This may get me back to Shapeways

[Alwyn Cutmore]

Jettuh,
Now you are talking real patterns. Can do the exact same thing in lost wax sterling silver. Now that is the way proper patterns are made. No distortion and sharp detail.

You are commended.

Regards

Al

[Jettuh]

You're welcome

Note that the polished version does remove small details.
You might not see it, but the side of the model was unpolished (on purpose by request during the trial) to see the difference.

As the model has this kind of shape on the side:

\
/

you will see some printing lines, but i'm sure you can easily get rid of this with a fine piece of sand paper.
Engraved details however will still be visible when you go for the polished version.

While I'm writing, this is a picture of White Strong & Flexible made smooth with car primer.
The model is H0 so FUD wasn´t possible:


Due to the small amount of details sticking out, a good layer of primer wasn't a problem at all.

What I'm trying to say: design your models in a way that will generate the best results.

[bbussey]

For example Polished Brass?

1:160 version of my V-IRM train in brass

It's just damn expensive.. almost $30 for this small part of the train.

Yeah, for for a casting pattern, it is worth it.

That looks much better than when they first introduced the metals.  Nice to see that this is now an option.  It sounds as if you had Shapeways polish it as part of the process.

[Jettuh]

Yes this is a different technique than for the normal Metal (Stainless Steel + finishes).
The bronze, brass, silver material are first 3D printed in wax and cast using the lost wax technique.

You can go for Raw, Polished and Gold Plated:
https://www.shapeways.com/materials/brass

[carlso]

Jettuh,

Thanks for responding to my question. I can see that you are on top of the newer options for printing.  You said that the small part cost nearly $30. I am interested in some of HuskerN's trucks and if they were printable in the brass or some other metal, I think I could pop for a higher cost because it appears that there would not be broken, out of scale, warped, and generally pieces of junk shipped out as sometimes happens with FUD. I guess that I am assuming the metal would provide the strongest, best print even if some small details were missed. I should be careful assuming anything, right ? Could something like a truck chasis, cab, and wheels be done in a soft white metal or brass ?

Carl

[Chris333]

I just ordered one of these:
http://www.shapeways.com/model/610956/n-scale-american-h-d-ditcher.html

Fingers crossed, for that price I will be asking for a re-print if they are horrible looking.

[robert3985]

I hate to burst the bubble, but (as has been pointed out already) Shapeways DOES NOT "print" their brass parts.

Another way of saying this, to make it clear, is "Brass/bronze parts from Shapeways are NOT prints, they are CASTINGS of PRINTS."

Here's the process. (1)  Shapeways (or a Shapeways subcontractor) takes your 3D model and prints it in wax, (2) cleans it up, (3) adds sprues and vents made out of wax (called a "tree"), then (4) INVESTS it (meaning immerses it in a watery plaster-like mixture) gets the bubbles out by (5) placing the flask (a stainless steel cylinder with a rubber base on one end that acts as a plug as well as a form for a conical space surrounding the base of the "tree" when the base is removed) on a vibrating table, then, if they're well-equipped, (6) putting a hard vacuum to it under a clear bell jar, so the outgassing doesn't cause the liquid investment from overflowing the flask.  After the bubbles are removed, the flask is (7) set aside to cure for a very specific amount of time because you don't want the water content to evaporate.  Then, ( 8 ) after bringing the burn-out oven to a specific temperature, the flask is (9) removed from the rubber base,  and (10) placed inside the hot oven so the conical space with the wax tree base sticking out of it is facing DOWN.  Following a strict time regimen, (11) the temperature is slowly raised in steps (this is so the investment doesn't crack, but the wax both melts and is vaporized by the heat and high temperature steam emanating from the water in the fresh investment).  After a specific time, the very hot flask (now the temperature of molten brass or bronze) containing now just a void where the wax used to be (hence the name "lost wax casting") is (12) placed in a spin caster or vacuum caster and just the right amount of fluxed molten metal is very quickly (13) forced into the void by either centrifugal force or sucked in by a high, sudden vacuum.  The flask is (14) removed from the caster, and (15) placed on a fire-proof surface with the "button" (the metal now occupying the conical space at the base of the "tree") facing UP.  Many foundries (16) let the metal cool to the point of just being solid, then they (17) throw the still very hot flask into a metal bucket of cold water, which cracks the suddenly cooling investment away from the now metal "tree"...which is your part, plus the sprues, vents and button.  Next, the foundry will (18) take your tree, and clip your part from it, (19) inspect it and if it's okay, then they'll carefully (20) remove any large pieces of investment still stuck to it and (21) put it into an ultrasonic bath of an acidic solution that's specifically designed to dissolve investment.  At this point, after your part has been divested and (22) washed, it is ready to (23) ship.  For model train parts, foundries don't usually trim and finish where the sprues and vents were, but just leave a nub of them sticking to the part.  However, Shapeways does a lot of "art" lost wax products, so their part to you can be polished, or plated for even mo' money.

So, your brass part you get from Shapeways has undergone a LOT of work after the wax master was printed, and was produced in a very ancient and traditional method by a foundry that is one their subcontractors.  Because of the high temperatures involved there can be significant shrinking of the brass part from the wax master.  Talking with your Shapeways person will assist them to know if the size of your brass/bronze part needs to meet tolerance spec's, and they can then print the wax master out to exactly the size needed to ensure your metal part conforms to your size specifications.

What y'all need to know is that the reason the brass part looks so smooth and nice is because of all the handling, modifying and inspections done to the wax master before it gets invested and cast.  Investment wax is an easy material to work with, as opposed to cured FUD.

There are several non-Shapeways methods of doing this.  Using Perfactory materials, machines and process, you can get a hard, smooth master print made from a material that will allow you to take a vulcanized rubber mold directly off of it, inject that vulcanized rubber mold with investment wax, then do the investment casting process as I have described above either yourself or at your local full-service jewelry store, OR use the Perfacory print as a master to make an RTV mold, then use that mold to cast resin copies.

When I take a bunch of wax parts to my local jewelry/rock shop, and if I supply the brass, they'll tree my parts up, invest them and do a basic cleaning of the brass tree for $25 bucks a shot.  That's a flask that's about 3" in diameter and 4" long.  My last tree of parts was several hundred parts which combined will produce 60 N-scale brass switch stands with five individual parts per kit.

The main problem for you with Shapeways, at least from their information about brass/bronze parts on their site, is that they won't gang the parts in a single cast...no matter what size they are, which forces you to pay a really high price per part.  For my miniscule N-scale switch stands, they would have charged me (according to their pricing schedule) nearly $100 per switch stand since there are five parts per stand.  Even if they allowed each kit to be cast as a single part, that would still be around $20 bucks per switchstand.   However, paying $100 bucks for 5 parts that will be HARD MASTERS, which I would then lay between four slabs of uncured rubber, use my press and make vulcanized rubber molds from, then inject my own investment wax masters for my local jewelry/rock shop to invest and cast for me, is okay price-wise because that brings the price down to less than a buck a stand for me if I produce over 100 stands for my use (which I will).  But, my advantage is that I have the vulcanized rubber mold making equipment and the pressurized wax pot/injector to make my own investment wax masters...which would probably cost between a grand and 1.5 grand nowadays.

As for getting HuskerN's trucks in brass...you'll have to pay about 20 bucks PER PART for them since they shouldn't be polished.  Even more if you want some of them polished.  Once again, that's going to be around 100 bucks for a kit with five parts and I think HuskerN's trucks have more parts than that.  You might be able to get Shapeways' price down if they'll cast up a single sprue of all the parts, but that is not what they say they do in their literature.

So, that's why you're paying so much for investment cast brass/bronze parts from Shapeways, lotsa handling and a pricing policy that discourages making kits from brass or bronze.

Thought you'd like to know.

[Alwyn Cutmore]

Jettuh,
It is understandable that the costs are going to be higher on the initial run. but in the long term and when the costs are amortized over 1,000 units or whatever your projected figures are the cost is quite small. The amortized costs are for a product made from high impact poly-urethane that will reproduced the quality of the pattern.

Most quality RP manufacturers will polish the model at a cost. That is their business and they know exactly what they are doing and if they stuff it up it is at their expense not your.

Keep up the great work as you are a breath of fresh air in the RP debate. 

I have to agree with robert3985 to get the HuskeyN vehicles in brass would be one hell of an expense but on the other hand if HuskerN produced brass patterns like the model shown he could produce thousands from those patterns in either pewter or urethane without any further finishing other that some flash. I only wish I had the skills of HuskerN to produce 3D drawings but with my business I pay someone to have it done.

Regards

Al

[carlso]

Thanks Bob , for the explanation. I'm just trying to learn about this RP process.

Carl

[bbussey]

Yes this is a different technique than for the normal Metal (Stainless Steel + finishes).
The bronze, brass, silver material are first 3D printed in wax and cast using the lost wax technique.

You can go for Raw, Polished and Gold Plated:
https://www.shapeways.com/materials/brass

What was the shrinkage factor, if any?

[Jettuh]

Thanks to Robert for the detailed explanation 

For your information, the models printed in wax are actually printed on the same machine as FUD.
It just uses the wax material instead of the FUD material.
However the minimum required wall thickness is 0.6mm and thus more models survive the whole process

for FUD people love to use 0.3mm which causes parts to break.
I personally always use 0.8mm for my trains and can happily tell you that my quality is almost always consistent, no breakages and no bad quality.

As for shrinkage, i don't know, I would have to check my model.
Note that for example the Stainless Steel material at Shapeways is actually printed slightly bigger (depending on the size) to minimize the shrinkage on the end product.
This way you will (almost) not notice any shrinkage even though the model did shrink.

[Zox]

for FUD people love to use 0.3mm which causes parts to break.
I personally always use 0.8mm for my trains and can happily tell you that my quality is almost always consistent, no breakages and no bad quality.

Interesting. It's a bit counterintuitive, but I wonder--could there be a correlation between the thickness of a part and the quality of its surface texture? If the FUD material is flexible enough in thin cross-sections, it's conceivable that it could deflect under the pressure of the next layer being deposited.

Some people seem to get better results from other services--do those services perhaps have more stringent requirements for parameters such as wall thickness?

(Please note that this is rampant speculation on my part--I have no actual information.)

[Scottl]

I found this comment very interesting as well.  I suspect there may be something to it.

[bbussey]

... As for shrinkage, i don't know, I would have to check my model.
Note that for example the Stainless Steel material at Shapeways is actually printed slightly bigger (depending on the size) to minimize the shrinkage on the end product.
This way you will (almost) not notice any shrinkage even though the model did shrink.

I would be very curious to know if you had any shrinkage on the lost wax castings.

Noticing shrinkage is less important than there actually being shrinkage.  I guess a test item is in order, such as a 1/2-inch cube, to see what the actual shrinkage is on the stainless.