Experimental Plug Track: 3D-printed, CNC-milled, laser-cut

[Martin Wynne]

@James Walters @Charles Orr

Hi James, Charles,

Good to chat last night -- many thanks. I think I have decided to get myself a laser cutter, although I shall be looking for some advice on which one! Thanks Charles.

Thanks for the better photo. I've been thinking about your ideas. The pip gap on the end of the timber is easy to do -- IF applied to the Templot kerf line. You could set the kerf width to zero if it is important to use the actual timber outline. We need names for this stuff so that it can be dimensioned in the dialogs. I have provisionally called the pip a "nib". *

Your gapped semi-circles are trickier. I have provisionally called this device a "gate". How does this look? Dimension a can be consistent and set as narrow as required to break easily. Two breaks, so could be narrower than the nibs? Dimension b is difficult to control because it is affected by the timber spacing. b would be variable:

Also straight cut lines are much easier than curved.

Just a first stab at the idea.

*p.s. -- I had the word "pip" in mind for something else:

(3D-printed bases for Exactoscale/C&L chairs)

cheers,

Martin.

 

[James Walters]

Martin,
I think you've come-up up with a typically practical arrangement there. An option to de-select the gate feature such that the waste drops out at the cutting stage might also be of benefit.
In my own case, I wanted to retain the waste during the building phase as it offered somewhere to place the chair labels. I suspect that for many they wouldn't be necessary. At the time I was thinking about something which might be a stepping stone to help a new-comer to turnout building - I still think there is a use case for some, because I still am a newcomer!

Also, second the motion of the 'nib' naming.

 

[Martin Wynne]

@James Walters

Hi James,

The easy way for identification of timber numbers, chairs, etc., is the same as for 3D printing and CNC milling, and the same as we have been doing since the beginning of Templot for riveted plywood rivet centres and general trackbuilding -- print a paper template on school tracing paper and lay it on top of the work. Inkjet printers work fine on tracing paper provided you feed single sheets at a time:

More info: https://85a.uk/templot/archive/topics/topic_283.php

Since writing the above 15 years ago, we now also have the option of adding the symbols to the printed templates:

More info: https://85a.uk/templot/club/index.php?threads/tip-of-the-day-construction-symbols.451/

With the benefit of a boiled egg for breakfast, there is an easier solution for the "gates" which is independent of timber length in addition to the timber spacing (easier to program):

The "gates" gaps could be set to any required width, and/or omitted if not wanted (or only one of them omitted).

cheers,

Martin.

 

[James Walters]

That's a great solution. There should be more boiled eggs in the world.

Agreed re. the annotations native within Templot. In my case above I'd removed only the timber vectors from Templot and was adding my own annotations to aid my personal naivety whilst experimenting.
That being the case the gates could be done away with, and the scrap pieces left behind during the cutting process.
However, there is still a valid use case for gates retaining the scrap, in that it prevents the waste dropping out onto the laser bed which can be a faff, especially when small bits drop into the voids on a honeycomb machine bed.
I routinely include 'nibs' on lasered parts for this very reason - it's much easier to pop scrap into the bin directly from the fret and it helps to keep the machine tidy.

 

[Martin Wynne]

@James Walters

Hi James,

Another day, another tick-box.

The "gate" gaps are now called "snibs" (a window latch):

Set any/all of the 4 snib spaces to zero if not wanted. Nib length is the distance away from the timber.

Defaults are my best guess?

All ignored in 3-D files.

cheers,

Martin.

 

[James Walters]

Fantastic! Can't wait for the next update to have a play.

 

[Martin Wynne]

@James Walters

Hi James,

First try in the DXF:

Trying to replicate the cutter kerf with line thickness in CAD.

It needs more thought where timbers are significantly shoved. I will look to add some additional controls on the shove timbers dialog, but some manual editing might be unavoidable for complex timber-shoved formations.

I will post some DXFs for you to try later.

cheers,

Martin.

 

[Hayfield]

Just a first stab at the idea.

*p.s. -- I had the word "pip" in mind for something else:

(3D-printed bases for Exactoscale/C&L chairs)

cheers,

Martin.

Being one of the few who see the existing Exactoscale P4 Turnout (& Crossing ) bases as a terrific building aid, which both saves a lots of time, possibly a bit of money but more importantly builds a far more sturdy turnout or crossing. Using the range of standard and special chairs to compliment this terrific advancement in railway modelling

As a stop gap this could be a a viable system for those wishing to get some building done

This system works equally well with turnouts in EM gauge, and with minor adjustments crossings and slips. As for 00 gauge it certainly opens up a whole new building option

Martin made a comment that I will have a go at building anything, If anyone could print me a base with or without pips to try out the idea I am happy to oblige

 

[Martin Wynne]

Martin made a comment that I will have a go at building anything, If anyone could print me a base with or without pips to try out the idea I am happy to oblige

Hi John,

Unfortunately the "exactopips" option isn't currently available in Templot. It was something I had a look at before I got the resin printer, when I was trying to do the whole thing using FDM printing.

I'm intending to resurrect the idea at some stage. The difficulty is that the Exactoscale/C&L chairs hold the rail canted at 1:20, whereas the plug track chairs hold the rail vertical. So any form of hybrid construction is going to be difficult. It needs to be one or the other all-through.

My objection to canted model rail is that it's an utterly daft idea which doesn't work -- plus the difficulty it causes in gauging during model construction. To hold the rail at 1:20 through the various bends and twists in pointwork would require heavy cast iron chairs, not flimsy bits of plastic.

Even typical sharp model plain track curves are difficult with loose plastic chairs. If the rail is canted round a curve, the head of the rail will be running along a different radius from the foot of the rail. That means one of them will need to be longer or shorter than the other. Not by much, but deforming metal rail so that the head is stretched longer than the foot demands far more force than can be applied by small plastic chairs. What happens in practice is that the rail refuses to be canted and springs back vertical on all but the gentlest of model curves. The prototype gets round this problem by gripping the rail tight in heavy cast iron chairs weighing around 50 pounds each, held down with several large screws or bolts. Plastic model chairs don't stand a chance. Which is why Templot plug track uses vertical rail throughout, and will continue to do so.

What makes the Exactoscale/C&L thing even more irritating, is that no-one has ever been able to look at a 4mm or 7mm model railway from any normal viewing distance and detect whether the rail is canted or vertical. You might think that you could look at the ends of the check rails -- but on the prototype check rails are always vertical, not canted.

Long-term readers will have detected a bee in my bonnet.

cheers,

Martin.

 

[Hayfield]

Martin

To backup your irritation is that most roller gauges and all 3 point gauges I come across hold the rail too tight (vertically) and when the chairs have relaxed back into their orientation the gauge has narrowed. Early C&L and the latest ones allow for head rotation

The light brown sprue is an Exactoscale sprue, the dark brown with square holes is a new style C&L sprue

I guess the design of a square hole is to aid production rather than hide a rivet, I must try one on an Exactoscale track base

By the next zoom meeting I will try sticking a few chairs to one of the track bases you have produced and report back

 

[Paul Boyd]

To backup your irritation is that most roller gauges and all 3 point gauges I come across hold the rail too tight (vertically) and when the chairs have relaxed back into their orientation the gauge has narrowed.

On that point, when I was building P4 track using Exactoscale and "old" C&L chairs it took me ages to find/work out why the gauge seemed to keep narrowing. It was probably Martin that put me right...

 

[Martin Wynne]

@James Walters

Hi James,

First try in the DXF:
View attachment 5158

View attachment 5159

Trying to replicate the cutter kerf with line thickness in CAD.

It needs more thought where timbers are significantly shoved. I will look to add some additional controls on the shove timbers dialog, but some manual editing might be unavoidable for complex timber-shoved formations.

I will post some DXFs for you to try later.

cheers,

Martin.

@James Walters

Hi James,

Looking at that again it is fine for single turnouts, but is going to be a minefield for complex formations. Even ordinary double track is going to fall to bits:

I think we possibly need a range of options for this function (more tick-boxes!):

The question is -- which one should be the default setting for cutting a kerf line? Or something else? Do we need an option to change the setting individually for each end of each timber?

Also, if it is undesirable for loose bits to remain on the laser bed, presumably something similar will be needed for the sockets? Without affecting the bash fit.

Is it reasonable to assume that everyone with a laser-cutter will have some CAD software and an ability to use it, to edit the Templot DXFs? It's my firm intention that it should be possible to make plug track using the files from Templot without needing any CAD software or skills. I'm confident I can achieve that for FDM printing, and hopefully also for CNC milling.

But I'm beginning to wonder for laser-cutting. The output at present can put a kerf-adjusted line around every timber and socket. But if it is laser-cut as-is, it's going to fall apart on the cutter bed and how will you know which timber goes where? Is there any backing sheet which the plywood can be attached to, which is unaffected by the laser beam?

I know some users of plywood bases put a linking web somewhere between the timbers. I put the sprues option on the timber ends so that they could be easily trimmed off after tracklaying without distorting the timbers. But they have similar problems to the above in complex formations. Some users put a web under the rails, where it is very difficult to remove after tracklaying without distorting the track, but if not removed it makes ballasting very difficult and destroys the realism of bullhead track -- no webs between the timbers here:

A noticeable detail in that photo is the clean square end on the check rail. One of the advantages of the loose-jaws option is that you can have such neat flat rail ends, because the chairs never get threaded onto the rail.

cheers,

Martin.

 

[Hayfield]

On that point, when I was building P4 track using Exactoscale and "old" C&L chairs it took me ages to find/work out why the gauge seemed to keep narrowing. It was probably Martin that put me right...

Paul

My own take on things which I have concluded by talking to both the designer and 3 of C&L owners, plus buying products including gauges of various age and design, is that at the beginning, tools were made available to accurately build trackwork

Then a commercial decision to expand the use of EM specification common crossings to include 00 (DOGA fine) without explaining the downside/need of this gauge in having to re-gauge back to back measurements. Failure to state the exact gauge or rather calling it an 00 gauge roller gauge

Then a large order for roller gauges (00,EM &P4) with deeper slots which is fine for copperclad construction, not for chairs with a cant.

Full marks to Phil, he bit the bullet, all roller gauges (OO, EM & P4) now allow the rail to rotate and the 00 roller gauges have 1,25mm flangeways. My plea for roller gauges not to have inbuilt check gauge has fallen on deaf ears, they have flats milled on now and check rail gauges are available (not promoted) as they are part of the 00SF range

In short I believe track builders are short changed by the trade

 

[Tony W]

I also think part of the problem is educating modellers new to track building how a set of track gauges should be used. The dimension most modellers are familiar with is the nominal track gauge. The wheel / rail relationship is, or should be part of a complete set of standards if reliable results are to be achieved.
Regards
Tony.

 

[Hayfield]

I also think part of the problem is educating modellers new to track building how a set of track gauges should be used. The dimension most modellers are familiar with is the nominal track gauge. The wheel / rail relationship is, or should be part of a complete set of standards if reliable results are to be achieved.
Regards
Tony.

Tony

Modellers have an excuse

Retailers don't

 

[James Walters]

@James Walters

Hi James,

Looking at that again it is fine for single turnouts, but is going to be a minefield for complex formations. Even ordinary double track is going to fall to bits:

View attachment 5164


I think we possibly need a range of options for this function (more tick-boxes!):

View attachment 5165

The question is -- which one should be the default setting for cutting a kerf line? Or something else? Do we need an option to change the setting individually for each end of each timber?

Also, if it is undesirable for loose bits to remain on the laser bed, presumably something similar will be needed for the sockets? Without affecting the bash fit.

Is it reasonable to assume that everyone with a laser-cutter will have some CAD software and an ability to use it, to edit the Templot DXFs? It's my firm intention that it should be possible to make plug track using the files from Templot without needing any CAD software or skills. I'm confident I can achieve that for FDM printing, and hopefully also for CNC milling.

But I'm beginning to wonder for laser-cutting. The output at present can put a kerf-adjusted line around every timber and socket. But if it is laser-cut as-is, it's going to fall apart on the cutter bed and how will you know which timber goes where? Is there any backing sheet which the plywood can be attached to, which is unaffected by the laser beam?

I know some users of plywood bases put a linking web somewhere between the timbers. I put the sprues option on the timber ends so that they could be easily trimmed off after tracklaying without distorting the timbers. But they have similar problems to the above in complex formations. Some users put a web under the rails, where it is very difficult to remove after tracklaying without distorting the track, but if not removed it makes ballasting very difficult and destroys the realism of bullhead track -- no webs between the timbers here:


View attachment 5166

A noticeable detail in that photo is the clean square end on the check rail. One of the advantages of the loose-jaws option is that you can have such neat flat rail ends, because the chairs never get threaded onto the rail.

cheers,

Martin.

Hi Martin,

To answer your questions in reverse order:

3. It is reasonable to assume most (if not all) laser users will have access to CAD software. That is to say the laser driver software (I use Lightburn) has some CAD functionality, and it is not difficult to adjust/delect vectors within that environment. I suspect that most (if not all) will also be using CAD software such as AutoCAD or Fusion360 etc. which they are using to create their own files. In which case they are probably more likely to use that to adjust the .dxf file Templot produces.

2. I hadn't given thought to the bits dropping out of the chair sockets when we spoke before, but these fiddlesome bits are the most likely to drop into honeycomb bed holes. But to attach them with nibs would likely require a modification to the chair plugs, as the remaining 'half-nib' which is left behind after breaking-out the waste will be difficult irksome to sand away.
I hope that makes sense, here's how I suggest the chairs might need adapting:

You will see I've added a clearance groove up the end of the plug.

I think that to modify the chairs to suit perhaps a minority of users with as laser might be to the detriment of the FDM/Milled plug track and if I were you I'd discount chair modification.


However, having just written that, and produced a drawing of a modified chair, I'm now having second thoughts, the half-nib would almost certainly compress - it might even help the bash-fit quality of the plug.
So, after all that I'd say a single "nib" in a chair socket would be a good way to go. Preferably on the 'long side' to avoid compressed nib residue affecting the gauge.

1. Given my answer (3) above, I'd say option 1 of the five you present would be the most useful and the one which I personally would like to see as a default, with the option to switch it off to leave an option 3 situation. If there was the facility to adjust the length of the upper vectors which cross I should think all bases would be ticked. It would be no hassle whatsoever to make further adjustments to these in CAD post Templot if someone chose to do so.
I'd be happy to do some testing, I can recreate what you have proposed above in CAD or can cut something from a test file which you produce.


With regard to the timbering falling apart when lifted from the laser bed, there are a few simple solutions, I'd suggest that either of the following would do the trick.
A. Draw a rectangle around the timbering, so that in-effect becomes the fret, The additional nibs we are discussing here keep the whole thing together, and importantly allow the fret to be snapped away either after the timbers have been glued down or the turnout built. The rectangle could be produced in Templot, or drawn in the laser software mentioned above (3).

B. Stick a line of making tape over the plywood across the timbering after it has been laser cut to keep all the bits together.

As I mentioned before, I think Templot currently has all that is required for laser cutting to be useful. And that most people doing the laser cutting themselves will have the skills to achieve what they required with everything as it is. Personally though, I'd find the nib function really useful and I'm sure others would too.

Finally, I couldn't agree more regarding sprues between the sleepers/timbers.

I hope the above is clear/useful,

James

 

[Martin Wynne]

If there was the facility to adjust the length of the upper vectors which cross I should think all bases would be ticked. It would be no hassle whatsoever to make further adjustments to these in CAD post Templot if someone chose to do so.

@James Walters

Thanks James for the detailed reply.

A setting to adjust the length of those vectors is already there:

For the sockets, I think nibs in the corners might be the best option, because there is already a setting to increase the corner relief on the plugs (for CNC-milled sockets with radiused corners):

Would 4 nibs be too many to push out, or do you just make them smaller and weaker?

I'm getting a bit nervous about talk of most users editing the Templot DXFs. I know folks have been doing that with the DXFs for 20 years, but they haven't been mentioning Templot plug track in the same breath. If lots of technical posts appear on the forums and YouTube about CAD editing of Templot Plug Track files, I just know it is going to put a lot of potential users off the whole idea. I'm getting frequent emails along the lines of "I would love to try building the plug track, but I'm a complete computer numpty". I keep reassuring them that if they are capable of printing paper templates from Templot on a 2D printer, they will be able to make plug track on a 3D printer.

cheers,

Martin.

 

[James Walters]

I think those adjustments are all that is needed, when the time comes I'll have a play.


I understand your concerns Martin re laser cutting, and I wouldn't want to add to any confusion. Hence why I've not previously mentioned my experiments on the web.
When I mentioned most users, I was referring to most using a laser cutter. These are likely to be the people who fiddle with the .dxf's - who on the whole are less likely to be computer numpty's - but more likely to post about about their experiments.

I don't know what to suggest really, as it's my guess that those who feel confident to experiment with the .dxf's will always do so. In the same way that someone with confidence in 'traditional' techniques might have cut-up and curved a paper template in the way things were done pre Templot.

I totally agree, and would defend that the plug track concept can be produced successfully with a 3d printer with no more computer skill than using an office printer. That is the joy and genius of the system which you have created.

Best,

James

 

[Phil O]

Laser cutting is not an area that I have much knowledge of, but I believe that it's possible to partially cut/burn away some of the timber, like a half-etched tab, when etching brass or nickel silver. If that's indeed possible, would that help in creating a gap under the rail, when using under the rail webs.

 

[Martin Wynne]

Laser cutting is not an area that I have much knowledge of, but I believe that it's possible to partially cut/burn away some of the timber, like a half-etched tab, when etching brass or nickel silver. If that's indeed possible, would that help in creating a gap under the rail, when using under the rail webs.

@Phil O

Hi Phil,

I think that's done by changing the colour in the DXF file. I'm not too clear how you burn away an area, rather than the normal process of cutting a thin line. Presumably an area 1mm wide would need 5 lines 0.2mm wide, at half-power. Or maybe the beam-width (focus) can be adjusted while cutting. I doubt the depth can be set with much precision, although it is presumably repeatable on the same material with the same settings. Over to James.

What I do know is that adding such tabs in Templot along the existing rail lines is out of the question, unless you can find me an extra year or two of coding time. Such half-tabs would need to be created separately, although they could be placed under the rails manually if desired.

Anyone who is using under-the-rail tabs at present is editing the DXF file in CAD to achieve that.

cheers,

Martin.