6/1/2000 | 5 MINUTE READ

Metalcutting Automation: Some Considerations

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 Turning & Milling & Turning

Nominally, the MT-250 from Mori Seiki (Irving, TX) is a “turning center.” Which means, lathe operations, of course, but in this case, machining center-type operations, too, as in milling, drilling and tapping. The point is to consolidate machining operations to a single machine, which not only means floor space requirement reductions, but also improved part quality (by not having to refixture the part)—to say nothing of the ability to produce more complex parts than would be otherwise possible to produce on a turning machine or machining center alone.

The machine is equipped with a magazine that handles up to 180 tools—turning or otherwise.

The maximum turning diameter is 22.4 in.

Speaking of consolidation, the company offers the RL-250, which is a dual-spindle turning machine. The 20-hp direct-drive spindle motors are located just 20 in. apart (the maximum turning diameter is 13.39 in.; maximum turning length is 7.09 in.): the point of this configuration is essentially an ergonomic one: it facilitates operator load-unload access.

And, again, it is an issue of floor space minimization: the footprint for this two-in-one machine is just 96 in. wide by 74 in. deep.

Machining Center Handles Bar Stock. And Exceedingly Fast Moves.

The MC 531/SM vertical machining center machines parts—from barstock. The approach is not a common one. In fact, according to a spokesman from Chiron America (Charlotte, NC), he knows of just one other builder of machinery that, like the new MC 531/SM vertical spindle machining center, machines parts starting with bar stock.

The machine is fitted with a special bar feed system that handles bars up to 157 ft. in length that can be cut into lengths of up to 31.5 in. The bar diameter capacity ranges from 0.4 to 3.15 in. The bar stock is loaded through a center hole in the built-in, tilting rotary table and a pneumatically clamping collet-type chuck device. Once the machine is setup, indexing the bar stock, clamping and unclamping, and part cutoff are all performed automatically. An optional tailstock is available—although it should be stressed that this is a machining center, not a turning machine.

According to Bill Carr, president of Chiron, the machine is not meant for high-volume production. And he points out that the applications that the machine has been put to work on include the cutting tool, medical (e.g., implants), and firearm industries—not automotive. That said, the advantage is the ability to perform five-sided machining in a single setup (and therein is found the key means of ROI): throughput times can be re-duced by as much as 90% compared to having to move the workpiece from machine to machine—and this is being done on one machine, not multiples, which means that not only are equipment investments minimized, but so is required floor space. (Actually, Carr explains, the machine is capable of performing six-sided machining, which is accomplished in at least three different ways, all of which require some additional mechanisms.)

In terms of the basic machine characteristics, the traveling column machine has a 25-hp AC spindle drive that offers speeds up to 15,000 rpm and provides a maximum torque of 170 ft.-lb. It has a 42-station tool magazine that handles CAT 40 or HSK-A 63 tools (weight to 33 lb.; length of 11.8 in.); chip-to-chip time is rated at 2.8 seconds. Traverse speed in all axes is 1,727 ipm.

For those who are interested in more conventional but exceedingly fast machining center operations, Chiron has developed what it is calling a “Speed Zone” manufacturing process for its FZ and DZ line of vertical machining centers. What this means is that all major aspects of machining are done posthaste:

• Spindle speed: 27,000 rpm. The spindle ramps to 8,000 rpm in 1 second. The full speed is hit in 1.5 seconds.

• Acc/dec: 1g. Positioning of all three axes: 2,400 ipm.

• Toolchange: 0.5 seconds. Chip-to-chip: 1.5 seconds.

• Workpiece change via a dual-pallet system: 2.0 seconds—with a repeatable positioning to 0.00025 in.

No matter what you measure—that’s fast.

Sky-High Results For Pilot

Richard A. Scheufler says, “Usually when you have a problem, you try to buy an improvement. But in this case, I couldn’t find it.” What he was looking for was an improved way to deal with operations such as deep-hole drilling and line boring, operations that are done with piloted tools. Scheufler, who has had experience in high-volume automotive production, is now the president of Scheufler Diversified Industries (SDI; Collins, OH), which he says, does a lot of work for several Tier One suppliers.

Scheufler is also an inventor. So because he couldn’t find a solution to the problem on what he considers to be excess wear in these applications, he developed—and patented (patent number 6,033,161; March 7, 2000)—a revolving pilot tool.

As Scheufler points out, when conventional stationary pilot tools are used in high-volume operations, there can be an assortment of problems encountered. When there is wear, the control of the centerline is lost. Which means that because the geometry of the tool is shot, so is the geometry of the hole. So the tool gets tossed. According to Scheufler, the routine is a counter bore tool with a fixed pilot and a life span on the order of 17,000 cycles (i.e., a tool with two inserts, one that does the counter boring and the other chamfering; insert changes at 1,700 cycles and 10 insert changes per tool; the viability of the pilot is determined to be lost when its diameter is 0.030 in. smaller than it was when it was new).

What he has come up with is a counter bore with a revolving pilot, a tool design, he says, that can be used for other operations.

The pilot on the tool is hardened and wear-resistant and should be 0.001 to 0.0015 in. smaller in diameter than the minimum drilled hole size diameter. There is a replaceable wear bushing pushed into the pilot and a retaining apparatus that holds the pilot in place. Finally, there is an element used to both keep pressure on the pilot and to keep dirt from getting into the area between the wear surface, bore and shank.

And as the name implies, the pilot rotates.

What does this do? Well, according to Scheufler, he’s talked to a number of people—both users of tools and suppliers of same—and he has been told when there is an improvement, “You usually only want to increase something by 100%.” Apparently, there is a concern if the improvement is too good. Which leads to a bit of a problem, since in testing, he found that his revolving pilot was in good shape after one million cycles—which is certainly greater than a 100% increase vis-à-vis the conventional 1,700 cycles.

One thing about Scheufler’s tool: You can’t buy it. Scheufler is looking for a company to team with on producing the tool. You can contact him by e-mail at rich_sdi@nwonline.net.