Multi-spindle machine in runout at ZPS America, in Indianapolis.

Making Multi-Spindle Design, Performance as Smooth as Possible

Sept. 22, 2016
The relationship between ZPS America and Mitchel & Scott shows that high-tech and high performance work together seamlessly Complexity in resources, simplicity in operation High-volume automotive OEM projects Standard CNC, PLC motion control on machines, bar feeders

ZPS America, in Indianapolis, builds high-production volume, multi-spindle machine tools, for a long list of end-product applications. Lately, its main focus has been precision machining technology for automotive OEMs, and one of its longest-standing customers is a nearby high-volume manufacturer.

Mitchel & Scott Machine Co. is a multi-skilled precision parts producer for manufacturers in the HVAC, agricultural, defense, and hydraulic systems sectors — but especially in the heavy-duty diesel and automotive OEM markets. 

Mitchel & Scott’s ISO/TSI16949-certified Indianapolis plant covers more than 150,000 sq.ft., and incorporates numerous machining capabilities, plus heat treating, chemical and vibratory finishing, assembly and kitting for its customer base.  It also operates a full metallurgical lab on premises.

At Mitchel

A second Mitchel & Scott plant in McMinnville, Tenn., is dedicated to its HVAC customers’ needs, and the company also offers vendor-managed inventory and has dedicated equipment in-house for select customer production needs.  According to director of engineering & quality Pat Mitchel, “This seemed risky at the outset, but our customers appreciate the value of these services and the fact that we can be very pro-active in our management of their ongoing production needs.”  

Founded in 1933 by Pat Mitchel’s grandfather, the company had long been a producer of high-volume production components, serving the heavy-duty diesel, HVAC and hardware markets. But, he noted, the gradual emergence of automotive business largely changed the company’s focus.  “We’ve had a concentrated effort in automotive for many years now and the word must be getting around, as we currently ship product to Europe and India plus over 10,000 parts per week to China for our customers.” 

With the delivery and ramp-up of the first ZPS machine in 2012, Mitchel & Scott accelerated this trend toward the high-volume automotive sector.   For one major European automaker, it supplies an entire range of components from Indianapolis plant. 

Typically, it runs automotive jobs ranging from 500,000 to 800,000 pieces per year. Examples of its capabilities include hydraulic check valves, camshaft nose and end-pieces, cam phasers, fuel injector housings, and direct inject fuel rail assemblies, among many other products. These are supplied complete with inline testing and 100% product inspection protocols in place.

Up to Speed, Quickly

ZPS — the North American arm of a Czech company, Tajmac Group — has supplied various Swiss machines and multi-spindle bar-fed systems to Mitchel & Scott over recent years. “A key component in the success of the equipment on our floor is the standard CNC and PLC motion controls on the machine tools and bar feeders from ZPS,” Pat Mitchel commented. “With no custom software overlays from the builder, our operators can quickly get up-to-speed with minimal training, a critical factor in our high-production environment.”  

Currently, the plant runs seven ZPS multi-spindle machines with bar-feed systems and post-processing gauging on the equipment, in the central hub of its manufacturing floor.  Typical materials processed in this department include 4140, 4142, 1141, and other steels, plus aluminum alloys up to 2.25-in. diameter bar stock. 
Examples of high-precision automotive parts manufactured by Mitchel
Mitchel credits the long relationship with ZPS to several factors.  “We’d worked with Olaf (Olaf Tessarzyk, co-owner and president of the machine tool builder) in the past and, as our needs changed, we turned to him for assistance.  The results have been outstanding, owing to the combination of high-quality machines, the application engineering assistance we get and the ZPS ability to provide us a turnkey system.”

He added that the proximity of ZPS to Mitchel & Scott in Indianapolis, as well as the long-time personal business relationship he’s shared with Tessarzyk, are contributing factors to the solid business collaboration between the two companies.  

Commenting on the controls used on the ZPS machines, both cam and multi-spindle styles, Mitchel emphasized the consistent quality of performance and "nearly zero" maintenance issues with the Siemens Sinumerik 840D sl CNC and Simatic S7 PLC systems.  For his operators, Mitchel noted, both the CNC and PLC have been very intuitive systems, with a notably short learning curve. 

Siemens CNC, motors and drives run motion control, often to 50-60 axes of motion with dual CPUs.

However, Tessarzyk said, “There is no customized software overlay onto the Sinumerik CNC or the Simatic PLC units we use.  On the CNC machines we offer, a second CNC CPU is typical, as our machines routinely run 50-60 or more axes of motion simultaneously, plus the CNC talks to the PLC on the bar feed system and our Artis tool and process monitoring system is engaged, so there’s a lot going on.”   

Despite the complexity of the control scheme and the multiple machines in this core operating department at Mitchel & Scott, Pat Mitchel maintained that, “it’s almost like the controls are invisible most of the time, as their set-up, operation and maintenance are seamless and really enhance our performance for customers.”  

The workhorses of the ZPS machines installed there are two Model 867 CNC machines, which each have 80-mm, 8-spindle, 16 +1 tool carriers, each with three tools onboard.  These machines are used on the most complex, large turned parts manufactured at Mitchel & Scott.  Quick-change Capto tooling is used on eight, independently driven spindles with a C-axis.  Each spindle provides 20 kW of power and the machine handles up to a 3-in. bar diameter and 12-in. chucking diameter.  When needed, the machine can function in twin, four-spindle operation, producing different parts. 

Supporting the ZPS CAM and CNC machines here are Cucchi (pronounced “cookie”) bar loaders.  On the 867 machines, these automatic bar loaders feed all eight positions in the multi-spindle configuration.  

“Because our company is completely vertically integrated, including the foundry where the machine bases are cast, we have great control over the quality on the machines, from the bottom up, literally,” Tessarzyk commented. "Plus, each of our machines is equipped with a fire-suppression safety system onboard.  We are cognizant of the need to protect our customers at every turn…and that’s no pun.” 

Tessarzyk also noted the presence of factory-trained engineers at the ZPS operation in Indianapolis, which helps to make machine installation and commissioning possible in as little as three days.  A further advantage of the ZPS business model is a thriving retrofit business.  Though Tessarzyk started ZPS America in 2008, there were already many Tajmac machines in the U.S. market: Today, older machines, often up to 20 years in service, are being retrofitted with new Sinumerik CNCs, Sinamics drives, and Simotics motors at ZPS America. 

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