When “Mini Cells” Back Up Multi-Tasking Machines, Everybody Wins

Posted by: 2. December 2015

Chris Guidotti of East Branch Engineering
Chris Guidotti, vice president of operations for East Branch Engineering, uses a pallet jack to maneuver a Southwestern Trak 2OP milling machine into position near one of the shop’s Brother VMCs. (Pictures by Derek Korn.)

Multi-tasking machines, such as multi-spindle turning centers, are becoming more prevalent as solutions for machining complex parts without multiple setups. But as Derek Korn, senior editor for Modern Machine Shop, discussed in a recent article, there are cases when running parts through a couple conventional machines can be more efficient.

Writing about Connecticut-based East Branch Engineering, Korn explains how the shop complements its single-setup capabilities with portable vertical machining centers that can be arranged as needed to form custom, multi-machine cells:

“[East Branch] also leverages a flexible and reconfigurable ‘mini-cell’ strategy with a pair of portable CNC milling machines that can be easily transported next to any of the shop’s conventional VMCs or turning centers and then perform secondary operations, run dedicated, small-batch jobs or machine prototypes. That way, a single operator can tend two machines rather than standing idly by, waiting on just one machine to complete its operations, and the shop essentially gains ‘free’ machining time by overlapping operations.”

Although Mini cells can’t always compete with single-setup production equipment, having the option is valuable for East Branch, Korn reports. After all, machines incorporating multiple processes can have downsides:

  • Setups require skilled personnel

  • Setups can take longer than they might on more conventional machines

  • For parts whose tolerances are a little less strict, or for small-batch work, multi-tasking machines may prove a bit counterproductive

  • Shops need a backup for when the more complicated machine crashes or is down for maintenance.

East Branch’s experience proves that the mini-cell strategy can make up for these potential challenges. One of the machines is a portable VMC from Southwestern Industries: the Trak 2OP.

The Trak 2OP at Work

The Trak 2OP CNC milling machine is designed for secondary operations and, as is obvious from the picture above, can be transported across the shop floor with a pallet jack in a process that takes about 5 minutes, according to East Branch. Beyond secondary operations, East Branch uses the 2OP as a standalone machine for basic jobs or pre-machining work. 

inside the Trak 2OP

As Korn explains, East Branch also pairs the portable machine with a larger VMC in a mini cell:

“In this case, it is first used to pre-machine a dovetail profile into Delrin workpiece blanks to enable them to be fixtured in a rotary indexer on a larger VMC. After primary machining is completed…the portable machine finishes the part by milling away the dovetail feature and drilling some holes (pictured above).”

The 30-taper, 3-horsepower mill provides XYZ travels measuring 14 × 12 × 17 inches while taking up only about 10 square feet of shop space (2.5 × 4 feet). A standard eight-station automatic toolchanger eliminates manual tool changes, and a Jergens Ball Lock fixturing system eases quick change-overs. Korn explains that this quick-change fixturing system also makes it easier to interrupt work on one batch of parts and replace it with a customer’s hot job; the operator can remove the fixture plate and save the tool offsets to the machine control.

As for the TMX control itself, its conversational platform also comes in handy when the user needs to leave the machine partway through a setup. The system is designed to offer screen prompts to show where the user left off.

Weighing Your Options

Southwestern’s portable machine is marketed for its easy maneuverability, but it’s not the only smaller-size mill of the sort. Haas Automation’s 5-horsepower OM-2A “Office Mill”, which offers XYZ travels of 12 × 10 × 12 inches and a 20-station toolholder, uses casters for movement across the shop floor. In addition to its larger tool capacity, this machine also features a bump in rapid traverse rates compared to the Trak 2OP.

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