The most commonly used materials for extruded stems are high-quality wrought AISI H-13 (1.2344) hot-work tool steel and forged tool steel. The stem is heated to austenitizing temperature, quenched, and tempered to a hardness in the range of 415-460 Brinell (Rockwell C44-48). Its strength depends on its sustained hardness at operating temperature and the absence of internal stresses. The Role of the Extruded Stem The extruded stem must operate repeatedly and continuously under very high compressive loads. Therefore, it is crucial that it remains perfectly aligned throughout its entire stroke length. Alignment should be checked weekly. Due to the high pressures to which the extruded stem is subjected, the load must be applied evenly. Uneven loading will eventually lead to bending or fracture. This can be caused by a variety of reasons, such as improper installation, platen deformation, and press misalignment. As mentioned above, these situations must be carefully avoided, as catastrophic fracture of the extruded stem is possible. Extrusion rods typically use a bayonet coupling that quickly and securely locks the extrusion head to the rod. This makes replacing very hot blocks much easier and faster than with traditional screw- or rod-type couplings. Supplementary stabilizing studs are used to prevent lateral movement on newer presses where alignment is not an issue. Care must be taken when designing and machining bayonet couplings in extrusion rods to avoid potential stress risers that could cause breakage. Extrusion Rod Maintenance Extrusion rods should be stress-relieved periodically, depending on the size of the press and the number of thrusts. Existing extrusion rods can be adapted to the bayonet system by attaching a spacer. The extrusion rod threads are cut and machined in the hole to attach the stud. It is important that the extrusion rod and spacer faces match exactly, with no gaps. Dowel pins must be installed across the diameter of the extrusion rod/spacer to prevent rotation. If gaps develop between the extrusion rod and spacer, the stud will bear the full force of the plunger, causing the threads to foul and becoming extremely difficult or impossible to remove. Extrusion rods should be placed vertically in an oven and heated to 1000°F (540°C) at a rate not exceeding 1000°F (550°C) per hour, then maintained at this temperature for one hour per inch (25 mm) of extrusion rod diameter. Remove from the oven and allow the extrusion rod to cool in still air at room temperature.

All aluminum alloys can be extruded, but there are some factors to consider when determining whether a particular part can be successfully extruded. Factors such as size, shape, alloy, tolerance, scrap rate, extrusion ratio and tongue-and-groove ratio. And whether you should use forward or reverse extrusion for production. The forward extrusion process is the most commonly used process in the extrusion industry. It is simpler in design and more flexible in profile manufacturing. The benefits of the reverse process (often called reverse extrusion) include reduced friction and improved consistency. The enhanced consistency is manifested in the dimensional and metallurgical structure along the length of the extruded profile. The reverse process is used to achieve more consistent workability, for example, in rod and bar products through more consistent metallurgical structure. Enhanced dimensional tolerances help rods used as screw machine billets. Forward Extrusion In the forward extrusion process, a heated aluminum billet is pushed through a fixed die by a cylinder head to form a specified shape. The aluminum flows in the direction of the plunger's travel, creating friction between the billet and the container. This increases the workload during the extruder cycle, resulting in higher temperatures before and after the extruder. This variation in work and temperature along the length of the extrusion results in a change in the metallurgical structure along the length of the extrusion. The temperature variation and increased work along the length affect the grain structure and microstructure, which are important for machinability. Dimensions are affected by the pressure on the die of the extruded profile, which decreases during the extrusion cycle. Pressures in the indirect process are highest at the front of the extrusion due to the additional force required to overcome the pressure. Reverse Extrusion In the direct extrusion process, as described above, the die is stationary and the ram applies pressure to the aluminum bar. In the reverse extrusion method, the extrusion head carries the die and applies pressure to the stationary aluminum bar in the opposite direction of the extrusion. There can be variations on this concept, but in all cases the aluminum bar is stationary relative to the container. Therefore, there is no billet-to-container friction effect and the forces in the extrusion process remain relatively constant from the front to the back of the extrusion. As an added benefit, the work also remains relatively constant, eliminating friction in the direct process. Advantages and Disadvantages of Reverse Extrusion The result of reverse extrusion is a more consistent work and less temperature variation throughout the length of the extrusion. This provides more consistent dimensions, grain structure, and mechanical properties. The reverse process does have its pros and cons. For example, since there is no friction, anything on the surface of th...

1) Correct die numbering. Die, suffix, backing, pad and feeder plate numbers are important. If the number on the die is wrong, it can be a loading and running error, leading to major problems. Also, the date and vendor ID are needed. Advanced factories now use lasers to put computer identification codes. 2) Check for metal chips or shavings from the manufacturing process. These tiny metal chips can hide in the weld chamber area or work belt area of the die and form die lines in the extruded product or may form. 3) Check that the die and related tooling meet Rockwell hardness standards. Although most die manufacturers check this thoroughly, it is not impossible to be off by a few Rockwell C points. 4) Tool diameter, thickness and step size. It is better to be safe than sorry. Checking the tool size will prevent the tool from getting stuck in the die ring or coming loose, causing misalignment and/or aluminum seeping into unwanted spaces, butt shear forces hitting the tool surface, etc. 5) Pinout of the die opening. This will tell you what the tool deflection on the die is, which is very useful for future dies. It will provide accurate information to zero in the minimum weight per foot, thus allowing for the maximum weight per die. 6) Support tool clearance. Check backing, shim, subshim and platen openings for interference. It is best to grind in some clearance, which will reduce the possibility of clogging and/or possible damage to the components. 7) Proper support for overhangs, etc. Make sure the backing and supports have proper support to eliminate as much tool deflection as possible and minimize the chance of tool breakage. 8) Proper exit size, check that the step behind the work band has proper clearance. Key tongues, screw bosses, etc. should have a minimum clearance. Too much clearance will cause the die to collapse and squeeze out the scrap. A blanking of approximately 0.040 inches (0.10 mm) is considered normal.  9) Proper die support. On the tongue, you want maximum support for best results. In areas with small or long tongues and screw bosses, a zero degree back taper is usually required.  10) Work band finish. Check the die work belt for: Wire cut lines, scratches from files, gauge pins or emery paper. Scratches from shipping Rail EDM or milling relief Burrs on the exit side of the work belt; it is best to catch one of these points and check before sampling or attempting a batch extrusion order.  11) Work belt flatness, verticality. The importance of these cannot be overstated.