Every so often, I like to present a few Web sites I’ve come across that are of special interest to CNC users. While some of the Web sites I mention have products to sell, they also have free information about CNC.

It’s getting easier and easier to find CNC-related Web sites. A search in Google (or any other search engine) for “CNC,”, “CNC training,” “CNC Programming,” “Parametric programming” or just about any CNC-related topic will render countless results. Here are a few of my favorites

It’s not a stretch to say that wire and sinker EDM technologies are cutting faster and putting a finer finish on products that are smaller, more delicate, and more complex than ever before.

Chief beneficiaries of these advances in EDM technology are US manufacturers in the mold and die, medical device, and electronics industries, among others searching for a competitive edge against their global competitors, principally from Asia. It’s not too surprising, then, that many of the advances in technology are aimed at taking the EDM process deep into the realm of micromachining.

To survive and compete US manufacturers must come up with new ideas and concepts to work with the very smallest parts,” says Gisbert Ledvon, Charmilles (Lincolnshire, IL). Ledvon explains: “Electrodes are required for parts that are so small that you have to rely on your ability to cut the part perfectly, because they are difficult to measure.”

Charmilles has adopted a two-pronged approach in developing its Roboform 350μ MicroTEC technology for micromachining delicate, complicated parts. “First we have focused on developing application-driven technology that addresses the customer’s requirements, for example, to produce a deep rib or produce a finish of a certain quality rather than to cut graphite into steel. Secondly, we have developed the MicroTEC generator to fine-tune power settings to match the complex details of smaller electrodes,” Ledvon states.

Producers of workshops, seminars, and instructional materials are encouraged to mail announcements to Training Briefs Editor, Electrical Apparatus. There is no charge. All dates refer to the current year unless otherwise noted.

Thermal operation in electric motors

What’s offered: One-day class on thermal operation in electric motors.

What’s covered: The first half of the class will demonstrate that the two-parameter thermal model is incapable of predicting maximum winding temperature during dynamic or intermittent operation. The second half will introduce the fourparameter model and will show why a motor’s winding heats up fast than previously thought. It will also show why a temperature sensor mounted inside the motor may not protect the winding adequately.

Where and when: St. Louis, Nov. 1.

Motor diagnostics

What’s offered: Three-day workshop on Level 1 motor diagnostics.

Offered by: All-Test Pro LLC, 123 Spencer Plains Rd., P.O. Box 1138, Old Saybrook, Conn. 06475; (860) 399-5937; www.altestpro.com.

What’s covered: On-line and off-line motor testing, as well as the latest technology used for each.

Where and when: Nashville, Oct. 3-5; Las Vegas, Dec. 11-13.

Batteries and UPS’s

What’s offered: Two- and three-day seminars on batteries and uninterruptible power supplies

You have gone through the effort of identifying opportunities for improving your plant’s operation. You have given thought to how long it will take and who is in the best position to make things happen. You have energized the staff through training and open communication and you think everything will work out, yet nothing happens. Your staff eventually gets lost in the daily ritual of putting out fires and trying to run a chaotic business, and all of the good ideas become distant memories.

Why does this happen? More often than not, it is because you did not have an implementation plan that was understood by those responsible fur getting it done. If you have encountered this problem in your company, consider the following steps for developing and managing an effective implementation plan.

1. Identify the action items to be addressed. Be sure they are written in a clear and concise manner and that everyone involved really understands them. Whenever possible, make these action items “achievement oriented.” Typical action items might include “reduce change-over time by 50 pecent on the CNC lathe,” “eliminate all unneeded items from the assembly area” or “develop a pull scheduling signal for the paint shop.”Avoid “activity oriented” action items such as “investigate the possibility of instituting a preventive maintenance program on the vertical machining center” or “evaluate running the machine at faster speeds and feeds.” If it turns out one of your achievement-oriented action items does not materialize, so be it. At least there was a clear vision of what was expected, and perhaps it can be revisited later.

2. Determine the person best suited to assume responsibility for the action item. This is not necessarily the person who has to do all of the work; rather, it is just the person who assumes responsibility for getting the work done. Obviously, the person will need access to resources to be successful, and this must go into the decision of selecting the right person.

3. Before you assign target completion dates for the action items, determine priorities. This will help in setting the target dates. Use any prioritization system you feel comfortable with, but be careful not to establish too many priority levels. At this point, a simple A-B-C prioritization identification may be sufficient. This forces everyone to examine which are the most important items and which can be put off for a while.

4. Determine target completion dates for each action item. Resource availability will generally dictate these dates, which should be reasonable (don’t forget you also have to keep the business running) and have the buy-in of everyone involved. It may be necessary to establish multiple phased dates for certain action items. For example, you may choose to list a date for an initial step in the process along with a completion date.

5. Document the implementation plan and post it somewhere in the company. The plan can be recorded on anything from a handwritten flip chart to a more formal computer-generated document. Posting the plan establishes a communication board for everyone to see.

6. Determine the frequency and type of follow-up meetings for the sole purpose of discussing progress with the implementation plan. In terms of frequency, more frequent is better than less frequent, especially early in the life of the plan. If follow-up meetings are planned too far apart, time may be lost upfront, leading to delays down stream. Intervals of 1, 2 or 4 weeks are probably the most common frequency for these meetings.

When it comes to meetings types, avoid long, drawn-out meetings that accomplish little and waste valuable time. Identify what should be discussed by the team and what should be taken off-line for discussion by a limited few. Many like the “15-minute stand up meeting” format that can be held anywhere. (For maximum effect, try scheduling such meetings at a quarter to an hour–maybe just before the lunch hour.)

7. Keep the implementation plan alive. This means doing what you say you are going to do, especially in terms of follow-up. Recognizing that there may be times when people are not available for meetings, they should send representatives who are authorized to speak on their behalf. Maintaining momentum and enthusiasm may also require being flexible with dates. When target dates are not met, or are in danger of not being met, immediately establish new target dates and keep moving forward.

Sometimes obvious improvement possibilities go unnoticed. It could be that you are too close to a problem (you can’t see the forest for the trees), or you may not be spending enough time out in the shop to spot them. Or, if you’re not communicating enough with your setup people and/or operators, they’re not going to be able to tell you when they’re having time-wasting problems.

For whatever reason, you may have room for improvements that aren’t being addressed. We’d like to offer some down-and-dirty suggestions to get your creative juices flowing again. Most of these suggestions are quite simple to implement, and they address common and obvious problems.

Color-code your pull studs. If you have machining centers made by two or more machine tool builders, even if they require the same tool holder shanks (CAT-40, for example), it is likely that each machine tool will require its own pull stud (a stud that allows the toolholder to be clamped in the spindle). Pull studs can vary dramatically from one machine tool builder to another. But sometimes the differences between pull studs are subtle and hard to spot. If the wrong pull stud is used, the results can be disastrous. At best, the tool will be insufficiently held in the spindle, resulting in vibration and chatter during machining. At worst, the tool might be thrown from the machine when the spindle is started. One easy fix is to use dye to color all of the pull studs for a given machine with a specific color. This way, setup people and operators will easily be able to tell if they’ve got the right pull stud(s) on the toolholders.

Use Velcro. Velcro makes a great way to keep needed components where they’re supposed to be. With turning centers, for example, you can Velcro the wrenches needed for changing inserts right to the turret, next to the turret station that requires them. You can Velcro the wrench that releases the bar feeder clamp into position next to the release bolt. For vertical machining centers, you can Velcro the vise clamp to the front of the machine. You get the idea. Velcro allows you to stick almost anything right where you need it to minimize searching time during CNC operation.

Get organized. Watch setup people and operators. It’s easy to tell just how organized they are. If they can quickly find each item they need, use it and then put it back where it belongs, they’re probably pretty organized. But if you see people searching the shop to find needed items and/or if you see them leaving items wherever they choose (or worse, if there’s no storage location for items), then there is room for improvement.

Get prepared. This goes hand-in-hand with getting organized. Appropriate preparation is the key to doing nearly anything in an efficient manner. When it comes to making setups, for example, just how prepared is the setup person? Is everything readily available, or does the person have to search the shop (while the machine is down) to find the components needed for the setup?

Document repeated tasks. I have often said the more often a task is repeated, the easier it is to justify improving it. The first thing you should do is ensure that the repeated task is appropriately documented. The more people involved with the task and the lower their skill level, the more important it is to provide adequate documentation for the task. Admittedly, the more a task is repeated, the more likely it is that a given person will eventually memorize how to perform the task. But the key word in the previous sentence is eventually. Until the task is memorized, the person performing it will struggle, which translates to taking more time to perform the task and possibly making mistakes when performing it.

How would you go about programming I.D. chucking on a Fortune V-turn 26 with Fanuc 18 since there is not a physical switch to change from O.D. chucking. Thank you, Marc Surie
Response:

If you’re machine does not have a physical switch that allows you to change from OD to ID chucking (and vise versa), it’s likely that the machine tool builder has included two M codes for this purpose. Check the machine’s list of M codes to find those related to clamping direction. Frankly speaking, more and more machine tool builders are not supplying the physical switch, since if this switch is thrown during the machine’s operation, the results could be disastrous. M codes help them avoid switch interfacing headaches.

Keep in mind that even if you have M codes for clamping direction, most machine tool builders do not intend that you use them in a program. Instead, you must command their execution in the manual data input (MDI) mode. Again, this gives you the ability to reverse clamping direction but keeps it safe and easy for the machine tool builder to provide clamping direction reversal.

I was wondering if there is any difference between NC programming and conversational. One of my co-workers says NC is more accurate and faster.
Response:

There are actually three types of programming methods, manual programming (which I think you’re referring to as NC), conversational programming (which is also called shop floor programming), and computer aided manufacturing (CAM) system programming. Each has it’s place and application.

Generally speaking, manual programming is best when jobs are simple, there aren’t all that many new programs required, and/or there is a need for the CNC program to execute as efficiently as possible. A programmer prepares the program in the same language that the CNC machine will execute it, which can be tedious and error-prone - but manual programming lets the programmer be as intimate with the CNC machine as possible. This means programs can be written in a way that they execute as efficiently as possible on the machine. While some CAM systems can generate pretty efficient CNC programs, I’d still recommend manual programming to anyone doing ultra high-volume work. You just can’t beat the efficiency of a well formatted manually written program.

Conversational programming is best done when programs must be created while the machine is down in setup. If, for instance, a company sees a great deal of repeat business, if lot sizes are very small, and cycle times are very short, it will be difficult (if not impossible) to prepare programs up front, while the machine is running production. Conversational controls can be thought of as a single-purpose CAM system, making it quick and easy to generate a program right at the machine. With print in hand, the setup person can step up to the machine and quickly create the CNC program. Conversational controls allow programs to be entered without any need for math, and take much of the tediousness out of programming. With one popular turning center conversational control, for example, average programming time is under ten minutes.

CAM systems are best used when there are a variety of machines to program (a programmer would have trouble keeping the language for each machine straight), there is quite a bit of new business (many programs to create), and/or jobs are quite complex (making it difficult to manually program). Like conversational controls, CAM systems remove the tediousness from programming. Workpiece geometry is first imported to the CAM system from a computer aided design (CAD) system, which eliminates the need for the programmer to define the workpiece size and shape. The programmer then specifies how machining is to be done. CAM systems vary dramatically with regard to how machining is defined, but most allow the programmer to choose machining operations from a menu and specify the machining parameters in fill-in-the-blanks fashion. The CAM system then generates a CNC program - the same kind of program a manual programmer will write. This program is then loaded into the CNC machine and run.

Note that there are some exceptions to what I’ve said. For example, since CAM systems are much more reasonably priced today than in years past, almost all CNC-using companies can afford to have one.

Also note that some companies don’t adhere to the general statements I’ve made. For instance, some companies will program on the shop floor (conversationally) even though they have ample time and personnel to do so off line. Or just the opposite may be true. They may have to prepare programs while the machine is in setup, but their programmer prepares programs off line manually or on a CAM system. Both can lead to under-utilization of the CNC machines.

I work at Boeing as a Manufacturing Analyst in R&D. Could you give me a detailed explanation of a new word going around called a “nurb” in the machining world? Thanks, Keith D. Hanson
Response:

I’m not sure how detailed I can get, since I’ve never used nurbs interpolation. There was a great article on nurbs interpolation in a previous issue of Modern Machine Shop (check your back issues or log onto their site to see if it’s still available). Frankly speaking, I feel that this feature is more of a band-aid for some of the problems related to machining sculptured surfaces than a long term solution. As you probably know, programs for five axis shapes can be very long. Some CAM systems (as well as add-on software) have the ability to massage the CAM system output, modifying the numerous tiny G01 motions into a series of (fewer) G02 and G03 commands. While this has nothing to do with nurbs, the goal with nurbs interpolation is also to minimize the length of extremely long programs.

Though I’m not familiar with the actual techniques being used, nurbs interpolation is a method of creating a series of movements for a three dimensional shape from a limited amount of input. I’ve heard mixed reviews when it comes to how accurately the shape being machined will be cut. And again, as true high speed machining controls become more and more popular (eliminating the problems associated with lengthy programs), nurbs interpolation will not be required.
Comments:

From Mike Koch of Euromach Precision Mfg. Inc.

O.K. fist of all I have never used nurbs interpolation so as to how well it works I can’t comment. Basically when you create a model in a cad/cam system the data is stored as nurbs data ( Non Uniform Rational Basis Spline). This a mathematical way of storing yor model (drawing), shapes are represented as lines surrounded by control points which have a certain assigned weight which controls the 3D shape of the lines.

Now when you create toolpaths from your model the cam system converts nurb spline data, tooling data and so on into an “intermediate numeric code” ( using Surfcam lingo) which is then used by the post processor to create a g code program for your cnc machine. Typically doing 3d surface cutting you will get a program that is comprised of many very small linear movements (g01) that the machine control processes into arc moves. These programs can be huge, you can filter these moves into arc and plane moves (g02 g03 g17 g18 g19) however this supposedly reduces accuracy. What I have read on nurbs interpolation is that instead of posting g code you post nurbs code (which i have done just to see what it looks like) if your machine control supports it. The theory is that the nurbs data is more efficnt in terms of information per line and the amount of processing power and time required by the machine control to do 3d surface cutting, resulting in greater accuracy and higher constant cutting speeds.( I read about this in a release from Sandvik on high speed machining.)

I would like to know if there is a way to change the value of the rapid clearance of .100 between pecks in the chip-break peck-drilling cycle (G73). We are drilling through plastic, copper and stainless steel tubing. In order to keep drills from breaking (we are drilling (380) #30 drill holes .625 deep.) We can only drill at .7 Feed using a ‘Q’ peck of .03. Therefore with the .100 Rapid Clearance we are wasting a lot of time drilling air. Any help would be greatly appreciated. Thank you, Herb Jeffery
Response:

Yes - if it’s a Fanuc control. There is a parameter that controls the retract in a G73 cycle. Unfortunately, the parameter number varies based upon Fanuc model, so I can’t tell you what the number is. If you look in your Fanuc operators manual in the G73 description, you’ll find the related parameter as well as how it is set. It can be set to any value, but I’d recommend about 0.003 inch or so - just enough to let the chip break.

I was reading your section on thread milling, and parametric programing and noticed that it said there was a difference. Thank you, Hal Linson, Uriah’s Metal Works, Moline, IL
Response:

Helical interpolation is required when thread milling a straight thread. Two axes (usually X and Y) move along a circular path while the third axis (usually Z) moves along a straight path. The radius remains constant throughout the circular movement in XY.

Spiral interpolation is required when thread milling a tapered thread with a taper thread mill to avoid leaving a nasty witness mark at the beginning/end point for the thread. As the tool moves around the thread in XY, the radius of the circle being machined must decrease (or increase, depending upon the machining direction) in order to compensate for the Z axis motion.