Feature Article
Setting Tools Makes Small Shop Sense
Some people think tool presetting can be justified only in large
operations. This Arizona shop shows how it makes sense almost anywhere.
By Tom Beard
Effective
isn't always complicated. Take DG Industries for example. This Phoenix,
Arizona shop specializes in making high quality aircraft parts and
assemblies, and their extensive knowledge in how to machine these
difficult workpieces makes the business go. Beyond that, however,
the philosophy on how to run the shop is keep it simple.
That certainly
applies to how the shop manages tooling, but make it efficient
applies too. DG once went the traditional route of keeping a
central tool crib and letting each machinist more or less fend for
himself, gathering tools and then going back to his machine to execute
the setup. Now the company has a much more streamlined method. The
crib attendant, who only really managed inventory before, has been
replaced with a skilled machinist who understands how and when each
job is going to run. Now he kits the tools for each job, and measures
each tool tip off-line. That way tools are gathered and offsets
are established before machinists begin their setups.
And that
is saving a huge amount of time. Here's how toolsetting makes the
difference in this 25-person shop.
Getting Started
A lot of
people have trouble seeing the payback potential for a tool presetter
in a shop the size of DG's, and initially, so did they. Basically,
the tool crib supports eight machining centers that do the bulk of
the work, along with a range of peripheral equipment. DG had a highly
skilled and experienced group of machinists who were not only capable
of doing their own setups, they could sharpen tools and do much of
their own NC programming too. With only a handful of machines to set
up and with that kind of talent in the shop, why bother with a centralized
toolsetting system?
According
to shop manager William Rogers, the idea initially came from one
of DG's best customers, Allied Signal. "They are very proactive
in working with suppliers to help improve their quality and cost
systems," he says. "They suggested that having a better command
of tooling-related issues would contribute on both counts."
The more
Mr. Rogers thought about it, the more he had to agree that there
was potential for the shop to grow more efficient by implementing
some of their customer's suggestions. So he began work on a new
setup strategy for the shop, complete with flow charts and a cost
justification. He looked both at the cutting processes and at setup,
and he quickly came to the conclusion that there was little to be
gained in cycle time reductions. Setup reduction was quite another
matter, however, and by the end of his investigation Mr. Rogers
was convinced that DG could at least cut setup time in half through
better handling of tooling. If so, that would recover well over
$200,000 worth of machine time for production over the course of
a year.
 |
| The optical tool presetter provides
a full profile of the cutting edge with a display resolution
of 0.00004 inch. The software will calculate tool nose radius
as well as cutter angles. |
The heart of
the problem was that responsibility for getting tools together for
a job rested entirely with the machinists, and that simply had them
spending too much time scrounging around the shop for everything they
needed to get a job up and running. The complicated parts that DG
machines often require that 25 or more tools be changed for a job.
Sometimes all the tools could be found in the crib. But just as likely,
some were out at other machines and it took extra time to run them
all down. Then when the machinist finally did locate everything he
needed, each one of those tools had to be loaded and touched off manually
to establish the initial tool offsets. Then trial parts had to be
carefully cut and closely examined to make sure the setup was ready
for production.
With the
new plan, however, responsibility for all tool preparation work
for jobs would be shifted to the tool crib, including the off-line
establishment of individual tool offsets. That, of course, would
require a new level of capabilities in the crib including the acquisition
of a tool presetter. It would also require a different skill set—that
is, the skills of someone who intricately understands the machining
process as well as setup procedures, and of course someone who could
be counted on to reliably kit and measure tools. What Mr. Rogers
really wanted was the ability to deliver a completely qualified
set of tools for a job to a machining center before the setup
began, and then once those tools were loaded, go right into production—no
on-machine touch-offs, no trial parts.
Making It
Happen
 |
| Bill Price makes sure all tools
for a job are prepared before the setup begins. |
What the new
tool preparation system required was some investment in equipment
and a large dose of discipline. As for the equipment, DG bought a
Speroni tool presetting system from KPT
Kaiser Precision Tooling (Elk Grove Village, Illinois), about
a $32,000 investment. The presetter allows tool edge profiles to be
exactingly measured as the tool rests in its holder so that offset
values can be determined right in the crib. DG also made some additional
investment in toolholders, because shop practice is to keep tools
in holders all the time, which Mr. Rogers believes is easily justifiable
in simplifying tool management and reducing labor.
As for the
discipline, Mr. Rogers felt so strongly about the need to get tooling
issues under control that he assigned one of the shop's most skilled
machinists, Bill Price, with total responsibility for job preparation,
including tools and fixtures. Now when a job is released to the
shop, the routing and tool list first goes to Mr. Price who gathers
and measures all the tools, and then loads them onto a cart that
will be wheeled to the machine for the setup. Initially, Mr. Price
noted all the offset values on the tooling sheet for the job which,
along with the rest of the job documentation, was delivered with
the tools. Later on, DG added the capability to download offset
values from the presetter directly into the CNCs' tool offset registers
via the shop's DNC system.
The critical
point: Now, no machine setup is begun until all tooling,
fixturing and material is ready to go.
The Results
 |
| The tool is measured in its
holder, and it can be rotated in the spindle to get multiple
perspectives if required. DG uses two different toolholder taper
sizes, which are accommodated inthe presetter with adapters.
A high-accuracy option holds runout accuracy of 3 microns when
switching from one adapter to another. |
Does the system
work? Mr. Rogers looks at their results in several ways, and all are
encouraging. As for the objective to go right into production with
no trial cutting, DG is mostly there. "We do it with everything but
the precision boring," he says, and that's mainly a matter of being
careful with some of the extremely demanding hole tolerances they
hold on a routine basis. Current practice is to set the boring heads
a bit undersize and then make a single adjustment after the first
cut. And for the moment DG is happy with that practice, though Mr.
Rogers believes that holding first part bore tolerances of 5 "tenths"
(0.0005 inch) is achievable with their presetting system.
On the other
milling and drilling tools, it did take the shop's machinists some
time to grow confident that the presets really were reliable, and
so eased into aggressively going after first-part production. In
time that confidence has grown, however, particularly given Mr.
Price's track record for getting the tool measurements right. In
a whole year of operation, DG has dramatically reduced their setup
scrap rate as a result of the presetting procedure—a far better
performance than was achievable under the old methods.
An indirect
benefit of the new discipline is that it provides a means to identify
tool availability problems—indeed, it forces the issue—before a
machine goes into setup mode. Checking out all the tools beforehand
allows more time to deal with shortages, be it ordering more tooling,
or substituting replacement tools
and making any necessary programming changes to accommodate the
switches. And, importantly, these activities happen off-line rather
than having people scramble to recover while a machine sits idle.
There are
qualitative benefits as well. Mr. Price believes that tools are
running truer from the start because of some problems the toolsetter
helps detect. For example, it is now possible for him to measure
tool runout within the holder, and he can correct some unacceptable
conditions right on the spot. There is also the elimination of the
occasional cracked insert that previously resulted from "touching"
the tools a little too hard when they were touching off on the machine.
As for the
quantitative setup reduction projections, while it's hard to make
a blanket statement on how much tool setting has saved, Mr. Rogers
is firmly convinced that it has at least done what he originally
projected, and probably more. To prove his point, we took a look
at some historical cost data on repeat jobs the shop had been running
for several years. In one representative case, a 100-piece job had
averaged between 60 and 100 hours of setup (for multiple setups
of several different pieces of an assembly) between 1993 and 1996.
However, once the job was run under the new system, setup was cut
to 33 hours and 50 minutes. And a random check of several other
repeat jobs showed equal or better results.
On balance,
Mr. Rogers believes DG has increased their spindle utilization by
about 20 percent. He figures about 75 percent of the setup time
savings comes simply from making sure all the tools are ready for
a new setup, and the other 25 percent comes from the elimination
of the need to touch off each new tool as it is loaded.
And for the
financial ramifications, there is little question at DG that better
management of tooling has been to their gain. MMS