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EXTRUSION TODAY IN NORTH AMERICA (Alum Times July 2009)

For Better Extrusion

Better extrusion is just now being done in North America than has ever been done before.  There are several reasons for this.  The first, perhaps, is that better extrusion actually can be done.  The productivity of any aluminum extrusion plant can be improved.  There are no exceptions to this basic rule.  And in fact, virtually every extruder knows how to do it.

Better extrusion begins with a sincere commitment to ongoing improvement by everyone in the company, beginning with the Chief Executive Officer.  In North America, however, a fairly common problem in the past decade or so has been that the CEO was not always an extruder.  Many companies were being run by so-called financial engineers on behalf of the investment bankers who owned them.  Often with almost no knowledge of the extrusion business in upper management, their goal was simply to increase the value of the companies in the short term in order to sell them. Priorities were more on short term financial gain than on long term improvement in productivity. Downloading to middle management any major decisions regarding investments in long term improvement just doesn’t work, because any personal reward for improvement is insufficient to offset the risk involved.

Situation Changing

This situation, however, appears to be changing.  A good example of the positive direction extrusion is now taking in North America is the fairly recent takeover of Indalex by the Sapa Group.  With headquarters in Sweden, Sapa today is the world’s leading producer of aluminum profiles, and an organization that is run by senior executives who are all very capable and experienced extruders.

Another reason that better extrusion is now being done, is that since the recent  economic crisis, many extruders have understandably become extremely well motivated to improve their productivity in order to remain in business. To paraphrase an old aphorism, nothing so focuses the mind as the possibility of imminent bankruptcy.

Extrusion Today

The evolution of the extrusion process, as we just now know it, has about reached its logical end. For example, in theory ram speed should be limited only by the optimal operating temperature of the alloy being run.  If all the components of a contemporary extrusion production process are operating at maximum efficiency, and interacting effectively together as a single holistic system united in common cause, maximum productivity may already be closely approached.  Consider the effective operation of an extrusion system having the following components, all of which are currently available.

- Billet Heater

A billet of the leanest possible alloy will be precisely taper-heated in such a way that the temperature reduction in the billet when it reaches the die will exactly match the temperature increase that results from the friction of the alloy passing through the die.  The flow-stress of aluminum is extremely temperature-sensitive.

-Die Ovens

A single-cell die oven will heat each die accurately, uniformly, safely, and quickly.

-Container

As the temperature of the die closely reflects that of the liner, the container thus controls the temperature of the die.

-Dummy Block

The dummy block will expand quickly under load, and maintain a secure seal with the container wall, leaving only a thin film of alloy on the round and straight liner.  -Extrusion Die

The extruded section is not made by the die, it is made in the die.  A good die will allow a profile to be made at the optimal operating temperature of the alloy being used.

-Quench

The production of no profile can be considered complete until it has passed through an effective quench to properly set the alloy.

-Visual Optimizer

This is the most useful tool yet devised to help the extruder maximize productivity.  A large back-lit monitor is positioned above the press, near the operator’s post.  On the screen, all critical temperatures and speeds that can be controlled by the operator during production are shown, plus the status of dies waiting to be run.  Target temperatures and speeds from a previously prepared formula are also shown.  Actual figures within 5% of target are shown in green, all others in red.  The operator can tell at a glance what needs adjusting.  The most productive formula from a previous run forms the initial formula for a repeat run.

Extrusion Tomorrow

As the economy once again improves, extruders that will be in the best position to succeed are the ones that didn’t mortgage their future.  Just now, most extruders are diligently looking for every way to cut costs and meet short term demands.  One of most common mistakes an extruder can make just now is to slash his maintenance budget, and the financing required to refurbish or replace components of his production system that have over time become worn or outdated.

The North American economy has not just been reduced, it has been reset. It is very unlikely to return to its 2007 level in the foreseeable future,  But the demand for aluminum product is quite likely to soar.  Aluminum is the metal of tomorrow, strong, light, and very recycleable.  The market for extruded aluminum in North America could surpass all previous records.  The greatest increase in available market share will go to the companies that are run by extruders who didn’t simply survive the present, but who planned for the future, and entered recovery well equipped both materially and philosophically to take best advantage of an unprecedented opportunity.

A bit of background…
The temperature of the billet should be closely controlled from the time it is heated until it passes through a uniformly heated die.  This is best done by immediately correcting any variations in the temperature of the container liner as soon as they occur.

The QR Container
The time taken to respond to a demand for heat is in direct proportion to the distance between the temperature sensor and the heat source.  In the QR or Quick Response Container, with at least four zones, vertical as well as horizontal, cartridge heaters are located close to the liner. Their purpose is to heat the liner, not the mantle, and thus maintain a consistent billet temperature as the alloy enters the die. Specially designed double thermocouples are used to monitor the temperature of both liner and mantle simultaneously.

The QR Container and Temperature Control
The heating elements are positioned close to the temperature sensors. The quick response that results ensures that the liner temperature will remain fairly constant. The risk of overheating, tempering, and softening the mantle is also virtually eliminated.  Also,since the demand for heat is so quickly satisfied, the cost of operation is minimized,

The viscosity of the alloy being extruded is extremely temperature-sensitive.  The die designer must, however, assume that the die will remain completely and uniformly at optimum operating temperature at all times during extrusion.  For this to happen, the temperature of the exit end of the container liner must be very closely controlled during the extrusion process, because the temperature of the die very quickly reflects that of the container.

Experience has shown that a QR container, which is designed primarily to heat the liner rather than the mantle, can reduce the amount of energy used by as much as 75%.

The thermal mass of the container is much greater than that of the die stack.  Accordingly, as soon as the die is firmly sealed to the end of the liner, heat transfer begins by conduction, and continues rapidly until a thermal equilibrium is reached.

Especially with large containers, unless closely controlled, heat lost from the bottom of the container mantle rises inside the housing, and considerably increases the temperature at the top.  With conventional containers, the vertical temperature difference at the liner exit is typically 150-200ºF (85-110ºC).

Achieving Precision through Better Temperature Variance
Thermal measurements have proven that during extrusion the difference in temperature between the top and bottom of the die is approximately the same as between the top and bottom of the liner exit.  Experience has also shown that for every 10ºF or 5ºC of vertical temperature variance, the runout length from the top apertures of a multi-hole die will exceed that of the bottom openings by approximately 1%.  This presents a serious problem for both pullers and cutting to length.  It also makes it difficult to maintain required tolerances on a profile with a high vertical component.

The problem of the vertical temperature difference which, if uncontrolled, will occur at the die end of the container liner, is further compounded by another vertical temperature difference in the die itself.

The die slide in which the die sits has enough mass to act as a heat sink and leach heat from the lower half of the die.  Equalizing the temperature at the top and bottom of the end of the liner will therefore not completely eliminate unequal runouts.  The liner temperature must therefore be made slightly hotter at the bottom than the top to eliminate any vertical temperature difference at the die exit.

The Quick Response Container with Total Temperature Control solves the problem of vertical temperature variance in the liner, and in the die, by employing at least 4 control zones, top and bottom, as well as horizontal.  The velocity of the product leaving the top or bottom of the die will therefore be the same.

In order to continue to use large dies in which the upper apertures have already been choked, the vertical temperature control may be suspended.  This will allow the die to assume the vertical temperature variance that initially required the correction.

Better Temperature Control has Real Impacts on Efficiency and Quality
Experience has shown that a QR container, which is designed primarily to heat the liner rather than the mantle, can reduce the amount of energy used by as much as 75%.

In addition, long-term savings accrue from extended mantle life.  By eliminating overheating, mantles retain their hardness.  Extreme internal thermal stresses that can cause cracking are eliminated.  The scrap resulting from vertical temperature difference in large dies is eradicated.  Large extrusions are now being produced to profile tolerances never before possible.  Extruders can now profit from savings on cost of material which can be made by consistently running product near the maximum tolerance when selling by weight, and near the minimum, when selling by length.

Shot sleeve wear and consequent replacement, can be an ongoing and costly problem for die casters.  Many mistakenly assume that sleeve wear results primarily from the gap between the plunger and the shot sleeve shrinking as a result of unequal thermal expansion.  Actually the opposite is true.  If the temperatures of both the shot sleeve and the plunger tip are not constantly and accurately controlled, the clearance may increase sufficiently to allow the aluminum alloy to penetrate the gap.  The abrasive silica in the alloy then soon erodes the sleeve.  This is in fact the principal cause of shot sleeve wear.

Effectively managing the clearance between the plunger and the shot sleeve is a prerequisite for any successful light metal extrusion system.  Clearance problems can only be resolved by good design and thermal management, not by lubrication.  The primary purpose of shot sleeve lubricant therefore, is simply to reduce the friction between the sleeve and the plunger, and to thus ensure the smooth passage of the plunger through the sleeve.  This is essential for consistent shot velocities, and to extend the operating life of both the shot sleeve and the plunger tip.

Too Little or Too Much?

The amount of lubricant used must be adequate, but care should be taken to avoid any excess. Lubrication should therefore be kept to an absolute minimum.

Every effort must be made to eliminate the possibility of any non-metallic substance getting into the mold.  Graphite-based lubricants, for example, can cause porosity in the casting. Lubricant should be applied where it is needed . . and only where it is needed. Any excess lubricant not actually used, is an unnecessary cost and a workplace pollutant.

Boron Nitride

Boron nitride is just now universally accepted as the most effective lubricant yet available for the aluminum die casting industry.  Its unmatched lubricity far exceeds that of all other traditionally used lubricants.  It is also completely benign, producing no toxic fumes.

Application

For small diameter sleeves of 4in. (10cm.) or less, a Lube-Drop system is usually adequate.  This incorporates an internal lubricant groove machined into the sleeve, combined with a metered dropper.

For larger and longer sleeves, it is difficult to adequately lubricate the complete interior.  This can be ensured with a Lube-Spray system A carefully measured amount of liquid boron nitride is vaporized to form a fine mist. This is blown throughout the length of the shot sleeve, ensuring that the surface is completely and evenly coated with a thin film of lubricant. The lubricant spray and air nozzle assembly is securely mounted just behind the pour hole of the shot sleeve.

Spray pressure and duration are both adjustable. This ensures complete coverage without costly overspray. A metered dosage injection pump provides the precise amount of lubricant required for each process cycle, with no danger of excess to contaminate the casting.

Worst Practices Check List

ڤ   Press is not precisely aligned.

ڤ   Die is not uniformly and adequately preheated.

ڤ   Die is too strong.

ڤ   Die bearings are badly oxidized.

ڤ   Billet is poorly cut, surface is not clean.

ڤ   Billet is insufficiently taper heated.

ڤ   Dummy block is no longer contracting.

ڤ   Container is overheating.

ڤ   Container liner exit temperature is vertically inconsistent.

ڤ   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 the Worst Practices List.  This includes common but avoidable problems in the 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.

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 the   optimum temperature for maximum speed as it enters a properly preheated die.  The prime focus of the 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 the billet, plus the use of some of the state-of-the-art technology currently available, is a certain formula for immediate improvement of 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, and without regard for its interaction with other components. Maximum productivity can only be achieved if all parts of the process work together as a coordinated interactive system.

• 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 the centre of the container.  If this is not done, good extrusion is impossible.  Regular inspection at operating temperature is essential, with emphasis always on preventing 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 the single-cell die oven.  This will bring the die quickly and uniformly to operating temperature.  To avoid the initial capital expense of a 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 counter-productive.    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 his 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 breakthrough pressure may be reduced by 30-40%.

A lower breakthrough pressure allows cooler billet temperatures, and thus faster press speed.

The die corrector used to modify dies primarily to bring the profile to the required tolerances.  The integrity of the 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 the 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 a 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 entrapment 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.

Billets 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 die 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 the 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, of course, 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 will 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 the real value of a dummy block is its ability to continue to contract fully after an unusually large number of pushes, before it takes a permanent set and no longer contracts.

There is a very considerable difference in the operating life of contemporary dummy blocks.

• Container is overheating.

If the container temperature sensors and heating elements are not close to the liner, overheating can easily occur.  Inconel sheath heaters, unless properly controlled, can reach temperatures of 1300-1400F.  The container mantle is usually of 4340 steel which may begin to temper and soften at 1000F.  If the mantle softens, bellying of the liner will likely occur.  This will allow a build-up of impurities from the billet skin that will eventually end up in the 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 that 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 die 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 liner, and at the end of the stroke, the butt would fall off.  Unfortunately this just 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 the 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.  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 the 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 a common practice.  The extruder’s supplier very often became a personal friend.  He then usually had an opportunity to meet any competing supplier’s price.

Next, almost all tooling was treated as a 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 his profit by improving his productivity.   He can no longer afford any poor practices.

Maximum productivity and maximum profit are today actually achievable for the first time by light metal extruders.

We have been asked by many extruders about butt thickness and suggested butt shears.

Butt Thickness

Butt thickness is generally driven by what can be satisfactorily sheared (or curled) on the shear blade and ejected. However it is known that billet surface layers and oxides etc  start to flow into the inside of an extrusion toward the back end (i.e. coring). This tends to start at around 15% butt length – much larger than typically used in most extrusion.  The inclusions however are all contained in the extrusion interior and are generally considered to be of no consequence – certainly they do not influence surface finish.

Of course there may be concern with such inclusions for structural applications and therefore for many 6061/6082 extrusions where the higher strength alloys means there are structural or load bearing considerations, the butt length is usually kept to around 15-16% of the original billet length.

Therefore two cases:

1. Non-structural applications (most 6063/6060 alloys) – as short as you can get away with.

2. Structural (most 6061/6082 alloys) – 15-16% minimum is recommended to avoid coring type defects

Butt Shear

Castool recommends using their scoop type shear blade for most 6000 series alloy applications, but there are several situations when the scoop design is not recommended.

The most effective blade design tends to more depend upon the butt length used rather than the alloy itself (of course, the alloy dictates the butt length).  It’s worth noting that some plants employ rather long butt lengths to some critical 6061 alloy products (e.g. automotive), and  tend to use the blockier blade design to ensure a good shear.  However having said the alloy itself is not instrumental in driving the optimum blade design, in the case of really soft 1XXX and 3XXX alloys, alloy stickiness  come into reckoning and it’s best to keep away from the curved scoop type blades.

A sharp knife edge blade works best for soft alloys such as 1XXX and 3XXX alloys.  The tendency is to run to very short butts (because of minimal billet shell zone there is no need to leave a longer butt) and the butt tends to naturally curl with a simple knife edge blade.  There is therefore no need for a radius to encourage curling – in fact because of the stickiness of these alloys it is arguably best to avoid prolonged contact with the blade.

Hard alloys like 2XXX and 7XXX need to run to longer butts (typically 15% of the upset billet length).  Because of this the butt will never curl and it is necessary to simply shear the butt from the die entry.  A sharp blade doesn’t promote a straightforward shear, and therefore typical blade designs for these hard alloys are more of a blocky shear design.

But do not include all 7XXX into this category.  The leaner 7XXX alloys such as 7003, 7005, 7020 fall into the same group as the harder 6XXX alloys such as 6061, and are run to shorter butt lengths typical of 6061 and therefore can use the scoop type design.

Indirect extrusion of hard 2XXX and 7XXX alloys should employ much shorter butt lengths than for direct extrusion, and in this instance it makes good sense to use the typical scoop type blade.

We reline containers when the occurrence of scrap increases from blisters, pick-up and die lines, and unscheduled down time increases from frequent dummy blocks changes and seal face cleaning.

I will briefly outline why this happens and how Castool’s QR container can extend liner life considerably.

1. In use, a container is subjected to stresses from a number of sources:
   1. Applied pressure during extrusion
   2. Shrink fit of liner in container body
   3. Thermal stresses from the temperature gradient both radial and longitudinal, in the container body
2. In time the container body will distort from these stresses – bulging/barrel effect
3. The liner will distort as the container body distorts and no longer provides ideal support, resulting in:
   1. The designed clearance between dummy block and container liner is exceeded
   2. Increased alloy skin thickness is allowed to accumulate on the liner bore
   3. Increased risk of blister
4. The sealing surface of the liner will degrade over time due to high compressive sealing stresses between the liner face and the extrusion die or die ring, resulting in:
   1. Increased risk of flares
   2. More build up on the container or die sealing surfaces = increase in pick up, die lines and blister
   3. Attempts to clear flares with propane torches or chisels further damage the sealing surface.
5. Recent design improvements that extend liner/container life are:
   1. Improved container seal geometry – modeling capability at Castool
   2. Improved temperature control with Castool’s multi-zone QR containers and elements located closer to the liner equals less thermal gradient in the container body and less thermal stresses.
   3. Improved Castool dummy block designs, better able to accommodate liner diameter changes due to the combined thermal and extrusion deformation stresses.

In normal operation Castool’s QR containers are achieving:

1. Liner life in excess of 1 year

2. Sealing face useful life (no flares) equal to liner life

3. Dummy block life in excess of 1 month

4. Mantle useful life (retention of hardness and minimum thermal fatigue) in excess of 5 years

5. Element life in excess of 2 years

6. Reduced scrap due to blisters, die lines, pick up, run out, dimensions and shape.

7. Reduced scheduled and unscheduled downtime.

8. And of course, today we must always consider the carbon footprint; energy consumption is regularly reduced by 50% or more.

We’re not just selling products to the extrusion and die cast industries, we’re very much part of the industries, and have been for about 25 years.  The Castool slogan is “For Better Extrusion” and “For Better Die Casting”.  That is our overall philosophy.  And along with a sincere commitment to ongoing improvement, it’s reflected in the products and service we provide.

We know that there’s a fairly wide gap between the productivity of some major companies that we call the Superextruders (Superdiecasters), and that of the average extruder (diecaster).  Most extruders (die casters) mistakenly assume that this somehow results from economies of scale.  It doesn’t.  These people are really better extruders or diecasters.  They understand the process thoroughly, and operate at close to maximum efficiency at every step in their production.  They also realize the real value of Castool products, and usually buy from us.

Much of our time is spent educating average extruders (die casters) . . showing them how to make better use of the production equipment they already have, as well demonstrating the advantages of Castool products.  Teaching them to become better extruders (diecasters).  This approach is very successful.  I’m often amazed at how much the productivity of some plants can very quickly be improved simply by going back to basics, considering the production process as a system with all the components complementing each other and working together in a common cause, and measuring everything. We tell our clients that anything that can be measured can be improved.  Usually this is true.

Robotic Die Expediter (die scheduling and heating system)

Why are our products successful?  They’re as good as any in the world, and better than most.