Wednesday, October 21, 2015

Renishaw - An Eyewitness Account of A Metrology Game Changer

Guest Post By Bryn Edwards, Vice President, Wenzel America

Before CMMs the only way to dimensionally inspect geometric parts to any kind of accuracy was either a surface plate with height gage and slip blocks or the shop jig borer with a dial indicator.

Having lived through the whole CMM evolution from then until today, my perspective on the industry might be of interest.

A brief, eyewitness history of CMMs

The CMM industry was actually started by a defense company in Scotland called Ferranti.

In about 1961 they invented the moiré fringe measuring scale that made low-friction, high-accuracy measuring scales available for the first time. Engineers at Ferranti actually devised the first CMM as a vehicle to sell the measuring scales themselves.

The device was very simple and effective. It was a small cantilever machine with two low-friction axes and a two axis digital readout. The concept was to use mechanical probes, ball, cylinder, or taper to manually contact the surfaces to be measured and record the positions from the digital readout. This same concept is still used today.

For the first decade after their invention, all CMMs were manually operated and very limited in scope. The only large machine made around that time was by Franco Satorio in Italy, the chief inspector at Fiat. He devised a large gantry machine to measure car body dies using a one-directional electronic indicator. His machines were also manually operated. Satorio left Fiat to form the DEA CMM Company.

Renishaw is born - The 70s brings a whole new player to metrology

In 1972, the whole metrology game changed. While working at Rolls Royce in Bristol UK, David McMurtry (now Sir David), applied his very innovative mind to the limitations of the rigid styli at the time that required manual control and a sensitive operator touch.

The resulting invention was a simple touch probe.  While it may have been simple in concept, it was genius in application and changed the entire metrology industry forever.

Shortly after patenting his new touch probe styli, McMurty founded Renishaw Plc. in 1973.

This first Renishaw probe design was basically a stylus assembly mounted kinematically in a housing and spring loaded using three bars in the stylus and six balls embedded in the housing. A small voltage was applied to the contacts to allow the resistance to be measured very sensitively and therefore identify precisely when the contact was broken freezing the related scale positions.
The spring loading allowed the stylus to “over travel” into the part without damage and return to its exact location after contact was removed.

At the time Sir David invented his first touch probe there were many other people looking at probing systems and electronic indicators trying to figure out a solution to the limitations of the CMM styli then being used.

The problem, as they saw it, was to identify the exact contact point with the surface. The Renishaw touch probe just simply ignored this issue and left it to be computed separately. A possible advantage that allowed this out-of-the-box thinking was the computing power that was readily available to Sir David working within Rolls Royce.

So now we had a device that would automatically freeze and record all axes of the CMM on contact. The three axis data could then be used to compute just about any geometry. This also allowed the axes to be motorized and the size and concept of the CMM to be reinvented and ended this first era of manually controlled CMMs.

Motorization changed everything - machines could now be made to any size and controlled by remote joysticks. Contact speeds could be controlled allowing accuracy and repeatability to be much higher independent of the operator, and a full DCC programmable control could be applied.

PH9 touch probe - a true game changer for metrology and CMMs

With the first Renishaw probe the potential for the modern CMM was set on a new path.

Many refinements were to follow including:  Driving at vectors normal to compound surfaces, allowing angular faces to be measured with a simple ball stylus radius correction. Following quickly was the utility of an indexing head, Renishaw’s PH9, along with probe changers and thus the foundation of today’s CMMs.

While CMMs may not have doubled in power every two years like was predicted for integrated circuits at the time, they certainly benefited from Moore’s law proving out, with advances in computer systems and resultant software. This was the time that computers went from huge main frames to “mini” computers and finally to PCs, allowing for suitable computing power to be added to the CMM and allowing ever more complex measuring computations.

CMM applications during those years were much more computer intensive than those used in NC machine tools.

In the case of CMMs, computers were used even before the machines were motorized, so it was logical to use the same computer to also drive the machine axes.

From the beginning, CMMs used this method for driving the machine as well as collecting and analyzing data.  Doing both simultaneously was a very demanding application and required a robust multi-tasking environment.

After these initial uses and innovations for high speed computing of geometries and machine drivers, additional software was developed for error mapping enabling simplification of mechanical design. Real time interaction with CAD files greatly improved the utility of the CMM.

It would be many years before the machine tool industry went in this direction as well.

Touch Probes - still the most universal metrology sensors

A lot of refinements have been added to metrology probes and sensors over the years including scanning and optical sensors, but even today the most popular CMM is still the touch probe indexing head DCC machine conceived some 35 years ago and enabled by Renishaw.

The reason for this is that the CMM has become the industry workhorse for universal inspection of precision parts. The application refinements have been effective for specific applications, but the universality of the touch probe still meets most requirements.

After 30 years, Renishaw changes the game...again

The CMM design remained conceptually the same for some 30 years until Sir David again invented a new game changer - the Renishaw Revo.

The 5-axis REVO took the basic concept of the touch probe CMM and reinvented it. The concept of CMMs is to freeze axis data on contact for touch probes, or to coordinate the axis data with a scanning probe. This has the effect of limiting the speed at which the axes can move without distorting the CMM frame and the resultant data.

The Revo collects data by rotating the head without having to move the axes of the CMM.  This allows it to scan surfaces up to 500mm per second, collecting thousands of data points per second at very high accuracy. In many applications this system can be 10 times faster than a regular touch or scanning probe because its speed is not axis dependent.

What further innovations this newest Renishaw game changer will usher in over the coming years are still to be seen. But, if the past is any indicator, Renishaw will have a hand in whatever comes next.

Applying innovation - the past, present and future of Renishaw

It is this dedication to innovation that has been the foundation for what is now a very large and successful UK company. Today, Renishaw’s products range from CMM probes and sensors, machine tool probes to transducers and laser systems and medical applications. The underlying theme of all their products still focuses on applying innovation to high-precision components for three-dimensional applications. For more information about Renishaw sensors, aftermarket products or fixtures please call us at 248.295.4300.  We also guarantee we'll give you the absolute best prices on Renishaw Probes.

Fixturing: An Important Part of CMM Accuracy

First, let’s take a look at what a fixture is from a Wikipedia article on the subject:

What is a fixture?

A fixture is a “work-holding” or support device used in the manufacturing industry.[1][2] Fixtures are used to securely locate (position in a specific location or orientation) and support the work, ensuring that all parts produced using the fixture will maintain conformity and interchangeability. 

What does a fixture do?

Using a fixture improves the economy of production by allowing smooth operation and quick transition from part to part, reducing the requirement for skilled labor by simplifying how workpieces are mounted, and increasing conformity across a production run.[2]

How is a fixture different from a jig?

A fixture differs from a jig in that when a fixture is used, the tool must move relative to the workpiece; a jig moves the piece while the tool remains stationary.[3]

5 Questions to Consider Before Fixturing

  1. How many parts are you going to measure?
  2. Is this just a one time run, or is this a part that will be measured over weeks, months or even years?
  3. How accurate does my measurement have to be
  4. What type of repeatability are you looking for? Who will be measuring the part?
  5. Will the part be measured by the quality personnel or will it be operated by a machine operator as part of a cell?

What are the different types of fixturing solutions?

Engineered Fixturing Solutions

Recently, a GM plant in Flint, Michigan built it’s millionth 1.4 liter engine. Considering the number of operations that are run on head, blocks and cranks, you have to assume that the fixturing used to measure the various machining operations are robust. Those fixtures are most likely engineered specifically for the part and/or operation. In most cases it would be desirable to have one fixture for all the operations on a part.

Modular Fixturing Solutions

Unlike GM, most manufacturers are not running a million parts. Maybe you are running off as few as thirty parts to prove a capability to a customer. In this case, it doesn’t make sense to pay for an engineered fixture due to cost and timing. In these cases, modular fixturing offers a great solution.

Modular fixturing allows you to buy either a standard plate size or custom. You then pick and choose the additional pieces to attach to the plate that create a fixture that supports and constrains your specific part. The modular system allows you to build a custom fixture to meet your needs. You can even keep the setup and buy new modular components and plates to make fixtures for all of your parts.

After you’ve decided between Engineered or Modular, now what?

It is important to think about how you are going to hold the part, so that you can access the datums and have access to the features to be considered. With an engineered solution someone else will have done that for you. In some cases you can re-use the fixture that was engineered to hold the part in the manufacturing process for the measurement as well.

When you create your own modular fixture you have to assemble it so all needful areas are accessible for measurement. Ideally, you construct the fixture so the part is in a “free state” with no clamping force on the part.

It’s a balancing act between keeping the part motionless and also not constraining in such a way that the part is deformed during the measuring process.

If your parts are small, or if your CMM is big enough, you may be able to nest parts so that you can stage several parts on a single plate and press one button to measure them all.

Other fixturing situations

Car Body, Aircraft Body parts offer unique fixturing challenges:

As do Vision Systems and CT - which need to allow the part to be “seen.” This could be visually, or in the case of CT, the fixture must be of a material that will allow the x-rays to pass though with very little energy loss.

When all else fails…there’s always duct tape

Sometimes, you just need to do a quick check. Maybe it’s a one-off or perhaps you are trying to settle a dispute. In these cases, you can create fixtures from a number of different items including: putty, double sided tape, v-blocks, clamps or hot glue guns. 

Even threading some stops into the bolt holes on the granite plate and pushing the part against them could work. 

And as we all know, duct tape can fix anything.

What have we used?

During a recent open house, we used R&R Modular Fixturing to measure a part across five of seven different sensor technologies. We used Styrofoam for the CT and Wenzel’s CORE optical system has a built in clamp. R&R Fixtures is a Renishaw company and so we offer special pricing on the full line of R&R Fixturing.

Perfect Business Partnerships - When 1 Plus 1 Is More Than 2

History is full of examples of successful and synergistic partnerships -- whether in business, science, sports, or entertainment -- there are numerous examples of One + One equaling more than Two.

In football, there was Joe Montana and Jerry Rice -- two of the most talented individual players at their respective positions in the history of the NFL. Both are in the Pro Football Hall of Fame, both broke and set many American football records.

But, working in partnership, they accomplished feats that neither may have ever done without the other.

If that is a legendary sports partnership, there are even more legendary business partnerships that forever changed the world -- from Orville and Wilbur Wright to Steve Wozniak and Steve Jobs and from Bill Gates and Paul Allen to Sergey Brin and Larry Page -- our world today is the result of these famous partnerships. 

Still others have names that have become synonymous with our everyday lives -- Johnson & Johnson, Hewlett-Packard, Bausch & Lomb… and of course Ben and Jerry’s -- all great examples of the broad and lasting impact a great partnership can have.

Partners, mergers, & an international family of measuring expertise

Over more than four decades in business, Wenzel has been fortunate to be teamed up with some fantastic companies, a number of whom -- Metromec, Steintechnik, and Xspect Solutions -- have become part of the Wenzel Group itself and are now an integral part of the fabric of our international family of metrology companies.

Other Wenzel partnerships, while not involving mergers or acquisitions, are no less important alliances that make both companies stronger and able to provide even more powerful solutions to our customers.

Renishaw and Wenzel –A Synergistic Metrology Partnership

One such partner, Renishaw, Plc., has been a vital part of our precision and accuracy since we made our first CMM over 30 years ago.

They have been, and are, a key partner in our growth and success with their world-class probing systems, positioning and motion control technology.

Like many of the earlier examples, our respective companies have visions, products, and technologies that complement each other and allow us to develop new products and services together that would not be possible without our collaborative relationship.

Cutting edge 5-axis probing meets rock-solid stability

An example is our early adoption of the Renishaw REVO 5-Axis Probing system. Pairing the REVO with the precision of Wenzel LH CMMs and our expertise as systems integrators allowed us to bring this technology to market quickly and successfully. We were able to rapidly introduce it to a wide range of customers.

By utilizing the Renishaw UCC controller we are able to provide a flexible, reliable platform for those of you that have mixed populations of coordinated measuring machines and metrology software systems. The open design of this controller also lets us leverage our network of third party service providers to give you a variety of choices for support and maintenance of your CMMs.

Our close relationship with Renishaw means we can also support any of your aftermarket needs faster and more economically as we leverage the infrastructure of the world’s largest styli manufacturer for all of your styli and probe systems.

More mergers means a bigger family of partners

Let’s not forget fixturing, Renishaw’s own growth has meant M & As for them as well. In 2012, their acquisition of R&R Sales added modular fixtures for CMMs to the Renishaw family of products.

For you this means because of the Wenzel America - Renishaw relationship we can now provide complete lifecycle solutions for your CMMs with the leading modular fixturing solutions for the metrology industry.

Real partnership is a two-way street

As with any partnership, to be truly long lasting it must go both ways.  
In that regard, over the years, Wenzel has provided numerous systems to Renishaw for use in their demo centers and R&D labs around the world.

We also often provide systems to display the latest Renishaw technology at trade shows. In fact -- you can see the debut of the Next Generation in REVO 5-axis scanning displayed on a Wenzel LHG at the upcoming Quality Show in Chicago October 27th - 29th.

What you really get with Wenzel America as your metrology partner

So, the truth is, when you choose us as your metrology partner you not only get Wenzel’s industry leading expertise in CMMs and integration - you become part of our longstanding successful collaboration with the industry leader in probing systems, motion control and fixturing - Renishaw.  Which only begs the question, “What are you waiting for?”