Computer programming pays off Essay

Computer programming pays off



Precise Tool & Mold, Youngstown, OH, is a small company
manufacturing injection molds for the plastics industry, including
companies in Canada, the West Coast, and Florida. They are doing well
because they have mastered the most difficult part of moldmaking
–making complex NC tapes quickly and efficiently.

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They can produce dies up to 48 66, using three NC machines, two
Hillyer 600s (66 X 44 Y 18 Z) and a Hillyer 700 (50 X 30 Y 18 Z).
All have General Automation controls so that all programs are
compatible, machine to machine.



They purchased their first CNC Hillyer in 1978 and did all the
necessary programming manually for the first three years. One
programmer couldn’t handle the load, so they hired a second
trainee. Programming time per tape was anywhere from one hour to two or
three weeks to write. When they added their second machine in ’81,
they added another programmer, but ran into trouble.



Programming bottleneck


“The more experienced we got on these machines,’ explains
Programmer Jody Soltesiz, “the more diversified our work became.
We were able to move into new areas that contributed to our growth. But
as we got into three-axis contouring in manual programming, it became
virtually impossible to keep up. This forced up to seek out a
computer-assisted programming system. We investigated several
suppliers, and tried one in-house for a year. But it didn’t work
out.’


That earlier system was obtained under a contract with a one-year
trial period. Final purchase was contingent on the system meeting with
their full satisfaction. “During this trial period, we experienced
several difficulties,’ Jody recalls. “One was storage
space–our parts were just too complex to fit on their hardware.



“We do a lot of 3-D contouring now. With the prior system,
the tape could only be so long, 300 ft to 400 ft. With the new system,
tapes can run well over 2000 ft. I don’t know whether the limit
was hardware, software, or both, but the system asked you to split these
longer jobs up.



“Obviously, for more money, we could have gotten a system to
handle our contouring tapes, but for less total money we’re getting
that and more from the system we purchased from Datacut Inc, Ardsley,
NY. We also got detaching capabilities, the ability to drop one program
and move to another while lengthy computations are going on. We
couldn’t process one program while we wrote another one before, and
we also like the flexibility we now have of being able to use multiple
terminals.’



Graphics interaction



“We really like the language,’ Jody says.
“It’s easy to understand, simple to learn, easy to write, just
everyday shop-floor language. We have interactive graphics on one of
our two systems, but I don’t use it much. But it is great for a
beginner or for 2-D programming. The time it takes to process a simple
box shape is approximately half as long as if you were to just type in
the coordinates and create a program. It’s a different process.
You’re creating a file and viewing it at the same time.



“But graphics is ideal for trouble-shooting a specific problem
area of a part. You can see the area as it develops, and the problem
and solution become quickly apparent. At any point, you can use
interactive graphics selectively to examine a specific area where the
program is hung up.



“Ordinarily, without interactive graphics, we would double
check what we’ve done anyway,’ Jody notes. “We take 15
min to 20 min to go over the program before making the tape. We can
plot it on the hard-copy plotter or view it on the screen if we choose,
for trouble-shooting, either before or after the tape’s been
run.’



Foam it first



“We also take other precautions,’ he adds. “We cut
test blocks out of pieces of hard foam, particularly where there’s
a lot of three-axis contouring. Then, quite often, after the block is
cut, we use this block on our tracer to rough-in the part to within
1/16. Then the part is transferred to our CNC machine for finishing.
The tracer can remove metal much faster. This is often the fastest way
to arrive at the final shape when the part is complex or has deep cuts.
When the part is a simple box 1 deep, for example, we wouldn’t take
this intermediate step. We would program it, rough it in, and finish it
on the same CNC machine.


“Most of the parts we do are not related in shape. I wish we
had the chance to do more families of parts. We do do some repetitious contours or related shapes for the door industry.’



Processing files



“It can take up to three hours to process a complex 2000-ft
file,’ Jody explains. “An average tape is 150 ft and some run
up to 450 ft.



“There are three different files. First, the PT file, which
is just the ARPT source code for initial processing. Processing this
file creates the DM file, which is the cutter-location file. The final
post processing changes the DM into DA, which is the file our machine
tools understand. The DM file is the largest in terms of computer
memory space requirements, and allows us to do all our plotting,
viewing, and analyzing of the program. But the DM file is not
interactive graphics. Once the tape is made, we destroy the DM file to
regain computer space. If it’s required later, to produce a
graphic, for example, we just create another DM from the original PT
file.’



Nothing’s too tough



With their EDM capabilities to supplement the precision
capabilities of the CNC machining centers, they can now get all the
precision they need. There is no longer any need to turn any job down.
“The programming language from the earlier system was a little
easier to learn,’ Jody admits, “but any user language is fine,
once you get used to it. What you want is results.



“Datacut is a small company that can relate to the problems of
a small user company much better than a big company like the one we
dealt with before.



“Service has been great. If you’ve got a problem, you
can call them and usually within an hour, you’ll have a reply. If
something goes wrong, they can send you a patch over the phone that will
tell you how to initiate what has to be repaired, step by step, guiding
you through the repair. Other companies didn’t want to let us
touch anything. They wanted to send a guy down here to do the repair,
and then hit us with a big bill.



“Their training was also excellent. You can come back from
that and start writing programs right away. But having some manual
programming experience beforehand is a big help for any programmer. The
key is to be able to relate ARPT language to machine code. Otherwise,
when you’re viewing a program with a problem in it, you can review
the machine file and it looks all right, yet you won’t know how to
find the problem.’



Watch out for huckster tricks when you’re checking out
potential systems, Jody warns. “In those trade-show demonstrations
where they are bragging about processing speed, they’re not taking
off multiples of 0.030 like we would be doing in our shop. That takes a
lot of tape. When we ask for the speed we need to keep processing time
down, they show you a sample program that takes only 6 min to run, which
sounds quick, but they’re stepping at 0.250 which requires only one
eighth the processing time as a 0.030 step.’



Photo: Jody Soltesiz at the console.



Photo: Some of the plastic products molded from dies made by
Precise Tool & Mold.



Photo: Tracing a foam tape-testout block can be a shortcut to
roughing out complex shapes without tying up the CNC machines, because
the tracer is faster at removing metal.

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