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CAD/CAM stuff


#1

Just wondering because I didn’t see it mentioned in any of the talk
about CAD stuff, has anybody considered using CAD to make a mold of
your model and then having it made via rapid-prototype machine. It
would be fairly easy after making the model in CAD to make a mold
around it, and I’m sure that there’s a RP machine that uses a
material that is capable of withstanding the injection wax temp. It
just seems like that would save several steps to me if you plan on
mass-producing something. And of course, it would be much cheaper
to have a mold made and inject the wax yourself than just having the
RP make all the wax models. -steve


#2

Room temperature molding with RTV is the way to mold RP patterns…
Jeffrey


#3

Hi Steve, Well, before I delve into the world of RP, let me first say
that it has been my experience that people who use CNC to make models
tend to make one model of a design and then have a standard rubber
type mold made from the model (correct me if I am wrong here guys).
The Rubber molds are used to reproduce the design in wax. I don’t
know of anyone that would make say 100 CNC parts of the same thing in
wax just because they needed 100 castings. Normally, due to the time
required to Mill a CNC part, it is not economical, and there is much
more waste doing it that way than shooting wax into a mold.

Ok, onto the RP (Rapid Prototyping) World:

For my 9-5 job, I work as a mild mannered Design and Project
Engineer for the cosmetics packaging world. In this job I have had
to have many of my virtual 3D models turned into RP parts. Most of
the RP methods do not have a good enough surface finish to be used in
jewelry, and there would be substantial cleanup after the fact.
However, STL are very capable of producing almost any shape, even
complicated undercuts and such. Another downfall of RP is cost. The
last job I did was using the STL process. I was making a new type of
roll-on applicator for the makeup word. The model was to be nothing
fancy, just the outside shape that was about the size of a small egg.
Cost for a normal STL was $175ea, the cost for a high definition STL
was $265. To tell the truth, I’ll be damned if I could tell the
difference between them when they arrived. I guess the detail was
very slightly better on the more expensive one. This is an ok price
for the cosmetics company to pay because they stand to make millions
of $ in sales on the finished item. However, this is too much for me
to prototype a new ring if I am not assured of an end profit.

There are several methods that are used. Parts done by the “STL”
(Stereo Lithography) process are probably the most common. These
parts are made of a medium hard plastic material. The STL parts are
not that great when it comes to detail (by jeweler standards). They
have a hard time with fine lines and small letters/details. With
any RP process, the bigger your detail, the better your end results.
Also, the dimensions of the finished piece are only good to within
B1.010" in most cases, thought they claim better. Let me quote from
one supplier’s website: “Stereo lithography (SLA) is often considered
the pioneer of the Rapid Prototyping industry with the first
commercial system introduced in 1988 by 3D Systems. The system
consists of an Ultra-Violet Laser, a vat of photo-curable liquid
resin, and a controlling system. A platform is lowered into the resin
(via an elevator system), such that the surface of the platform is a
layer-thickness below the surface of the resin. The laser beam then
traces the boundaries and fills in a two-dimensional cross section of
the model, solidifying the resin wherever it touches. Once a layer is
complete, the platform descends a layer thickness, resin flows over
the first layer, and the next layer is built. This process continues
until the model is complete. Once the model is complete, the platform
rises out of the vat and the excess resin is drained. The model is
then removed from the platform, washed of excess resin, and then
placed in a UV oven for a final curing. The model is then finished by
smoothing the “stair-steps.””

Next comes FDM (Fused Deposition Modeling)

Forget it for our industry. These things are made from some rigid
plastic and they look really terrible, hold no detail, and don’t cost
much less than the STLs. Not to mention that the plastic they are
made from is horrendous to do anything with. Think about what it
would be like to try to make a detailed model from Styrofoam and you
might get the idea.

Website Quote:

"Stratasys Inc. introduced fused Deposition Modeling (FDM) in 1990.
FDM is a solid-based rapid prototyping method that extrudes
materials, layer-by-layer, to build a model. The system consists of a
build platform, extrusion nozzle, and control system. The build
material, production quality thermoplastics, is melted and then
extruded through a specially designed head onto a platform to create
a two-dimensional cross section of the model. The cross section
quickly solidifies, and the platform descends where the next layer is
extruded upon the previous. This continues until the model is
complete, where it is then removed from the build chamber and cleaned
for shipping. "

Last for tonight is SLS (Selective Laser Sintering):

When made in plastic, this in on par with STL, though I think it can
get some finer details. However, there is at least one supplier
that I have run across that uses a Metal Version of this process
which looked quite feasible for our industry. The metal version
seemed to be able to hold almost perfect details and should be fine
for duplicating an original. Problem is again cost. I had asked for
a quote on the metal process for two 1" diameter pendents. Nothing
spectacular, just something like a recessed Yin-Yang symbol. The
quote was $345 for the pair + s&h. This is not a bargain in my
opinion. Perhaps if I was going to make and sell 100s of them, but
for the little guy this is just not practical

Website Quote:

"DTM Corporation introduced Selective Laser Sintering (SLS) to the
commercial world in 1992. SLS uses a laser to sinter powder based
materials together, layer-by-layer, to form a solid model. The system
consists of a laser, part chamber, and control system. The part
chamber consists of a build platform, powder cartridge, and leveling
roller. A thin layer of build material is spread across the platform
where the laser traces a two-dimensional cross section of the part
sintering the material together. The platform then descends a layer
thickness and the leveling roller pushes material from the powder
cartridge across the build platform, where the next cross section is
sintered to the previous. This continues until the part is completed.
Once the model is complete, it is removed from the part chamber and
finished by removing any loose material and smoothing the surfaces.

Now, I belive that all the plastic materials above can hold a heat up
to about 280B0F before they melt, which is good enough to shoot wax
into, if you were to RP a mold with these processes; However, as I
have pointed out already, since the detail of a 3D model in these
materials is not great, why would you even want to consider making a
model mold with this process. Also, if a part costs this much $,
imagine how much more a mold for the part would cost. Perhaps if I
was going into full production and needed a metal mold I would
consider metal SLS; but I think rather I would have the Metal Part
made from the SLS and then send that out for silicon molds.

The nicest things that I have found about the RP parts are that:

  1. They are very quick to get done

  2. They tend to be less $ than having a regular machine shop do it
    with CNC

  3. They can be of better quality than CNC parts, but not always.

  4. They can handle very complicated shapes that might be impossible
    or impractical to do via machining.

  5. Did I mention that they were quick? Some places can turn them
    out overnight for you.

Now that I have expelled my wind for tonight and have completely
forgotten

the question that started this all. I hope I have answered at least a
little of what was needed.


#4
    Just wondering because I didn't see it mentioned in any of the
talk about CAD stuff, has anybody considered using CAD to make a
mold  of your model and then having it made via rapid-prototype
machine. 

Steve, I haven’t seen RP used for making a mold directly - I think it
would be quite difficult to do this satisfactorily - but you can get
models made in epoxy resin which will are strong enough to allow you
to make moulds from them. The one big drawback with the epoxy system
is the cost. I enquired about the possibility of setting up a small
machine of my own - apart from the high cost of the machine, the cost
of the epoxy itself to fill the 1 foot cube tank would have been
about 12 thousand UK pounds (say $18000)! This technology is used by
a local company, Wren turbines, to make the blades and shafts for
miniature jet engines for model planes.
(http://www.wren-turbines.com/ ) There is also another technology
which uses a kind of sintered metal to build the parts - a special
metal powder coated in resin is printed in thin layers and
subsequently fused into a solid block by heat.

Best wishes,
Ian
Ian W. Wright
Sheffield UK


#5

Hi Silverfoot

 Hi Steve, Well, before I delve into the world of RP, let me first
say that it has been my experience that people who use CNC to make
models tend to make one model of a design and then have a standard
rubber type mold made from the model (correct me if I am wrong here
guys). 

Rubber molds are not often made from milled models. I usually will
either make a one-off by milling directly into wax, or I will mill a
metal mold for duplicates, and inject hard carving wax into the mold
at fairly high pressure (as opposed to injection wax at low
pressure). The wax duplicates are all identical in weight and
definition.

  Ok, onto the RP (Rapid Prototyping) World: 

In regards to your comments regarding RP and jewelry, I feel
compelled to mention that SLA is infrequently used for jewelry
models, Solidscape and Sanders rather exclusively owning that
application with their wax droplet printing process (PatternMaster,
ModelMaker2, T66, and RTM). Probably the best work coming out of
Solidscape machines in recent history is from Stafford’s 3D Design
Group (producing on PatternMaster machines) in Centerville, OH. The
models I receive from them show no stepping, have all but extremely
tiny details, and are quite smooth.

Jeffrey


#6
Probably the best work coming out of Solidscape machines in recent
history is from Stafford's 3D Design Group (producing on
PatternMaster machines) in Centerville, OH. 

I have heard of this technology, but have not yet tried it with any
of my own applications. How much does a pattern tend to cost?
Also, do you have their contact info?

Silverfoot-
Jewelry Designer and Craftsman
Main Site = www.firescale.com


#7

et all, Whilst it is not considered the norm to produce metal molds
by most jewellery CAD/CAM users, it is however being done. The
approach could either involve Keltooling or electroless nickel to
produce the master molds. Keltool is a process that is licenced to
Companies to offer as a service, the electroless nickel is something
you could do in house. Best Regards. Neil George 954-572-5829


#8
    In regards to your comments regarding RP and jewelry, I feel
compelled to mention that SLA is infrequently used for jewelry
models, 

A little note. I have been using SLA almost exclusively until now.
It is a lot cheaper than Sanders models. The detail is a little
lacking and leaves some finishing to be done, but for the perfection
of symetry, I don’t complain. I am still shopping for models that have
no stepping and are reaasonably priced.

The expense can be written off quickly on production work, but is
hard to include in special order jobs created for resale.


#9
The expense can be written off quickly on production work, but is
hard to include in special order jobs created for resale. 

Agreed. I can’t very well sell say a custom finished Silver
bracelet for $300, when the RP pattern cost me $225. Since most
customers won’t pay more than $300 for a custom plain Silver
bracelet, it just leaves you to have to find other cheaper routes to
produce the pattern.

Silverfoot-
Jewelry Designer and Craftsman
Main Site = www.firescale.com


#10

Call John Jr. at Stafford’s Diamonds in Centerville Ohio. His
pricing is far more reasonable than any other service bureau I have
used, and the quality is exceptional. I only do one-offs, and my
retail customers have not complained about the costs.

SLA processes must have decreased in price, as I always found it
more expensive. Are you receiving patterns that burn out cleanly?

Jeffrey


#11

Hi My Internet service seems to have been interrupted momentarily. I
believe the contact is www.staffordsdiamonds.com Ah,
here is their phone number 1-937-436-3090 Ask for John Jr. and please
tell him Jeffrey Everett sent you! :slight_smile:

Cost wise, the pattern cost depends completely on dimension and
volume. You can expect to pay approximately from $100 for a smallish
ring to about $200 for a larger man’s ring. I recently had 2 - 6 mm
Celtic weave bands (man’s and lady’s) grown at a cost of $327 for
both. The lady’s ring had a Celtic weave bezel for a 2 ct. diamond.

Jeffrey Everett


#12

I haven’t had any direct experience working with SLA or other
additive processes, my main focus has been cnc wax machining. The
machinery and consumables less expensive permitting me to have more
control of the process. While there are more limitations on the
geometry, a 4 axis machine and a bit of creativity can work wonders.
It might be necessary to mill in more than one piece; or mill,
rotate and mill from a different side; or cut and ‘unroll’ the model
then mill using a rotary axis as the unrolled linear axis. However
accomplished the result is in a wax which we are quite familiar.
Knowing the process I probably unconsciously design my own work
within the limits, but I’ve also milled work originally designed for
a SLA process… the client’s built pieces didn’t take kindly to his
platinum investment. Having your designs milled can be a better
option than SLA, at least it offers a different set of limitations
and benefits.

Jeff Demand
Demand Designs
Analog/Digital Modeling & Goldsmithing
http://www.aztec-net.com/~jdemand


#13

Hi Neil

 et all, Whilst it is not considered the norm to produce metal
molds by most jewellery CAD/CAM users, it is however being done. 
  • Maybe most jewelry crafts people using CAD/CAM are milling wax
    now, most of the folks I knew when I first started milling were, as
    was I, producing either brass molds or bismuth molds respectively for
    plastic or wax injection.
    The approach could either involve Keltooling or electroless
nickel to produce the master molds. Keltool is a process that is
licenced to Companies to offer as a service, the electroless nickel
is something you could do in house. Best Regards. Neil George
954-572-5829 
  • Did you confuse Rapid Prototyping with CAD/CAM? At least your
    comment was a bit confusing to me. Of course, in my comment in the
    first part of my response was in regards to CAM (milling).

Best regards to you. Long time no see… :slight_smile:

Jeffrey Everett


#14
  . I only do one-offs, and my retail customers have not complained
about the costs. 

That’s a real problem for me, as I am a trade shop. Those costs
can’t be smeared out throught rent, utilities and absorbed through
stone sales. They come right off of my bottom line. BTW. I do no
production work, so all of my work is unique as well. After spending
a lot of time on the learning curve learning to model in a
reasonable time, I really have to watch every penny. Sometiomes, I
find myself winning, though.

    SLA processes must have decreased in price, as I always found
it more expensive. Are you receiving patterns that burn out
cleanly? 

Burnout is great. I couldn’t ask wax to burn out any cleaner.

Bruce D. Holmgrain


#15

Hi Jeff

    You can expect to pay approximately from $100 for a smallish
ring to about $200 for a larger man's ring. I recently had 2 - 6
mm Celtic weave bands (man's and lady's) grown at a cost of $327
for both. The lady's ring had a Celtic weave bezel for a 2 ct.
diamond. 

SLA seems to start out at around $65. Set up costs are around $50 of
that, so multiples and volume become rapidly cheaper. When I have
links done, they seem to cost about $5 each including the spruing.

Bruce D. Holmgrain


#16

Hi Jeff, Great to see you again. Long time since we had a phone
powwow :slight_smile: My apologize by the way. The reply I sent, was in reply to
Steve Warden’s post and not yours. I have no idea what happened
unless I was half asleep :slight_smile:

Anyway Steve wrote:-

Just wondering because I didn’t see it mentioned in any of the talk
about CAD stuff, has anybody considered using CAD to make a mold of
your model and then having it made via rapid-prototype machine. It
would be fairly easy after making the model in CAD to make a mold
around it, and I’m sure that there’s a RP machine that uses a
material that is capable of withstanding the injection wax temp. It
just seems like that would save several steps to me if you plan on
mass-producing something. And of course, it would be much cheaper to
have a mold made and inject the wax yourself than just having the RP
make all the wax models. -Steve

An amendment to my original reply, because I do see where the
confusion was. Very easy to understand when you are the one writing
it :slight_smile:

Whilst it is not considered the norm to produce metal molds by most
jewellery CAD/CAM users via RP, it is however being done. The
approach could either involve Keltooling or electroless nickel to
produce the master molds from the prototyped male parts. Keltool is
a process that is licensed to Companies to offer as a service, the
electroless nickel is something you could do in house.

Best Regards.
Neil George
954-572-5829


#17

Finally, I have a handle on properly casting the various materials
that CAD-CAM modelmakers generate. I’ll share the couple that are
working out for us or some of our customers…

Each of the materials seem to have issues- The Viper resin is tough
to burn out, the “wax” Solidscape uses that is so investment
permeable, and the expand before burnout plasticized waxes or
plastics which often display a poor surface after casting.

Strategy 1- Make a RTV “insurance mold” and cast conventional
injection wax with all its advantages (allow for the shrink before
generating the model)

Strategy 2- Use a high speed/high temp “dental” high temperature
investment that will not permeate the green wax from Solidscape, and
will burn out at 1600 to deal with the Viper resinous material.

Further strategies are material specific, and a bit lengthy for an
Orchid post. I have heard that Tyler Teague of Jett Research has (or
is working on) a material for coating the Solidscape wax. Any more
strategies out there one would care to post? Anyone with a lot of
experience with the Viper?

Thanks!
Daniel Ballard
Precious Metals West


#18

A few weeks ago a question was raised about hand carving a model
after it has been CNC milled. I’ve changed my take on the subject
after working closely for 5 days with a very adept wax
carver/mold/modelmaker.

We had a limited time to work together and a lot of work to get work
done, so we milled some multi-stone pendants from the top only (to
save time on the machine). In a matter of a few minutes he burred out
the backs to a very consistent thickness. He wanted to use them for
production, so he RTV molded the waxes, creating a “hard copy” mold
in addition to the CAD file of the design. He did this with wax as
well as butterboard models.

The benefit of this method is the wax model isn’t as subjected to
loss of detail or shrinkage from casting a master model, finishing,
and then molding, casting and finishing again. Even for one-offs,
having a “hard copy” mold can be a good thing, in case something goes
wrong with the casting.

-Jesse


#19

Well, I was talking with one of my SLA suppliers today and found out
why the patterns are so costly. I was informed that a smallish
machine (500mm x 500mm) costs about $750,000 and that buying enough
resin to fill the pattern chamber is $25,000. Now, you might be
asking, just how much resin do they get for $25,000. The answer is
only 12 gallons. A little more expensive than filling the tank in
your car, eh?

So, now I will still complain about the cost of the SLAs, but at
least I know why the cost is so high.


#20

Hi Daniel Long time long no see… I received this tip from Irene at
Platina for coating Sander’s wax… Spray the wax with Teflon. It’s
thin enough to not fill in any details, and closes the pores. I’ve
just had several Sander’s patterns (highly detailed patterns) cast
into platinum by Bobo at BestCast, which is a good deal more
problematic than gold, with good results.

Jeffrey Everett