Quiet earth (was: Exercise module for Plettenberg railroad in 1/22.5 scale)

[WP Rayner]

It's endlessly fascinating to see this come together and watch your processes. Bill has an interesting idea to solve the seam issue. As an alternate, could you not remove the exhaust stack and piping that obstruct the seam, then chuck the entire assembly between live centers in a lathe, then clean up and contour the seam with small gravers and files?

[Hydrostat]

Bill, Paul,

thank you for the input - much appreciated! I lack a lathe and so Bill's idea is the way to go. I can at least remove the safety valve so even if I can't get around it helps to work the pronounced front area. If you don't hear from me for more than three weeks, it didn't work  .

Cheers,
volker

[Lawrence@NZFinescale]

you need to distinguish brass casting at Shapeways and at an usual jewelry investment caster.

Shapeways (and I guess all the other consumer providers) does wax print the item 'as is' and cast it via the lost wax process. There's no mould involved, which means it gets expensive if you need an item more often than once, because they would wax print every item again and again, but cheap, if you need only one part or an assembly of parts, which is counted as one part. My guess: When doing assemblies you have to be aware that they 1.) put all the cast parts into a tumbler, which means loss of sharpness and detail, and 2.) their limitations of 0.6 mm wall thickness is not a limitation of the casting process but rather of the tumbling they are not willing to relinquish and 3.) their wax printers don't run on highest resolution.

The valve turning handles' 'wire' have ~0.6 mm diameter (0.5x0.7), but you can see, that the sprues are even thinner; well, obviously they thought it would work and it did. All items need to be connected with a sprue of at least 0.8, better 1mm diameter to allow brass to flow in: at the valves for example to the thickest part; the other sprues rather serve to make it stable for the following tumbling. You don't need to think too much about geometry, because brass seems to flow nearly everywhere in vacuum centrifugal casting process.

Constructing or assembling parts for brass casting via a mould is another deal, because you have to think about where the mould can be devided later on. This is going to be quite difficult with rather complex parts. It's to complex to discuss here (at least for my limited expressive powers), but if you like you may contact me by phone or skype; just send me a p.m.

Cheers,
volker

Printing and casting is something that I do just about every week (Although I contract out the actual casting bit). In the past I made patterns and sprued in brass.

So some thoughts on this:

1. Very nice :-)
2. Metal flow is worth thinking about.  However investment casting is pretty forgiving.
3. Depending on the print technology used, it pays to make digital patterns easy to print.  This is generally a far bigger issue than easy to cast when using a LCD/DLP/SLA style printer. Volker's valve render would be hard for me to print and has more support/feed than I used when I did similar parts in 16mm. I find that generally the needs for print support are consistent with good metal flow.
4. Shapeways is constraining and pretty expensive.
5. There are various techniques for making the wax.  Modern 'castable' resins have come a long way and work well in a consumer printer.  A bit of a learning curve involved for DIY though. I think Shapeways use a different technology that is less constrained on the print side - so some benefits in that regard.

The pic shows some 4mm scale (OO9) NG couplers.  Note that the tommy bars on the slack adjusters have cast well (0.3mm).  There is plenty here at well less than 0.6mm wall thickness.

The sprue is printed in two parts, joined prior to casting.  You can see how some of the print supports have been used as casting feeds (not the best example as most of these have shorted).  My caster does not tumble them so the surface is as it comes (I think the investment is water blasted away).

[Hydrostat]

Lawrence,

I compared the prices of Shapeways and of a jewelry caster with wax printing service. If you're able to print your own 'castable resin' prints and only need a caster this sure is going to be cheaper as Shapeways - or did I miss something?

Cheers,
Volker

[Lawrence@NZFinescale]

Lawrence,

I compared the prices of Shapeways and of a jewelry caster with wax printing service. If you're able to print your own 'castable resin' prints and only need a caster this sure is going to be cheaper as Shapeways - or did I miss something?

Cheers,
Volker

You are exactly right.  Wax printers are expensive, so no matter who does it the price tends to be high. My caster offers that option, but the cost is prohibitive for general model making. The option you don't mention is someone such as myself who uses a resin printer in a commercial way.  Castings are typically much cheaper.  Quality is different and there are different constraints.  Detail resolution is typically better on resin prints, but there is more effort involved in optimising the parts for printing/casting.  Resin burnout can be as good as wax, but isn't always.  I get some castings that are poor (my risk - not supplied to customers), others that are good and many that are superb.  But there is some variability. At the present time casting equipment and methods are well established for wax - the influx of resin prints is relatively new.  As it becomes more mainstream, expect consistency to improve.

The hardware and materials to do this are easily obtained and inexpensive.  Expertise and casting services are a bit harder to come by.

Of course, in many cases a resin print will be adequate, so the casting process can be avoided altogether.  Personally, I like building in metal and for 1:64 locomotives I will likely stick to castings. For larger scale and static models resin may be better. You can get a higher level of detail in a print than you will in a casting as the extra step inevitably loses something.

Pic shows 16mm vavles and fittings drawn and cast by me on a customer's model.

[Bernhard]

Lawrence, your pieces look really good. But if you don't have your own 3D printer, you'll inevitably have to go to a service provider like Shapeways. And of course there is the question of how to arrange and connect the parts so that you get an optimal result. But I will discuss this directly with Volker.

Bernhard

[Lawrence@NZFinescale]

Lawrence, your pieces look really good. But if you don't have your own 3D printer, you'll inevitably have to go to a service provider like Shapeways. And of course there is the question of how to arrange and connect the parts so that you get an optimal result. But I will discuss this directly with Volker.

If I'm doing castings for others (and drawn by them) I generally ask for the CAD file and do the support/sprue, print and cast.  I have not found instructing others how to do this (in a way that I've found to be optimal) is very effective.  Not that it is particularly difficult, just more time effective for me to do it myself.

For the valves in the previous pic, the half sprue looked like the attached, and this is what would have gone for casting.  The green is support/sprue (There would have been some extra support added in the print software too).  Note that the mounting spigots are offset.  This makes printing very much easier, minimising support.  There are also some little fillers.  In theory these degrade detail, but in fact it is often better to take this approach rather than trying to support every little detail.  Supports cause problems of their own and a clean print with marginally less detail can be better than a fully supported model damaged when removing supports, which is harder to control.

Lawrence

[Lawton Maner]

Recover some of your investment by selling some of the brass castings as Steam Punk earrings.

[Lawrence@NZFinescale]

Recover some of your investment by selling some of the brass castings as Steam Punk earrings.

Way ahead of you there...

My wife has some Westinghouse pump earrings in sterling silver that I cast years ago :-)

Lawrence

[Ray Dunakin]

Nice work! The corroded beam is particular is very convincing.

[Hydrostat]

Well, I didn't find a rod of suitable diameter and so time and patience led to a result.









Oh, I forgot the color and pigments.

Cheers,
Showoff-Volker

[finescalerr]

Superb. -- Russ

[Lawrence@NZFinescale]

Showoff-Volker

Rightly so!

A perfect mix of casting, 3d print and basic materials superbly finished.

Lawrence

[WP Rayner]

Excellent work... it is entirely convincing. The finish is perfect!

[Barney]

SUPURB in every way + Excellence in finish and the build
Barney