Lower cost (?) shiny metal parts

[Patrick Matthews]

First, kudos to those who can use handwork to create beautiful shiny metal parts from real metals. Me- I'm lazy, and will go to 3D Printing every time!

I have previously shown that 3D Printing can be used to create waxes for lost wax casting of real metal parts in a variety of alloys. As one might expect, it's not a low cost approach, especially for larger parts. 

 

But a modeller in the UK shared some results that offer another approach. He's working on a large scale Admiral's Barge, which features a polished brass stack and cowl vents. I designed the parts for him, and he procured them in the lowest price 3D Printed plastic, sintered nylon (grainy porous stuff, "fine detail plastic" would cost twice but be much easier to work with). Anyway, he filled the grain, polished that, then applied silver-bearing conductive paint. Next, brush plating of copper (which can be further buffed), followed in this case with brass plating. One can also brush plate nickel for the look of stainless or a fair-enough chrome, or invest in rhodium plating for a more convincing chrome.

 

Pictures show the raw plastic parts and the final product.

[Jim Rogers]

WOW

[wefalck]

Personally, I would turn simple parts, such as the smoke stack, from brass - depending also on the size, as brass is quite expensive.

 

However, complex 'free-form' shapes, such as cowl-vents are not that easy to machine from the solid. Here I see a lot of potential for the described technique. I wonder how well any putty would adhere to the nylon ? This could be critical for the longer-term stability of the parts.

[Patrick Matthews]

Nylon- smooth nylon is not so good for painting. But this is fused powder, so primer/filler paints lock on mechanically. I have had no problem at all painting it... but again, I would prefer the "fine detail" plastic for this sort of work, which takes painting just fine, even on its smooth surface.

[wefalck]

'Fine detail plastic', at least in Shapeway's parlance is acrylic resin, right ? Then it should take acrylic paint very well, just like Plexiglass does.

[Landlubber Mike]

Wow, that's very well done.  I bet 3D printing will revolutionize the model industry.  The detail you can get is fantastic, and my guess is that you don't have to worry about molds and the like.

[stuglo]

There is no end of innovative brilliance. Well done. But my poor brain has trouble assimilating these new technologies. Maybe for the "one-off" parts they will be commercially available

[Patrick Matthews]

2 hours ago, wefalck said:

'Fine detail plastic', at least in Shapeway's parlance is acrylic resin, right ? Then it should take acrylic paint very well, just like Plexiglass does.

It takes acrylic and enamel just fine. But for either (and Shapeways will not tell you this), you MUST post cure with UV light to complete the solidification process. Shapeways happily ships parts with an incomplete cure, and the traces of uncured resin WILL leech out and ruin the paint.

[turangi]

I wonder if the uncured parts could just be put out in the sun to cure? A strong source of UV light as my Dermatologist will attest.

[dvm27]

On 6/16/2020 at 3:01 PM, turangi said:

I wonder if the uncured parts could just be put out in the sun to cure? A strong source of UV light as my Dermatologist will attest.

My last Shapeways product was painted then immersed in epoxy resin. The paint leached into the resin, ruining the project. I just read where direct sunlight will cure the resin so I will leave the next one out over a sunny day, then paint it. Perhaps a varnish after to seal?

[wefalck]

We had this discussion here in another thread: why are people so keen to put layer over layer of stuff onto their parts ? What is the point of 'immersing' in epoxy resin after painting or to 'seal' it ? If its going to be toy that will be handled that makes sense, or if you want to change the sheen of the surface, but otherwise your paint is the surface treatment.

 

UV-induced polymerisation does have a time constant and can be sped up by adding more quantums of UV-light. The printing process just induces the process, but the cross-linking may not have completed yet once the part is taken out of the printer. That's why the parts are exposed again to UV-light, either in a special UV-chamber or to natural sunlight. It is important that the resin is fully cured before you cover the part with something that likely absorbs the UV-radiation, as pigmented paint would.

[dvm27]

1 hour ago, wefalck said:

We had this discussion here in another thread: why are people so keen to put layer over layer of stuff onto their parts ? What is the point of 'immersing' in epoxy resin after painting or to 'seal' it ? If its going to be toy that will be handled that makes sense, or if you want to change the sheen of the surface, but otherwise your paint is the surface treatment.

 

UV-induced polymerisation does have a time constant and can be sped up by adding more quantums of UV-light. The printing process just induces the process, but the cross-linking may not have completed yet once the part is taken out of the printer. That's why the parts are exposed again to UV-light, either in a special UV-chamber or to natural sunlight. It is important that the resin is fully cured before you cover the part with something that likely absorbs the UV-radiation, as pigmented paint would.

The Shapeways part is a roller coaster. After painting I am placing it in an epoxy resin cube and making a lamp out of it for a grandson. Lots of cool epoxy resin videos on YouTube with 3D printed parts inside.

[wefalck]

OK, that is a rather unusual application. Paint pigments, particularly those used for high-quality air-brush painting are so small that they seem to diffuse into other materials. I had an issue with that.

[Moxis]

Very clever indeed. Could it be possible to brush plate brass directly on the conductive paint? And which products he was using for brush plating?

[Bob Cleek]

3D printing may revolutionize modeling, but it somehow lacks the "organic" qualities of traditional materials and, perhaps, their archival qualities. There does seem to be a way, however, to get the accuracy and detail of 3D printing and the tradition and archival quality of noble metal parts. I think.

 

I'm curious if anybody has ever made metal parts by copper electroplating or electroforming? I've never done it, yet, but I've been checking it out on YouTube, which has a lot of information on what is a common jewelry-making process. Parts can be made with other metals, such as nickel or zinc. It would seem that one could make a part like a ventilator funnel out of dental wax (or a 3D printed part,) or a lot of them out of a mold made from a master pattern, and coat the wax pattern with a metal conductor, such as rattle-can spray zinc paint or India ink and graphite, and let the metal, say copper, build up on the outside. When a desired thickness is achieved, the wax can be melted away in boiling water or however one's creativity dictates and a hollow copper part is yielded. 

 

At least that's my fantasy for the moment. If anybody knows anything about the process, I'm all ears.

 

 

 

[Moxis]

Very interesting. It begins to be clear that you can electroform or electroplate items relatively easily at home with copper, but us ship model builders would need parts made of, or at least look like made of brass. So I think it is not possible to apply brass surface directly on conductive paint, but you need first to electroplate the part with copper.

But how about gold plating, can it be applied directly on conductive paint? Gold plating could be perfect on small items, it will look like polished brass, never oxidize and very thin layer of gold doesn't cost very much more than plating the parts first with copper and after that with brass.

[Bob Cleek]

3 hours ago, Moxis said:

Very interesting. It begins to be clear that you can electroform or electroplate items relatively easily at home with copper, but us ship model builders would need parts made of, or at least look like made of brass. So I think it is not possible to apply brass surface directly on conductive paint, but you need first to electroplate the part with copper.

But how about gold plating, can it be applied directly on conductive paint? Gold plating could be perfect on small items, it will look like polished brass, never oxidize and very thin layer of gold doesn't cost very much more than plating the parts first with copper and after that with brass.

I don't see why one couldn't use the process for brass as well, although I think it might be faster to build up thickness with copper and then brass, nickel, or gold plate the copper. In the days of real chrome trim on autos, I believe they plated the iron with copper and then the copper with chrome.  The plating process is the same for any metal, although the electrolyte mixtures may vary, I think. All the brass and copper fixtures on the old "boardroom models" of the great ocean liners were gold plated. It wasn't "realistic," as they were all painted on the prototypes, but it was a style in modeling at the time. 

 

[wefalck]

One has to distinguish between 'plating' and 'galvanoplastic'. Technically the processes are similar, but the product and the set-up is different.

 

Plating is, what is called a redox-reaction, whereby a metal is reduced from its soluble salt-form (broadly speaking) to the solid metal and deposited onto a metal or conducting surface. The redox-reaction can be purely chemical, then we talk about chemical plating, or it can be induced or supported by an electrical current, then we talk about electroplating. In the latter case most of the metal to be plated onto a conducting surface or another metal is dissolved from a solid electrode of that metal. The solution is thus continuosly replenished with that metal.

 

Chemical plating can be done with a variety of metals. I just googled and there are many commercial kits available on both sides of the pond. The process can be done as a dipping or a brush-on process. It normally requires a metal surface and with the right chemistry, most metal can be substrate for chemical plating, though aluminium probably not, due to it quickly forming oxide layer.

 

I regularly tin-plate etched or machined parts to give them a silvery look and to facilitate soldering. Often only the addition of flux is needed. Self-tinning solutions can be bought either ready made or as dry mixtures of the salts. They are also used by the fraternity that produces home-etched printed circuit-boards.

 

Electroplating also can be done with many different metal. The surface to be plated can be a metal or any other conducting surface, e.g. a graphite lacquer. Not all metals can be plated on every other, so nickel-plating on steel requires a first plating in copper. Again kits are available on the market for doing this in a bath. For repair purposes also so-called tampon-plating kits are available. Here a felt 'tampon' is soaked in a solution containing the metal to be plated with, a cable is clipped to the part and the tampon pressed onto the surface to be plated. These kits are availble easily from jewellers supply shops for copper, gold, rhodium, silver and some other metals.

 

Galvanoplastic is similar to electroplating, but a thicker layer (up to several miliimeters) of metal is deposited, with a corresponding need of electrode material. The model normally is non-conductive material, such as wax, plaster, wood or plastics that is made conductive by a graphite or silver lacquer. The process can be done as positive or negative. For the positive one a model of the object is made and then covered in the conductive lacquer. The final object is slightly larger than the model and some of the surface structures will have been evened out during the process of plating. Alternatively, a mould can be made from the object to be reproduced and the inside of the mould is covered with the conductive lacquer. The metal electrode and the salt solution is put inside the mould. The process reproduces every detail of the mould. It has been used since the 1840 to reproduce coins, statues and other metal objects.

 

Today, CNC machining opens up new possibilities of model and mould making. Models can be milled or 3D-printed from jeweller's wax for either lost-wax casting in brass or for galvanoplastic. I German colleague now prints 3D-models in wax and has them cast. And @Valeriy V here on this forum CNC mills cores for ventilators for his cruiser VARYAG from wax and deposits copper on them to form the ventilators. The wax is removed by heating. One can do this also with acrylic glass or styrene and dissolve the plastic in acetone. The negative process with a mould has the advantage, that several copies can be drawn, while for the positive process you need a new core every time.

 

As a kind of curiosum I should mention another process. I know an octogenarian in the UK, who sculpts the decoration for his model of the ROYAL OAK (1769) in Z-brush, has them 3D-printed in acrylic resin and then vacuum-plated with gold. This process, called 'sputtering' is a preparation step normally used in electron microscopy, when you want to examine fine surface details. In EM only a one atom layer of gold is required, for plating you need a bit more, of course. He is lucky that his sun is a researcher with access to the facilities. The process is not cheap because of the machine-time and the amount of gold needed. However, the results are just phenomenal - beats every carving with respect to detail and definition ... well, not exactly a low-cost option, which was, what this thread was about

 

[Roger Pellett]

At least 10 years ago there was an article in the Nautical Research Journal about the construction of a model of the gunboat USS Bennington.  I believe that there was a connection to the San Diego Maritime Museum.  The author formed cowl ventilators by electroplating a metal plug that he had cast.  The plug was cast from a metal used by gunsmiths to cast impressions of gun cylinders.  This metal (maybe called Cerro?) has a melting point close to the boiling point of water.  After electroplating, the plug was immersed in boiling water leaving only the electroplated shell.

 

Roger

 

 

[Bob Cleek]

Thanks, wefalck! That adds some more information to it all.  Every bit counts. One of the interesting things about modeling boats, and building full-sized ones, is that so many different crafts and technologies have to be explored and, to one extent or another, mastered. I find it fascinating. (Other's don't and buy kits. There's no accounting for taste.)

[wefalck]

There are many low-temperature alloys that could be used for this purpose, such as Wood's Metal, Rose's Metal etc. Melting points are somewhere between 50°C and 90°C, so that they could be liquidised by boiling in water. However, I am not sure, whether they wouldn't be contaminated by the plating metal ions and then change their melting point. They are also rather expensive compared to jeweller's wax for instance. I think I would rather go one of the above mentioned methods, than using one of the alloys.

[Roger Pellett]

It certainly worked for this guy.  The alloy that he used is readily available from gunsmith supply houses such as Brownell’s and I believe that the material is reusable.

[wefalck]

I have not doubt that it works. The point was that there are cheaper materials and that there is a risk that the alloys change their properties due to contamination from the plating metals. So they may or may not be re-useable. But one would need to try.

[jackieofalltrades]

On 7/24/2020 at 10:13 PM, Moxis said:

Very interesting. It begins to be clear that you can electroform or electroplate items relatively easily at home with copper, but us ship model builders would need parts made of, or at least look like made of brass. So I think it is not possible to apply brass surface directly on conductive paint, but you need first to electroplate the part with copper.

But how about gold plating, can it be applied directly on conductive paint? Gold plating could be perfect on small items, it will look like polished brass, never oxidize and very thin layer of gold doesn't cost very much more than plating the parts first with copper and after that with brass.

gold plating would need to be plated with nickel first

[grsjax]

Copper can be plated directly on to non-conductive surfaces.  The process is called electroless copper plating.  It is a fairly simple process but does require the use of formaldehyde as a reducing agent.  Using this process a thin layer of copper can be plated over almost any surface.   Electroless copper plating is used to make printed circuit boards.   The advantage is that the metal layer is uniform over uneven surfaces including inside holes.  plated items can be used as is or as a base for electroplating with other metals like nickel.

BTW brass electroplating is possible.  Caswell sells a kit for it.

 

EDIT Here is a PDF of a process for electroless copper plating.  http://www.nmfrc.org/pdf/p0295g.pdf  This process can be done with chemicals available on ebay and Amazon.  WARNING  Sodium Hydroxide and Formaldehyde are not chemicals you want to be careless with.  Wear gloves, eye protection and a mask when handling them.  Sodium Hydroxide is a powerful corrosive base that can cause a lot of damage to your body.  Formaldehyde is a poison.  Treat these chemicals with respect.  Work carefully and always work in a well ventilated space.