Time To Turn To CNC Multi-Spindles?

Looking around at CNC turning machine tool technology, one sometimes wonders what remains to be developed or invented. CNC systems are faster and more flexible, and you can integrate them from the other side of the planet, if you wish.

In my opinion, U.S. machine tool builders were among the pioneers of high-production turning machines­, such as cam-driven multi-spindle automatics. Therefore, it was surprising to be told by a German machine tool builder, Index Werke of Esslingen, that there appeared to be no real interest among U.S. production managers to acquire CNC multi-spindle autos.

The observation came from a company that, in July, sold its 800th CNC automatic. I asked one of the company's executives why the U.S. market appeared to be so unresponsive to CNC multis. He had spent some years in the United States and said many machine shops “don't care if a part is produced in one hit or three to four hits. They use cheap labor, so seconds do not cost anything.”

Another reason given came in two parts. First, if you have a shop full of single-spindle CNC lathes or autos, it doesn’t matter if one breaks down, American companies say. A second response from these shops was: “So a CNC multi saves floor space? So what? Come to the door. There is the prairie. Do I need to save space?” He added that they had not even begun to talk prices yet. Half million dollars on one machine? One could imagine a similar reaction from someone out West in the 1860s with 100 horses asking why he should pay a few thousand dollars to buy a railroad train.

We find similar attitudes among machine shops in the United Kingdom and, I dare say, in some parts of Europe, too. One would have thought that any machine tool that would promise to undercut piece part prices of a competitor was worth investigating in more detail.

Some people are under the impression that CNC multis take one and a half shifts to change-over and that you need a contortionist to get into that cramped work area to change tooling. But Index disagrees. According to the company, it takes up to 4 hours to do a complete change-over on a six-spindle CNC automatic, including changing over the barstock magazine. If you are using the same stock, then change-over takes about 1 minute per tool or 1.5 to 2.5 hours.

As for the contortionist tool setter,­ well, I confess that I had not looked in depth at Index since 1997. In that year, the company introduced its front open type multi-spindle. What happened to the tool carriers?

Now the work area of a multi-spindle looks like a dial machine on its side. There are up to five compound slides and two longitudinal slides, and most importantly, you can get to them. You can have a synchronized spindle unit mounted on a compound slide. It can pick up the part from its opposing main spindle and back work the part, providing that the part length is within 3× to 4× bar diameter.

A novel approach by Index to producing lots of parts requiring three or four operations is to incorporate a four-axis Scara robot in one slide. The robot has a synchronized spindle, so it picks up a part from a main spindle and processes it through one or two back working operations.

Machining is not limited to bar work, however. Multi-spindle automatics can be robot-loaded for machining forgings or billets. In Europe, the new diesel engine fuel technologies have “blown the roof off” in terms of demand for precision CNC multi-spindle machine tools, according to Index. The company supplied 130 machines during 2003, with some customers (in the automotive industry) buying 13 machines in one order.

If I am beginning to wet your appetite to at least look again at what the modern CNC multi-spindle automatic can do, then take a look at suppliers in the field. Take a global look at your operation. How fast can you react to customers’ orders? Is your shop management a bit complex? Maybe it is time to check out a CNC multi-spindle machine.