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by Kip Hanson

Machine all the parts you want: you still have to inspect them  

Much of today’s manufacturing environment calls for low volume orders of complex parts.

Linear pallet systems and robotic part handling allow shops to set up dozens of jobs and run them after everyone’s gone home for the day. Unless your inspector likes to work nights, you’re sure to have a big pile of parts waiting to be checked in the morning. It gets worse. If you’re not machining generously toleranced aluminum parts, you’ll need to make some tool offsets. Maybe you can find some night owl machine operators to carpool with the inspector. 

The next renaissance
It might be better to forget that old school way of thinking and get yourself some automated inspection equipment. Industrial metrology supplier Carl Zeiss LLC has a number of in-line gauging solutions that are excellent alternatives to unruly night shifts and sleep-deprived employees. “Our classes of in-line gauging machine are typically based on volumetric part size,” says Jose Torres, software engineer at Zeiss’ Michigan office. “If you can hold the part in your hand, we have a machine for that. As parts get heavier and require more automation to manipulate, we have other solutions. All of them are candidates for machine integration."

There’s more to this than checking a few parts, explains Torres. Today’s “production” runs often require 100 per cent inspection. That’s because you’re no longer supplying 10,000 parts with a delivery three months from now, but releases of 200 pieces every week for the next year. All that changeover warrants a high degree of inspection: customers want it, and manufacturers need it in order to assure no rework or scrap. That means they’ll measure everything. “We have a customer who does that in the Toronto area. They enter the order, make the fixtures, program the machines and go home. Everything is queued up to run during the night, including the inspection."

Torres calls this the second renaissance of manufacturing production. “It started about two and a half years ago. Manufacturers started reshoring. There are a number of reasons for this, one of them being quality issues with stuff done overseas. And people are generally becoming more pro-North American, especially in Toronto and the Midwest."

The problem, says Torres, is how to stay competitive without lowering wages. "These shops decided, 'let’s have automated cells, ones that can not only make the parts but check them too.' The result was a big rise in manufacturers calling for in-line gauging. Even small job shops and mid-range automotive, medical, and electronics suppliers have moved in this direction. So we had to provide a solution."

Neither rain, nor heat, nor dark of night
One of these solutions is the Zeiss MaxLine, a portfolio of continuous contact scanning-based CMMs for production use. For somewhere around $60K and a few weeks to setup and integrate, you can add an entry-level DuraMax to your manufacturing cell and be checking parts round the clock with little human intervention. Torres says this line of equipment is especially suited to small shops with adverse environments. “Our high-end CenterMax, for example, handles just about any sort of temperature fluctuation and high humidity conditions. We’ve even sprayed water on it and the machine will still run."

Zeiss isn’t the only one addressing challenging inspection locations. Metrology supplier Renishaw offers an alternative solution to hard gauging that compensates for shop floor environmental variations. “The Equator utilises a simple yet powerful comparative measurement technique," says David Chang, technical sales manager of measurement and automation products for Renishaw (Canada) Limited, Mississauga ON. “This technique employs a two-step process of measuring a production component on a CMM in a controlled environment. The metrology is then transferred to the gauge (the Equator) and the now calibrated component, or master, is measured one time. From this point forward the gauge is able to measure production components; the simple process of re-mastering is only required if the environment moves outside of pre-described limits."

Like the Duramax, the Equator utilizes a full-contact scanning method. Integration to lathes and machining centres is likewise fairly straightforward. However, the design of the Equator looks more like a piece of modern art than a highly accurate coordinate measuring machine. "The Equator is a highly repeatable non-Cartesian structure. Its innovative design offers high speed, a small footprint, and a price point at under $30K,” says Chang. “The system also offers full integration capability via an optional automation interface and the capability to provide close loop feed back to a machine tool."

It’s important to recognize that those prices do not consider integration. Unlike CNC machine tools, which leverage industry protocols such as MTConnect, metrology equipment is often a pay as you go proposition if you want it to talk with your other equipment. Peter Detmers, vice president of sales at Mississauga-based Mitutoyo Canada Inc., says Mitutoyo has the ability to integrate virtually any piece of equipment in its catalog to a machine tool. “We pretty much cover it all as far as automation of our in-line measurement.” Where things get complicated is when you want the CMM or vision machine or white light scanning system to send measurement feedback to the machine control. "Fanuc, Siemens, Mitsubishi, they all sync in very different ways."

Add to this the fact that one CMM might be checking parts for multiple machine tools, each of which is running multiple part programs and using dozens of cutting tools. Things can get complicated in a hurry. The solution, says Detmers, is to use a go-between software package, one that can interpret feature measurements made during the inspection process and feed this information back to the correct machine control. "There are a different vendor products out there. The companies we’ve dealt with never have a problem giving the machine controllers the data they need to make the right decisions."

If you have the sales to support it, investing a million bucks on a lights-out manufacturing cell might be a no-brainer. After all, everyone wants to see more work come home from low labor cost countries, and unattended machining is clearly one of the paths to accomplish that. But you’d better do your homework first: success in this arena requires a lot more than high-tech CNC machine tools and the know-how to operate them. You still need to check the parts. SMT

Kip Hanson is a contributing editor. This email address is being protected from spambots. You need JavaScript enabled to view it.

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