POP DISPLAYS INC.
POP Displays is the world's leading manufacturer of promotional
point-of-purchase displays. From initial design through engineering and
mass production POP is a complete manufacturing facility and captive
injection molder primarily servicing the cosmetics sector. Look in any
Walmart, Genovese or any other major department store and you will see
Revlon, Almay, L'Oreal wall systems with hundreds of our plastic molded
components. In Sears you will see our Circle of Beauty counter systems.
In any store you will see multitudes of our promotional displays working
on the concept that the customers' impulsive buying habits override
their brand
loyalty when they see attractive and creative product displays. With 20 injection molding machines, from a 750 ton Husky to
250 ton Goldstars, several roll-fed in-line and sheet fed open end vacuum forming machines,
wood working production facilities, plastic fabrication including 4
large bed CNC routers, silk screening, hot stamping, sonic welding and
many others, POP has full capabilities for producing a vast array of
creative display systems. POP also owns a mold and die shop in Portugal.
The design and engineering departments utilize the latest rapid
prototyping equipment including Stratasys FDM 1600 and SLA 5000
systems. The process starts with the design department delivering
to the customer concept models and detailed graphic presentations of the
display assemblies rendered in 3D Studio Max and Photoshop. Then the
engineering department creates 3D CAD parametric models of the
individual component parts and the complete assembly in AutoCAD
2000 and MDT 4.0. Then rapid prototype SLA models are produced to
evaluate and confirm the accuracy and functionality of the engineering
models. Manufacturing engineers direct production to assure the
most cost effective and rapid process. Finally the approved CAD drawings
are sent to the Toolroom and to various mold shops for tooling
production. The last step is to mold the plastic parts in the
required quantities and assemble and distribute the complete display
systems. 5 million pounds of plastic raw material in pellet form is
injection molded annually. The common plastics used for molded parts are
Crystal Styrene (GPPS), Impact Styrenes (MIPS/HIPS), ABS, Polypropylene
and some special formulations such as NAS. Polystyrene, PVC and PETG are
used for vacuum
forming and Acrylics and Styrene sheet are used for fabrication.
THE TOOLROOM
I work in the Toolroom together with a staff of top notch mold
makers and manual machinists. I have also worked in the engineering
department modeling parts. Mold making is a very demanding craft with
critical tolerances and precision shut-offs and seal offs and slide
action cams. We have 5 CNC vertical machining centers. We have an
old Hurco conversational knee mill that we are upgrading the
control to a 4 MB capacity PC based system which is capable of inputting
large G code part programs. We have a new Hurco VMC capable of both conversational
and G code programs which is networked via FTP link. There is a 5 year
old Bridgeport VMC 760 with a DX-32 control that has negligible look ahead
such that it is often necessary to run 3D programs slow at feeds of 20
IPM or less. We also have 2 new Fadal VMC's, a 4020 and a 4525. They are
both DNC linked to networked PC's which drip feed the program data via RS
232 cables at baud rates of 38,400 kbs. The 4525 has the newer feature
of a vertical tool turret so that chips wont fly in. The Fadals have a
sufficient look ahead for high speed machining including the Fadal Analyzer
software which speeds up the feed to a maximum of 300 IPM on linear
moves and slows it down to a crawl on sharp turns. We have found the
Fadal to be an all around better machine than the others, stronger and
more rugged and easier to operate. Most of the molds are machined in
7075 aluminum and 6061 is used in vacuum form tooling. Sonic welding
horns and hot stamping fixtures are also designed and machined here.
Recently due to the need for higher volume production for part
quantities in the millions we have been using P-20 steel for many molds.
Special multi-flute roughers are used and 4 flute carbide cutters are
used for finishing, running the CNC programs at much slower feeds and
speeds than for aluminum. There are 2 CNC programmers who work on the
Fadals and the Bridgeport VMC and occasionally the Hurco's. There is one
mold maker who keeps the Hurco VMC busy programming it conversationally.
We have 2 set-up men who maintain and operate the CNC machines. There
are also about 20 additional men who complete the Toolroom staff whose
functions include manual machining, turning, grinding, mold making,
polishing and maintenance.
CNC PROGRAMMING AND MOLD DESIGN
Mold making is a very demanding and challenging craft that takes
many years to master. It is far different than production CNC machining.
CAD/CAM systems have made the job faster and more efficient and can
create curved surfaces formerly impossible with manual machining.
However, today there is a much greater demand for experienced people
skilled in mold making and CAD/CAM than there are opportunities to learn
and become proficient in it. For precision mold manufacturing It is necessary
to factor in such conditions as heat expansion of the spindle (+.005 in
the Bridgeport), warping and bending of the metal after roughing
(.003-.005 with aluminum), off concentricity of the tool holder (+/-
.001), tolerance and wear of the cutting tools, over-travel and look ahead,
and other factors. Many of these factors are not that critical for
production machining.
I work in a small glass enclosed office looking out on the shop
floor together with another programmer. My co-worker uses MasterCAM to design the tooling and drive the
toolpaths. I use AutoCAD and MDT to design the molds and tooling and NC
Polaris which works inside AutoCAD to create the CNC programs. I will
describe the process that I use to design the mold components to produce
machinable surfaces to drive the toolpaths. I first receive
the approved part drawing and use AutoCAD tools to manipulate the part
model and create the mold design. The part model is a 3D parametric
solid model created in Mechanical Desktop. I create core and cavity
blocks as solid models with the proper dimensions, add center holes,
leader pin and return pin holes if necessary. I study the part and after
determining the parting lines and which side the core and cavity will
be, I lay out the part model or multiples of the part in the blocks and
perform boolean subtractions and additions to leave the inside
mass standing on the core block, generally speaking, and the outside
surfaces cut out of the cavity half. This is of course is an
oversimplification of the process whose difficulty is determined by the
complexity of the part. I now have 3D solid models of the core and
cavity halves of the mold. I then add ejector pin holes on a different
layer in AutoCAD. I create the geometry for the runner system, the gates
and air vents if necessary. Waterlines and other external features are
drilled and machined manually. There is mold design software on the
market which automates this process and has catalogues of standard DME,
Hasco etc. mold bases and components. MasterCAM has a C-hook called Mold
Plus which separates core and cavity surfaces from the part model. Once
I have the machinable surfaces ready to program I fire up NC Polaris and
start to drive the toolpaths. We always take our reference from the
center holes in the CAD geometry and on the machine. I use a combination
of 2-1/2D and 3D cutting techniques to program the mold geometry. I use
such cutting strategies as 3D Z-level roughing for complex surface
roughing and 3D Z-level finishing for bosses, hills and valleys and 3D
XZ horizontal cutting for flatter curved surfaces. We have
recently purchased a seat of MasterCAM for me to use and we are in the process
of migrating over to MasterCAM for all our CNC machining needs.
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