3D Printing in 2mm Scale

[Atso]

8 hours ago, TomE said:

Getting to grips with the Mono X, still some tweaks to make to exposure times but the detail is pretty impressive 

 

 

Tom. 

 

That's look fantastic Tom. I would be most interested to know what exposure times and orientations you are using for the Mono (I've got one now, but not the X!).

[TomE]

2 hours ago, Atso said:

 

That's look fantastic Tom. I would be most interested to know what exposure times and orientations you are using for the Mono (I've got one now, but not the X!).

 

Hi Steve.

 

The orientation on that was X4, Y11.95, Z14

 

The exposure time was 1.5 seconds with the UV power set to 50% on the Mono X. It seems that anything above 65% UV power and I start getting a very thin layer of full screen size cured resin forming with the long exposures for the base layers. Seems this is a known issue with some, but not all Xs.

 

Cheers, 

 

Tom. 

 

[TomE]

Like a glove 

 

 

An association chassis fits perfectly in the recess behind the printed solebars. 

 

Tom. 

[Kylestrome]

2 hours ago, TomE said:

Like a glove

 

The thing that has put me off 3d printing has always been the visible layers, but it would seem that they're really only visible in 'cruel close-up' photos. I've just viewed that image at the actual size of the model and realise that they must, in fact, be invisible to the naked eye. In that case, I wonder why it's still deemed necessary to print models at an angle, which I thought was meant avoid making the layers too obvious?

 

David

[TomE]

1 hour ago, Kylestrome said:

 

The thing that has put me off 3d printing has always been the visible layers, but it would seem that they're really only visible in 'cruel close-up' photos. I've just viewed that image at the actual size of the model and realise that they must, in fact, be invisible to the naked eye. In that case, I wonder why it's still deemed necessary to print models at an angle, which I thought was meant avoid making the layers too obvious?

 

David

 

Hi David.

 

Printing at an angle helps reduce the surface area of the print which reduces the suction forces as the print separates from the FEP which reduces the chance of distortions creeping in or the print failing altogether. It also reduces the amount of support required although it does depend on what you are printing to some extent. 

 

The Palvan image on my screen is probably about O Gauge, and you really can't see any layering or pixelation lines on the actual model unless you get it up close and in the right light. Under a layer of primer/paint you'll probably see them even less. 

 

Tom. 

[richbrummitt]

On 27/11/2020 at 13:47, TomE said:

Getting to grips with the Mono X, still some tweaks to make to exposure times but the detail is pretty impressive 

 

 

Tom. 

 

Tom,

 

Could you walk us through what the sacrificial raft support (above the circular/cone shaped supports and not the 'skate') is like or point us to where you already discussed this. I expect that this is the missing ingredient in avoiding distortion that I believe is caused - at least in part - by the necessary wedge shaped tool removal from a build plate. e.g. does your van have a complete floor, how does the supporting structure beneath the solebar look like in cross section, &c.?

 

TIA,

 

Richard.

[MikeTrice]

On 21/11/2020 at 08:38, TomE said:

I have encountered a strange issue on the PALVAN prints however, in that the last few layers seem to be compressed, or deformed:

 

 

I’ve never had this on the OG Photon so slightly baffled to what might be causing this at the moment. 
 

Tom. 

It looks as if you have resolved this. Any idea how?

Edited November 30, 2020 by MikeTrice

[TomE]

1 hour ago, richbrummitt said:

 

Tom,

 

Could you walk us through what the sacrificial raft support (above the circular/cone shaped supports and not the 'skate') is like or point us to where you already discussed this. I expect that this is the missing ingredient in avoiding distortion that I believe is caused - at least in part - by the necessary wedge shaped tool removal from a build plate. e.g. does your van have a complete floor, how does the supporting structure beneath the solebar look like in cross section, &c.?

 

TIA,

 

Richard.

 

 

Hi Richard.

 

The image below probably shows the structure of the body best. I was suffering from distortion at the closest point of the model to the print bed where it transitions from support to model, so I added raft to try and 'absorb' that transition. It also has the added benefit of reducing the number of supports interacting with the body, and I've actually added some to the model itself (shown in red below) to reduce the need for these to be added in the slicer software and allowing me to add them exactly where I need them.  Once printed I separate the model from raft, run it over some wet & dry and job done, a nice flat edge. I do add a few supports running along the centre of the floor, otherwise it tends to sag in the middle. 

 

 

There is a floor, and longitudinal and cross bracing running through the centre of the model, each quarter having it's own drainage holes.  The first prints without these did exhibit some warping, but this seems to stop it. This was on @Atso's suggestion so I can't claim credit there! 

 

 

I tend to air on the side of too many supports rather than too few, just to try and further lessen the possibility of distortion. 

 

 

39 minutes ago, MikeTrice said:

It looks as if you have resolved this. Any idea how?

 

In this case simply by changing Resin! I finished my bottle of Elegoo ABS like and switched to a bottle of Phrozen ABS like and no more roof sag! 

 

I did find a small gap in the roof when was doing the cross section, you can see it in the cross section image above as the little black line in the roof section, so I'm thinking that may have contributed. 

 

Cheers, 

 

Tom.  

Edited November 30, 2020 by TomE

[NScaleNotes]

1 hour ago, TomE said:

There is a floor, and longitudinal and cross bracing running through the centre of the model, each quarter having it's own drainage holes.  The first prints without these did exhibit some warping, but this seems to stop it. This was on @Atso's suggestion so I can't claim credit there!

 

Hi Tom

Impressive work so far.

Quick question though, how do you make sure you get enough UV inside the model to fully cure that resin with just four small holes?

 

Simon

[TomE]

56 minutes ago, NScaleNotes said:

 

Hi Tom

Impressive work so far.

Quick question though, how do you make sure you get enough UV inside the model to fully cure that resin with just four small holes?

 

Simon

Thanks Simon. 
 

I usually give it a another blast under the UV once I’ve removed the plinth and with the model sat in its roof so as much light as possible can get through the holes. 
 

Also making sure they’ve had a very thorough clean to remove as much uncured resin from inside is essential. Monocure Resinaway seems to be much better than IPA for this. 
 

Tom

[monkeysarefun]

31 minutes ago, TomE said:

Thanks Simon. 
 

I usually give it a another blast under the UV once I’ve removed the plinth and with the model sat in its roof so as much light as possible can get through the holes. 
 

Also making sure they’ve had a very thorough clean to remove as much uncured resin from inside is essential. Monocure Resinaway seems to be much better than IPA for this. 
 

Tom

I have often wondered how much of the resin gets cured in the case of  thicker sections of a model. For instance imagine a solid one inch cube of resin, would the UV penetrate all the way in or is there a point somewhere below the surface where  the resin is still uncured if you cut it open.

 

If it is cured  all the way through then you'd assume that the inside of your model would be cured in the same way without needing to specifically try to get UV into the depths of it. 

[TomE]

That’s why you wouldn’t print a solid object in an ideal world, always hollow it! 
 

If you have uncured resin trapped it can eventually lead to the model ‘exploding‘, not in the kaboom sense, but through layer separation/cracking
 

Tom.

[monkeysarefun]

1 hour ago, TomE said:

That’s why you wouldn’t print a solid object in an ideal world, always hollow it! 
 

If you have uncured resin trapped it can eventually lead to the model ‘exploding‘, not in the kaboom sense, but through layer separation/cracking
 

Tom.

I've not seen anything on how 'thick' an item can be before the UV doesn't penetrate - I guess I should get back onto the 3D printing Facebook groups and get 173 different expert answers.

[TomE]

I try and keep to a thickness of 1mm or less, which should be more than adequate for 2mm scale. I haven't seen any evidence of uncured resin causing failures so far in anything I've printed. 

 

Tom.  

[njee20]

I printed a wagon once and forgot the drain holes, it exploded quite quickly. More than just layer separation too! 

[Yorkshire Square]

12 hours ago, monkeysarefun said:

I have often wondered how much of the resin gets cured in the case of  thicker sections of a model. For instance imagine a solid one inch cube of resin, would the UV penetrate all the way in or is there a point somewhere below the surface where  the resin is still uncured if you cut it open.

 

If it is cured  all the way through then you'd assume that the inside of your model would be cured in the same way without needing to specifically try to get UV into the depths of it. 

 

Surely a solid 25mm cube is printed in say 1250 slices of 0.02mm each. Are you saying that each layer is not sufficiently cured as it is printed? How would making a hollow cube with 1mm walls be any better? There will presumably be totally uncured resin adhered to the inside walls that has no likelihood of seeing UV. Does a breather hole, with potential to wash out most of that uncured resin, suffice?

[monkeysarefun]

8 hours ago, Yorkshire Square said:

 

Surely a solid 25mm cube is printed in say 1250 slices of 0.02mm each. Are you saying that each layer is not sufficiently cured as it is printed? How would making a hollow cube with 1mm walls be any better? There will presumably be totally uncured resin adhered to the inside walls that has no likelihood of seeing UV. Does a breather hole, with potential to wash out most of that uncured resin, suffice?

No mate, I'm not saying anything - I was just wondering how 'deep' the UV penetrates the resin in the curing process. I used the cube as an example of a cured  object that would presumably still have uncured resin towards its centre since the UV wouldn't penetrate all the way through.

 

I was just wondering at what depth  into  the cube if you cut it open that you'd find cured resin giving way to uncured, kind of like the earths crust giving way to the lava-ry stuff if you go down deep enough...

 

I assume length of UV exposure and maybe resin translucency would play a part but I've not seen any figures telling me how 'thick' I can make something before I start having issues with the resin not able to be cured the whole way through.

 

I've printed walls for model buildings that are up to 4.5mm thick, without giving the thickness and its issues a thought. So far I've had no  problems but if I cut one open would I find goo inside that might cause issues later?

 

Or am I misunderstanding how resin curing works?

Edited December 1, 2020 by monkeysarefun

[Crosland]

10 hours ago, Yorkshire Square said:

 

Surely a solid 25mm cube is printed in say 1250 slices of 0.02mm each. Are you saying that each layer is not sufficiently cured as it is printed? How would making a hollow cube with 1mm walls be any better? There will presumably be totally uncured resin adhered to the inside walls that has no likelihood of seeing UV. Does a breather hole, with potential to wash out most of that uncured resin, suffice?

 

It will be cured only enough to allow the print to form in the machine. You then need to cure prints off the machine. It all depends how far the UV used for the final curing penetrates the partially cured resin.

[Caley Jim]

I know nothing about resin printers, but how deep the curing goes will depend on the strength of the light and the translucency of the resin.

 

This was an issue with light cured dental filling materials.  Deep cavities had to be built up in layers, partly to ensure that the resin was cured all the way through and also to overcome the contraction which occurred in the polymerisation process.

 

Jim

[Yorkshire Square]

Thanks guys, that sort of confirms my thinking. I do my post curing on a windowsill and even on these darkest days the prints harden off without too much bother. 

 

I've been using Elegoo black resin and curing 0.02mm layers for 6 seconds without any issues. Despite the colour, it is quite translucent up to around 0.3mm (15 layers). 

 

I've also printed some quite large blocks - up to 10mm deep without problems. I guess that if you get the exposure level right at the printing stage, the internal structure isn't critical to some extent. Bear in mind though that increasing the exposure time will lead to bleed around the edges of the print. 

 

I can't imagine a scenario where you print a solid block and there is liquid in the middle. Maybe slightly softer layers, but not liquid or gooey. 

 

Interestingly I had to have a couple of fillings recently, the first in a while, and these were done in resin. The dentist explained that they were cured using "blue light" and were built up, as Jim says, in layers (just like a printer really). The exposures were typically 20-30 seconds per layer. I'm guessing that they were more than 0.02mm deep per layer! 

Edited December 2, 2020 by Yorkshire Square

[Yorkshire Square]

Some interesting reading:

 

https://www.sciencedirect.com/topics/engineering/photocurable-resin

[Ian Morgan]

I would be happy to describe how I produce 3D models, but I use Blender to create models that will be printed by Shapeways. Someone else using different software to produce models to be printed on their own resin printers would probably do things completely differently to me. Plus, a couple of Blender updates, and Shapeways changing material specifications would soon make my description obsolete.

 

However, in general terms, there are two types of modelling (which can also be combined). The first is like building a model using Lego. You just keep adding different shaped blocks to build up a model. The second is like modelling using a block of clay. You poke, squeeze and pull the clay to produce the shape you want. The 'lego brick' method is good for things like wagons, where everything has defined edges. The 'clay' method is good for more 'organic' shapes, humans, animals and streamlined and curved vehicles.

 

[Yorkshire Square]

I use Blender too. It's certainly not a CAD package. As I understand it, it is mainly for 3D gaming developers.

 

However, once you have mastered a few basic techniques it is fairly easy to get going and model digitally (as opposed to draw digitally with CAD). If you want to do something more complex, there are dozens of tutorials online to guide you along. 

 

I like it! 

[Ian Morgan]

Like most 3D software, there is a lot in Blender for animation , texturing (applying colour, etc) and rendering (creating nice images or video) which we do not need to use when creating models for 3D printing. We only use a small part of its capabilities.

[monkeysarefun]

5 hours ago, Ian Morgan said:

Like most 3D software, there is a lot in Blender for animation , texturing (applying colour, etc) and rendering (creating nice images or video) which we do not need to use when creating models for 3D printing. We only use a small part of its capabilities.

On the other hand it does have some features that are incredibly useful. It was a revelation when I discovered that architectural (archipack or something) add-on thingy that comes hidden inside it.

I find it great for roofs - it even models the tiles for you!

Edited December 2, 2020 by monkeysarefun