The FDM machine is "not" a printer. It is an "extruder". Meaning, the material on the FDM head is forced out of the extrusion head via pressure from a wheel that turns. This wheel has the thermoplastic wound around it like a weedeater. The PolyJet is a "printer" that uses Piezos that are energized when printing the bitmap it needs to lay down, pretty much like the same technology an inkjet print head uses in your desktop printer. The major difference between the Acuta and Sanders machine is that the PolyJet from Objet uses UV light to cure layers. Objet owns the patent on this technology that uses UV light to cure layers. Yes, support must be put down to support wall structures, but speed is not compromised because the support nozzles and model nozzles are fired at the same time during full platform passes anyway.
Yes waxes are low melting point thermoplastics. You hit on the key: they are LOW molecular weight. Because of the investment
casting process a.k.a. "lost wax" process, you must have a low molecular weight wax with very low ash content (<.1%). Typically,
thermoplastics are high MW and high ash. This ruins a part in the investment casting industry. It results in a part with occlusions,
pitting and sometimes massive structural failure. Not to mention the fact that it gums up the autoclave. Typically waxes are fired
in the lost wax process at 1200-1500F for 1-2 hours. Thermoplastics require 2000-2500F for 4-5 hours. This is not practical for
a production foundry, plus it requires special handling and recalibration of equipment (furnaces, etc.)
One of the big reasons we want wax is to allow the foundry to use their "normal" production processes in making a prototype. Deviation from this can also affect the quality and material properties of the casting. If you're doing development work, you can no longer trust your prototype to be truly indicative of a production part.
Hope this helps...
Thanks GFL for the reply. I'm gradually getting a better idea of the capabilities of the varios machines. One point I'd like
to make though is that waxes are thermoplastics. Waxes just have lower molecular weights and consequently lower melting
temperatures. I'd be surprised if the Actua machine couldn't be adjusted to deposit a wax. My apologies to the SSYS thread readers for
bringing in this discussion of the TDSC machine, but I think we'll all be better off if we understand the merits of the competing
machines. GFL, thanks again for sharing your knowledge.
Interesting... The Actua machine uses the new "ink-jet" technology to deposit material. Something we tried with casting wax with a machine from a little co. called Sanders Prototyping in Nashua, NH. Note the Actua still uses thermoplastics, not wax as our application demands.
The ink jet technology is new and neat. But it does have its problems. Jets clog, droplet deformation parameters are difficult to control, and material feeding systems are tough to thermally regulate. Plus (big one here) you cannot build a hollow sphere without massive support structures. We've built parts as much as 30 degrees off vertical with the SSYS machines with NO SUPPORT.
I don't know if this is possible with Actua. The nature of ink jet technology almost demands continuous supports be designed into the part. You find yourself spending more time designing and building supports than designing the part!
Advantage of this tech is that the droplets can be very small and can give excellent resolution on small "simple" parts.
Here's the link to the Actua machine. Still curious if this would work in your application. I'm trying to figure out the strengths of the competitors in this business.
All the companies in this industry are experiencing a shift in their marketing strategies in regards to product development
and positioning their products in specific market segments. The entry into the medical segment (Stratasys) is a pioneering
effort. The major insurance carriers (in the US) will not pay for medical models as a practice ( there are no medical procedure or
billing codes for these medical models). 3D Systems is positioning themselves as solution providers in the manufacturing segment
with their SLA line while covering the engineering segment with their office modeler (Actua). The change from marketing
engineering solutions to manufacturing is not an easy one. The latter is a very pragmatic market rather than visionary. Look for growth
in this area when market targeting becomes a little more refined.
I have some SSYS stock and it seems to me that they are growing in every way like number of employees, gross sales, etc.
Unfortunately, their earnings per share are not growing. As you know the stock market does not treat kindly companies whose earnings don't
grow. Perhaps if they can pull in the reigns on the spending they can slow their growth a little and show some earnings. I may
even buy more of this company. I know one of these RP companies is going to be a big winner. People who understand what these
machines can do can easily imagine the possibilities for the future.
I'm not familiar with 3D's Actua machine as I am no longer involved in the RP area.
I think the reason this industry has seen slow growth is a multifacted issue. Despite the incredible ROI's on RP systems
(our original ROI was 12 mos. on a $120,000 investment), many co's don't have the cash. Remember, you've got to buy software
(SDRC, Pro-E, etc.) that is high priced. Plus you need hardware: high end NT workstations or SGI's, Sun's, etc. And unless you're
in an industry that uses molds to product parts, RP's cost savings can be hard to quantify. It's easy if you eliminate
prototype tooling at $10k per tool, but it's much more difficult if you are developing machined parts where you get hit with machining
costs anyway. Plus there's the staff to run these things. Most require skilled design engineers (who can design 3D parts) and have
the technical background to operate machines and do mold design. Fortunately, I'm one of these types. But when I was hiring
designers, it was difficult to find talent, and when I did, it was expensive to hire them.
Eventually co's will see the light. Expect continued growth in this area in many diverse industries.
The volvo carbeurator example is fine and good, but
if your engineers arent' smart enough to remember to
put all the venturi ports on the carbeurator in the
first place, they've got problems that niether
SSYS or 3D can solve.
I'm sure that there are many other examples of this where
3D modeling has been helpful - I'd love to have access to
something like that for many of my projects.....
That's a great example of establishing how these machines can save the user bundles of cash. My question is why haven't TDSC
and SSYS been able to make money and grow? Growth is slow so there must not be much demand even at prices that generate lousy
margins. Yet, as your example demonstrates, they can save the manufacturer of almost any part that is three dimensional a heck of a
lot of time/money. To top it all off there are other entrants into this business which so far generates less than a combined
$100 million per year in machine sales. With all the mechanical design software in use it seems that this business should be a
faster grower. I don't get it. Does anybody have any answers?