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Great Southern Railway (Fictitious) - Signalling the changes...


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How bad is the oversize printing? And has that come from a rumour or experience so far?

 

The other reason for using a tilt is something to do with the greater surface area of a flat part needing more force to pull it off the bed, which can break parts. A small tilt can drastically reduce the area printed on each layer. Or something like that, it's been a while since I used a resin printer :)

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The oversize printing was enough that a roof and coach body printed on an SLA printer fitted together perfectly but those printed on a Photon from the same file were too tight and needed quite a bit of modification. I believe that it's about 0.1mm on each side of a part in the XY plane, so parts are nearly a quarter millimeter oversize. Doesn't sound like much until you're trying to get a 3.2mm part into a 2.8mm hole (both drawn at 3mm)!

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1 hour ago, Skinnylinny said:

The oversize printing was enough that a roof and coach body printed on an SLA printer fitted together perfectly but those printed on a Photon from the same file were too tight and needed quite a bit of modification. I believe that it's about 0.1mm on each side of a part in the XY plane, so parts are nearly a quarter millimeter oversize. Doesn't sound like much until you're trying to get a 3.2mm part into a 2.8mm hole (both drawn at 3mm)!

 

Ah, I thought you were worrying about it from a scale point of view rather than a fitting point of view. Most people won't notice something 0.25mm oversize!

 

I think the oversize issue is not specific to the Photon though, it's certainly been the case on every FDM printer I've used, so I tend to make holes 0.05mm oversize and inside parts 0.05mm undersize on all my CAD. Most things so far have been push-fit or just require a light sanding to fit.

Edited by TurboSnail
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6 hours ago, Skinnylinny said:

A print was put on overnight, and this time I have a complete set of brakes and buffers for a Stroudley carriage. Add these to the axleguards etc and... I think it is time for a bigger test print. One advantage of these resin printers is that if a print fails (by not sticking to the build plate and staying attached to the FEP film at the bottom), you don't waste gallons and gallons of resin - just one or two layers' worth - as they just form a skin on the film, blocking any more resin from being solidified, and stopping it from being wasted. This is an advantage over the FDM (squirty nozzle) types, where you end up with a pile of plastic spaghetti of filament that the printer has merrily extruded despite there being nothing underneath it...

image.png.152df632eb2a974b899e2ea812c39151.png

Psyduck?

 

6 hours ago, Skinnylinny said:

With that in mind...image.png.52bca583204f30ef86d81e203a8fc096.png
I'm out for the day today so when I come back this will either have printed, or failed. I'm expecting a failure around about the floor level, but we shall see.

Never hurts to try. Well, except for wasting plastic and time obviously.

Edited by RedGemAlchemist
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Indeed, all part of the learning curve as Mike says.

For example, from this print I have learned:

  • Resin does not seem to like sticking to the outer edges of my print bed, instead curling up at the corners of the base of the print
  • 0.5mm square handrails seem to print absolutely fine as long as I add a support at the base
  • There is some diagonal warping part way up the ends of the carriage, which I suspect to be a combination of the base curling up and a slightly loose print bed - I'll re-tighten that.
  • Stepping *is* present but is fairly unobtrusive unless right up close to the print - how much this is a problem will have to remain until primed/painted to be seen.

I'm also impressed with how little resin this seems to be using!

Time to try another test overnight with longer supports and a thinner base.

 

837699562_D43SecondPrint.jpg.86c0abbfd3f7a14ad1749c5b89553ede.jpg



 

Edited by Skinnylinny
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11 hours ago, Skinnylinny said:

Indeed, all part of the learning curve as Mike says.

For example, from this print I have learned:

  • Resin does not seem to like sticking to the outer edges of my print bed, instead curling up at the corners of the base of the print
  • 0.5mm square handrails seem to print absolutely fine as long as I add a support at the base
  • There is some diagonal warping part way up the ends of the carriage, which I suspect to be a combination of the base curling up and a slightly loose print bed - I'll re-tighten that.
  • Stepping *is* present but is fairly unobtrusive unless right up close to the print - how much this is a problem will have to remain until primed/painted to be seen.

I'm also impressed with how little resin this seems to be using!

Time to try another test overnight with longer supports and a thinner base.

 

837699562_D43SecondPrint.jpg.86c0abbfd3f7a14ad1749c5b89553ede.jpg



 

Ghost coach.

 

Pretty damn good for a first attempt. I'm certainly impressed. 

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12 hours ago, Skinnylinny said:

Indeed, all part of the learning curve as Mike says.

For example, from this print I have learned:

  • Resin does not seem to like sticking to the outer edges of my print bed, instead curling up at the corners of the base of the print
  • 0.5mm square handrails seem to print absolutely fine as long as I add a support at the base
  • There is some diagonal warping part way up the ends of the carriage, which I suspect to be a combination of the base curling up and a slightly loose print bed - I'll re-tighten that.
  • Stepping *is* present but is fairly unobtrusive unless right up close to the print - how much this is a problem will have to remain until primed/painted to be seen.

I'm also impressed with how little resin this seems to be using!

Time to try another test overnight with longer supports and a thinner base.

 

837699562_D43SecondPrint.jpg.86c0abbfd3f7a14ad1749c5b89553ede.jpg



 

Can I suggest that before reprinting you place the print bed on a radiator to warm it up (likewise the resin if you have not poured it in the vat yet). I have found this helps adhesion considerably. If the print bed is slightly loose as you mention then make sure you have levelled it as part of the tightening process. Assuming this coach has a floor present try adding some supports inside to support the ends.

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That's useful advice, Mike. How warm do you let them get? Warm to the touch? Hot enough that they're uncomfortable to hold for more than a few seconds?

 

I printed one body with a thinner base and long supports, which detached from the plate at both ends. I then printed another one at an angle as you suggested and one end has come out beautifully, but the end closest to the print bed has collapsed against the bed.

 

Before the next print I'll be giving everything a good, thorough clean and relevel the print bed, just to be sure.

 

I also managed to get a quick mist of primer on one of the failed prints, and it shows the solebars bolt heads and the footboard support straps very nicely. The handrails aren't as fine as Ian's, but they feel fairly robust.

 

IMG_20190507_181132028.jpg.91cc74fdad8b0e52fe3badef94b07811.jpg

 

I realised I haven't put up a picture of the finished buffer and brake parts yet either, although these are still in green so you'll have to imagine them in black under a carriage!

 

IMG_20190506_093901267.jpg.a4da9d3f897a4ca8a3923f4b66f4ff7f.jpg

Edited by Skinnylinny
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1 hour ago, Skinnylinny said:

That's useful advice, Mike. How warm do you let them get? Warm to the touch? Hot enough that they're uncomfortable to hold for more than a few seconds?

 

 

Enough to take any chill off.

 

What resin settings are you using? For the Anycubic green, recommendations are:

Layer: 0.020, Normal Exposure Time: 7.5, Offtime 6.5 (machine never takes less than this), Bottom exposure: 40 or 50, Bottom Layers: 8

 

Don't be frightened to add bracing inside the end thus:

internal.jpg.82feff1b154884013776f1b7c55a0224.jpg

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Hi Mike,

That's helpful, thanks. I've been using mostly the same settings as you, except that I've been doing 50 micron layers, and so exposing for 10 seconds. I might add a couple of seconds to that as the parts are still quite soft when coming off the printer.

I say, that file looks awfully familiar!

I think I'm finding that the further from the centre of the bed I print, the more likely parts are to peel off the build plate. Does that suggest I need to relevel it? Alternatively, I wonder if I might be better slicing the coach body into two halves...

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10 seconds should be fine for 0.050 layer thickness. but it will not harm to increase it a bit, it will just take longer to print.

 

Yes that file should look familiar and was idea for me to show what I meant with internal supports.

 

Peeling off the build plate can be put down to the following:

  • Bed needs levelling
  • Resin/bed too cold when bottom layers are printed
  • Incorrect exposure settings
  • Insufficiant raft size on bed

Slicing the coach into two halves would have the advantage that each half could be tilted say 10 degrees. I had to do this with JCL's GNR Railcar:

IMG_8175.JPG.2ae2badde238f2be4f2bc67679c67914.JPG

 

IMG_8179.JPG.b47e0d5f4bf70a1354701b72b0ab9c56.JPG

 

IMG_8231.JPG.322369d4634b1d1bf44952189a710389.JPG

 

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Just thought. I have seen references to people roughening the bottom of the build plate with sandpaper to improve grip but personally would exhaust all other options first.

 

I assume your build plate is flat and not bowed in any way?

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Hi there, also, with the printer I have, there is a minimum temperature for operating based on the resin being used. Standard resin should be at 25C+ and the 'HiTemp' should be 30C+ . For this reason I have a seedling heater pad inside the cabinet of my printer. The floor of the coach might also be causing the problem as it increases the suction between the part and the vat. It's one of the reasons why a lot of people print at an angle. I've decided not to print floors because of this problem.

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Thanks all for the useful information. I'll probably have another poke at the printer this evening but I'm out at the Glenrothes exhibition today. 

 

I've spotted a Hornby T9 (no.729 with narrow cab and six wheel tender in Southern green) and I'm tempted... But what would need doing to backdate it to 1900-1910 condition? Obviously the smokebox is too long but are there other details I've missed?

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  • 2 weeks later...

Well, it's been a while - I've been rather playing catch-up with life over the past few weeks.

I bought the T9 at Glenrothes, and also The Drummond Greyhounds of the LSWR by D L Bradley. This book, apart from one useful drawing, doesn't actually contain much by way of details of the modifications to the class which would be relevant to this model. It does, however, have a general arrangement drawing, so the loco will eventually be backdated as a narrow-cab version, possibly also receiving a cross-tube firebox. The model came fitted with a DCC chip, although this was removed and passed on to a club member who uses DCC in exchange for a blanking chip, which he seemed happy enough with. It was then given a running-in turn on the club's Glendevon layout on a railtour - how else does one explain an ex-LSWR T9 in Scotland? It runs very sweetly indeed. I may even be able to forgive the traction tyres!

 

image.png.91aa0fcb18c98bd1d5b837b10f5948f4.png

 

I also picked up something rather different - an old Stewart-Reidpath 0-6-0 chassis (still in its original box and with instruction sheet. These instructions include the wonderful line "LUBRICATION is important. ... DO NOT use heavy oils - a light machine oil is best - certainly NEVER use the drainage of a car-sump or even olive oil!").

On testing, it runs powerfully and surprisingly well for its age and motor/gearing combination (3-pole motor with 25:1 gearing), with the armature acting as a surprisingly powerful flywheel, helping the chassis run well over points and isolating sections. My plan for this chassis is, if I can't find a genuine bodyshell, to design and 3D print a facsimile of the Stewart-Reidpath generic 0-6-0. The first model of NWR no.1 (well, the first *electric* model!) was such a beast, and I'd very much like to have GSR no.1 be the same basic design. image.png.275ec6343230a87afe8c58621d72b6f5.png

 

I also very nearly bought a rather nice model of Stepney, but the price was a little too high at £4 so I passed...
image.png.231d982d8c69674efbcc39e2ebcc4460.png

I've also been playing around a little more with the Photon - I seem to be getting better and better results as I tune the machine and get to know its foibles, although there are still occasional strange occurrences. I've nearly finished re-drawing my SER D-ended open wagon (which I had previously designed for laser-cutting) and decided to do a test print. In general it's come out rather nicely!
image.png.36be6785b582b4511d931e4108ba18d3.png
However, there are a couple of minor flaws on the other side - a couple of raised lines which have printed for some reason on only one face of the model, and a chunk missing from the bottom of the solebar. The axleguard is missing because I broke it off while removing supports - I'm going to be beefing these up a little as well as making the solebars and springs a little deeper. The photo does show just how crisp the details that can be produced with the Photon printer are, and I'm delighted with it, although drawing up 3D models definitely takes much much longer than the laser-cut kits.

image.png.67f113640dafb64bdc3cbf9b7df9c136.png

I reckon that If I were to get to a point where I were able to sell these wagons, the price point would not be far off that of a laser-cut kit, maybe a pound or two more a wagon.

Finally, last Tuesday was the Edinburgh and Lothians MRC model building competition. Having won this last year with two of my laser-cut Stroudley coaches, I decided to enter a complete goods train, this time with my backdated Bachmann LBSC E4 (I know it's still missing a numberplate and handrails!), an LSWR open (Cambrian kit), the above 3D Printed wagon, and assorted SER and LBSC wagons and brake, laser cut by myself. To my surprise, having brought back the trophy for the competition, I promptly walked back out with it again!

IMG_20190521_2117212102.jpg

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1 hour ago, Skinnylinny said:

Well, it's been a while - I've been rather playing catch-up with life over the past few weeks.

I bought the T9 at Glenrothes, and also The Drummond Greyhounds of the LSWR by D L Bradley. This book, apart from one useful drawing, doesn't actually contain much by way of details of the modifications to the class which would be relevant to this model. It does, however, have a general arrangement drawing, so the loco will eventually be backdated as a narrow-cab version, possibly also receiving a cross-tube firebox. The model came fitted with a DCC chip, although this was removed and passed on to a club member who uses DCC in exchange for a blanking chip, which he seemed happy enough with. It was then given a running-in turn on the club's Glendevon layout on a railtour - how else does one explain an ex-LSWR T9 in Scotland? It runs very sweetly indeed. I may even be able to forgive the traction tyres!

 

image.png.91aa0fcb18c98bd1d5b837b10f5948f4.png

 

I also picked up something rather different - an old Stewart-Reidpath 0-6-0 chassis (still in its original box and with instruction sheet. These instructions include the wonderful line "LUBRICATION is important. ... DO NOT use heavy oils - a light machine oil is best - certainly NEVER use the drainage of a car-sump or even olive oil!").

On testing, it runs powerfully and surprisingly well for its age and motor/gearing combination (3-pole motor with 25:1 gearing), with the armature acting as a surprisingly powerful flywheel, helping the chassis run well over points and isolating sections. My plan for this chassis is, if I can't find a genuine bodyshell, to design and 3D print a facsimile of the Stewart-Reidpath generic 0-6-0. The first model of NWR no.1 (well, the first *electric* model!) was such a beast, and I'd very much like to have GSR no.1 be the same basic design. image.png.275ec6343230a87afe8c58621d72b6f5.png

 

I also very nearly bought a rather nice model of Stepney, but the price was a little too high at £4 so I passed...
image.png.231d982d8c69674efbcc39e2ebcc4460.png

I've also been playing around a little more with the Photon - I seem to be getting better and better results as I tune the machine and get to know its foibles, although there are still occasional strange occurrences. I've nearly finished re-drawing my SER D-ended open wagon (which I had previously designed for laser-cutting) and decided to do a test print. In general it's come out rather nicely!
image.png.36be6785b582b4511d931e4108ba18d3.png
However, there are a couple of minor flaws on the other side - a couple of raised lines which have printed for some reason on only one face of the model, and a chunk missing from the bottom of the solebar. The axleguard is missing because I broke it off while removing supports - I'm going to be beefing these up a little as well as making the solebars and springs a little deeper. The photo does show just how crisp the details that can be produced with the Photon printer are, and I'm delighted with it, although drawing up 3D models definitely takes much much longer than the laser-cut kits.

image.png.67f113640dafb64bdc3cbf9b7df9c136.png

I reckon that If I were to get to a point where I were able to sell these wagons, the price point would not be far off that of a laser-cut kit, maybe a pound or two more a wagon.

Finally, last Tuesday was the Edinburgh and Lothians MRC model building competition. Having won this last year with two of my laser-cut Stroudley coaches, I decided to enter a complete goods train, this time with my backdated Bachmann LBSC E4 (I know it's still missing a numberplate and handrails!), an LSWR open (Cambrian kit), the above 3D Printed wagon, and assorted SER and LBSC wagons and brake, laser cut by myself. To my surprise, having brought back the trophy for the competition, I promptly walked back out with it again!

IMG_20190521_2117212102.jpg

 

Very impressive.  Great work on the SER Open and the goods train; a well-deserved prize. 

 

Very wise to pass on that Hornby Terrier; hold out for the Rails one. 

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4 hours ago, Annie said:

Wow!  A Stewart-Reidpath 0-6-0 chassis.  Those are the stuff of legends; - what a great find.

 

He had another one too, but I decided on 4'6" driving wheels over the 3'9" wheels of the other chassis. I could be tempted though... Not bad for £17!

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