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Is manual programming really important?
- CNC Tech Talk
Author: Mike Lynch
I am often questioned about the scope of this
column. The most common question is: "Why do you continue to
discuss manual programming techniques when almost all companies
are using CAM systems?" Aside from the fact that other columnists
are addressing issues related to computer Integrated manufacturing,
I believe that a firm understanding of manual programming is of
paramount importance to all CNC people. It is important not only
for short term issues and specific applications, but for the long
haul in every CNC environment--from a person's first acquaintance
with CNC through their attainment of expert status.
For entry-level CNC programmers, course related
to manual programming pro. vides an excellent platform to address
some important CNC issues--issues that form the foundation of a
person's understanding of CNC. Features such as program zero, coordinate
systems, absolute versus incremental, motion types, the various
compensation types and special programming features are best presented
during a discussion of manual programming.
Trying to present these features to entry-level
students while they're trying to learn a CAM system will confuse
them and have limited success. Starting at CAM system level without
understanding the basics of manual programming is like learning
to use an electronic calculator without understanding basic arithmetic.
Entry level CNC setup people and operators must
eventually understand at least some manual programming techniques
if they will be expected to edit programs at the machine during
a program's verification. While not all companies expect this, the
more setup people or operators understand about manual programming,
the better they can perform.
Consider what it takes to run the first workpiece
using a new program. The setup people will place the machine in
single block mode and step through the program. As they do so, they
must be sure that each upcoming command is correct. Regardless of
whether the program is originally created manually or with a CAM
system, how can they safely do this without understanding manual
programming?
An understanding of manual programming is important
far beyond a person's introduction to CNC. Some of the best machine
utilization enhancements (reducing setup and cycle time, for example)
can only be accomplished with manual programming techniques.
Indeed, utilization enhancements--and the manual
programming techniques that allow them--have been the topic of many
past CNC Tech Talk columns. Efficient range changing on turning
centers and machining centers (September & October 1998), shortening
a program's execution time with G01 for positioning (February 1999),
programming trial machining operations (April 1999) and using secondary
offsets (March 2001) are a few examples of techniques that are best
applied with manual programming techniques.
Programming method is of utmost importance when
it comes to cycle time reduction. One factor that contributes to
bare minimum cycle time is how the program is formatted. While CAM
systems are getting more powerful in this regard, no other programming
method beats the intimacy that can be achieved with manual programming.
As production quantities grow, every second of
program execution time becomes more critical. Again, CAM systems
have come a long way, but it can be difficult, if not impossible,
to cause some CAM systems to output CNC programs as efficiently
as can be done with manual programming techniques.
Manual programming is also important if you have
any interest in applying parametric programming techniques. All
applications for parametric programming require a firm understanding
of manual programming.
Admittedly, there are people who rely exclusively
on their CAM system to prepare programs and have little or no understanding
of manual programming. Yet they successfully create programs, machine
good parts and meet production schedules. Maybe they have extremely
complicated work that can only be programmed with a CAM system.
Maybe lot sizes are so low that cycle time is of little importance.
Maybe there is very little repeat business, so every program must
be created before the job can be run. In these cases, cycle time
may not be critical.
But if you don't know manual programming, how
can you be sure your CAM system is outputting programs in the most
efficient manner? The first step to making any improvement is knowing
what's possible.
COPYRIGHT 2002 Gardner Publications, Inc.
COPYRIGHT 2002 Gale Group
About the Author
Monthly magazine for metalworkers and machinists offers industry
news, product and book reviews and expert advice.
Visit: http://www.mmsonline.com/
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