an experienced matrix spotter.. When he plans to adjust the next matrix, then scrolls in my head, least, following extrusion press parameters, with which it works:

• matrix temperature;
• container temperature;
• workpiece temperature;
• pressing speed;
• the degree of alignment of the press;
• technical condition of the matrix;
• the degree of wear of the auxiliary matrix tool (matrix holder holder, lining, bolsters).

A good matrix corrector always has more than one way to solve a specific matrix problem.. Therefore, some consider, that matrix adjustment is closer to art and intuition, than to science and technology.

Nonetheless, over the years, some typical - and completely technical - matrix adjustment methods have developed in the production of aluminum profiles. At least, simpler, solid matrices.

When correcting solid matrices, the following methods are usually used:

• Adjustment of the working zones of the matrix.
• Correction of the matrix body for the redistribution of metal flows in it.

Correction of working belts

Acceleration – brake angle at the outlet of the girdle

To accelerate the flow of metal in a certain section of the profile in the corresponding place of the working belt of the matrix, expansion is performed at the exit from the belt. To do this, a file or a drill cut off at an angle the edge of the plane of the girdle on both sides of the channel. In the new matrices, all the original bands are usually horizontal and parallel. The Russian term for such an operation is execution brake angle on the working belt.

The figure 1 It is shown how the spotter balanced the flow of metal by performing a brake angle on the belt.

Figure 1 – Releasing angle on the working band of the matrix [1]

English term for brake angle - relief. This word has many meanings., among which there is even the word "relief", but its main meaning is “relief”. Applied to aluminum extrusion - this means facilitating the flow of metal, i.e. its acceleration.

Slowdown – angle of braking at the entrance of the belt

To slow down the flow of metal in a certain section of the profile at an appropriate location in the matrix band, the angle of the band is cut, but no way out, and at the entrance (figure 2). This angle is called braking angle.

Figure 2 – Deceleration angle on the working band of the matrix [1]

English term for braking angle - choke. This word also has many meanings., and the main ones are the noun "throttle" and the verb "choke". Applied to aluminum extrusion - this means braking or obstructing the flow of metal, i.e. its slowdown.

Alignment of metal flow over the profile section

When pressing a profile such as a channel or a similar element of a more complex profile, the following problem often arises: the metal in the flanges flows too quickly compared to the wall. This is manifested in the waviness of the shelves (figure 3).

Figure 3 – Waviness of channel flanges [1]

To correct this uneven flow of metal, it is necessary to accelerate the flow of metal in the wall. To do this, in the girdle of the wall perform a brake angle, as shown in Figure 4.

Figure 4 – Releasing angle for channel wall acceleration [1]

Correction of "filling up" shelves

Another typical case: the shelves of the channel "overwhelm" – inward or outward (figure 5). Depending on, the shelf falls in or out, the spotter of matrices will perform on the belt with a file or a drill immediately and the braking angle, and brake angle, to make the shelf move in the right direction

Figure 5 – Correction of the collapse of the channel flanges [1]

The figure 6 shown, as the spotter performed on the right shelf the brake angle on the inner belt and the braking angle on the outer belt. After such operations, the regiment will move inside the channel.

Figure 6 - Correction of the working belt of the channel
when the right shelf is rolled out [1]

The figure 7 shown, how to perform on the right shelf the brake angle on the inner belt and the braking angle on the outer belt. After such operations, the regiment will move inside the channel.

Figure 7 - Correction of the working belt of the channel
when the right shelf is folded inwards [1]

Redistribution of metal flows

The figure 8 it is shown how to perform the adjustment by redistributing the metal flows through the matrix. The working belts are always at an angle of 90º to the matrix mirror. In this case, the spotter accelerates the flow by cutting metal on a matrix mirror around those sections, which require acceleration. The same result is obtained by cutting off part of an excessively long girdle from the back of the matrix. Both methods are widely used and both give good results..

Figure 8 – Acceleration of metal flow by reducing the length of the working belt [1]

Source:
1. Luis Bello, Die Corrections for Changing Flow Characteristics, Aluminum Extrusion Technology Seminar, Chicago, 1977