Extrusion of Aluminium Profiles
1. About Project
The project relates to the author work on an aluminium profiles plant. ( Anybody may to get acquainted with the technology on the site: https://aluminium-guide.com/en/metallurgiya/ekstruziya/ . рус., engl.), [1]. Production control and management were so far from perfect. Illogical behavior of the officers will not discuss here. But this was the cause of several developed improvements were not inserted to production. Firstly some partial improvements of the technology were developed They were also accompanied with unjustified restrictions. Figuratively, when two legs of a man are broken. And due to any restriction or trivial laziness you heal only one. As a result you will have in any case – disabled. This logic appeared as example when tool releaser machine was developed. Unjustified decision was taken to make one half of the machine – release tool block from the base ring. Other half of the work, tool disassembly, were leaved on the 19th century level – hand work with jackhammer. This sample shown here with the aim, that THEORY not takes into account environment factor. It makes impossible to put on the Time-Dimensions-Cost operator.
Some of the technology elements are considered in brochure [2]. In the fullness of time it was set the task – reducing rejects. As part of it – to lessen metal loss. After analysis the problem was divided to parts - trivial step. Solving start was also trivial – human (factor) resources efficiency improvement. Difficulties were due to atmosphere of absurd (“non-human” factor as apart of environment). Particularly, systematic conscious lies in reports really bothered. Further main part of the problem – improvement of the profiles extrusion process.
2. The process analysis
The improvement required detail study of the technology. It was necessary to reveal clearly what happens inside container during extrusion. First of all, it was discovered the point of view of a number of operative specialists do not match any sense. As example, metal flow in contra verse direction to dummy block movement. It is impossible physically, energetically and what common sense tells. Further… more sadly. Theoretic monographs and text books gives also a horrible picture. Some drawbacks noted in Foreword and Introduction of “Analyses” in brochure [2] and article [3]. First part of “Analysis” published in site [1] (in Russian). As it was promised earlier, in brochure (part 8, Afterword) some key examples of the technology elements are given. All with improvement problem formulated.
2.1 First problem - Sticking of the billet material to dummy block front surface.
In part 8.2.1 of brochure formulation is given: “Functional analysis gives preferable way – constant surface covering, which meet all other requirements: tenacity to high temperatures till ≈ 500ºC and high contact stresses ≈ 650MPa”.
Solution (here given first time).
Part 1. The borating covering was chosen. Several probes of dummy block punch covering fulfilled by author. Characteristic obtained: depth – 0.2mm; surface hardness 51…52 HRc, slightly above of the steel H13 hardening 48…50HRc. Full scale tests were not accomplished by the same “non –human” factor influence.
Part 2. In order to avoid sticking reliably it’s worth to analyze aluminium conditions. This needs to imagine whole process (character cycle). Dummy block got cooled out of container before new billet loading. Billet just heated with the growing gradient of temperature from back to front. The die and butt temperature raised to maximum during extrusion. At the end of stroke temperature gradient of butt got rather more than at extrusion start. On the length ≈ 20…50mm – from ≈ 430 ºC till ≈520 ºC. ≈ 430 ºC – as appraisal, because of the heat transfer through dummy block. The aluminium strength in the dummy block surface (dead zone) seriously over the strength of the rest butt. Therefore at the backward movement of dummy block the metal rupture occurs not on the dummy block surface but at any distance from it. This happen independently on the adhesion conditions. The question arises is what have to do to prevent it? The only right answer is – to heat the dummy block all the time it stands out of container to temperature higher than billet one. The last, what still remain is to validate this solution.
2.2 Second problem
The butt elimination (part 8.2.2 in brochure). The work by billet to billet scheme. The quasi continuous process is possible with relation, that no any contaminations will be inserted into container. This mean the previous problem just solved.
3. Third problem (Not signed anywhere till now)
Two described above just solved. They relate to the process improvement. The third one defined by author as drastic technology change. By appraisal its solution relates to5…6 level by H. Altshuller classification. In part 7.4, p.38 of brochure wrote: “The additional stress field revealed near the die zone”. Earlier, in part 4.4.1, its distribution in billet volume and stresses numerical estimation was fulfilled. The yielding direction have been to take into account (part 5.3; 5.4, pp.31…36 brochure) – transverse relative to principal active compressing stress. Inevitable consequence from it is that transverse direction much more profitable, ≈ 2 times, for extrusion. It is not need to explain to operative specialists advantages of the extrusion force decreasing.
Author ready to consult, if somebody will take to “dress” this idea with metal.
4. Scientific results
The extrusion process first time presented with physically correct grounds. During analysis were defined:
1. Ratios between stress components, as the sample of deliverance of the theory incorrect assumptions.
2. General metal flow relations.
Except this, it’s remain a lot of possibilities for new extrusion mechanism detailing and development.
References
1. Aluminium Guide Ru , https://aluminium-guide.com/en/metallurgiya/ekstruziya/
2. B. Nudelman, Aluminium Profiles Extrusion Process Analysis. Mechanical aspects, Lambert Academic Publishing 2019, www.omniscriptum.com
3. B. Nudelman, Aluminium Profiles Extrusion Process Analysis. Вестник ОГУ №1 2018, Технические науки, http://vestnik.osu.ru/
DOI: 10.25198/1814-6457-213-92