Archive for January, 2010
The same old results are no longer good enough!!
Happy New Year,
We enter the second decade of the 21st century with some understandable apprehension. 2008-9 were years of change, a change which may very well mark the end of the world as we’ve known it. But it was not the end of the world.
We can’t just hunker down, save our pennies, blame the brokers, and go back to business this time. The recession prompted a sudden end to borrowing, lending and spending, but we can’t simply quit everything. We have to learn to live and spend in moderation, and to be much more concerned about our health, and the health of the planet on which we live.
At this point in time, admitting that we are not certain exactly how to proceed may well be the key to a successful future.
In serving both the extrusion and die casing industries, further increases in productivity will require imagination, confidence, and determination. The only way to stay ahead is to pioneer the next generation of technologies that the increasingly industrialized world will require. The entire global business world has been reset, and we must act accordingly.
Now is the time for innovation. Question everything. In going from A to D, we’ve always gone through B and C. Is it possible to go directly to D? Do we really need to go to D anyway?? In almost any industry, most of what is done is based on what has been done before. Light metal extrusion and die casting are no exceptions to this rule. And, of course, everything is governed by that great empirical certainty that if you keep doing the same thing the same way, you’re going to get the same results.
And as we enter the second decade of the 21st century, the same old results are clearly no longer good enough.
Conscious Capitalism
Paul Hawken, warns, “Without a systematic and coordinated approach to climate change, energy production, oceans, food, militarism, poverty, and other issues, there will be an ecological and corresponding social collapse because the shadow side of private enterprise is narrow self-serving interests”.
Socialism doesn’t work, and communism doesn’t work. Capitalism also has its problems but it just needs to be modified a bit and practiced in a way that is not so mercenary.
Capitalism needs a rebirth, one that puts sustainability at the center. Conscious Capitalism is being discussed a lot these days. It moves corporations to refocus on purpose instead of profit. In other words making a positive difference in the world.
Also, the business should endure long for the long run. This requires salespeople who anticipate customers’ needs so that they get everything that they need, and that the company continually evolves and gets better.
The Conscious Capitalist leader manages in a manner to create synergies instead of trade-offs. Very often, companies who are truly CC will also give a percentage of their profits to charity and put a ceiling on executive compensation relative to the average employee’s compensation.
Most corporate law requires companies to maximize the return to their shareholders. The CC company considers factors other than just earnings in its decision making. They institutionalize values into the company. These need to be clear standards, not just nice stories. Typically these companies will consider environmental and social factors, as well as short-term profit every time they make a major decision.
A CC company sells good things and treats its employees, shareholders, customers, and suppliers well. The more they thrive, the more goodness they can spread.
Castool Tooling Systems makes the industries it serves better, while always considering the environmental and social impacts of its products.
Knowledge versus Information
Before discussing the advantages of knowledge, we must first understand the difference between knowledge and information. These words are often used interchangeably, but they should be clearly differentiated. Information usually consists of a body of recorded facts, opinions, ideas, theories, principles and models. On the other hand, knowledge refers to a person’s state of mind with respect to some body of information. This includes ignorance, awareness, understanding, familiarity, facility, and so on.
Knowledge can also be defined as the productive use of information.
Having separated knowledge from information, knowledge can then be further subdivided into two categories, explicit and tacit. Explicit knowledge is formal knowledge that can be explained, articulated, and communicated between individuals. On the other hand, tacit knowledge, or informal knowledge, is based on individual experience, and involves personal belief, perspective, and values. In the vernacular, this is usually referred to as ‘know-how’, and is a particularly worthwhile but often undervalued asset of any company.
Norton Returns
I am a fan of both motorcycles and creative business persons. I found this article about Stuart Garner and Norton, and thought I would share it with you. I wish Stuart Garner success.
By Ian Kerr Classic Motorcycles
It’s only been a few years since Kenny Dreer’s dream of relaunching Norton fell to earth. Despite attracting huge interest and praise, the move from prototype to production took more resources than Dreer and company could muster, and the venture folded before any production bikes were built.
But now, less than three years later, the Norton name is back in the U.K., this time under the sole ownership of a British businessman with passion for motorcycles, Stuart Garner.
The new face of Norton Garner secured the Dreer prototypes and rights to the Norton name in October 2008, and since then he’s been busily tying up lose ends in other countries, making sure he’ll have total ownership of all aspects of a brand that had been gradually split up over the past three decades.
Various projects surfaced over the intervening years, but with the exception of Dreer’s attempt, they were little more than high profile PR stunts, rather than earnest rebirths of a once proud racing brand.
This time, it’s serious. Garner has purchased two factories in Donington Park, one of the most historic racing circuits in the U.K. and current home to the MotoGP. He’s moved into one, while the second, a 15,000-square-foot facility, is being prepared.
A local man, Garner was born and bred within earshot of howling race engines circulating Donington. A successful entrepreneur, his extensive and diverse business interests have left him “comfortable,” but still interested in a challenge, and with a healthy interest in turning things around. Including, it seems, motorcycle brands.
Talking with Garner it quickly becomes clear this is not a business enterprise designed to be sold off to the highest bidder at some later stage; he intends to be part of it for a very long time. “I still have to remind myself each morning how lucky I am to be given the chance to own Norton,” Garner says. “I really look forward to going to work each day, and I have structured some of my other companies to allow me to concentrate on getting Norton back into production. By the end of this year our first customer will have taken delivery of their bike, which is after I have the first one to ride to work each day!”
Garner speaks with passion and sincerity, and while he clearly has a comprehensive business plan that he is willing to share parts of — on and off the record — he is moving slowly, getting things right.
“I am very aware that over the past few years there have been lots of public promises about new Norton machines that have come to nothing,” Garner says. “As a result, I also realize people may well be skeptical about my taking over and the future of the company. I cannot answer for the past, but I am not going to be rash and fall into the same trap as those in the past have done. “I was in the U.S. within 24 hours [of learning Norton Motorcycles was for sale] and, three days later, had signed the first lot of paperwork to buy it,” Garner continues. “At the time, I did not know exactly what I was getting into, but I had a feeling it was the right thing to do. Some advised me that I could not do the deal, but I proved them wrong and here we are,” he says with a huge grin.
Below Garner’s office in the building that will become the production plant are some of the prototypes developed by Dreer and his team. “People are expecting me to have the bikes ready now, but a prototype is just that — getting the tooling right and making sure the bike can be assembled on a production line are two different things. Everything must fit, there is no time to fettle things and we are currently getting the bike ‘productionized.’”
Along with these, one of the new rotary-powered NRV racing machines built by Brian Crighton and his team next door in the Spondon factory sits looking ready to go. At the time Dreer’s company folded, British frame builder Spondon (now owned by Garner), was licensing the Norton name back from the U.S. for a new rotary-powered race bike, the NRV588. The rotary was being developed by Crighton, the man responsible for the Norton rotary racers of 20 years ago; its revival is part of the rebirth of Norton.
Garner is intent on having as many components as possible made and produced in the U.K. “We may have to use some overseas suppliers, but these will be kept to a minimum, and only when a U.K. source cannot be found,” he says. “First up will be the 961 Commando, because that is a fabulous looking bike and reminds everyone of our heritage. At the same time we will sell race NRVs before moving on with a range of four machines based on an engine platform we have already established.” A limited run of road-ready NRVs is also planned, starting in 2010.
Garner says the first 200 961 Commando SEs will begin rolling out of the factory in August. Not surprisingly, they won’t be cheap; expect to pay roughly $26,000 at current exchange rates. Garner says 7,000 people have expressed interest in buying a 961 — he’ll offer the first bikes to them.
While Garner appreciates what John Bloor has done with Triumph, he has no intention of following his model. Garner is going to do things his way, and why not? It’s his money. Of course, not everyone is going to agree with his methods. For example, he tells us, there will be no U.K. dealerships. “We will handle sales at the factory and deal direct with the customer. The bikes can be serviced here and we will be able to offer them some track time and other incentives to make them realize they are buying a premium product and consequently can expect a level of service above and beyond the normal. I want to inject some fun and pleasure into ownership and make it special,” Garner says. “As far as possible I want to have an ‘open-door’ policy with customers, which is why I am working closely with the existing owners club. That is also one of the main reasons we are going racing to have some fun and generate some excitement.”
The original plans were to race the new Norton NRV588 at the Isle of Man TT this year, with Michael Dunlop, son of previous works rider Robert Dunlop and nephew of TT legend Joey Dunlop, at the controls. Unfortunately, rain and a cancelled practice run kept the team from qualifying for the May race.
Garner will be looking to appoint an importer in key markets like the U.S. and Australasia as well as Europe. Likewise, he has licensed various companies in the branded clothing market, where the use of the name had gotten out of hand. “Quality products have been licensed and other companies have been told to quit if they are producing products that are not in keeping with the brand,” Garner says.
Merchandising is one of three strands to his business plan, racing and road bikes being the others, but for now it is on the back-burner, hence his licensing of existing firms. “The bikes must come first to show we are serious and re-establish ourselves. I am aware of how well Harley does out of the merchandising of their brand and the income stream it gives,” he continues. “However, if we do well at racing and create a demand for the bikes, it will naturally follow.”
It is clear that despite his intention to have fun, Garner is very serious about bringing Norton back as a motorcycle brand to be taken seriously. “I would be happy to be on a par with Morgan cars, full order books and a waiting list of customers who are happy to wait for a quality product,” Garner says.
That product though will be a modern motorcycle. The 961 Commando SE is a link with the past that will eventually drop away when a new model appears. One link that Garner does want to keep, however, is with the descendants of Norton founder James “Pa” Norton, who have already visited and given him their seal of approval.
There are going to be plenty of doubters watching Garner’s progress with a certain dark interest, but I think they could be disappointed. Stuart Garner has already succeeded in other very diverse fields, and I have no doubt he will bring Norton back for good. MC
Resources: www.nortonmotorcycles.com
Failure
We typically think about failure in two ways: It’s either something to avoid or something from which we can learn simple personal lessons about perseverance and character. By encouraging risk-taking, the tech industry allows bad ideas to get out of the way so good ones can take their place.
Failure can change the world. They can serve as the necessary first round of innovation, or vision or breakthrough before perishing.
Everywhere you look, our world has been shaped by failures. Preston Tucker produced only 51 cars, but many of his ideas about safety prefigured the era of airbags and three point seat belts.
Every innovation will eventually be a failure. Each will be surpassed by something that does the same thing more cheaply or more effectively.
David Pye wrote in his book, The Nature of Design, ” Nothing we design or make ever really works. We can always say, what it ought to do, but that it never does. Everything we design and make is an improvisation, a lash-up, something inept and provisional”.
We need to take a look at technology as a steady march, a progression of increasingly better mousetraps that succeed based on their merits. But in the end, evolution may provide a better model for how technological battles are won. One mutation does not, by itself, define progress. Instead it creates another potential path for development, sparking additional changes and improvements until one finally breaks through and establishes a new organism.
In his book, The Evolution of Technology, George Basalla states that, “Only a few variants have the potential to start a new branching series that will greatly enrich the stream of made things, have an impact on human life, and become known as great inventions of turning points in the history of technology”.
Top 10 Worst Extrusion Practices (And How They Can be Avoided)
Worst Practices Checklist
- Press is not precisely aligned.
- Die is not uniformly and adequately preheated.
- Die is too strong.
- Die bearings are badly oxidized.
- Billet is poorly cut, surface is not clean.
- Billet is insufficiently taper heated.
- Dummy block is no longer contracting.
- Container is overheating.
- Container liner exit temperature is vertically inconsistent.
- Too much Dag is being used.
Much has been written about Best Practices for the extruder. A number of major multi-plant extruders already have Best Practices manuals. These are usually very detailed, and are meant to ensure that all their facilities anticipate anything that may prevent 100% quality and maximum productivity. The obverse to this is Worst Practices List. This includes common but avoidable problems in production system between the billet and the die. From this preliminary list, an extruder may identify some of the areas in his process that can be improved. Few extruders can honestly claim to have none of these problems.
It’s Not Just the Die
The die is the heart of the extrusion process and, until fairly recently, it was the main focus of the extruder’s attention. Now however, many die makers can provide dies that will make perfect product from the first push but only if the alloy is at optimum temperature for maximum speed as it enters a properly preheated die. The prime focus of extruder is now on improving the efficiency of his production process.
No attempt has been made to prioritize these problem practices since their real importance and frequency is impossible to quantify. For the extruder who is sincerely committed to ongoing improvement, concentrating on the basic purpose and function of each component involved in managing the temperature of billet, and utilizing the state-of-art technology currently available, is a certain formula for immediate improvement in both productivity and profit.
In discussing the function and effect of different parts of the extrusion process for the purpose of improving efficiency, it is advisable to avoid evaluating any part individually, without regard for its interaction with other components. Maximum productivity can only be achieved if all parts of process work together as a coordinated interactive system.
Overcoming Worst Practices
Press is not precisely aligned: Press alignment should always be the first item on any list of extrusion practices. Good extrusion depends on all components of the press being physically in precise alignment, and the die being mounted exactly in center of the container. If this is not done, good extrusion is impossible. Regular inspection at operating temperatures is essential, with emphasis always on pre-venting rather than correcting misalignment.
Die is not uniformly and adequately preheated: The die is usually designed to already be completely at operating temperature when the first push begins. If it isn’t, a perfect profile is usually impossible until one or two billets are wasted in heating the die. The answer to this problem is single-cell die oven. This will bring the die quickly and uniformly to operating temperature. To avoid the initial capital expense of complete battery of single-cell ovens, dies may be held at a moderate temperature for some time in a traditional chest oven, then the necessary heating quickly completed in a single-cell oven when the die is needed.
An extruder today should be able to assume that his die will produce good product immediately, and concentrate on optimizing his production process.
The die is too strong: Anything that prevents the die from creating good product at maximum speed and with minimum scrap is counterproductive. Unfortunately the die maker usually does not have the luxury of making a perfect die for perfect operating conditions. In real life he must provide a die that is best suited for its anticipated actual use.
If the die maker knows that die will not likely be uniformly at operating temperature before the first push, he must make it strong enough to withstand the resulting high breakthrough pressure. Press speed can then never be maximized. A strong die is a slow die.
If the die maker knows that the die will be uniformly at operating temperature before the first push, the break through pressure may be reduced by 30-40%. A lower breakthrough pressure allows cooler billet temperatures, and thus greater press speed.
The die corrector used to modify dies primarily to bring the profile to the required tolerances. The integrity of profile can now usually be taken for granted. The die corrector’s prime function now is to provide feedback on temperatures and breakthrough pressures to help the die maker to provide more productive dies.
Very high breakthrough pressure, for example, can bend die, and cause the core to deflect and distort the profile, once this danger has been understood and included in the design equation, large, thin, complex shapes that were previously thought impossible to efficiently extrude now become viable.
Die bearings are badly oxidized: When a die is held too long at or near operating temperature in chest oven, the bearings will oxidize. A satisfactory finish cannot then be obtained on the extruded product. The solution to this problem is, of course, the rapid and controlled heating of single-cell die ovens.
Billet is poorly cut, and surface is not clean: To avoid the air temperature and blisters from poorly sheared and two part billets, logs can now be precisely cut with an in-line narrow-cut saw, then welded together before being automatically cut into billets. When the end of the current log is detected, a new log from the magazine is positioned in the cutting line. The logs are then locked firmly in place, and their ends welded together. The joined logs then pass through the cutting and loading process as if no weld existed.
Billet should always be kept clean, because the skin may be inadvertently carried into the product. Scrap will inevitably result.
Billet is insufficiently taper heated: The friction of the die bearings causes heat to be increasingly generated in the alloy as it is pushed through the die. In order to achieve isothermal extrusion, that is, to allow the alloy to pass through the dir at its maximum operating temperature and speed at all times, the billet must be initially heated to a temperature that reduces from front to back in order to compensate for this heat of friction.
Taper heating the billet can best be achieved by electrical induction heating. To combine the economy of gas heating with accuracy and repeatability of induction heating, billets may be first preheated to a base temperature in a gas-fired oven. The hot billets are then transferred to an auxiliary induction billet heater where multiple separately controlled heating zones are programmed to quickly and accurately provide the necessary taper heating. Once the taper heating program for any shape has been confirmed by both calculation and experience, it can again be successfully used for even a single billet. If the temperature of the billet is not adequately tapered before extrusion begins, maximum press speed is impossible.
Dummy block is no longer contracting: For the dummy block to work properly, a thin film of alloy must remain between the block and the container liner at all times during the extrusion process. Its thickness should be uniform. With a soft alloy, the clearance that creates this film be only about 0.006 in. If the clearance is more, the alloy will penetrate the gap in the first push. If much less, this essential film of alloy will be stripped from the liner. Stripping the film of aluminum off the liner results in scrap due to blisters, and also to inferior alloy being carried into the extrusion, instead of being discarded in the butt.
An effective dummy block must expand quickly under load. It must separate cleanly from the billet at the end of the stroke, then contract immediately and return through the container without stripping the film of alloy from the liner. The measure of real value of a dummy block is its ability to continue to contact fully after an unusually large number of pushes, before it takes permanent ser and no longer contracts. The operating lives of contemporary dummy blocks can vary widely.
Container is overheating: If the container temperature sensors and heating elements are not close to the liner, overheating can easily occur, Heating elements, unless properly controlled, can reach temperatures of 1 ,300° – 1 ,400°F. The container mantle is usually of 4340 steel, which may begin to temper and soften at 1,000°F. If the mantle softens, bellying of the liner will likely occur. This will allow a buildup of impurities from the billet skin that will eventually end up in extrusion. Scrap will result.
Container liner exit temperature is vertically inconsistent: At the die end of the container, the temperature of the top of the liner is usually considerably higher than at the bottom. This is caused primarily by the heat rising inside the container housing. The result is that the alloy entering the die at the top is less viscous than at the bottom, and therefore flows at a greater velocity through the upper apertures,
A rule of thumb is that every 10°F difference between the top and bottom of the liner will cause 1% difference in the runout length. On a long table, unless the upper doe apertures are choked, major problems will occur, especially when using a puller. The solution is for the container thermal control system to have top and bottom as well as axial temperature control zones.
Too much Dag is being used: In the billet delivery system, the final factor is the introduction of lubrication. Ideally, the dummy block would pass smoothly through the container, and at the end of the stroke, the butt would fall off. Unfortunately this doesn’t always happen.
Too much lubrication has always been anathema to extruders. The old saying used to be, “Use no lubrication, then wipe off any surplus.” We have learned much about extrusion since then, and much about necessity and the effective use of lubrication.
At the end of each extrusion cycle, the fixed dummy block must separate instantly and cleanly from the butt, without pulling the extruded section from the die and also without breaking the mandrel or stud in the dummy block. Sticking can be a serious problem. It is essential, therefore that both the dummy block and the billet are properly lubricated to provide immediate and effortless separation.
Effective lubrication ensures instant and clean separation of dummy block from the butt. It also ensures clean butt release from the shear. It keeps the container seal face clean and free of alloy, and reduces scrap due to blisters.
Powder or liquid boron nitride, developed specifically for light metal extrusion, is today universally considered to be the ultimate lubricant.
Conclusion
Over the years, the buying practice of most extruders has gradually evolved. At one time relationship buying was common practice. The extruder’s supplier very often became a personal friend. He then usually had an opportunity to meet and competing supplier’s price. Next, almost all tooling was treated as commodity, and price took precedence over all else. Now, the astute extruder is making every effort to measure the real value of his purchases. He understands the importance of the interaction between some components, the value of undivided responsibility whenever possible, and the need for a detailed and tight specification to ensure that competing suppliers will provide products of at least equal value.
The successful extruder’s focus now is on improving profit by improving productivity. We can no longer afford any poor practices.
Key Temperatures
Tempering Temp. of Common Materials
H-13 46-48 HRC 585°C (1,085°F)
4340 34-38 HRC 540°C (1,000°F)
Max. Billet Temp. 485° to 500°C (900° to 930°F)
Max. Exit Temp. 570°C (1,085°F)
Alloy Melt Pt.
6063 600° to 650°C (1,110° to 1,200°F)
2024 500° to 640°C (930° to 1,185°F)
7075 475° to 649°C (885° to 1,185°F)
Heating Elements
Not Controlled 700° to 760°C (1,300° to 1,400°F)
Torch (Open Flame)
Not Controlled 3,000°C (5,000°F) Plus
Editor’s Note: After reading the most recent issue of Light Metal Age which included an illustration of a press operator with an open torch near an extrusion die, Paul Robbins sent this quick guide to key temperatures. We are including this key as part of Robbins’ instructive extrusion practices article to encourage better practices in the extrusion industry.
Aim Lower
Many of us have set 2010 goals for both ourselves and our businesses. I found myself thinking back to this blog posted in early November, and thought I would publish it again. I hope it is useful.
Paul
If you find yourself intimidated by the magnitude of an upcoming task, you avoid it. You put it off. That’s just human nature. but there’s really nothing wrong with lowering your aim. Break down the big project into a number of smaller ones that are more easily completed. You then have the gratification of reaching the goal you set for yourself, and often in a glow of self-satisfaction, you exceed it. By scaling down each goal, you can overcome your own inertia.
For example, I live on a 15 acre property. It’s mostly grass, some small gardens, and 70 Canadian Maple trees. Because of these lovely trees, I used to dread the annual fall clean-up.
Maple trees are green until late fall when they turn to brilliant reds and yellows. Then, not surprisingly, the leaves all fall off. There follows a brief window of opportunity when these colourful dry leaves must be raked up and disposed of before the first snowfall. If this daunting task is not done in time, next spring the melting snow will, to my chagrin, reveal a particularly unsightly soggy mess.
This major annual task caused me much trepidation until I set myself small goals of an hour or two hours raking at a time. And when my time is up I cheerfully quit with a clear conscience, knowing that I have reached my preset goal.
Much has been written about stretching goals, and if you feel particularly empowered, stretching your goals may be a useful test of your ability, but if you feel at all overwhelmed by the job ahead, stretching goals is an almost certain recipe for failure.
These more modest steps help us to conquer the apprehension that deters us from accomplishing many major tasks with confidence.
RDX (Robotic Die Expediter)
Castool’s Robotic Die Expediter schedules dies, accurately and safely heats dies, and compliments existing press practices.
The goal is to have the temperature of the die the same as the billet during the first push. Only then can we accurately predict break through pressure, and optimize die design.
Dies lose 5 degrees C every minute in air, and 10 degrees C every minute in the die slide. Break through pressure is increased by 1% for every 5 degrees C the die is below billet temperature.
The RDX monitors the die temperature from the moment the die is removed from the cradle by the press operator, until the ram pushes the first billet.
Fact vs Fantasy in Light Metal Extrusion (Part 1)
In extrusion, as in most other industries, there are some theories that seem logical and therefore often remain unquestioned. There is also some misinformation that calls for debunking.
A useful approach is, “If it sounds too good to be true, it probably isn’t.”
The following facts have been proven, and can be documented.
Regarding the Heating of Dies
Fantasy: Several years ago, a misguided but enthusiastic supplier actively promoted the use of microwave to quickly heat extrusion dies from within. He even claimed to reduce energy costs by using only the part of the infra-red spectrum that heats H13 steel.
Fact: A microwave oven generates heat by dielectric heating. It uses microwave radiation to heat water or other polarized molecules. This obviously does not include H13 tool steel.
Fact: Only the surface of the die is heated by radiation, the interior of the die is heated by conduction. Bringing the die completely and uniformly to the required steady state operating temperature can only be accelerated by increasing its surface temperature, and allowing it time to stabilize.
Fact: There are two main limiting factors in heating dies. The first is the danger of softening the die by heating it beyond its annealing temperature. For H13 steel, this is 1085ºF. The second factor is the danger of dissipating the nitride. This can begin at about 1000ºF.
Fact: The time required to heat any die can be accurately calculated from the following factors – surface area, mass, material specific conductivity, rate of energy input in KwHrs, rate of heat loss from the heating chamber.
Fact: The rate of heating depends primarily on the conductivity of the steel used.
Assurance
All the facts shown have been proven to be true, under standard operating conditions.
I will welcome any questions or comments.
Note: This is a 3 part blog, part 2 tomorrow and part 3 Wed.
Fact vs Fantasy in Light Metal Extrusion (Part 2)
In extrusion, as in most other industries, there are some theories that seem logical and therefore often remain unquestioned. There is also some misinformation that calls for debunking.
A useful approach is, “If it sounds too good to be true, it probably isn’t.”
The following facts have been proven, and can be documented.
Regarding Container Temperature Control
Fantasy: The increase in temperature caused by the friction of the alloy passing through the container liner is responsible for overheating and annealing the mantle, and the eventual bellying of the liner.
Fact: Container mantles cannot overheat solely from heat inflow from the billet – even at a billet throughput of 3 tons per hour on an 8” press.
Fact: Container mantles overheat and anneal, and liners belly, due to inadequate temperature control systems.
Fact: Isothermal extrusion is best achieved by taper heating the billet before it is placed in the container. Some speed control will also assist in maintaining constant exit temperature.
Fact: Mainly due to temperature build-up within the container mantle/housing, the alloy exiting the die at the top is usually hotter than at the bottom. This is particularly true of large containers. Since the viscosity of the aluminum alloy is reduced as its temperature increases, allowing it to flow more easily, any increase in temperature will be directly reflected in variable runout lengths with multi-hole dies, or shape issues with high vertical aspect profiles.
Fact: Accurately predicting and measuring the relationship between the viscosity of aluminum alloy and its temperature is difficult.
Fact: A practical rule of thumb used by some major extruders, is that a 5-10ºF increase in billet temperature may result in at least 1% increase in runout. If the difference in temperature between two vertically separated apertures in a die is 40ºF, the difference in runout could therefore be more than 4%. On a 200 ft. runout for example, an 8 ft. difference in length can certainly cause problems for the extruder.
Fact: Container temperature control cannot replace taper heating the billet for isothermal extrusion. However, if zoned vertically as well as axially, an effective thermal control system can eliminate any bottom to top increase in temperature in the die, and consequently eliminate an unacceptable increase in runout.
Fact: As it is often the most costly component of an extrusion production system, the operating life of a container and liner is important to any extruder. Containers almost never fail because of inadequate material, nor because of excessively high operating temperatures, containers usually fail due to overheating during preheating, as a result of inadequate temperature control systems.
Assurance
All the facts shown have been proven to be true, under standard operating conditions.
I will welcome any questions or comments.
Note: This is a 3 part blog, part 3 tomorrow.
