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					                                      operating for extended              age of machines sparking during
                                                                          the day, percentage of machines
                                      periods without human               that started and ended the night
                                      intervention, managing              sparking, and the percentage of
                                                                          machines that started and/or
                                      these assets so that they           ended the weekend sparking.
                                      spend the majority of               From your notes, you should be
                                                                          able to make a reasonable esti-
                                      time making sparks is the           mate of the sparking hours per
                                                                          year for each of your machines.
             by Roger Kern            path to the promised land           During my numerous visits to
                                      of improved EDM pro-                shops large and small, I often
       Techtips is a collection of                                        observe the majority of the EDMs
      useful ideas, techniques, and   ductivity and profitability.        are not sparking at any given
     procedures designed to further
                                          There are 8,760 hours           time. If your machines are “only”
            EDM knowledge.
                                                                          sparking 2,000 hours per year
                                      per year available for              (and that is a lot for some shops),
                                      sparking. How many of               it is obvious that there is a huge
                                                                          potential for improvement.
                                      those hours are your
                                      machines making sparks?                 While Peak Current,
 Managing for                         Please note that I said
                                                                          On-time, in2/hr, and in3/hr
                                                                          are the terms that excite the
CNC                                   sparking, not waiting
                                      for a program, being set-
                                                                          technician in most of us, it
                                                                          is the often overlooked and

EDM                                   up, or waiting for
                                                                          tedious management
                                                                          process that needs to be
Productivity                          the next job!                       getting the lion’s share of
                                                                          our attention, if we want to
    The “inconvenient
                                           If you have a sophisticated
                                                                          maximize the profitability of
truth” concerning EDM                 job costing and reporting system    the EDM Department.
productivity is, that for             that isolates cutting time from
                                      set-up time, you can readily            The potential for productivity
most shops, the greatest              determine the situation for your    improvement by managing your
potential for improving               shop. However, an informal ran-     EDM assets is enormous, espe-
                                      dom survey can be almost as         cially when compared to the
the throughput of the                 effective. Daily, take a walk       productivity improvement pro-
                                      through your EDM Department         vided by technology. Let’s say
EDM Department has lit-                                                   that in one shop they increase
                                      first thing in the morning, a few
tle to do with the cutting            times randomly during the day,      cutting speed by 25% in an EDM
                                      and just before going home at       Department that is sparking
speeds of the EDM                                                         “only” 2,000 hours per year. That
                                      night. During each walk-through,
machines! Since CNC                   note if each of your machines is    25% increase in performance is
                                      sparking. At the end of two         equivalent to adding another 500
EDMs (both wire and                   weeks, review your notes to         production hours. Compare this
sinker) are capable of                determine the average percent-      increase to another shop that, by


12                                                                                  EDM Today, May/June 2007 Issue
managing its assets, increases its   Why is the machine                    machine on the ragged edge). A
sparking hours to 4,000 hours per                                          machine sitting for just a short
year, doubling its capacity with     waiting for an                        time waiting for a an operator to
little or no capital investment.                                           rethread a broken wire, quickly
And even at that, the second shop    operator?                             gives up the advantage of that 5%
is only operating at less than 50%   • Job is finished                     extra speed obtained by pushing
of theoretical capacity. Not only    Why aren’t there multiple             the envelope. Many machines
have they doubled their capacity,    jobs set up?                          now have re-threading capabili-
but they have also cut their fixed                                         ties, or can proceed to the next
                                         CNC EDM’s are quite capable
costs per hour by 50%. I know of                                           cut or job. Training of operators
                                     of having a number of jobs set up
a number of shops that purchase                                            and programmers is the key here.
                                     on the table with matching elec-
and operate a battery of 20 year                                           Many shop owners decline the
                                     trodes in the tool changer. Some
old “obsolete’’ machines, yet suc-                                         invitation for operators to attend
                                     shops set the jobs up in the tool
cessfully compete against shops                                            factory training. Here is where
                                     changer and mount the electrodes
with “state-of-the-art” equipment                                          that training would pay off.
                                     in a magazine on the table.
by running these older machines
                                     Scheduling jobs and setups is cru-
120 hours per week.                                                        • No operator available
                                     cial to the efficient operation of
                                     EDM machines. Night jobs need         Why is the operator not
   In this issue, we’ll attempt to
                                     to be setup at the beginning of the   available?
uncover opportunities for
                                     day, so that, no matter what hap-       • Working on other
improved productivity by repeat-
                                     pens during the day, the job(s)           machine(s)
edly asking the question “why”.
                                     will be ready when it’s time to go
This simple, but very powerful,
                                     home. Similarly, weekend burns
                                                                             • Operator is on break
method of process improvement                                                  (bathroom, coffee,
                                     need to be ready to go long
theory will lead us to the root                                                lunch)
                                     before Friday at 5:00 PM. A num-
causes of machine idle time and
                                     ber of highly successful shops
toward suggested solutions.
                                     devote much of the daytime
                                                                             • Operator is out (shift
                                     weekday hours to assure that              over, weekend, sick,
Remember, a machine is               evening and weekend hours are             holiday, vacation)
either sparking or waiting,          devoted to unattended
so let’s begin by asking             sparking.                                 It has been my experience that
why a given machine                                                        most EDM Departments are under-
                                     • Slug removal                        staffed. Since EDMs are capable of
isn’t sparking?
                                     Why doesn’t the program               long periods of unattended opera-
                                                                           tion, many shops underestimate
• Waiting for an operator            proceed to next opening?
                                                                           the manpower required to keep
                                          An inventive process plan can
• Waiting for a job                                                        the machines running for extended
                                     eliminate the need for off-hours
                                                                           periods. While increased staffing is
• Waiting for the set-up to          coverage. For example, roughing
                                                                           often considered heresy in today’s
                                     all the openings in a block during
  be completed                                                             world of cost cutting, in fact, just
                                     the night, while leaving the slug
                                                                           such increased staffing can dramat-
• Waiting for consumables            cut-offs for the following day.
                                                                           ically improve the productivity of
• Waiting for maintenance                                                  an EDM operation. I know of a
                                     • Wire Break                          production EDM operation with
• Waiting for repair                 Why did the wire break?               more than twenty machines with
                                       • Wrong wire selected               just two operators. Since they can’t
   Let’s continue by examining                                             keep up with the loading and
each of these topics further by        • Inappropriate                     unloading of parts, yet are required
repeatedly asking why, and then          technology selection              to keep as many machines spark-
suggesting possible solutions.          Wire breakage can often be         ing as possible, they turn down the
                                     avoided by proper wire and tech-      feedrate overide on all the
                                     nology selection (not running the     machines! One more operator

 EDM Today, May/June 2007 Issue                                                                            13
would increase the throughput of      Why is the set-up                        good EDM tooling is expensive,
the department by a phenomenal                                                 but a properly tooled machine
40%, yet that solution was not        taking so long?                          can often do the work of two
open for consideration in order to                                             machines, even without a robot.
“keep costs down.” Additional
staffing, whether it is accom-
                                      • Blanks or electrodes not
plished by more staff, cross-train-   properly prepared                        Why is the machine
ing, or flexible scheduling                                                    waiting for
designed around the process, can      Why weren’t the blanks
substantially improve the bottom      prepared?
                                                                               consumables?
line.
                                                                                    A machine being down solely
                                         A missing start hole or
                                                                               because the shop is out of wire
Why is the machine                    improperly ground reference
                                                                               or filters is inexcusable! “Just in
                                      edges can spoil the best laid
waiting for a job?                    process plan.
                                                                               time” may be the catch phrase of
                                                                               the day, but the security of hav-
                                                                               ing an extra box of wire, box of
• Blanks not ready                    • Program has errors                     filters, belt, flush cup, or dielec-
• Program not ready                      Why wasn’t the pro-                   tric fluid is worth far more than
     Scheduling the flow of jobs         gram tested in advance?               the cost of a small inventory of
through the shop is a topic in                                                 these essential items. A weekend
itself. However, by utilizing a           Complicated programs                 of burning lost, due to lack of
computerized shop scheduling          should be tested in advance,             consumables, could easily mean
system that “backward sched-          either with off-line screen simu-        $2,400 in lost revenue, in addi-
ules” from the delivery date,         lation, or when the machine is           tion to the havoc it will wreak on
based upon the operations that        not being used.                          the EDM Department schedule
need to be performed and the                                                   and the schedule of subsequent
estimated time to complete these      • The operator has to study              operations.
operations, management can
plan when a part will need to be
                                        the job
in the EDM so that programs,               If the operator doesn’t have a      Why is the machine
parts, electrodes, and fixtures are   clue as to the orientation of the
completed by that time. The           parts or electrodes or the process
                                                                               down due to lack
EDM Department staff needs to         sequence, a fifteen minute setup         of preventative
be apprised of that schedule in       can take hours. Communication
advance, so that they can proper-     can be as elaborate as a process         maintenance?
ly allocate those jobs to the day,    sheet and layout drawing, or as sim-
night, and weekend schedule.          ple as markings on a print, but               There is nothing more frus-
This type of management activity      there must be effective communica-       trating than having a hot job
is tedious, but not rocket sci-       tion between all parties. In addition,   ready to go into the machine at
ence. Someone needs to be             if the EDM staff is apprised of the      5:00 PM on a Friday evening,
responsible for seeing to it that     schedule for the machines in             only to find that suddenly the
the parts, electrodes, programs,      advance, much of the preparation         wire won’t thread because the
fixtures, and drawings arrive at      can be completed in advance.             threader needs cleaning. Most
the EDM Department not only                                                    maintenance items are pre-
on time, but as a completed                                                    dictable, and scheduling regular
package.                              • The tooling is inadequate
                                                                               preventative maintenance, so
                                                                               that it doesn’t interfere with pro-
                                          A high quality tooling pack-
                                                                               duction, can significantly con-
                                      age with enough components to
                                                                               tribute to improved productivity.
                                      allow multiple jobs to be pre-set
                                      off the machine, is essential to
                                      minimize set-up times. Certainly

14                                                                                       EDM Today, May/June 2007 Issue
Why is the machine still waiting for
repairs?
    Unexpected breakdowns, while rare, are an unpleasant
fact of life. How we respond to them can make the differ-
ence between a day of downtime and a week of downtime.
Immediate and persistent contact with the OEM service and
parts departments, combined with timely parts orders and
utilization of premium transportation, can minimize non-
sparking time due to breakdowns. It also helps immeasur-
ably if someone on staff has a basic knowledge of electrici-
ty and electronics to communicate problems to the factory
and carry out the suggested diagnostics.

What about robots?

    You may have noted that I haven’t advocated the use of
robots in this exercise. While, at some point, a robot is an
essential ingredient to utilizing the majority of the 8,760
hours available for production each year, it takes a highly
sophisticated management system to actually achieve the
potential productivity a robot can provide. Unless and until
your company can implement management practices that
get you to the 4,000 hour production level, your manage-
ment system will most likely be inadequate to even consid-
er integrating a robot into your EDM production system.

Summary
    The marginal cost of each additional unattended spark-
ing hour for an EDM machine is minimal compared to the
additional revenue generated. The combination of cutting
performance improvement, and the application of sound
management practices to substantially increase unattended
hours will pay substantial dividends to those shops willing
to take on the challenge.


                  Any suggestions for future
                       topics are welcome.
                    Tell us what you would
                        like to read about.
                        rjk@gedms.com




EDM Today, May/June 2007 Issue                                 15

				
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