Another key attribute for an advanced manufacturing system is going
to be specialized tools for tool design. You will want tools, depending
on your processes, for injection mold, for castings and forgings, and
for progressive die design. You don't want to have to go out to a
separate system to be able to complete all of the manufacturing
engineering tasks required to get these jobs out the door.
One
of the most common tasks in tool design is the core and cavity
creation. It needs to be associative to the design model, meaning that
if that design part changes, you want your tool design to change. On
the other hand, if you have made part modifications within your tool
model, you want those to stay - keep your rounds and your drafts. But
if the customer changes a diameter or a draft, or adds a feature or
deletes a feature, you want your core and cavity to update. You need to
be able to put in those features, such as shrinkage, and then you need
to be able to build the tool geometry, build parting lines and parting
surfaces, sliders and lifters, all of those various pieces that make up
the mold. You want specialized, easy to use tools to quickly build
these, maybe even automatically build them, and give you the
flexibility to build exactly the tool geometry you need.
For
those of you in the injection mold world, you want to choose from a
library of vendor moldbases to be able to complete your moldbase
design. You might want to take an existing moldbase and customize it to
your needs, store it in your library, or even build your own custom
moldbases from scratch and store in your library. Either way you can
reuse them, quickly and repeatedly. You probably want to do a cavity
layout in 2-D, looking at various arrangements for quick what-ifs. But
then you want 3-D models to fall out from that 2-D arrangement, with
solid models of all tools, plates, and equipment, along with a complete
bill-of-material and drawings for all components. Then you can finalize
the designs with cooling designs and ejector pins, all of the
information necessary to generate models and drawings you can send to
the shop floor or send to your vendors.
Finally, if you are
truly working art-to-part, you will take that core, that cavity, your
tooling plates, and take them down to the shop floor and machine them,
and you will want your manufacturing system to be able to accommodate
that. You want it to be fast, very automated, but you want it to apply
your machining strategies, not some default methods. You want to have
defaults to use one tool for roughing, a second tool for reroughing, a
third for a semi-finish pass, and so forth. You want to store that
strategy and simply apply it for each new part. You might use
high-speed milling wherever possible, and as always, you want it to be
associative, all the way back to the design part. If the design part
changes, your core and cavity changes, your moldbase changes, and your
toolpaths to cut out the tooling changes. That's where you really start
making money with an advanced manufacturing system.
Let's
look at that from an injection mold standpoint, taking a part all the
way, from art to part. In this case we will go back to our top level
assembly, and look at the headlights that we have on the top of the
cage. Here we have a fairly simple assembly, and the back piece is a
plastic housing that is both the reflector and the bulb holder. That's
the piece we want to work with today.
I have my design model
complete, or more likely nearly complete, and we will go in to my
manufacturing model. Here is where I will bring in a copy of my design
model, because what I want is that if that model ever changes, I want
my manufacturing model to change immediately, I will look at maybe a
rectangular pattern of cavities, or maybe a circular pattern, and I
will go ahead and put in the shrinkage. Maybe I want 2% shrinkage,
whatever is appropriate for the material. I will put that part inside
of a workpiece, as this is what I will build the core and cavity out
of. The system automatically looks at the model and suggests a minimum
size, and I will add and extra inch or two as needed, whatever I need
to build my tooling plates.
Once I have that, since the
system already knows the pull direction, I can have it look at the
model and generate a silhouette curve. For a part that is well drafted,
I can simply pick on that curve and extend it out, and there is a
parting surface, or at least the start of one. That is the sort of
quickness and flexibility that you really want. You might go in and
make it more complex with a shut-off plane and a shut-off boundary, but
you want to be able to quickly build that parting line and build that
parting surface. Once I have that surface, I can select it and have the
system split the workpiece, extracting out the geometry of the part,
split it at that parting surface, and generate 3-D solid models of the
core and the cavity along with any sliders.
I'll take that
solid model, in this case the core, and put it inside of a workpiece.
Staying in the same environment, now let's build a milling operation. I
apply my standard strategy, in this case starting with a certain end
mill, a certain step depth and stepover, all the ways I like to machine
these parts. In this case I brought in the roughing tool that we see
here, and then I will bring in a bull nose cutter for a rerough to
clean up what the first tool left behind. Maybe I'll bring in a ball
end mill after that for a semi-finish cut. Again, I define this
strategy once, and then just apply that strategy for each new job. I
might have different strategies depending on the job and the materials
used, but I define them once and then reuse them over and over. That is
the sort of productivity that I really want to have.
So I
have my core and cavity milled out. Next I might want to put them
inside of a moldbase. I will start in a 2-D layout environment where I
can quickly see how many I can use with the various size plates. I want
to choose from a library of various vendors, maybe a DME or a Hasco or
a Futaba. I'll bring those library components in, work with them in 2-D
for my layout, but then I want the system to automatically generate a
3-D model of this entire tooling assembly. I can always go back to the
2-D layout, maybe change the size of the plates or any other
components, but when I am done I have a complete 3-D model. For any
given piece, I can open it up individually and see the cutouts based on
the appropriate tolerances. For each plate, I want to have a drawing to
send to the shop floor, maybe with a top view and a couple of
cross-section views, whatever I have defined in my standard drawing
package.
So, we have defined our moldbase, I have machined
out a core and a cavity, and of course this is when the customer calls
and says, "The first part in the field failed, we need a stiffener
bead!" I can make that change since I have a complete CAD/CAM system,
or maybe I bring that updated model in from the customer. Either way, I
have an updated model with whatever changes need to occur. So what
happens to all of that geometry that we created downstream?
With
a truly advanced manufacturing system, what that means is that my part
is updated. If I look at my mold model, it already shows that my core
and cavity have been updated, in this case with the geometry to create
the new stiffening rib, exactly what I want. Here is my new core model
and I can replay the toolpath, and it automatically accommodates all of
the design changes. If we zoom in, maybe on the semi-finish operation,
we can see how it is diving in there. So my roughing has been updated,
and in this case I'll probably add one more mill sequence to mill that
out with a small cutter. It is still up to me to say that the tool is
appropriate, but for all of the changes, I just let the system do the
update.
Back to the moldbase, it's the same situation. If I
blank out the fixed half and zoom in, you can see that any changes are
automatically reflected downstream. That is what you want in an
advanced manufacturing system for tool design.