Clogging of aluminum extrusion dies is a relatively common phenomenon. How to prevent clogging, reduce the occurrence of clogging and the harm to dies, equipment and personnel caused by clogging? And accurately collect the mold material heads and samples, and obtain the correct and detailed on-site information of defective products (trial molds) during production, which is convenient for mold correction. It is something that every front-line operator must take seriously!
Model Blocking Campaign
Die blocking refers to a phenomenon where the aluminum substrate gets stuck at the working band or the blank blade. During and after the die blocking process, the extrusion force rises to a high position, and sometimes it is extruded out in the shape of a blank blade. After the mold is blocked, the true condition of the profile cannot be accurately reflected and must be corrected.
Analysis of the Causes of the clogging die accident in Aluminum extrusion dies
Classification of causes of mold blockage
There are numerous reasons for die blockage, among which uneven die flow rate and extrusion operation are the two most prominent phenomena. The probability of other situations occurring is very low. Some of them can be explained in one sentence. I hope that when I write too little specific content, I won't say I'm stingy.
Mold blockage caused by mold reasons
2: Die blockage caused by extrusion operation reasons
3: Mold blockage caused by tooling reasons
4: Mold blockage caused by equipment reasons
5: Mold blockage caused by foreign objects being pressed in
6: Mold blockage caused by temperature reasons
7: Mold blockage caused by speed reasons
8: Mold blocking related to the shape of the profile
9: Mold blockage caused by other defects (such as bubbles, tears, material, center position, strong tail shrinkage, strong deformation, overburning, etc.)
Here is a real case of mold blocking and plug:
There is a set of extrusion dies, using a 180-ton machine with a φ184 extrusion cylinder. One side of the aluminum profile has a 40*40mm cavity with a wall thickness of 2.5mm. Connected to it is a 0.8mm wall thickness arc arm extending to the other side. The total outer diameter of the profile is 210mm, the cantilever diameter is 170mm, and the arc length is even larger. The weight per meter is about 1.5. No matter how large or small the machine is, it cannot be produced. It must be produced on a φ184 cylinder, which is an extended die.
Due to the significant difference in the thickness of the two side walls, the thin-walled arc part must protrude from the working band first, and the thin-walled extended part at the far end must also protrude first. If it comes out slowly, it will wrinkle in the working band. If it comes out quickly, it will bend towards the thick part and wrap the material head about 10 times, which can block the mold about 7 times.
Later, thin-walled products are taken out to remove and flatten the bent parts before being put back on the machine (note that the rods should be short, the temperature should be high, and the time for changing and removing the molds should be tight). Repeat this process 2-3 times in a row, reducing the number of mold blockages to one or two out of ten.
There is also an extrusion die. The outer diameter of the aluminum profile is 80*80mm, the outer wall is 4mm, and the inner diameter is 2.5mm. Inside, there are 12 male heads of various shapes and sizes. The middle male head is particularly small. After being put on the machine, some male heads are pressed off or even broken, and then the die is blocked. If the machine is not stopped in time after blocking, more male heads will break out. This set of molds is a one-time mold for the customer, with a quantity of over 2 tons of aluminum profiles. The customer provided 3 sets of mold models. The aluminium materials have been produced for two months. N sets of extrusion dies have been scrapped, but few qualified materials have been produced. All the extrusion dies have been damaged due to clogging.
The following measures were later adopted:
The working band in the middle part is shortened as a whole to reduce resistance.
2. The empty knife and the drainage groove should all be smoothed to reduce adhesion and lower friction.
3. The male head column base is lowered to reduce collision and sway;
4. Press up slowly at high temperature. When the aluminum is about to come out of the working zone, remove the mold. Apply graphite lubricating oil in the middle part of the die cavity knife and then press up slowly again. Place the extruded profile under the base plate to guide its straightness and prevent it from shaking. Two sets of molds were used to produce over two tons of profiles. The only difference was that there was a slight deviation in the thickness of the middle ribs. The customer accepted it and the task was completed.
The more complex the shape of the aluminum profile is, the higher the difficulty of aluminum production is, and the more attention should be paid to the unevenness in flow rate. This type of extrusion die should adopt a high-temperature and slow-speed extrusion method, with completion as the top priority rather than competing for speed and output.
