Wednesday, January 21, 2015

Not All Coordinate Measuring Machines Are Created Equal

Do your CMMs Have Rock Solid Accuracy & Durability?

The structures metrology companies use for CMMs are not all the same.  Most companies have moved to aluminum alloy for their metrology material of choice because it is lighter and cheaper. The problem with this is that they sacrifice the very thing automotive parts, aerospace parts and medical device manufacturers rely on most:

ACCURACY

Their solution to the accuracy problems caused by cheaper and lighter materials like aluminum, is to put complex error-mapping software on top that compensates for the inherent inaccuracy of the machines. 

From an engineering perspective this is backwards, overly complex correction of errors or inaccuracies, instead of starting with higher accuracy and correcting from there, is never considered an optimum engineering solution. The only real benefit we can see is maybe a slightly lower cost machine for the buyer and slightly a better margin for the seller.  

But at what cost to everyone? In-built inaccuracies with unnecessary added complexities can create thousands of unusable parts or, worst-case, result in massive recalls. The cost-benefit ratio at that point is not worth it.

We build our CMM structures from granite for one reason only - Accuracy. 

We're traditionalists. We use what works best from a proven engineering perspective - always.  

Granite remains the perfect structure for CMMs due to its long term stability, resistance to temperature change and incredibly high stiffness.

The granite we use is sourced from hand-selected South African quarries. We work with very specific suppliers of Black Impala granite in the region. This particular type of stone is the least porous, most consistent, and the most structurally and thermally stable granite known.

Getting a that raw stone from the quarry and made into the quality thermally stable granite CMM in your shop is a feat of skill and logistics that is actually pretty incredible. But interestingly, measuring machines from Wenzel cost no more than other systems made from cheaper materials and processes.  The coordinate measuring machines we make are machines fit for a lifetime. You get a solid, stable metrological workhorse that gives consistent results over many years of service. 

Why Black Impala Granite?



The story of your CMM starts in South Africa. After more than four decades investing in and sourcing only the best granite from the best quarries, there are only a few we work with. For our Bridge and Gantry LH CMMs we need very large, unflawed pieces of raw granite and only a handful of quarries can mine and handle what we need.

Have you ever seen a  tiered wedding cake?  That is what the mountain resembles once the large blocks of granite are literally ‘sheared’ from its side. 

As you might think, there is considerable time involved in mining and shipping these huge raw granite blocks to Germany where we cut, finish and hand lap to precision Wenzel standards.  We pre-order the giant slabs based on experience and forecasts of future orders then they are mined and stored at the quarry until we need them. 

Precision German Engineering - From Rough Start to Fine, Hand-lapped Finish

These giant rough slabs are then sent out on ship across the Atlantic, loaded onto heavy-load trucks and taken to Wenzel Steintechnik in Germany. Steintechnik (literally "Stone Technique" in English), have been processing granite since 1988 and for the last 8 years they have been part of the Wenzel Group.

To get the rough blocks ready for precise machining,  large CNC saws cut them within 10 mm of the finished size. 

After this, the granite is ground, honed, and polished to a flatness of plus or minus 2 mm. This is also when the craftsman add any additional required slots and inserts.

At this point the tables,  X-beams and quills are then trucked 40 miles down the road to the Wenzel Prazision (Wenzel Precision) factory in Wiesthal, Germany.

After a few days of temperature stabilization and relaxation of stresses, large CNC grinding machines are used to machine the components to their finished size.

Many other CMM manufacturers would call it a day after the previous step, but we add one final step that ensures we get the optimal and  intrinsic accuracy. 

Each part is then thoroughly inspected with laser interferometers to make sure the exacting flatness, parallelism and squareness tolerances are met. Large tables are inspected with digital levels.

This inspection is particularly critical for the Z-axis quill as straightness of this part dramatically affects the accuracy performance of the finished CMM.
After inspection our engineers can see if grinding process delivered the required form on every piece of granite.  If it hasn't, a team of technicians will hand lap out any errors. The skill of these engineers is unmatched. No other company takes the time and care nor has the experience necessary to produce granite CMMs of this caliber.  
Now all components are assembled into the most stable and intrinsically accurate CMM structures to be found anywhere in the world.

It's easy to see why, with all that is involved in building truly accurate granite CMMs so many have moved away from the number one material in metrology.  We see it as our key difference and commitment to precision.  

With our years of experience in sourcing the world’s best granite to the painstaking, laser-precise measurement and craftsman-finishing, our processes and product quality are unduplicatable. We're confident no other coordinate measuring machine company can compare to the expertise and standards we maintain in all of our machines.

Wenzel America is your North American Source for the world’s finest coordinate measuring machines. We proudly sell and support these products with personalized customer service and training. We are always happy to answer any questions you have about CMMs, Gear Measuring MachinesCT Scanning servicespre-owned machinesRenishaw probes or any other aftermarket coordinate measuring products or services.  
















If you need measuring equipment and want to discuss your measurement processes and needs you can contact one of our CMM experts here.  To get signed up for our monthly educational newsletter Metrology Matters you can do that as well, right here.   

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