Derek Korn

Derek Korn joined Modern Machine Shop in 2004, but has been writing about manufacturing since 1997. His mechanical engineering degree from the University of Cincinnati’s College of Applied Science provides a solid foundation for understanding and explaining how innovative shops apply advanced machining technologies. As you might gather from this photo, he’s the car guy of the MMS bunch. But his ’55 Chevy isn’t as nice as the hotrod he’s standing next to. In fact, his car needs a right-front fender spear if you know anybody willing to part with one.

Posted by: Derek Korn 22. July 2015

Large-Part Grinding: Two Key Technologies

Advances in steady rest and in-process measurement technologies enable large crankshafts to be ground complete in one setup.

Advances in steady rest and in-process measurement technologies enable large crankshafts to be ground complete in one setup.  

Junker, manufacturer of high-speed CBN grinding machines, has developed its new JuCrank series for cylindrical and non-cylindrical grinding for large crankshafts. The series offers a swing diameter of 470 mm and a part length capacity of up to 4.8 m, and can accommodate crankshafts that can weigh as much as 1,000 kg. Because these parts are so big and unwieldy, the company integrated two technologies to streamline setup and processing.

First, Junker developed its own steady rest system, believing that existing systems were too bulky and not rigid enough for high-speed grinding. These new steadies are CNC-controlled and have only one axis each, which is said to increase their stability and stiffness. A maximum of 11 steadies can be controlled individually and applied to a section at any time—even during the grinding process—to enable higher sequence flexibility.

Second, the company integrated an in-process measurement system. That’s because large crankshafts are mainly produced in small batches (in some cases as single pieces), and the forging and hardening costs are so high that scrapping a part is not an option.

To start the crankshaft grinding process, the machine’s two wheels, each mounted on a wheelhead with its own X and Z axis, pre-grind the main and pin bearings. Those diameters are measured during the process, and then the entire workpiece is measured after pre-grinding, including features such as the taper of each element, the bearing widths and lift heights.

Based on the measuring data, the machine completes the grinding process while using the WK axis whereby the grinding spindle swivels to compensate for tapers. The machine can also provide each main and pin bearing with its own profile shape with specific crowning. If necessary, the shaft ends can also be ground, which also often feature a taper. As a result, the crankshaft is ground complete in one setup.

Another application for the JuCrank machines is re-grinding of used crankshafts, whereby the crankshafts are ground based upon the measurements taken by the machine. This grinding platform also can be effective for other large-scale applications, such as printing rollers and electric motor shafts.

Posted by: Derek Korn 16. July 2015

What’s a Parakeep?

This parallel keeper is said to be quickly adjusted from approximately 1 to 4.2 inch to hold parallels against the vice jaws as the vice is open and closed during workpiece loading/unloading.

“Parakeep” is what Rimeco Products Inc. calls the adjustable parallel keeper it developed. The company says the device can be used with any standard set of parallels on any machine vise, holding workholding parallels in place while the vise is opened and closed during normal use.

The Parakeep has a spring-loaded housing with an adjustable screw that enables a machine setup person to quickly adjust the device’s parallel stabilizing mechanism with each new job. It serves as an alternate method to conventional means (using different length springs, scrap material, washers and so on) to hold parallels against the vice jaws as the vice is open and closed during workpiece loading/unloading. An individual Parakeep unit has a work envelope of 1 to 2.25 inches, while the kit covers 0.25 to 4.25 inches.  

Posted by: Derek Korn 8. July 2015

Metal Alloy Analysis Made Affordable

handheld XRF metal alloy analyzer

This handheld XRF metal alloy analyzer uses a process similar to static electricity to generate x-rays, bringing the price point down to a level that’s attractive to a wider range of manufacturers.

Traceability is becoming a bigger issue for shops, especially those serving the aerospace and medical industries. Handheld X-ray fluorescence (XRF) spectrometers are commonly used to identify, analyze and tests a broad range of metal alloys for positive materials identification (PMI). Such analysis is commonly performed on raw material as well as finished parts prior to customer delivery to confirm alloy grade. That said, the price point for these devices hasn’t been all that attractive.

Tribogenics says it is the first company to offer an XRF analyzer for less than $10,000. Its Watson XRF device uses a process similar to static electricity (known as the triboelectric effect) to generate X-rays. The company says conventional XRF devices use technology originally developed in the 1800s that relies on bulky, expensive high-voltage transformers to generate X-rays. Tribogenics-effect technology is said to lower both the cost and size for an XRF device using a small (less than 250cc) battery-operated source. Watson also uses replaceable, interchangeable X-ray sources that function much like inkjet cartridges. These cartridges are available in different power levels to address different analyzing needs. They are said to last one to two months and cost $300 to $400. 

Posted by: Derek Korn 24. June 2015

Want to Test Drive Cryogenic Technology?

Low-temperature liquid nitrogen flowing through a cutting tool has the effect of turning the cutting tool into a heat sink, expanding its capacity to absorb energy while improving tool life.

Okuma and 5ME have formed a partnership to establish two cryogenic machining demonstration centers, one at 5ME’s Technical Center in Warren, Michigan, and the other at Okuma’s Aerospace Center of Excellence in Charlotte, North Carolina. Visitors can test various machining processes using Okuma machines equipped with 5ME’s cryogenic machining technology. Pete Tecos, 5ME executive vice president, says the partnership will continue the development of cryogenic machining applications in in difficult-to-machine materials such as titanium, Inconel, hardened steel and compacted graphite iron (CGI).

In short, cryogenic machining technology flows liquid nitrogen at -321°F through the cutting tool, improving tool life. The nitrogen evaporates upon contact with the air. This article explains more about the technology.

Posted by: Derek Korn 17. June 2015

Two-Minute Video: Advantage of Twin-Pallets/Dual-Station Vises

The BT-360D VMC from Bulova Technologies includes an integrated twin-pallet changing system. This video (okay, it actually runs 2:01 minutes) shows how this type of machine platform, combined with Toolex dual-station vises, can maximize spindle up-time by enabling operators to change-out workpieces on one pallet while parts are machined on the other.

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