IT’S QUESTION AND ANSWER TIME

Recently, many readers have posted questions that might interest many of you. Here are a few that generated some head-scratching. If you have more and can?t wait until we meet at IMTS (see note below), don?t hesitate to ask.

Q. We still do our set-ups by scratching with a tool. Any better way?

A. In the JOG mode, you measure the clamped workpiece and the control calculates the position and work offsets. The workpiece coordinate system is automatically adjusted to the machine coordinate system. During linear motion, for example, in the X direction on the workpiece edge, the machine traverses in parallel to this point, even then the workpiece is clamped at an angle.

In AUTOMATIC mode, similar measuring cycles can be programmed into the NC for set-up, then used as often as needed. A tool or work offset can be performed or simply stored in the measuring report. On a practical level, the measuring cycles can be used for determining proper fixturing, even to the height of setscrews.

Q. Plunge turning and grooving are done every day at my shop. How can the new CNC help me here?

A. Plunge turning requires a new programming concept. Since material is removed in both the forward and backward movement, the advanced CNC simply allows you to describe the contour, then select a conventional or plunge turn, as the CNC automatically calculates the cuts and the transversal movement of the tool for the entire cycle. In some cases, it might be advantageous to use a standard tool for roughing, then the plunge turn to avoid idle passes. This also reduces tool change time to speed your production.

Q. Getting the rotary axes aligned on our machines is a real problem, so how can the CNC do this job for me?

A. On today?s CNC, a special cycle is available that can automatically measure the rotary axis vectors with the aid of a simple calibration ball and probe. In use, this cycle makes position checking very simple and improves the process quality throughout the cycle, as corrections to the axis vectors, for example due to temperature fluctuations or mechanical damage, can be checked automatically and adjusted accordingly.

The ball is mounted to the table for measurement. It?s then measured in three angular positions for each rotary axis and the axis vectors are calculated in the plane. The CNC performs the complete calculation of the machine kinematics when all rotary axes have been measured. The corrections can be entered into the parameters for the digital alignment of the axes, or simply for checking.

Q. We do moldmaking and other one-offs, so what can an advanced CNC do for us?

A. The short answer is a lot. Three-axis machines can benefit greatly from today?s CNC technology, because all the functions required for trueness of shape, surface quality and faster execution of programs are onboard. That last one is really helpful in your world. NC programs for free-form mold surfaces usually come off a CAM system and are executed by the machine controller without deviation.

Nowadays, the memory-intensive NC programs are transmitted to the CNC by Compact Flash card, Ethernet or USB. During the execution of the mold programs, however, the CNC converts the linear traversing blocks into splines. This radically reduces the block change times and achieves much faster data processing. Special CNC features such as jerk limitation for rapid traverse and feedrate, as well as following error compensation and look-ahead functionality, can adapt for acceleration jumps and significantly improve surface quality and trueness of shape.

Q. We?re a busy job shop with very demanding customers and a lot pressure in our production scheduling. How can the CNC improve our throughput and also help train our operators, who often run multiple machines on the same shift?

A. Glad you asked, because today?s shop environment isn?t just about making chips, and machine controls can go a long way to helping in these other areas. The newest CNC models on the market can provide an operator with a step-by-step, plain language sequencing of events, while all those events are linked to the geometry of the finished part. From the onboard cycle simulation software to the library of tooling characteristics and material settings, even beginners can complete the everyday tasks in short order.

Changing milling data, object measurements or even making modifications to mating parts without completely reprogramming the machine tool are all possible with advanced CNC technology. Operators can also transition from a drill to a mill to a lathe without great difficulty, plus they can use the CNC?s ability to communicate via phone, fax or email (and soon texting) to make more changes on the fly and even modify extremely complex programs instantly. In today?s competitive world market, such CNC advancements have many upsides for the job shop.

Thanks for your questions and now let?s get together at the show! I?ll be attending IMTS (where else would I be?), so stop by the Siemens booth (E-4933) and say hello. Bring your CNC questions, too. See you in Chicago and thanks for reading!

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Randy Pearson is the sales support manager for U.S. dealers and OEMs of Siemens Industry, Inc., Drives Technologies, Motion Control ? Machine Tool Business, 390 Kent Avenue, Elk Grove Village, IL 60007, www.siemenscnc.com. A veteran of the machine tool industry, his interest is the training aspect on CNC machine tools, which he conducts through seminars and classes at votech schools and shops, and at Siemens training facilities. For questions or comments on this column, contact Randy at 847-640-1595 or randy.pearson@siemens.com.