Evening all,

As per Fizzy's earlier request, here are a few photos of a couple of test prints on an Elegoo Mars resin 3D printer.

The two items shown are a Great Western 5-plank wagon body in O-Gauge and a spinner for a Hawker Hurricane in 1/24th scale. Both drawn up in Fusion 360 and exported as STL meshes.

There are a few things I need to address; understanding "supports" and possibly adding in extra solid areas of resin to be later removed.

Both parts took about 2 hours each to print. I have another wagon in the printer as I write this with finer layer build-up and supports. There were no supports in this first attempt and it appears to have gotten sticky around the edge of the wagon bed.

The spinner might have benefited from some kind of skirt to support the wide edge. It has a wavy line where it should obviously be flat.

Regards,
Ed.

The planks are 1.6mm thick.

Holes appear to print quite well.

I also modelled the plate that the spinner would mate to but only the supports for it came out. The plate somehow got disconnected and floated around in the resin.

You can see the layers on the inside of the spinner which are accentuated by the camera flash. To the naked eye the layers are barely noticeable.

Actually, they're meant to be bolts Bazyle. Some of them came out ok.

They are 0.55mm AF.

Ed.

Neil,

Yes the warping is apparently a known issue with the printer's Z axis. On my printer there is some shift in the Y axis (~0.5mm), even though it doesn't have a Y axis and the inital layer heights are inconsistent …the first layers resemble puff-pastry.

There is an upgrade available to swap the rod type linear rail for a double rail and truck, Hi-Win kind of setup. But I'll see if I can engineer that out first.

This printer uses a UV light underneath an LCD screen to partly cure a layer of liquid resin. Each 'sliced' layer is masked from the UV light by switching on/off pixels on the LCD screen for 8 seconds (controllable in software). The very first layers are exposed for about 50 seconds to make sure they stick to the build plate.

When the model is taken out of the printer it needs further curing via either sunlight or a dedicated UV light source of 405nM, which is what I'm using.

The layer height for this print was 50 microns, 0.05mm and took about 2 hours to print.

———-

Michael, very small !

Ed.

Hi Jim,

Yes, for this printer, a respirator is required for both the resin and the cleaning of parts with Isopropyl alcohol or similar. Gloves too as the resin is pretty nasty stuff that we can develop a sensitivyt too if it touches the skin before it's cured.

There are resins which are water cleanable, but the dirty water then has to be dealt with in an environmentally friendly way.

Ed.

Thank you Roger,

I started another print a short while ago and have elevated the model about 10mm on heavy supports, with more in each corner. The second print I did last night failed because the model started to pull away from the build plate.

I noticed the detail in the rest of the model was better due to the printer's minimum layer height of 25 microns.

Ed.

Good day, hope you're all doing ok.

After finding some original wagon drawings online I abandoned my previous 3D model and set about drawing a full scale accurate under-frame with all the brackets, screw and rivet holes. I assembled it in fusion 360 and scaled down to 1/43.5 (Scale Seven). it's taken quite a few hours.

I continued on and made a couple of test prints of a sole-plate, complete with end bracket and rivets (it's the long beam that runs the length of a wagon), It's shown in the first photo below. The result was quite promising so I set up a print of the whole under-frame and loaded it into the printer.

Some 13.5 hours later no less, the print was ready. It was removed from the build plate, washed in IPA and removed from its supports. Due to careless impatience I managed to damage a couple of small areas but these can easily be repaired.

Ed.

Test print.

Finished printed frame.

Drip drying.

All supports removed.

A close up which shows the structure of the print layers.

A better close-up.

Edited By Ed Duffner on 10/04/2020 12:08:29