Rapid prototyping Machines

Hey on a side note we got a sample of some new silicone We cant seem to de-gas it its pretty thick and platinum cure. Its made by Smooth-on   Smooth-Sil 920. Any Ideas ?

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DK666 and RLW -

This is really great stuff - thanks for taking the time to share this info.

I just did my first simple resin casting today, and I'm totally hooked - it worked out great, and it's nice to see here what complicated things can be done with some clever thought about the molds.

Bruce

DK666 wrote:

Hey on a side note we got a sample of some new silicone We cant seem to de-gas it its pretty thick and platinum cure. Its made by Smooth-on   Smooth-Sil 920. Any Ideas ?

I had a sample (same company, plat, may not have been the 920) of it year, 18 months ago and liked it except for the expense.  I used a club vaccum pump and chamber and as I recall it did not gas as much as expected.  But I didn't have any problems. 

I also tried another method which was to warm up the master (if possible) and dip it into the mixed RTV.   There were a couple of surface bubbles and once popped, and filled in with RTV it was then framed and poured normally.  It also created quite a mess so I haven't used that method very often.

The real question is or will be if there are any bubble problems with the slow or minimal de-gas.

DK666 wrote:

..... I may be able to laser scan ..... and get the mesh files that way.

• Are there any particular characteristics involved with the scanning.?
• Does color affect it?
• Could the object to be scanned for example, be something in blue plexiglass?
• Is there any restrictions on the 3 dimensions, for example, could an object be 4" X 4" or round and 1/8" thick like a large medallion
• Can it be reduced once it is scanned in?
• Does reduction create a loss of detail to any perciptable degree?

I know there are more questions, but I'm not fully engaged yet this am

BTW

How much is a 3d scanner on the cheap end or used?

Regards RLW

bwr1 wrote:

I just did my first simple resin casting today, and I'm totally hooked - it worked  .....

Well Bruce,

Are we going to see any pictures of your endeavor?

And, what else are you planning that we might assist you with?  How about a picture of something that you think is complex, and your thoughts on how you intend to proceed?

What is the mold material your using?

Regards RLW

bwr1 wrote:

Any suggestions/thoughts on casting jet engine nacelles ...

Ok Bruce,  I'm splitting questions and comments into two responses.  This one is reference to the engine nacelles.  Here is a generic view that I pulled off the web to illustrate the point.

Which parts do you want to inclued?  How many components do you want to group together in a single casting?  What specific interior detail do you want to show?  Aren't there already some plastic or vac formed engines of the type you want that could form the basis of the mold desired?

None of the individual components are particularry difficult.  For example, it would be a piece of cake to make a mold of the Fan Cowl in one casting showing both interior and exterior.  However, much planning would have to go into the Front Cowl and the front of the blades.

bwr1 wrote:

Any suggestions/thoughts on ..... landing gear

The nose assembly is straight forward without the tires on.  It looks like if a master was available, I would make a mold with the parting line from top to bottom on the main strut, and on a center line that is parallel with the long axis of the plane.

I would then either pour Low Melt Alloy directly into the mold (if made of the right material) or I would follow my Lost Wax Casting procedures and produce a wax, invest it, burn out, and then pour the Low Melt into the cavity.

Either method would require just a minimum amount of cleanup of the parting line.

The pictures don't show a lot of detail for all of the undercuts, but I don't think they represent a serious problem, and if they are significant, I would simply make a multipart mold to overcome the undercut areas.

RLW

http://www.aircraftresourcecenter.com/Gal4/3301-3400/gal3372_AB380_Greutert/gal3372.htm

He's working in 1/144 scale - at 1/72 things will be a bit different. I think at 1/72, photoetch for fan blades may actually be visibly too thin for the scale, so I'm thinking of making them out of something else. As far as what details to include, I'm thinking the bypass fan, the initial compressor blades and supports, and the final end-stage turbine blades (pretty much what you can see by looking into either end of the engine). I don't plan on including any open panels with engine detail. So the parts breakdown is something like 1. inlet cowl + fan cowls, 2. fan spinner, 3. blades (maybe PE, but maybe from some other material), 4. exhaust nozzle, 5. exhaust cone, 6. thrust reversers cowling, and 7. the pylon. With that breakdown, I think all of it could be done with simple molds. I'll probably start working on this in a month or two - I've got the reference materials (plans, photos, etc.) I need, and I just need to finish a couple of other projects first.

Im Back.

The reason I have been absent is we host a Annual Rapid Prototype Modelmaking Workshop for Educators we bring in about 50 educators from around the country and Teach them Rapid Prototyping and Modelmaking for a whole week. That being said. RLW I have your models done however I havent had time to ship them yet but I have tomorrow off (well deserved I think) so I will Priority them to you and you can get creative and stun us all with your product of work. BTW do you also need a JSF ? and I just got access to a jewerly patternmaking machine (uses either blue or green casting wax) that I'm just dying to do a part on. I will post some pictures of the conference soom so you can see what it was like. Also we have 2 new laser scanners. The answer to your scanning questions are;

No limit on scanning its free form.

Yes black is bad but we talc the part so its no problem nothing like glass or mirrors (laser passes right through or bounces off)

Yes but we have to talc it first.

I can scan up to 14feet by 14 feet so if its bigger than that I have to target it and stich it together which is no problem I have software for that.

Bigger or smaller no problem just some software settings.

It can but I can remesh it and restore detail.

Cheers

e-

I have built the prototypes of the actual c-17 nacelles I may be able to find them (its been 4 years) and I could get you the CAD data.

Cheers

e-

DK666 wrote:

BTW do you also need a JSF ? and I just got access to a jewerly patternmaking machine (uses either blue or green casting wax) that I'm just dying to do a part on.

Yes, I have a small pewter one that is in the center of a Christmas Ornamaent but it is not accurate.  So I'm reluctant to make a mold and reproduce it in more pewter or silver.

And, if you want to design a ring for yourself or a pendant for your significant other, do it in Blue Wax, and send it to me.  You will receive by return mail, the memento in Silver or Pewter.

Another project that I have been working on is a JSF ICE Medallion.  I was ajdunct on the proposal lead for the ICE effort.  We had about 40 people on the team for 2 years.  I have not been able to get a good solid model from Laser because of the detail in the flags and letters.  It works at about 4 inches in dia but trying to get it to about 2 - 2 1/2 has been difficult.  I'll send you the files in a bunch of different formats, and the small center jet that I want to use.  Everything but the jet is laser cut, the jet is done in relief for a coin that I salvaged.  I'll send the blue plexiglass of the medallion and the center jet to get your opinion.  I'll have to wait to get your address when I receive you package.

Oh MY    This Is Fun  --  Here is the jpg rendition of the finished project

This is just great stuff you guys are doing!

Here's some pictures of my first ever resin casting - it's pretty basic stuff but I'm pretty excited how it turned out.  It's prop spinners and exhausts for a Bv.238 flying boat.  The prop spinner is basswood carved to rough shape and then chucked in my dremel and sanded to final shape. The exhausts are kit parts from a Hasegawa Bf109G kit:

Here's the mold.  I think I used too much RTV here - but I figured a bit too much around the edges and too deep was better than too little for a first try:

I made 6 castings - I had to use a toothpick to get rid of some air bubbles in the exhausts, but that's probably because I poured too fast and directly into the cavity:

The assmbled engine (right) next to the original kit parts (left) for comparison (the original engine shape was wrong, so I've also reworked that with strip styrene and aves putty):

Probably won't have anything else to cast for this kit, but I'm excited to start working on the An-124 and An-225 soon for more casting opportunities.  Next prop I have to do, I'll probably build a full master propeller (spinner plus blades) and cast it with a two-part mold, but since this was my first time I really wanted to start slow and get something successful.

Also, I'd be interested in the CAD data for the C-17 nacelles.  Probably going to be a year or so before I start working on those kits (I'm going to do the C-17 and C-5 kits around the same time), but you never know what info/data can come in handy.

Thanks,

Bruce

bwr1 wrote:

Here's the mold.  I think I used too much RTV here -.....

Yes, I agree, your mold looks very much like some of my TOO THICK molds.  It really doesn't hurt anything, just is expensive material.  Here is a trick that I read about and tried once and it worked well.  Take an old mold that your not going to use anymore and grind it up.  I use scissors to chunk it and then put it in a CHEAP blender [don't use your wifes, it really makes em mad].  Now take and make your mold as usual but instead of  all new liquid, try the following.  Add the finely groun RTV into areas away from the master to take up space.  Then pour in the new liquid normally allowing it to flow over the master.  As long as the two materials are the same, the RTV will adhere to itself.  You can judge fairly eaisly how much you are able to save by looking at how much space you have put used material into.  I also take a toothpick and mix old and new in the area where I have stacked it.

bwr1 wrote:

I made 6 castings - I had to use a toothpick to get rid of some air bubbles in the exhausts, ....

I agree this is an absolute pain without a vacuum pump.  I was fortunate in that I bought one from a jewelry widow that had been setting around for a couple of years.  She had got rid of most of the jewelry tools and ovens, but had a bunch of Misc Junk left in his shop.  I agreed to take and clean out what was left good and bad, and thus clean out half of her garage. A half day of work and kicking in a few bucks I came out with a ton of interesting stuff.  You really should consider trying to fiind a vaccum pump on e-bay or maybe if your handy like most hobbiest, build your own.  Here are some website:

http://www.housatonicrr.com/VacChamber.htm

http://www.sas.org/E-Bulletin/2003-08-01/labNotesAS/body.html

http://www.dream-models.com/eco/vacuumpump.html

Another observation, ya'll seem to be concerned with weight.  If every small ounce counts, it looks like when you poured the resin, the spinner was solid.  I haven't worked with resin, but with wax, you can pour it in and then pour the excess out.  Thus creating a hollow inside rather than solid.  I do this with head and bust reproductions that I do for my wife's Clown Collection.

bwr1 wrote:

..... Next prop I have to do, I'll probably build a full master propeller (spinner plus blades) and cast it with a two-part mold,

Given what I said above about a hollow product, you may want to reconsider the putting them together, unless you design it so you can still make the spinner hollow.

Hope I not being too presumptious.  Just trying to share some things across the boundary line of hobbies.

Regards Caster / RLW

A good rule of thumb we use is 1/4" surrounding the object.

Cheers,

e-

Just started with my coffee. Something like this. Let me know.

Cheers,

e-

Next Item.

Cheers,

e-

DK666 wrote:

Just started with my coffee. Something like this. Let me know.

Yup,  very good.

Your too much.  Don't you ever stop to rest [I should talk]

Didn't know how to attach files in this forum so I have sent you some files under separate cover via e-mail.  Should save you some construction time.

Now another question.  If you know the specific gravity of something like silver, and I'm sure that your fancy software can caculate volume, can you tell it that you want it to weigh approximately 2 oz (60 grams) with a thickness no greater than 3/32 to 1/8 inch can it size the object.  Sort of thinking as size as the independent variable.

Forgive my Systems Engineering (Systemic) thinking

Regards RLW

I can do the SG thing but I have to finish the model first. I can of course resize it to meet your material needs. Are you spin casting or gravity casting and in which alloy ?

Oh. How much Draft do you need ?

Cheers,

e-

BTW got the other files thanks.

DK666 wrote:

spin casting or gravity casting and in which alloy ?

Gravity with vacuum assist on the investment canister. 

Alloy will be Sterling   .925  Alloy from fine to .925 will be copper.

DK666 wrote:

Oh. How much Draft do you need ?BTW got the other files thanks.

I really don't need any draft.  Both RTV and Rubber flex enough to bend away from the model.  If it is too severe, then I'll do a multi-part [more than two] mold.

How's This ?

Just have to get the JSF, Mountians & Trees and I'll make one tomorrow.

Cheers,

e-

DK666 wrote:

How's This ? Just have to get the JSF, Mountians & Trees and I'll make one tomorrow.

Awsome!.  The exe file you sent does not do the medallion justice because of the color.  There is very little difference.

Questions:

The letters look shallow, can they be deeper? 

Could the surface that is recessed be a "very tight peen look" if that is possible?  While the top surface should be a very high polish in Sterling Silver.

Can the exe that you convert to be shaded to show the detail better?

Regards RLW

RLW wrote:

Hope I not being too presumptious.  Just trying to share some things across the boundary line of hobbies.

No, not at all.  This is very useful stuff.  There are models I want to build that I know will never be kitted, so I've got to learn about a lot of scratchbuilding techniques (casting, photo-etch, vacuum forming etc.), and it's really helpful to get advice from someone who's been there and done that.

Thanks,

Bruce 

Last nights fixes.

I will build one this morning should only take about 45 minutes.

Cheers,

e- 

DK666 wrote:

Last nights fixes.  I will build one this morning should only take about 45 minutes.

I   LOVE the textured effect in the recess and the smooth finish on the top surface.  This will be outstanding when done in Sterling Silver.  I'm also going to try to cast and finish one and then blacken (oxidize) the recessed portion.

What do ya'll think?  Any other ideas out there?

Regards Caster (RLW)

1 hour 45 minutes later. Poof.

Being sent your way today.

Cheers,

e-

DK666 wrote:

1 hour 45 minutes later. Poof. Being sent your way today.

I can't wait , I just can't wait , I'm so excited , Hurry , Hurry , Hurry

The round is downrange. Should have them tomorrow or wednesday.

Cheers,

e-

Did you get it yet ?

e-

DK666 wrote:

Did you get it yet ?

Yup Got em.  Wanted to surprise everyone.

Here are the Weapons that I choose to Cast, 6 out of the 10

Putting the Sprue on the first of 6

Here are all 6 Sprued and Waxed to the Investment base

Now they have been sprayed with a liquid to decrease surface tension prior to pouring the investment.  And, the canister has been mounted on the base almost ready to pour and vac

Here is the medallion with 4 sprues attached.  one on the edge center, two on each edge side at about 90 deg and one up the back into dead center of the back

Now it has been sprayed, and mounted on the base ready for the investment.

Here are the canisters fully invested and setting on the vacuum plate.  The process is to mix up a closly measured amount of investement with a closly measured amount of water for 2 minutes, vacuum in the mixed mode for 2 minutes (I get about 27.5 in of merc, pour it into the canister and vac and vib for 2 minutes.  Counting the slack time for moving around, 7 to 7 1/2 minutes have passed. And the investment will set solid in another minute or minute and one half.   The base is then removed and the surface top and bottom is trimmed and made concave with a plain old knife and left to dry out as much as possible.  I try to do it overnight.

Now put them in the oven to bake.  2 hours at about 450f, 2 hours at about 1000f, 1 hour at about 1400-1500f, rest for another hour after the temp is down to 1100f

The medallion has been poured and she took the picture during the pour of the small Weapons

The quench.  After the sprue turnes dull grey, it is submerged sprue end first in water and then totally.  The canister and investment create steam which blows the investment out and the object can be removed

Success on the Medallion

5 of the 6 Weapons turned out.  I mounted them in various positions to see if there was a good or bad way.  One of the horziontal ones must have broke loose during the investment because the sprue end turned out great.

Ed,  I'll contact you with some changes that will be required to be successful.

Regards Caster (RLW)