Injection
Molding, August 2000
Reprinted with permission from Abby
Communications, Inc. |
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MANUFACTURING
E-Stands for Ergonomics in this EOAT
- by Carl Kirkland
You may have
recently read in the trades of an award-winning
dead-blow hammer from Emerson Tool (see May 2000
IMM, p.202). Sold at The Home Depot under
the |
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loaded hammer handle skeletons with
automatically inserted machined metal cores wait
for the robot at the assembly station in Goshen
Rubber's multimachine manufacturing cell (far
right). The robot deposits the reusable cores
retrieved from downstream in the top tier of the
rotary station (center), and then descends to
remove the core/skeleton assemblies for further
overmolding (right)
The Ridgid hammer features an ergonomic handle
molded of two materials in three steps.
Goshen Rubber's Alfred Dassler (right) worked
closely with his suppliers, like EOAT specialist
Trent P. Fisher of SAS Automation, to design the
multimolding cell. Fisher was called on to
supply a custom-built EOAT with two sets of
independently acting grippers capable of
handling right- and left-handed hammer handles.
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Ridgid
brand name, the hammer features an ergonomic
handle flawlessly molded of two materials in
three-steps (see photo below). Though there was
a lot of news in the initial reports about what
the handle was made from, there was little on
how it was made. IMM went to find out.
At the Englewood, OH plant belonging to the
handle's molder, Goshen Rubber, IMM finds a
highly automated manufacturing cell with a robot
transferring subassemblies from station to
station, while simultaneously handling reusable
machined-metal core inserts, used to both
facilitate robot handling and ensure overmolding
position accuracy. The cell consists of three
small presses, two of which are serviced by a
multitasking servo robot with an end-of-arm tool
(EOAT) as ergonomically designed to fit the
production process as the finished hammer is
designed to fit a human EOAT.
Here's how it works:
Press #1: Left- and
right-handed handle skeletons are molded with
reddish orange
Montell-Hivalloy PP in a two-cavity cold runner
mold. Handle overmolding involves use of six
two-cavity cold runner tools: three for
right-handed hammer handles, and three for left.
The skeletons are appropriately boxed for use on
demand. Mattex production monitoring systems
keep track of everything.
Press #2: Skeletons are
manually loaded onto a two-tiered, rotary-table
assembly station. The reusable cores are
pneumatically inserted into the skeletons. The
robot removes core/skeleton assemblies from one
tier, after positioning reusable cores retrieved
downstream into the other tier for assembly. The
core/skeleton assemblies are then positioned by
the robot for overmolding ergonomic and stylish
details into the hammer handle with AES
Santoprene 8000 TPE in a color blended to match
the reddish-orange PP skeletons. The over-molded
TPE detailing covers the molded-in letters that
identify the skeletons as being right- or
left-handed. Maguire blenders are used though
out.
Press #3: The overmolded
skeleton/cores are then positioned in the third
press and are overmolded again, this time with a
gray Santoprene 8000 TPE. The extremely tight
tool tolerancing and robot alignment of the
skeleton ensure precise seal off between the
different colors. Also, the words
"Right" and "Left" are
molded into the base of the handles here. The
cores then are hydraulically pulled. Finished
parts fall onto a Dyna-con parts conveyor
underneath the press clamps, as the transfer to
upstream assembly.
Battenfield Gloucester granulators recycle any
scrap. Final assembly of the hammer and handle
takes place at Emerson.
Robotic Ergonomics
Alfred Dassler, project manager of Goshen
Runner's Thermoplastics Div, attributes the
success of this complicated cell to the
cooperative activities of all the parties
involved, not the least of which is Eagle Mold
Co. of Carlisle, OH.
Eagle Mold designed and built all seven of the
molds for the project. The cell cost $400,000,
minus the tooling. One month after the project
started in October 1998, Dassler says Eagle Mold
started cutting production tolling. Dimensions
were taken directly from shared CAD files.
Battenfeld, intimately involved since day one,
choreographed all of the cell automation and
supplied the machinery, including three 88-ton
Model BA 800 CDC molding machines, and the
company's Model R-10 servo robot. A 33-tonner
nearby also runs vibration-dampening plugs used
in the final assembly. Dassler makes special
mention of the contribution of Trent Fisher,
general manager of SAS Automation. SAS, also in
the loop from the project's onset, designed and
built the custom EOAT that makes the entire cell
work.
SAS designed a two-by-two, all-aluminum,
all-pneumatic EOAT with a total of four part
nests. The top and bottom sets of grippers are
designed to work independently and to handle
both left- and right-handed handles. Fisher
explains that the 45-durometer TEE was too soft
for positive gripper contact and required
alignment accuracy's. This prompted
collaborative work between SAS and Eagle Mold,
resulting in, among other improvements, a
redesign of the core inserts that allots the
robot to grasp pins at the tops of the metal
cores, rather then the handles themselves.
Looking back, Goshen Rubber's Dasher says the
project went quite well. "Sure, we
definitely had our share of hiccups and bloody
noses," he Save "but we learned what
can be done when you work closely together with
people that you can count on."
| Contact
information
Goshen
Rubber Cos.,
Thermoplastics Div.
Palmer Plant
Englewood, OH
Alfred Dasher
Phone: (937) 836-3303,
ext. 117
Fax: (937) 832-1727
SAS Automation LLC XENIX, OH
Trent P. Fisher
Phone: (937) 372-5255
Fax: (937) 372-5555
Web: www.sasgripper.com
E-mail getagrip@sasgripper.com
Eagle Mold co.
Carlisle, OH
Wilbur Wisecup
Phone: (513) 746-333.
Fax: (513) 746-3332 |
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