be considered at four levels, all interrelated:
Planning
Process planners or supervisors have to evaluate many aspects of the production. One of their key considerations is the number of parts produced in a single batch. The more batches per period of time, the more expensive each batch will be, mainly because of the repeated setups. Assuming that more parts produced in a batch will have no negative side effects (for example, on inventory), fewer batches per period of time might provide part of the solution.
Programming
CNC programmers can literally do wonders to decrease the cost of the first part through the program. Here are only some ideas. Using consistent tool numbers for commonly used tools saves time during setup, as tool registration and many related offsets will not change. Another very effective programming method is to include one or more trial cuts with the block skip function in the program. These cuts will only be used for the first part testing, but turned off for a full run (except the occasional inspection). Don’t forget to provide sufficient comments in the program, so the operator knows the purpose of these special cuts. Another consideration, especially for programs developed manually, is to invest in reliable CNC simulation software. Although no software can simulate every detail of CNC machining, it can be an excellent tool to find errors and areas of improvement.
Setup
At the machine, the CNC operator is normally responsible for setting up tools and fixtures, registering tool numbers and various offsets, troubleshooting the program, and monitoring the operation. Speeding up the non-productive time required for setup is the most significant single saving available. Modular fixturing, common tooling, general setup consistency, and the operator’s skill all add up to make the transition between setup and operation faster and smoother.
Machining
During machining, the CNC operator relies heavily on the program itself. During the first part run, it should not be enough for the CNC operator to look just for errors or monitor the program flow. Operators can and should do much more at the same time. For example, they can think about optimizing the program for better performance. Speeds and feeds are the most common areas to focus on, but many more “little things” also influence the cost of manufacturing (including the first part).
Lowering the cost of the first part should be a team effort. CNC programmers may be the key people in such efforts. However, mutual cooperation of everybody involved will offer many benefits and have a positive effect on the proverbial bottom line.
 | Are You a CAM Machinist? April 2004, updated February 2013 |
The main topic at a discussion I had several years ago was quite simple: CAD/CAM Learning Curve for CNC part programming. How long does it take to learn CAD/CAM software to produce a quality part program for a CNC machine tool? This type of part programming is often associated with the term CAM programming. Having looked at many courses offered by many more providers, the picture is still a bit cloudy. From an introductory three-day course (eighteen hours in reality, breaks included) to a three-level course running more than one hundred hours, there is something for everyone. All that in addition to self-starters, books, and multi-media resources.
Learning a CAM system can be quite intuitive for someone experienced with computers. For such a person, creating geometry (mainly points, lines, and arcs) can be child’s play after a few short hours. On the other hand, the same CAM software can be somewhat intimidating for somebody whose experience is with machining parts but not with using computers. That brings up an important question: What is required from a CAM programmer? What type of knowledge and skill should a CAM programmer have in order to develop often complex tool paths that make parts on expensive CNC machines?
During the discussion I mentioned above, the word skills was indeed used many times, mostly related to computer skills. Even the term creating geometry (also used quite frequently) is simplistic. The correct phrase should be creating toolpath geometry — and here lies the big difference. It is fairly easy to develop a geometry that looks right on the screen. It is not easy to create a toolpath geometry that guides the cutting tool and can often make or break a small shop.
In CAM programming, the purpose of geometry is not to recreate a paper drawing as many beginners try to do. Its purpose is to create a working toolpath. True, most CAM systems have hundreds of features that make the entire process simpler and faster. Features such as lead-in and lead-out, multiple contouring passes, segmentation of depth cuts, and stock allowances all contribute to a software that becomes easier and more efficient to use. Their inclusion requires another important skill — understanding the actual purpose of all these features. You must understand when to use them and how to use them correctly. You must also have a solid knowledge of machining techniques.
There are many times when even the best features of CAM software may not provide the desired result. Often it is necessary to add a bit of geometry here and there, a little extra tweak to get the exact result required. The part programmer should have an exact vision of the tool path in mind — before even starting to use the computer.
With all this in mind, what is a reasonable learning curve for using CAM software? Is the computer guru in the shop, who has minimal if any knowledge of machining, better suited for the task than the experienced machinist with limited computer knowledge? Most people will agree that learning how to operate and use a computer and software may take a few weeks at the most, whereas learning the art of machining takes years, even a lifetime.
The learning curve for any individual will also depend on other personal and professional skills. Even in CAM programming, there is always some math involved. There is also the entire area of understanding productivity, efficiency, and safety issues in manufacturing. On the technical side, knowledge of the machine tool, the control system, the fixturing, tooling, setup methods, speeds and feeds, and so on, is most important for each and every program developed. In a nutshell, the same qualities and skills required from a part programmer using manual methods are required from a CAM programmer. Unfortunately, this is not always the case.
So who is this CAM machinist from the headline? I believe that the inescapable truth is that you have to know how to machine a part before you can be a successful CAM programmer. You have to become a part programmer with high machining skills — a true CAM machinist.
| CAD/CAM or CAD and CAM? May 2004, updated February 2013 |
In various forms and on various platforms, CAD/CAM is not a newborn idea. Even before Personal Computers (PCs) started occupying every designer’s desk, Computer Aided Design/Computer Aided Manufacturing software — known simply as CAD/CAM – was available on expensive mainframes and mini computers. Needless to say, it had a matching price tag. This was the dawn of a new way of design. The convergence of design and manufacturing became a hot topic. Designing a part in CAD and developing the tool path in CAM seemed like the way to go for the foreseeable future. Most Fortune 500 companies applied CAD/CAM to manufacturing and it worked very well for them in the competitive market place.
What is the situation today in small and medium machine shops? How do they handle the design and the toolpath convergence? Before I get into it, you have to consider one major advantage that the large manufacturing companies have — they have their own product. They have their own in-house team of engineers, and they generally use a big CAD/CAM system. The success of such convergence is measured only by the effectiveness of each company.
Overall, small shops are of two kinds, those
