Experimental Plug Track - file exports for 3D printing

Martin Wynne

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This is a continuation from previous topics about the 3D printed track in development.

To jump forward to details of functions now available, go to this post:

https://85a.uk/templot/club/index.php?threads/229/post-2028



Very pleased with the first results from the Elegoo printer. :)

The CAD:

resin_chairs1.png

Straight off the printer -- 4mm scale (difficult to photograph without any paint):

resin_chairs2.jpg


resin_chairs3.jpg


resin_chairs4.jpg


resin_chairs5.jpg


resin_chairs6.jpg


I will write some more after a meal.

cheers,

Martin.
 
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Martin Wynne

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And the verdict is?

I used the bog-standard default slicing settings for the Mars 2P in the Chitubox software. I was tempted to try changing things for finer detail, but decided to leave that until I know what I'm doing. :) In the event the result was very good, so it was probably a wise decision.

The end 2 chairs in each row failed to print. I got only the support pyramids with no chair on top. But the 3rd chair from the end in each row printed perfectly, and all chairs in between.

* This suggests that the UV illumination is not even, and drops off suddenly at each end of the build area. This probably means that only the middle 80mm square area of the build area can be used for fine-detail models. This may be on my machine only of course (Mars 2P).

* edit: see next post.

I found the missing bits of half-printed chair lurking in the resin, partly stuck to the FEP film, but easily removed. This surely affects the idea of leaving the resin in the tank unfiltered for next time? They would clearly impede the first layer of the next print. So if doing that, it would be important to check that the previous print was fully formed with nothing missing.

I set the dimensions in Templot to match Exactoscale code 75 steel rail, and it worked out very well. The chairs can be threaded onto the rail without difficulty (much easier than threading Exactoscale moulded chairs), but then hold the rail vertical (as intended) with no wobble or play. As you can see in the photos, there is no infill below the key (this is an option in Templot), so that the rail is held entirely by the key against the rail web as on the prototype, and not by means of the rail foot:

index.php


index.php


The plug under the base of the chair gives it a lot more "heft" than other 4mm chairs (if you can use such a word for such a tiny thing) so that there is no distortion and the chair sits flat after threading (unlike Exactoscale chairs).

Dimensionally there has been about 1-1.5% shrinkage. I don't know where in the process this occurs, but I suspect in curing. The finished sizes are:

chair length: 4.79mm. Prototype 14.5" = 4.83mm (Exactoscale 5.08mm, noticeably larger than scale alongside these).

chair width: 2.64mm. Prototype 8" = 2.67mm (Exactoscale 2.79mm, noticeably larger than scale alongside these).

plug length: 4.12mm. Design 12.5" = 4.17mm.

plug width: 1.97mm. Design 6" = 2.00mm.

Some allowance for the shrinkage may need to be included in the files. On the other hand, the shrinkage on the plug is maybe welcome to ensure a clearance in the sockets. But we don't want too much because they will be setting the gauge. Some final tweaking of the dimensions is likely to be needed.

I'm attaching the .ctb file below for Charles and anyone who wants to try repeating my antics in an Elegoo. But you won't be able to make any actual use of the chairs until we have some timbers with matching sockets.

(This file is ready to use on the Elegoo printer, it is already sliced and ready to go -- just save it onto a USB stick.)

p.s. I'm using the "ABS-like" Elegoo resin. Results with the standard resin may differ. Colour grey, results with other colours may differ.

cheers,

Martin.
 

Attachments

  • _32_chairs_s1_exacto_rail.ctb
    1.5 MB · Views: 76
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Martin Wynne

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I would be very grateful if you or any one else could let me have some stl files of chairs/sleepers etc to try out and experiment with print settings.
I'm modelling in 4-SF.

Hi Charles,

See my previous post for the CTB file of the chairs with plugs, ready for printing.

Here's an STL file which you might like to try. 8 sleepers in 4-SF / 00-SF with S1 chairs for Exactoscale/C&L rail:

stl_for_charles.png


The offset webbing is to indicate which side is MS. it is 1mm square.

I have never printed this, so I've no idea if it is any good. :)

p.s. ignore the message in Chitubox that it is too small. Every single thing I've tried has been allegedly "too small".


cheers,

Martin.
 

Attachments

  • exacto_rail_8_sleepers_4_sf.stl
    2 MB · Views: 70
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Charles Orr

Member
Location
Leicester UK
Hi Martin,
I've set the printer up and the first print is excellent. I've attached some photos below.
I'm very pleased with the quality.

20210318_155654.jpg20210318_155705.jpg20210318_155422.jpg20210318_155510.jpg20210318_155607.jpg
I'll have a go at the stl file tomorrow.

Charles
 
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Martin Wynne

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Hi Martin,
I've set the printer up and the first print is excellent. I've attached some photos below.
I'm very pleased with the quality.

View attachment 643View attachment 644View attachment 645View attachment 646View attachment 648

Charles
Hi Charles,

Those look great! I'm glad you're pleased. :)

Did you get all 32 chairs, or lose some at the ends of the strip?

Your close-up photography is better than mine, and for the first time I can see the square tops and random angle on the chair screw heads. Well on two of them anyway:

charles_chair.jpg


I notice that you've lost one corner of the chair base. That happened to me in handling, too. I will look to thicken it up a fraction. It's prototypical for an occasional chair, but not too many.

I can also see some layering from the slicer on the side of the base. I set the standard 0.05mm Z layers in Chitubox, which matches the X-Y pixel resolution for the UV image. It's possible to go finer for the layers only, some tweaking experiments are called for. On the other hand, the layers will probably vanish under the paint. The chairs are infuriatingly difficult to photograph unpainted, even though the raw resin seems quite a dense grey.

I've been working for the last couple of days on getting a direct STL export from Templot, instead of needing to convert from DXF. It's now beginning to look promising, after a rubbish start.

Thanks for posting your results.

cheers,

Martin.
 
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Martin Wynne

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I'm pleased to report that Templot can now export 3D files in STL format in addition to DXF:


stl_ex_templot.png


stl_ex_templot_pad.png


This removes one bottleneck from Templot 3D printing which has been bothering me for some time. It's very difficult to find a free or low-cost CAD package which supports 3D DXF files. 3D Crafter seems to be the only one, but it's very clunky and buggy and seemingly no longer being developed. All the others are quite expensive. Now you don't need one.

It's not all good news. As far as I can find the STL format does not support nested blocks. It's a single flat fully exploded file -- unless anyone knows otherwise?

This means that STL file sizes are massively inflated compared with the corresponding DXF file:

The above in DXF: 750 KB
The above in STL: 7900 KB

More than 10 times larger.

Also the STL files from Templot (just like the ones converted from DXF in TurboCAD) are not solid objects ready for slicing. For that they first need to be "repaired" in a mesh editor program, such as this free online tool:

https://www.formware.co/onlinestlrepair (others are available).

The above trackpad shot (EM gauge) shows that full 3D resin printing of complex pointwork is not going to be very practical on a small printer such as the Mars. The purple outline is the effective size of the Mars build plate. A large formation would be a jigsaw of small pieces to be aligned and fitted together.

But I'm not planning to do that. The timbering will be either FDM (filament) printed, or laser cut from plywood. Only the plug-in chairs need to be resin printed, and they can be bunched together in a single print (STL file size permitting). For FDM printing the build area is much larger at 200mm square on my machine, but that still requires some careful planning of jigsaw pieces to create a full pointwork formation.

As you can see, I still have a long way to go. Only the ordinary S1 chairs are finished. The L1 bridge chairs so far have a base and keys, but no chair jaws. All the other special chairs are also unfinished.

But with STL exports done I can now see the way forward to a usable system. Threading chairs one at a time, and then plugging the rail vertically onto a base, has got to be so much easier than feeding the rail into a base from one end. Especially for complex slips and crossings. And with Wayne Kinney's new cast crossings likewise plugged straight onto the base, we should have a new trackbuilding system which anyone can use.

Dream on -- still a long way to go. :)

Martin.
 
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Martin Wynne

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Thinking about gauge widening and angled chairs on points, would this be dealt with on the sleepers?

Hi Tom,

Yes, the individual chairs will be matched to the standard REA drawings as far as possible. The sockets for them in the timber will determine the angle and position of them, and thus also set the gauge.

I haven't given any thought to gauge widening at this stage -- one thing at a time. :) It could be done as part of the shove timber functions. It can't be set from the turnout size alone, because it depends to what extent they are curved, and in which direction. Also the track standard plays a part -- P4 needs gauge-widening where 00 doesn't. So it's difficult to see it becoming fully automatic.

cheers,

Martin.
 
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Martin Wynne

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This afternoon's entertainment was to get the chair plugs into the 2D:

plugs_2d.png


I have put a 1/2" break across the plug corners for a clear fit in the sockets. For the bridge chairs I have increased the base overlap, so that the sockets do not get too close to the edge of the timber.

The plugs and screw centres aren't really needed in 2D, but the only way to check that the code is putting every one in the right place is to draw them on the screen.

One more tiny step on what is going to be a long journey.

Martin.
 
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Martin Wynne

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Hello Martin,
Is there a particular reason why you are using square/rectangular sockets for chair location? Would a round socket allowing them to rotate not enable one to adjust a chairs position indefinitely without restriction? Or am I missing something really obvious?

Hi Trevor,

The angle of a chair on a timber is determined by the turnout geometry, there isn't any option for it to be at some other angle.

The idea is that the timber base is 3D printed, or laser cut from plywood, and the chairs plug straight in to the exact position, requiring no gauges or other adjustments.

But I'm not printing the bases or the chairs -- you are. :)

If you want to edit the DXF or STL files to use round plugs and sockets that's up to you. There will also be options in Templot to change the size of the plugs, or have no plugs, or change the chairs to some other design, or flat-bottom baseplates, or whatever you want.

But don't hold your breath. I have a long way to go, and I'm distracted by other things. It's high time I got the 227a update finished and released, it's got a lot of new stuff in it which some folks are waiting for. On top of that I still have the migration to the new server unfinished, and no archive of the old forum yet ready. Strictly speaking getting the Elegoo printer was a mistake, as it's a fresh distraction and has now added a re-write of the 3D output to the pile of other unfinished stuff I have waiting. Templot is supposed to be my hobby, it's not supposed to feel like work. :) But I will get round to everything in the end.

cheers,

Martin.
 
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Martin Wynne

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If I might ask, how are you eliminating the rail inclination? Are you leaving the bottom of the rail in the same position and pushing the top out, pushing the bottom in or rotating the rail so the bottom moves in and the top moves out?

Also, are you leaving the base full size or are you reducing its length at all?

Hi Andy,

The rail gauge-face is the datum, and all the chair dimensions have been referenced to scale from there. So I guess that means I have moved the rail foot inwards to bring the rail vertical.

It's a stylised geometrical design, with some intentional changes. For example the key is tapered at both ends for easier threading, and contacts the web fully in its centre only (the prototype key should be wedge shaped). The base edge thickness is increased to avoid damage in handling and allow at least two 0.05mm slicer layers (the scale thickness would be only 0.08mm or 3 thou).

The chair base dimensions are as the drawing, I'm not clear why you think I might have reduced the length?

cheers,

Martin.
 
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Wayne Kinney

Member
Location
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Hi Guys,

It's really nice to see this thread, the work I've seen so far is fantastic!

It certainly reminds me of my last 12 months of the research and challenges in developing my Finetrax Easy Build turnout kits, which use a similar process.

Martin, I printed the STL's you uploaded on my machine, using the same resin mix I use for my Finetrax bases. They also went through the same post processing.

print01.jpgprint02.jpgDSC05623.JPG



Your chairs look great and fit the EMGS bullhead rail well. I did notice the rail leaning 'inwards' a bit, which I believe is because you left the gap underneath the keys.

I'm looking forward to following this thread and contributing where I can as I've got quite a bit of experience on this now ;)

Thanks,
Wayne.
--------------------------
Home of FinetraX Easy Build Turnout Kits - www.britishfinescale.com
 
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Last edited:

Martin Wynne

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@Wayne Kinney

Hi Wayne,

Welcome to Templot Club. :)

Good to see you here -- how much of Templot is in your kit designs?

Your prints look good. Can you tell us a bit about your printer and resins? I know you regard it as something of a trade secret.

Filling below the keys, so that the rail foot is firmly located, will be an option in Templot:

dxf_key_fill.png


It's off by default because that's prototypical. It's also possible to "beef up" the chair jaws overscale, to make them stronger. That's likely to be needed in the very small scales, 3mm etc.

The rail I have here (Exactoscale steel bullhead) is standing vertical in the chairs. If yours is leaning it may be due to variations in the rail web section -- if you turn it round does it lean the other way? There will an option to fine-adjust the track gauge for any rail-lean by moving the chair jaws relative to the chair base.

All this is still a work-in-progress. I haven't had a chance to get much done recently -- I want to get back to it soon. :)

cheers,

Martin.
 
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Wayne Kinney

Member
Location
UK
Thanks Martin,

I use the 2D DXF's from templot as the basis for the bullhead stuff. I import these into Solidworks, and work from there. I do modify a couple of things from the template, mainly gauge widening around the switch. I also use the exported DXF as the basis for the cast crossings.

Yeah, I don't want to say too much on my chosen machine and resins, but it does use a similar process and to the same resolution and layer height. The output from your machine should be about the same.

I think what you are working towards is amazing, to be able to export a 3D CAD model out of Templot that can be directly 3D printed, it's a fantastic prospect!

Designing my kits is a very tedious affair, having to locate and oriented each chair manually. it does give me much design freedom, however.

After measuring the gauge of your STL I printed, it seems OK anywhere between 16.17 - 16.25mm. Looking again the rail doesn't seem to be leaning as much as I first thought.

I wish I could have a play with the 3D export features you are working on, obviously it's disabled in the current release...
 
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Martin Wynne

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I wish I could have a play with the 3D export features you are working on, obviously it's disabled in the current release...
@Wayne Kinney @graeme @Alistair Ward

Hi Wayne,

Yes, I wish you could too! There's still such a long way to go.

I've had the FDM filament printer for a couple of years -- see the previous topics on the old forum. I spent a lot of time trying to FDM print acceptable chairs. They were ok in 7mm scale, if rather fragile, but in 4mm were hopeless. Also very slow of course. Andy B did much better than me.

I then tried the idea of FDM printing ready-chaired rail, for battery/radio control. That still looks a possible in 7mm when I get time to develop it further. But a bit too fragile in 4mm, and battery/radio is a rare thing in 4mm scale.

The only way forward in 4mm seemed to be resin for the chairs, so I obtained the little Elegoo 3 months ago. I made the initial test prints you tried, but since then I have hardly done anything with it because I have been too busy with other Templot stuff and life. I want to get back to it soon while I still have a usable brain -- it's fading fast. :)

I accidentally left the experimental chairing switched on in version 227a. :) I will switch it back on for you in 228a which I will be releasing in the next few days. You can then play with some chaired plain track in different gauges and radii, but there is no guarantee that the various settings and options will be working. Or that the results will match what eventually gets released.

If you are into programming I will also be releasing the code as open-source in this topic:

https://85a.uk/templot/club/index.php?threads/t1-files.192/

so any coding contributions gratefully received. :)

cheers,

Martin.
 
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Wayne Kinney

Member
Location
UK
Hi Martin,

It would be great to have a play around with the 3D export feature, thanks!

Charles, thanks for your purchase. I'll get that posted tomorrow!

Yes, after releasing a matching diamond and slips, I plan on making a smaller A5 turnout kit.

In time, I will have A5, A6, B6, B7, B8, C9 & C10...

Thanks,
Wayne.
--------------------------
Home of FinetraX Easy Build Turnout Kits - www.britishfinescale.com
 
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Martin Wynne

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I plan on making a smaller A5 turnout kit.
Hi Wayne,

Don't do that. Make it a 9ft-5.

Shorter, but with easier radius. No need to make a loose-heel switch, it works equally well as flexible. Blade planing is same as A (1:24).

cheers,

Martin.
 
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Martin Wynne

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I accidentally left the experimental chairing switched on in version 227a. :) I will switch it back on for you in 228a which I will be releasing in the next few days. You can then play with some chaired plain track in different gauges and radii, but there is no guarantee that the various settings and options will be working. Or that the results will match what eventually gets released.

I shall be releasing 228a shortly.

This is primarily a fix for the return-curve bug in 227d.

I'm also reducing the shortest crossing angle Templot can handle from 1:1.5 to 1:0.5

This is mainly for greater convenience when making diamond-crossings at an intersection. I'm also trying to improve the default timbering of such short-angle diamond-crossings. It's not simple -- reconciling the requirements of different model gauges and flangeway gaps with the prototype dimensions in such a short lead space is all but impossible. The need for some timber shoving is inevitable.

But I'm also going to switch the experimental chairing back on -- you may remember that I left it on accidentally in 227a. :)

This is so that anyone who wants to play with 3D printing can have a go.

But PLEASE, PLEASE, note this is an UNFINISHED work-in-progress. Lots of stuff is still missing or wrong or broken. I know about all of it, so PLEASE don't write in to tell me. :)

You should be able to make a usable DXF/STL export of plain track with ordinary REA S1 chairs and wooden keys. In any gauge or radius or sleeper spacing. In 4mm/ft scale the chairs should fit C&L/EMGS rail.

But if you try to export turnouts you will see more things wrong than right -- chairs missing, chairs without jaws, jaws without keys, keys without jaws, keys where there should be stock-rail bolts, ... -- like this:

chairs228_4.png


chairs228_1.png



If you switch off the TIMBER3D layer in your CAD, you will see that the chairs have plugs and support pyramids buried in the timber. You can switch them off on the DXF dialog:

chairs228_2.png


chairs228_3.png



STL version:

chairs228_stl.png


Hopefully it's an exact match to the DXF. Anyone spot any differences?

As you can see, there is a long, long way to go. But I want to get back to it as soon as I can, otherwise it never will be finished. That means other things, such as writing a user manual, will have to wait. :(

cheers,

Martin.
 
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