By retrofitting CNCs to three manual Hardinge lathes, Mansfield Screw Machine Products Co. (Lexington, Ohio) increased the throughput on these machines by about 15 percent. That's the estimate of shop floor supervisor Keith Reed, who performed the retrofits, and now writes the machines' NC programs. But improving performance was not the main reason for the retrofits; the machines were always productive. Instead, retrofitting was a way to keep them productive, even without an experienced machinist in control. That became important when one of the company's best Hardinge operators retired. "We just can't find machinists with those skills anymore," Mr. Reed says. So the company purchased retrofit kits from OmniTurn (Farmingdale, New York), a supplier offering these kits for a variety of Hardinge lathes.
Now, the upgraded machines run more productively. The underlying lathes were all over ten years old. With the newer, more rigid axis drives, the machines cut accurately at higher speeds and feedrates than the previous drives would permit. At the same time, there is now far less time lost to manual toolchanges. The retrofit kit includes a gang tooling system allowing the machine to employ several tools in one cycle, like almost any CNC lathe. And because the machines are now NC, they deliver these performance gains regardless of the skill level of the operator.
The retrofitted machines also improve the efficiency of the shop's process overall. A part featuring a surface finish requirement of 15 microinches illustrates this. Using the manual machines, the shop couldn't hold this finish consistently, so bench work was needed. But since the retrofit, "those parts come off of the lathes smooth enough to ship," Mr. Reed says. Benching has been eliminated.
For other parts, savings come from eliminating expensive time on more costly machines. Like many automatic machining contractors, Mansfield Screw Machine uses CNC equipment for secondary operations. However, to provide customers with just-in-time delivery, this shop routinely runs blanks in large volumes on the automatic machines, then performs the CNC machining in small batches, to complete the parts only as the customer needs them. But now there is an alternative to higher-end CNC equipment for some of this work. The retrofitted lathes have the capability to perform many of the same complex machining routines as a full CNC lathe, including single-point threading.
The retrofit kits came largely pre-assembled. Working with an electrician, Mr. Reed performed each retrofit in about a day and a half. He writes the NC programs for these machines on a PC at his desk, using software which also came with the kit. Once the program is written and the correct tools are loaded, he says, the operator's only role is to load each workpiece, start the cycle, and check parts against the specification.
This simplicity, combined with the efficiency gains, has convinced Mr. Reed that CNC retrofitting was the right investment to make. At least one other manual Hardinge lathe operator in the shop is nearing retirement, he says. "And when he goes, I think we'll retrofit two more machines."—PCZ