Rapid prototyping Machines

I just read an article on using them for the aftermarket companies. They seem to be incredible at their abilities. I'm not sure that resin and etch in the traditional sense would be able to compete with the level of detail that they can produce. The article I read had such a level of detail on the jet engine pod that it  made it imposible to use as a master pattern and cast in resin later. It also said of cost, that may also make the whole process too expensive to the average modeler. I am guessing that you read the same article DK. Sure would be nice to have access to one and a designer for a couple of weeks wouldn't it?

The article I was reading (and can't find again) was from a design engineer who had an RPM. He designed an engine pod for a "heavy lifter" (I don't recall the plane. Something like a 707) in 1/72 scale for a friend. Anyway the detail that was able to be made in the turbine was so close to the real thing. With the spindle mounts and depth UNDER the compressor blades. The pic did not do it justice. The problem was cost. The time it took him to design and make the parts was not a day project to say the least.

I'm not an design engineer so I'm not sure how the hobby will be able to benefit from the advantages they offer. The cost and production time may make these unaffordable to the majority of the building public. But then again, the past has shown that we will pay for details. I think for the start of this new detail industry would be limited to the highest detail oriented parts. The remainder, road wheels and such, will likely remain in the resin market for the time being.

Imagine: A 1/24 car with the hood up, the engine apart showing pistons, cam shaft, push rods, timing chain and sprockets and all as one piece. How about a jet engine showing the internal turbines(cut away). A tanks open transmission. The possibilities are endless and limited by what we want! And I must stress want!

Drew

MortarMagnet wrote:

You could build a F-105 with all its 467,358,749,745,324,673,612,896,067,086 parts.

You forgot the three rivets on the HUD!

I have several RP machines I'm just looking for projects. I would like to produce a article for FSM on the differeent technologies.

e-

I hope our sillyness gave you some ideas DK. As far as an article, I would love to see it. I think a project may be what you are into building, armor? Help with ideas or something, post your general ideas, and pick the one you like from the replys.

Drew

DK666 wrote:

I have several RP machines I'm just looking for projects. I would like to produce a article for FSM on the differeent technologies. e-

DK666,

I ran across your posts while doing a search using the following  --"rapid prototyping" hobby  --.

I make molds of all types  --  Vulcanized Rubber, Low Melt Metal, RTV, Ferris, etc.  I then use the molds to create waxes and then to do "Lost Wax Casting" in various precious metals, primarily Silver and Gold.

I want to do a Chess Set and wonder, if I came up with the CAD, is RP a viable medium to generate the master in order for me to create the mold?

RLW

MortarMagnet wrote:

Drew you are absolutely right.  My drawing, which ..... model.  They could be used to make a master pattern for resin casting, but, this sounds weird, some of the detail would be lost.  .....

I just posted a note on RP and the viability of it for my casting.  I'm not sure that I agree with you on the detail comment, it may be true with a resin cast or a cheap mold but not with the hobby work that I do.

I have recently made a mold of a tie-tack gun appx 3/4" long of a Colt 6 Shooter.  On the side of the barrel was engraved "Colt 6 Shooter" (or something similar).  It was so small that it could only be read effectively with a mag glass.  The vulcanized rubber mold that I produced replicated the gun and the engraving such that the wax and subsequent silver was still able to retain the legibility of the engraving.

I don't have any experience with resin casting so the problems may be different.

Regards RLW

MortarMagnet wrote:

I don't know if resin is capable of holding that sort of detail.  Did you make the mold or the pattern with the RPM?

I don't know either on the resin.

The gun master was a tie-tack that I actually took off of a tie at a club meeting that belonged to a fellow caster.  It was made from metal but I don't think it was Silver (It may have been)  I thought it was just cute until he pointed out the engraving on the side.  At which point I thought it was incredible.

I really didn't expect to be able to reproduce the engraving and was pleased when it turned out.

I could probably post a picture (very close-up) of it tonight when I get home if anyone is interested.

FYI  --  Vulcanized molds are done at a temperature of 315F and held at that temp for appx 1 hr per inch of thickness.  Since Pewter melts at above 450 it would be suitable for reproduction, as would tin or other metals.  The only real problem is with some low melt alloys.

If I get something that melts at lower temp, I do have access to some exotic composit mold material that will vulcanize at about 160 F.  However it's expensive.

The other alternative is for me to do a "Cold Process" using great care, high vaccum, and long cure times.  Then use that to produce a wax  --  use the wax to produce a Silver  --  do any required cleanup on the Silver Master  --  use the silver to produce a high quality vulcanized rubber mold and then create master waxes from that mold.

Hope I haven't bored ya'll  --  Regards RLW

Some Photos.

Some My Photos  --  I have made all of the molds, produced the waxes and cast each of these in Silver.  The infant ring is setting on a 1/8 in burr to hold it upright

Ok, I found the original article I was reading on the use of them. here.

RLW welcome to the forum

RLW, I was not referring to figures or jewelry per say. You do great work with yours. It's impressive. I was going towards scale modeling like what is shown in the article. That piece would be impossible to cast as one piece as the stator vane blades are away from the compressor blades. The under cutting of the compressor blades may not be able to be cast either. The vanes would need to be added after. The detail level that can be achieved is almost unimaginable in my opinion. Like Morter said earlier, an F-105 with all it's parts and rivets. It may be a diffrent machine than you have though.

Thanks for the great discussion, this is what these forums are here for. I luv it! Can't wait to continue.

DrewH wrote:

Ok, I found the original article I was reading on the use of them. here. RLW welcome to the forum ...That piece would be impossible to cast as one piece as the stator vane blades are away from the compressor blades. The under cutting of the compressor blades may not be able to be cast either. ...

I agree impossible AS BUILT.  However, with some advanced thinking the the master could have been built in just two parts with the separation between the stator and compressor.  In fact there is a dividing line already visible on the exterior of the vane assembly.  It might (not likely) require a three or 4 part mold but that is not a real problem. 

I have had laser engraving done on a couple of objects by a local supplier for some medallions.  I then made molds of the plexiglass master and then produced the wax from the mold.  Problem is that they are fundamently 2D with the 3d dimension being the thickness of the material selected.

In my thinking the real advantage is to do the design work such that the Stereo Lith can produce a master and then proceed from there to make a mold and the parts from the mold.  The industry is not ready to produce Stero Lith in mass for a single customer unless it is for resale.

I did have a quote for one of my medallions about a year ago with some complex lettering.  The price for a single stero lith was ~$300 but if I wanted 50 they would do them for ~$10 each.  The rationale was that they could fit all of them on the same platform at the same time.

OFFER TO EXPERIMENT

If any one is interested, I would be willing to take one of your parts and go through the process of making a Vulcanized Rubber Mold that one of you could experiment with using resin.  Perhaps we could get some additional detail that is not available with your current methods.  I do know that you can do Die Cast of Low Melt alloys directly into my rubber molds.  They would of course be heaver than resin.

Regards RLW

Small Chess Set

Concept JSF 1 piece build 33" Long

SONY Solid Creation System 8000 SLA Machine Bigger than the one in the reference article 

Fine bit of casting work RLW.

We make our mold masters on the STL machines including gates, runners, vents and parting planes. When it comes out we just clean it up and pour the RTV A & B Sides.

OK, you caught my interest. Since I'm from Texas, and work at LM in Ft. Worth, and am assigned to the JSF Weapons team.  Who did you do the model for?

FIRST QUESTION, NOT SURE I CAN BUT if I can get CAD Weapon files  (Unclassified and ITAR Releasable) (probably outer mold line) can you scale them and produce some small models about the size of a tie-tack.   And, maybe smaller so that I could put them on the side shank of a ring with a JSF on the top.  Visualize a class ring. 

You would of course be rewarded with a silver replica of each as my expression of eternal gratitude.  And do it without getting anyone in trouble?

SECOND QUESTION, did you do the chess set?  If yes, how did you get the CAD images, if I know that, maybe I can find some small cowboys and indians to do an experiment with? 

Regards RLW

A large areospace company.

I can find the cad just tell me what weapon you want and what the final Size you need is.

Yes I did the chess set. I may be able to laser scan some cowbyus and indians and get the mesh files that way.

DK666 wrote:

I can find the cad just tell me what weapon ..... and ...the final Size ...... Yes ..... laser scan some cowbyus and indians and get the mesh files that way.

1)  Each of the following 2cm in length

2)  Each of the following 1.25cm in length but only 1/2 (flat on one side) on the Longitude such that it has a flat back and can be mounted on a ring shank

AIM-132

AIM-120

JDAM / GBU-31

GAU12

On the Cowboys and Indians, I have some ideas and more to follow.

Regards RLW

BTW if this is getting boring to the rest of the crowd, we can move this off line.

Nope, not bored at all. Just saw what was happening. WOW! you two are good.

Sorry DK, I missed that you posted some of your work too. It's great. 

As for some of the rest, modelers do use RTV silicone rubber molds a lot. They are easily accessible and resin (two part liquid plastic)is the easiest medium for us to cast in. Even with the low temp alloys, "white metal" (I use the term loosely) is not feasible for most due to the handling requirements and the specialized equipment. Loss of detail is a concern too.

I do my own molds and casting. Very crude (compared to yours) as I need a degassing chamber to improve the finished quality of the castings. Trying to get any fine detail is near impossible. I know multipart molds are used daily, but have never figured out how to do them. Any help there would be HUGELY appreciated.

Thanks guys for the very informative and provocative info thus far.

Drew

DrewH wrote:

....WOW! you two are good.

Flattery will get you everywhere!

DrewH wrote:

Very crude (compared to yours) as I need a degassing chamber to improve the finished quality of the castings.

The molds that I describe below do use a vaccum chamber to remove air and increase the density of the resulting molds.  I've tried cheap vac pumps but it really does take a good one.  E-bay often has them for .25 on the 1.00 if your inclined to do it that way.  ALL of my casting equipment was purchased used

DrewH wrote:

multipart molds are used daily, but have never figured out how to do them. Any help there would be HUGELY appreciated.

Let's try to remove the mystery of that.  Following are TWO DIFFERENT APPROACHES TO A SIMILAR PROBLEM

FIRST APPROACH NEXT THREE PICTURES  --  The RTV used in this mold is Castaldo Liqua-Cast 2 part 10 to 1 mix.  I really like it a lot and the cost is very inexpensive compared to others I've used.  It allows for better carving that the normal RTV two part blue.  The first picture is of the Master (White) and the end result of the mold, a wax to be used in Lost Wax Casting (Blue).  I'm sure that many of you have run into the problem illustrated, there is no single parting line that will suffice to get the part out once the material has been poured in, regardless if it's resin, or wax, or Low Melt Alloy

This next picture shows the first cut of the mold.  BTW I do both carved molds as well as multi-part pours as in the second example.  The objective is to be able to separate along a parting line that will cleanly separate some portion of the master while leaving the balance embedded in the other part.  In this case the initial first cut exposed one half of the body and two of the four legs.  The remaining legs are embedded in the other half (Left)

The third photo shows the cut that will allow the part to be removed.  I had to prop it open with a sprue rod (1/8 inch brass).  The trick is think where the cuts will have to be in 3d.  The other trick is to orient the mold and know where the object is inside.  I usually put a yellow sticky on the inside of the mold prior to pouring in the RTV with a drawing on the sticky facing out.  Then I know where I can safely cut to get to the model.  I have even taken pictures of objects sitting in the mold prior to the pour.  As you do these cuts, you need to be aware of how it will fit together when you are ready to pour or in my case inject.  You don't want to have square or straight cuts that can slip.  You need to leave enough mass to act as the hinge.

SECOND APPROACH NEXT TWO PICTURES  --  The RTV used in this mold is a no-name 2 part equal parts mix.  I like it for different reasons, it is easier to work with when creating molds by a barrier separation method and is easier to work with when there are undercuts because it is soft and flex. The cost is more expensive.  It doe not allow for carving since it is too soft and it will tend to break when bent compared to the pink. 

The parting line determination method is the same as previous, you simply have to see in 3d and visualize how you want to achieve separation.  In the construction of this mold:

1. I took the master, a sterling silver pendant and put tape around the rocker portion thus creating the insert part.
2. I mixed and vaccumed the RTV
3. Poured it into the pony sitting upside down, thus creating the mold that would be the space between the rockers.
4. I then vaccum again with the pony in the chamber upside down
5. Set aside to cure.
6. Next I carved out the locating shape in the center of the rockers thus insuring that I could get solid and consistent position of the removable part.
7. I then embedded the pony, with the insert in place, up to the desired parting line.  The left picture would represent the clay and the right picture will be the second pour.
8. After embedding in the clay, paint your parting agent on the inside of the box edges, on the clay, and very important on the first pour of the RTV.  This is so the second pour which you about to do will not adhere to the part between the rockers.
9. Mix, vaccum, pour, vaccum and set aside to cure.  When step 9 is complete you will have mold part number 2 with a post that now fits into the hole previously carved.
10. Remove all clay and put it back into the mold box with the two parts assembled and in a fashion that will allow you to pour the third and final part
11. Paint your parting agent on the inside of the box edges, and very important on the first two pours of the RTV.  This is so the third pour which you about to do will not adhere to the assembled first two parts

I'm not sure how good this explaination is but I'd be more than happy to answer any questions.

Regards Caster (RLW)

Simple Direct manufactured Mold Positive and Negative 11120 ABS type clear epoxy resin. Start to finish urethane (Tan) & Silicone (Clear ?)  pour 3 hours Including CAD.

DK666 wrote:

Simple Direct manufactured Mold Positive and Negative 11120 ABS type clear epoxy resin. Start to finish urethane (Tan) & Silicone (Clear ?)  pour 3 hours Including CAD.

"quit it" <GRIN> You make me fell like I'm a caveman with a iron / stone chisle and hammer.

I LOVE technology.  Have ya got an old one I can buy and put in my garage?  Oh BTW I've only got about $105.00 to spare.

Regards Caster (RLW)

These particular molds we made on a system that goes for about $ 850,000. That dosent includes the 265 Liter of resin at $305.00 a Liter. The real itty bitty stuff we make in a machine that can hold 16 microns and cost a lot less (That a relative statement) but we can only build 8 ½ x 11 ¾ x 7 ½ inch models.  the models are out of photo-acrylic great for casting. But don’t worry you will see them soon enough. I’m going to have to hand model the GAU12 I'll do it in Solidworks and send you some of the renders. Here is a Big mold we did. Its a full size 14" pipe wrench we did several castings in 8lb foam for a movie prop.

I am in the process of buying 1 for my garage its used has an 8x8x8 platform size. I got a good deal on it. But the lase is almost dead (about 200 hours left on it) BUT it will only build .004 layers but I can deal with that. Take a look at http://www.solid-scape.com/index.html

One went last on ebay for 7500.00 I think that you could have a lot of fun with that.

Cheers.