Shops that run complex high-precision parts on single-spindle Swiss or other similar types of CNC equipment at production volumes that force using three or more of these types of machines for one job should consider CNC multispindle machines. In many instances, one CNC multispindle can provide the production volumes of three or four singlespindle Swiss-type machines or as many mechanical camdriven machines.
Unfortunately, CNC multispindles often are mistakenly thought of as applicable only to long-running, high-volume jobs because they take so long to set up. To make matters worse, the machines inherently have constrained work envelopes and often lack spindle power, which limits their operations.
Machine tool builder Tajmac-ZPS addressed these misconceptions and design issues when it developed its CNC multispindle machines. The Czech Republic company is part of the Milan, Italy-based Tajmac-MTM SpA and sells its machines in North America through ZPS America LLC.
At the heart of Tajmac-ZPS’s six-spindle Mori-Say TMZ 6-42 CNC (52-mm bar diameter) and its recently released eightspindle Mori-Say TMZ 8-67 CNC (72-mm bar diameter) is a special drum design unlike those found on other CNC multispindle machines.
Basically, what the company has done is located all the spindle drive motors away from the spindle drum itself.
Drive motors reside at the machine end opposite the end housing the spindle drum. A shaft made up of a series of hollow shafts within one another extends through the machine’s main body to connect spindles to drive motors.
Each independently controlled spindle has a gear that meshes with a gear mounted on one of the shafts. There are six shafts for the six-spindle model and eight shafts for the eightspindle model. At the opposite end of the drum side of the machine, motors drive gears and pulleys in a gearbox that then drives the spindle shafts.
Pulleys and belts at the drum end of the machine are always engaged, even when the drum indexes. The drum indexes by way of another separate shaft and motor, also located away from the drum at the opposite end of the machine.
The company said the advantages of this design are numerous. One is that there are no integrated drives in the machine’s spindle drum, so there are no issues concerning heat generation to worry about. That eliminates the need and costs associated with having to cool the drum.
The Tajmac-ZPS design also eliminates the need for programming in an “unwinding” index for the spindle drum and allows spindle rpm to be independently controlled. Shops can program each spindle to rotate at a different rpm if so desired, unlike other types of CNC multispindles where all spindles have to run at the same speed.
Another advantage of the Tajmac- ZPS design is that it opens up machine real estate. As a result, there’s room to accommodate more powerful spindle drive motors, work areas are not as constrained, and the space allows for a more robust powerful nonhydraulic clamping system.
The Mori-Say TMZ 6-42 CNC sports 6,000-rpm spindles powered by high-torque 10.5-Kw motors. These motors make for shorter spindle-speed ramp-up time, so the machine invariably uses less energy.
Because ample machine work area is available, Tajmac-ZPS can build more axes into its CNC multispindles. The Mori-Say TMZ CNC 6-42 can accommodate 44 axes and can have as many as five backworking tools.
To oversee all their axes, Tajmac- ZPS machines are equipped with two Siemens 840 D controls. These dual controls make it possible to add axes even after the machine has been in the field for a while.
The machines use standard G code and CAD/CAM for programming. Shops program each spindle one at a time using special software from Tajmac-ZPS called TMIS, which also provides full simulations.
According to Michele Tajariol, general manager of Tajmac-ZPS in the Czech Republic, CNC is what gives the multispindle machine its flexibility to changeover quickly from job to job without losing days of production.
Tools also are changed over faster thanks to a system where motors and gearboxes remain on machine slides. To change a milling attachment for example, operators simply swap out only the head end of the attachment – the heavy parts stay on the machine.
Multispindles in action
At Metusan, the decision to add CNC multispindle technology to its shop full of mechanical type single-spindle automatics was customer driven.
The shop, in Wolkersdorf, Austria, experienced an influx of jobs involving lower volumes of more complex parts, some of which required as many as 26 operations. These parts could not be cost effectively done on the shop’s other machines, mainly because set ups would have taken too long.
Metusan’s two Mori-Say TMZ 6-42s allow it to run such lower volume jobs – such as those below 100,000 parts – cost effectively because, for the shop’s various jobs, it only takes about 3 hours to change the machines over. Some of its other machines can take half a day and longer.
The shop currently runs 80,000 to 100,000 orders through the Mori-Say TMZs per year, the bulk of which are families of parts.
Trafimet SpA in Vicenza, Italy, is another shop that met increasing customer demands through CNC multispindle machines.
The company manufactures MIG, TIG and plasma torches and spare parts, adaptors and accessories. It needed to increase its production of plugs and sockets for connectors. “
We produce about 4 million to 5 million plugs and sockets per year. And while our mechanical multispindle machines were made for such part quantities, they took too long to set up when part styles changed,” Ugo Simioni, industrial director at Trafimet, said.
He said the shop’s two Mori-Say TMZ 6-42 machines provide the flexibility to quickly set up for style changes and to run jobs with fewer pieces cost effectively.
The shop runs jobs averaging 5,000 pieces on the Tajmac-ZPS machine and changes the machine over for different jobs 2 times or 3 times a week. Parts that once took one minute apiece are now done in 12 seconds, and with that kind of efficiency, the shop is moving more work from other machines to the Tajmac-ZPS machines, especially jobs where parts had to be processed on multiple machines.
“The important factor is that we are able to drastically reduce setup times and cut production time by running families of parts at shorter cycle times. As a result, one Mori- Say CNC 6-spindle machine does the work of one of our 8-spindle mechanical machines when working on the same job,” Simioni said.
He also mentioned that the ROI for the Tajmac-ZPS machine was experienced in a short time period. Within the first six months, the machine was running at 70 percent efficiency. That was increased further by the reduction in set up times and with some guidance from Tajmac-ZPS technicians. The machine is now at 90 percent efficiency for several jobs.
At BRB, an Italian shop with half its work coming from the automotive sector, a Tajmac-ZPS six-spindle CNC multispindle 6-24 played a pivotal role in winning a substantial automotive job. The on-going order calls for delivery of 200,000 pieces every four months, with the total order amounting to about 1,700,000 pieces.
Fabio Valente, administrator at BRB, indicated that the job wouldn’t have been worth taking if the shop had to rely on its other equipment. Parts would have had to move from one machine to the next, making it practically impossible to meet the job’s accuracy requirements.
“These parts are a bit more highprecision and complex as compared with what we usually deal with, and the Tajmac-ZPS multispindle lets us machine the parts complete on one piece of equipment and easily meet the tolerances. The fact that the customer saw we were willing to invest in such technology as the Tajmac-ZPS machine to do the job made a big impact toward winning the work,” said Valente.
BRB got its six-spindle CNC TMZ 6-42 machine in September, 2008, and has changed jobs on it only three times so far. The shop also has an eight-spindle CNC TMZ 8-67 on order because it plans to win more jobs involving complex, highaccuracy parts.