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Resin Printing Newbie Saga


MojoBob
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I'm using this model, a 1:100 scale Artilleriewagen, to try to iron out some issues I've been getting with my resin prints.

 

2021-11-16-Artilleriewagen_PrintTest-001


You can see some diagonal lines running across the turret where something has shifted during printing — I don't know yet what caused that, and some research is in order.

It has happened at least twice, and as a result the profile of the turret has been distorted. Not enough to make it unusable; I've had worse misalignments in cast components from commercial manufacturers, but it's annoying.

 

2021-11-16-Artilleriewagen_PrintTest-002

 

It may just be that the various bolts and screws on the platen and rail need tightening, and that's always a good first step. Or it may be that the FEP is getting a bit flaccid.

 

More successful is the rigidifying of the box-like body of the model.

 

I like to hollow the models for printing, partly because it means they use up less resin, but mostly because having less contact area on the FEP at any given level makes a suction-created print failure less likely.

 

2021-11-16-Artilleriewagen_PrintTest-003

 

Having as much as possible of the non-visible bottom surface cut away gives me maximal access to the interior for washing away uncured resin, which means less chance of warping and cracking problems later. It also gives more access to the innards for the UV curing lights.

 

However, especially on a boxy model like this, thin walls means a less rigid and strong model. I could keep the walls thicker, but in this instance I've also added some internal bulkheads which provide a great deal of strength to the whole thing, as well as supporting the tabs on which the wheels are set. These bulkheads are 2mm thick, and I could probably halve that in safety.

 

Something that I find a bit annoying is that because 3d printing takes so long, every time I change a variable to test what's going wrong, it takes another few hours before I can see the results of my change. Hey-ho, I'll just have to learn to reign in my impatience.

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On 11/10/2021 at 8:17 PM, MojoBob said:

I've read that Chitubox can create infill that doesn't impede resin escape, but I can't figure out how to do that (I'm using the free version).

 

The only infill I know of in the free version is under Hollow.  Change "Infill Structure" from "none" to "Grid 3D" and then type in the density you want.  I assume the paid version has more options, but I don't know.

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My attempts to fix my layer shifting problem have been disastrous. Now I can't even get anything to stick to the build plate.

 

I've lubricated everything, replaced the FEP, and releveled the plate, all without any improvement. Last night I releveled again, but using two sheets of paper instead of one — I think my separation distance might have been too low, judging by what was left stuck to the FEP — but if that doesn't help, I'm pretty much at a loss.

 

I hate it when things that have been going along quite smoothly just mysteriously crap out. :(

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My re-re-leveling seems to have done the trick, and I'm up and running again.

 

Thinking back, from the results I was getting with my rafts before, I suspect I had just lucked out with my original leveling's separation distance, and it was hovering juuuuust at the point of workability, but was really too low. Now, having levelled with two sheets of paper instead of one, the undercuts on my rafts are much more cleanly defined, and it's a lot easier to get the spatula in under them to get the print off the build plate.

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Here's the test print of my latest 1:100 (15mm) digital model, a Soviet BA-27M armoured car of 1931.

There were still about 120 of them in service when the Germans invaded in 1941, so although it was an interwar design, it also counts as WWII equipment for the Soviets, and captured examples were also taken into German service.

 

It mounts the same turret as used on the T-18 tank, with a copy of the French Puteaux 37mm gun and a 7.62mm machine-gun.

 

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AVvXsEhJ0j_e25cOYTJVvPkZjMWQB3imzysOFMzC

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3 hours ago, Corsair said:

@MojoBob that printed up really nice! What were your settings?

They're the default settings that the Mars Pro came with. I've seldom found the need to make any changes at all; I did do a couple of models with lower layer heights, but haven't really found that the results justified the effort.

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AVvXsEggZlKE92hQkkl8eTFUIB0K8fiuiZMKudSm

 

AVvXsEgZCaYpbImeBkpTfrtNTqzD2ZmwgSOr74Tg

 

Here's a WWII British armoured car, the Humber Mk.II in 15mm/1:100 scale. It mounts a BESA 15mm heavy machine gun with a coaxial 7.92mm machine gun, also a BESA. It was used in North Africa from late 1941, and stayed in active service in Africa, Europe, and the far East in various configurations throughout the war.

 

The vehicle is a Bergman design, and I've opened up the hatches and added a commander that I'd sculpted previously. It's printed in eSun water-washable resin on my Mars Pro.

 

In spite of my best efforts, I still had a couple of support issues. I missed supporting the ends of the sand-chutes on the back of the hull; you can see how they're bowed at the bottom, where they should be rectangular. And the rear right wheel printed distorted, and is supported now by a glob of epoxy resin which I will probably have to trim back at some point.

 

The hull was hollowed and printed with the front up at a 30 degree angle, so the glacis was dead level. In retrospect it would probably be better to angle it with its backside in the air, and the glacis vertical.

 

There's a certain amount of detail on the underside that is really redundant for a wargaming model, and if I was doing it again I would probably level it off and remove most of the floor for ease of washing. With the model as it is, ChituBox was very reluctant to punch holes through the floor, and I ended up having to push them through the sides of the turret socket.

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2022-04-02-HawkerHart-001.jpg

 

Some time ago I designed a 1:144 scale digital model of the Hawker Hart in Blender, and from time to time I have another go at 3d printing it.

 

The silver one on the left is printed in FDM on my Ender 3; the STL for that one is split longitudinally and the model is printed in two halves. The resulting print is okay, but as usual with FDM the surface texture is quite striated, I end up with a lot of little nubbins where supports rest, and the struts and undercarriage are really quite rough. It will do as a wargames model, but I crave something smoother.

 

However, I've had very little success when it comes to printing aircraft in resin, like the one on the right. This one was also cut in half, but fore and aft this time.

 

Part of the issue is that resin isn't all that dimensionally stable, and warping in the curing process is fairly common. But the recurring problem, again and again, is deformation of one or more wing-tips. Even when I've supported both sides completely symmetrically, I'll often get one side failing to print properly. In the case of this print, the profile of the whole port side is screwy, and I honestly have no idea why.

 

I'm trying another print right now with the front half of the plane in a different orientation, but to be honest I'm getting a bit pessimistic.

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Success at last!

I had a couple of breakages when the supports came off (one of the wing struts, and the undercarriage) but they glued back together okay with some raw resin, cured with a UV flashlight.

 

2022-04-03-HawkerHart-001.jpg

 

There is a little bit of sanding to be done where support nubbins exist, but it's the best result so far.

I'll print one more, and paint one in the silver peace-time livery and the other in the dark earth/dark green it would have been repainted in if it had to go to war.

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5 hours ago, MojoBob said:

Success at last!

I had a couple of breakages when the supports came off (one of the wing struts, and the undercarriage) but they glued back together okay with some raw resin, cured with a UV flashlight.

 

2022-04-03-HawkerHart-001.jpg

 

There is a little bit of sanding to be done where support nubbins exist, but it's the best result so far.

I'll print one more, and paint one in the silver peace-time livery and the other in the dark earth/dark green it would have been repainted in if it had to go to war.

If you wouldn't mind, I would love to see how the Hart would do on an Ender6 with the newest software.

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