| [metlfax/incl/99mfx.htm]
FUNDAMETLS
by James Smith
President
CNC Innovations Inc, Enfield, CT
Set up shop for presetting success
System approach maximizes benefits
The most valuable component of a presetter
is not in the scales, slides, base, electronics or optics, but the information
created by the presetting operations. To maximize the benefits of your presetter,
turn your attention away from the hardware and the details of measuring
tools and take a systems approach to integrating the presetter information
into your manufacturing processes.
Whether you transfer information to and from your presetter with a fully-automated
computer-based approach, or you use a paper-based method, the basics are
the same. Maximizing the benefits of your presetter depends on a strategic
plan that takes into account the source of tooling information, the needs
of the tool preset operator, and the distribution of the preset information
to your CNC machines.
There are two general types of information associated with the use of
presetters--input or operator information, and output or manufacturing execution
information.
Operator information
The operator needs to know what tools to assemble and measure, the dimensions
to measure, and the target values and limits for each of these dimensions.
Getting this information to the operator can be handled on paper or electronically.
The paper approach is simple to implement and requires no investment in
software or hardware but is more subject to human error than an electronic
approach. The electronic approach provides automatic coordination and updates
of documents across several departments, but often requires a more complex
implementation and some investment in computers and software.
The implementation plan needs to answer the following questions:
- For each job, who will create the list of necessary tools and how will
that list be sent to the tool preset operator?
- Where will the tool drawings and nominal dimension values be created?
How will this information be stored and how will it be sent to the preset
operator?
- When this information is updated, how will the documentation at the
tool preset station be kept in synchronization with the information in
the engineering department?
Different approaches
Getting information out of your presetter into your manufacturing process
can take three general forms--paper, semi-automatic and fully automatic.
The paper approach offers simpler implementation but requires continuous
manual operations, generates less return on investment, and is subject to
more human error. An electronic approach, whether semi-automatic or fully
automatic, generally results in more productivity gains.
Most presetters today have serial (RS232) output capabilities. For paper
operations, this is usually connected to a label printer. Actual (or offset)
measured "X" and "Z" dimensions can be printed on a
single label and the label affixed to the tool. When the machine operator
loads the tool, he is required to manually enter the dimension information
into the CNC control. This is both time consuming and subject to operator
input error and/or omission.
Make it automatic
Automatic approaches are usually based on a PC connected to the serial
port of the presetter or directly to the scales. A semi-automatic system
allows tool dimension information to be output to an NC program format file
that can then be loaded into the machine control with a portable disk device
or computer.
The process of converting the dimension information to machine-readable
format is called post processing and is analogous to the post processing
used in CAM systems. Electronic approaches usually involve job "kitting,"
where all the tools for a specific job are "kitted" into one group.
This tool list information is presented to the tool preset operator to indicate
the tools to measure. The tool list information is also used in the post
processing operation to determine which tools to include in the NC format
CNC file.
A fully automatic approach involves linking the PC running the tool preset
software to a DNC system. When CNC machine operators request the NC program
for a particular job (or part and operation), a properly configured system
will automatically send the NC program or programs as well as the tool offset
file. Then when the CNC operator executes the offset file, the machine registers
are automatically updated. This type of approach brings even more time savings
to the process and further reduces the potential for human error.
Other automated solutions involve using bar codes or ID chips. Software
at the presetter can read/write bar codes or ID chips to identify tools
and record dimension information. Complimentary software at the CNC machine
control can read the tool information from the bar codes or chips and automatically
update the machine offset tables.
For CNC machines with tool-life management and redundant tooling, the
transfer of additional information between the presetter and the CNC machine
may be involved. For example, when tools are taken from a machine, their
total time-in-use may be recorded on an ID chip. This information may then
be read at the presetter so the preset operator can determine if the tool
can continue to be used or if it needs new inserts. It is important that
any plan to implement tool presetting take into account all of these variables.
[metlfax/incl/99mfx.htm]
|
