Multiple layer etchings

[Hawk]

I wonder if anyone have anyone have tried etchings with multiple layers?

 

I am quite familiar with conventional 2-sided etchings, but would like to try a three layer design with both rivet detail and fold lines on the same side of the parts.

 

Something like this: 

 

 

I know that PPD and other etchers  offers  multi layer etching, but I would like to hear from someone who has actually tried this type of etching before diving too deep into the matter. 

 

Pictures of actual parts would have been lovely!

 

[The Nth Degree]

I've not heard of this, is this a new development? It would open up a lot of opportunities if this is possible in the materials used in etched kits.

[Gordon A]

I think Bill Bedford experimented with a three layer etch some time ago. I believe he was not happy with the crispness of detail that was available at that time.

Bill is a contributor on the forum, so may comment on your question.

 

Gordon A

Bristol

[Hawk]

I think Bill Bedford experimented with a three layer etch some time ago. I believe he was not happy with the crispness of detail that was available at that time.

Bill is a contributor on the forum, so may comment on your question.

 

Gordon A

Bristol

 

I was fearing that crispness could be an issue. As I understand it, you have to add a new layer of resist after the first etch, and then expose it.The raised detail will prevent a tight fit between the film and the resist, and my guess is that this could lead to stray light that might blur the exposure.

 

But I am pretty sure that the technique is used by Korean producers of ready to run brass engines, so I hope somebody knows how to work around the problems. 

[finelines]

It isn't possible to do the way you show it, but you can with the rivets on one side and the bend line on the other. It is actually 4 layers. Say you start off with 15thou. Layers 1 & 2 are etched by 3thou giving surface detail on either side. In practice it is normal to etch surface detail on layer 1, layer 2 has the bend lines only. Layers 1,2,3 and 4 all have the cut line. The end result is 12thou with rivets on the front and bend lines on the back.

 

The drawback is the bend line only penetrates the material by 3thou which gives you a very hard bend. Drawing the artwork requires mental gymnastics and test etches can get very expensive if you put lines on the wrong layer!

 

Roger

[jamie92208]

It should be no problem to produce that with normal 2 sided etching. As usual do your fold line in red and then put your rivets on in blue which will produce a half etched hole on the back that you can then punch out with a rive punch. If you have the right sized punch you will then get a nicely rounded rivet head on the surface of the material which in my opinion always looks better than the rivets that have been etched from the front as the shape of the punched rivet is more prototypical.

 

Jamie

[Hawk]

It should be no problem to produce that with normal 2 sided etching. As usual do your fold line in red and then put your rivets on in blue which will produce a half etched hole on the back that you can then punch out with a rive punch. If you have the right sized punch you will then get a nicely rounded rivet head on the surface of the material which in my opinion always looks better than the rivets that have been etched from the front as the shape of the punched rivet is more prototypical.

 

Jamie

 

Very good point. But I am a lazy bum and I am looking for any shortcuts available for a new mineral wagon project of maybe 20-25 wagons.  

I guess I will have to make some tests for punch-out rivet parts and see what speeds I can achieve.

 

But I see a lot of situations where multi-layer etchings could be a nice way of solving design problems, so more input on this type of etchings is welcome!

[jamie92208]

Very good point. But I am a lazy bum and I am looking for any shortcuts available for a new mineral wagon project of maybe 20-25 wagons.  

I guess I will have to make some tests for punch-out rivet parts and see what speeds I can achieve.

 

But I see a lot of situations where multi-layer etchings could be a nice way of solving design problems, so more input on this type of etchings is welcome!

I've done many thousands of rivets for Lancaster Green Ayre using a home made drop hammer that a friend made. I can achieve rates of 500 or more in half an hour which is a useful session, using a cutting mat as a base or the hardboard that the etch comes packed in. It is surprisingly quick.

The multi layer scheme sounds good but will probably very expensive. As t0 20 to 25 mineral wagons it is probably similar numbers of rivets to the work I did on the Greyhound bridge on Lancaster.

 

Jamie

[billbedford]

The way three part etching is done is to etch the deepest parts first to half the required depth, strip the resist, reapply the resist to those parts that are not to be etched and then re-etch to the full depth. The problems come with edges between the full and half depth layers. This edge is effectively etched twice, not only does it become rounded, but it is difficult to control the final position of this edge, especially where the full depth edge is narrow, e.g. if it is a fold line.

 

Some of PPD's output is to the jewellery trade where having soft edges to the deep etched layers maybe a design feature.