Garden Railway Forum

"Man cannot live by number plates alone" and having proved that the resin printer is capable of detailed small items I wanted to find out it's limits. The lattice cube test print gave me an idea and a bit of searching found me the Colin Binnie drawing of a ffestiniog slate waggon. In fact this is little more than a sketch, but using it's basic dimensions I drew it up properly and added detail from various photos, then I discovered that it actually just fitted on the build plate of my resin printer, so I put it into the slicer and then started the print. After about an hour, I could see that the print wasn't going right so I stopped it. Went back to the slicer, adjusted the position and tried again. This happened about 3 times, before I realised that although the waggon just fitted the build plate, the bases of the supports were actually running out wider and were off limits.

OK, No.1 lesson learned!

I turned the drawing through 90deg and tipped it to almost vertical to ensure nothing was out of limits and tried yet again. This time it worked and 10 hours 50mins later (Yes, really), the build plate lifted up with the wagon suspended below it.

The model was removed from the plate, washed in IPA and then put under the UV lamp for an hour.

Next comes the exciting part, removing all the supports.

At this point I learned Lesson No.2.
I have watched various YouTube video's and seen references to never using the Automatic support generator feature in the slicer, but decided to use it anyway and found out the problems the hard way. If the supports run too close to the model there is a danger that the slightly viscous resin will bridge the gap and fuse the model to the supports, and that is exactly what happened. Some of the supports have to run between the bars of the slate wagon which leaves very tiny gaps and on one side they did indeed fuse in several places. Getting them separated left distinct scars on the bars which can be seen on some of the pictures. However that aside, cleaning up was not difficult, the resin sands and files quite nicely.
Now in works grey to show up defects:
....and with a quick paint job.

The wheels were quickly printed just to see the complete effect because I haven't got any 'proper' ones in stock. Also, I know there are some differences from the prototype photo, mostly down to my drawing but easily correctable if I wanted to actually build and run a slate train. Although the 11 hour print time seems excessive, included in that is all the detail such as rivet and bolt heads, nuts and washers, the turned spindles, planking, corner plates and anything else required, which I reckon is a lot quicker, easier and cheaper than trying to fabricate or buy in.

I weighed the print after curing and before removing the supports and it came out at 50.3g. Since the resin is £13.99 for 500g, that gives a cost of only £1.40 for the print. However there is also wastage in the washing plus the cost of the IPA, so a generous overall cost would be about £2.50 -£3.00 ( plus wheels) for the detailed model.

That is a very satisfactory outcome.

Not only all the detail - but at a sensible price as well. The 11 hours isn't a problem - just leave it overnight. 10 days later there are 10 of them!

I have made slate wagons (12 off) on the filament printer - but not with that level of detail.

Oh and the wheels will probably be satisfactory as well. I am using filament printed wheels - and I bet those are even better. I find that I can get them to run true every time by mounting each wheel in the lathe, centre drilling, drilling 2.8mm and then reaming 3mm. Any other method seems to leave lots of wheels out of true. I wonder if yours will mount true straight from the printer!

Trevor

Sorry Trevor, I can see why I confused you, but the wheels were filament printed, for convenience, since they are only for effect. They are a long way from being true, because I just used a hammer to bang the axles through the wheel holes!

I don't think resin would be hard wearing enough for functional wheels, although there re heavy duty resins availablea whicg are supposed to be similar to ABS, but at much higher prices.

That is truly amazing work Philip, my hat to you sir.

Resin wheels do work, but they are very brittle and I have had a few snap, so I would suggest sticking with PLA for now unless you really fancy paying for heavy duty resin.

The level of detail is very impressive. Seems to take a lot longer to print than a conventional 3D printer, though.

I wonder what 3D printers will look like and be capable of in 10 years' time .....

Rik

Yes, it is slower, but then again, the layer thickness is only 0.05mm, so by definition it will take twice as long as a filament print at 0.1 and almost 4x as long as the typical 0.18, but that's a large part of the fine detail it can reproduce.
Plus, the volume is limited so it is really more suited to non-load bearing added detail or small items. The slate wagon is just about the limit size-wise, so in general terms it won't be much use for wagon and coach bodies, however the 11 hour print time, plus, say, 1 hour faffing about and cleaning up, gives a complete wagon ready to paint in 12 hours. Like any job it's a question of using the right tool for the job in hand.

The thing with resin printers is it doesn't matter how much volume is in the print like an FDM printer which bases the time on the volume of filament it extrudes. The time it takes a resin printer to print purely depends on how many layers it does, no matter how much volume is in that layer, be it 1mm, or the full size of the plate, it's around 10 seconds per layer, plus lift and drop time.

I agree with Philip though, if you want the detail, resin is the way to go at the moment, bulky items like wagon and coaches are best left with FDM for now, besides which FDM is far cheaper to print with.

That's VERY impressive Philip! As Trevor said, it's exciting to think that with a week or two's printing you could have a whole train...

How strong does the finished thing feel - would it withstand a derailment or collision, do you think? I know nothing about the different types of resin - Swift Sixteen's cast resin models are nice and strong, ut perhaps that's an entirely different material?

Andrew.

Andrew wrote: Sun Dec 13, 2020 8:28 am
How strong does the finished thing feel - would it withstand a derailment or collision, do you think?

I doubt it tbh. I did crack the centre rail on one side, twice, whilst trying to remove the fused supports. I believe that the resin continues to cure for some time but I'm not sure whether that increases the brittleness or increases the strength. Without wheels/axles, the finished thing weighs only 35g (1 oz) which gives you some idea of the delicate nature of it.
Of course the slate waggon is fairly delicate because of its thin members maybe a more conventional vehicle would have more inherent strength but of course that would be too big to fit in this printer.

Andrew wrote: Sun Dec 13, 2020 8:28 am I know nothing about the different types of resin - Swift Sixteen's cast resin models are nice and strong, ut perhaps that's an entirely different material?

Yes, I suspect casting resin would be a different animal, although in tables of resin types I have seen references to printing and casting resins in the same table, but never actually looked at the details.

I think that if I wanted to produce a whole train of these I would investigate one of the more robust resins. As I said 3 quid would easily cover the cost of what I've done so even if the stronger resin was 4x as expensive, you'd still be getting a waggon for about a tenner each ( I think there would be less wastage with a continuous production run, and fine tuning the supports would probably save on resin as well).

I believe (and don't take this as correct) that casting resin is epoxy based which is significantly stronger than our UV resin we use. Although they all come under the term "resin" they are worlds apart in strength, weight, usage etc.

The key to this is going to be working out how to make a specific model to take advantage of the strengths and weaknesses of each technique.

Lots to experiment with!

Trevor