The Joys of 3D Printing – The Learning Curve 4 – Angles

OK!  We’re seasoned veterans of resin 3D printing already by this point!  We’ve printed test models, dialled in all our settings, and can print anything, right?

Sadly, no.  There is yet more to learn.

Most free models out there aren’t pre-supported.  And sometimes you want to do wacky things like scale a model up or down.  And sometimes the presupported models aren’t that happy on your printer.

What we need to do is understand how best to prepare 3D models on the build plate without any supports, in order to get the best, most reliable prints once we add those supports ourselves.  And one of those tricks with “best” is to try and ensure that the supports attach to parts of the models that we aren’t as worried about so any dimples caused by removing the supports are noticed least.

And now, we’re into a wierd mix of art, science, and understanding the results on your own printer.  Please we very much aware that your mileage may vary!

Angle models to support themselves

One of the key tools when it comes to placing models on the build plate in the slicer software is rotation.  You aren’t altering the model – just changing the angles the model sits on the plate.   If you can rotate the model so there are fewer isolated sections or overhangs that need to be supported, it significantly reduces problems supporting the model.  If generally the models limbs point towards the ground?  Printing it with the head near the bottom and the legs higher up means every level attaches to the level below without any additional supports.  Even small changes in angle can make a big difference.  A characters chin?  If it starts away from the neck and below the rest of the head?  Well, that will need to be supported.  Change the angle so the chin is the same or higher than the rest of the head?  Its attached, won’t need supporting in the same way … and is much more likely to print.

The fewer supports needed to give isolated starting points something to attach to, the better.

Angle models to let supports connect to locations that matter less

Removing supports can leave slight blemishes on the output – just like cutting sprues from parts can leave slight blemishes.  The supports are tiny, but can be noticeable, particularly on areas like faces or key details.

Think of a model of a person.  If its all the other factors are pretty equal, would you place the model face up, or face down?  All the supports will attach from the build plate – so you probably want the model facing up to avoid connections on the front and face that you’ll mostly be looking at.

Basically, try to make the most important details face up!

Angle models to avoid them being flat

One real key to making prints successful is to angle the models slightly to reduce the amount of the model being printed with every layer.  The smaller each layer is, the less force the print is subject to as every layer is pulled off the release film, and the more likely it is to be successful – too much force could deform the layer – or just pull the print off the supports!

Think of a 40mm x 40mm x 5mm square base for a model.  If you angle that, you reduce the surface area on the plate massively!  Try an angle of 10-20% – it really does make a huge difference.

Angle models to reduce the height

The higher the models are, the more layers you need to print.  More time, more cost, more impact on the life of the screen, more chance the printer gets rocked, or the power cuts.  Reducing the height of print makes it more likely to be successful overall.

Avoid suction!

Try to avoid hollow spheres or the like when printing – instead of pulling a bit of plastic from the base, you effectively make a sucker that sticks the plate to the base!  That … will not end well.  Angling a model so a hollow cup or basin is sidewise will massively help prints end up well.

Try to have joins towards the bottom of a print, rather than the top

If you have a delicate model, with two legs moving up towards a join, any slight variation in the position of the legs could cause extra tension or cracks in the join.  Starting at the join, and then moving up the legs?  That’s more likely to be successful as you don’t have the tension of the legs working against the join.

Contradictions!

Of course, these all contradict each other.  You want to reduce the height of the build, so you lay the model of a person down.  You need to ensure its angled to reduce the surface area – so you tilt it up 15% increasing the height!  You need to angle it to reduce overhangs – so you tilt it around to have the a pointing arm going up – increasing the height again. 

It’s essentially a game of compromises, balancing improvements for the whole print success against smaller detail and cost.  It truly is an art.  And there are no guarantees of success until you actually print the model.

 

The Joys of 3D Printing – Learning Curve 3 – Designing the Build!

Right!  We’ve worked out all the perfect settings for our printer.   We have the lift speeds sorted out.  We have all our exposure settings sorted out.  We know what we’re doing for safety.  Its time to just hit print, right?

I’m afraid not.  This is where the learning curve can go a bit into hyperdrive.  We have to put 3d models onto a virtual build plate using “slicer” software, and prepare a file for the printer to know exactly what settings to use and the exact pattern of UV light to shine to set every individual layer.  We’ve discussed the general settings we need already, so they should be entered into the slicer software.

Now, if you have a model that is “presupported”, you can simply import that into the slicer software, make sure it fits nicely on the plate, run the “slicing” software to prepare the final output file, save that onto a USB stick, plug it into the 3D printer, and print it!  Huzzah!  We’re pretty much there! (I use Chitubox with the Elegoo Mars Pro, incidentally).

Or are we?

Let’s think back to the first article – costs.  What costs do we  incur with every print?   Resin costs are dependant on the number or size of the models printed, of course.  But the cost of the gloves?  If we can fit two models on the plate to print at once and use one set of gloves to clean then up and cure them safely?  That halves the number of gloves we’d use.  In addition, the running time on the screen is exactly the same for 8 models on one build plate as it is for one model (assuming the same height, of course!).

In terms of cost and efficiency, it’s generally best to print as much as possible on the plate that you think you can print reliably in one go.  All those associated costs per mini just fall massively.  40p of gloves for 8 separate models each is about £3.20.  40p of gloves for 8 models in one go is 40p.  A 9 hour detailed print run for 8 separate models is 72 hours clocked up on the run time of the UV screen (that’s overly simplistic, of course, as much of the time the light is off moving the build plate up and down, but the ratio is true), while a 9 hour detailed print run for 8 models at once is 9 hours clocked up on the screen.  For older printers like mine, the screen is only rated for around 150 hours usage.

So ideally we should be thinking of maximising our prints, optimising the available space and minimising all the associated costs.

So we need to import more models (and for this article, we’ll assume they are all presupported) onto the plate, arrange them to ensure that all the models and supports fit into the build area, that they don’t overlap or conflict, and we may need to rotate them a little bit to fit in easily.

And now we actually can prepare a sliced image, save it onto a USB stick, and try printing it.

Though … a lot of 3d models aren’t presupported.  Or sometimes presupported models aren’t supported well.  So we’ll look at tips and tricks for preparing more complex models on the build plate next article!  The same principles will hold true though – we want to maximise our printing while minimising our costs.   We just have to be aware of quality and ensure we get successful prints too.

The Joys of 3D Printing – The Learning Curve 2 – Vrooom speeds!

So, we have our exposure times sorted out.  We’re golden now, right?  Time to hit print!

Well, no.  It’s still not that easy.

Resin printers have a build plate that pushes close to the transparent membrane in the bottom of the resin tank, the UV sets a layer onto the build plate, then the build plate actually mechanically raises itself up pulling the set resin off the membrane, allowing fresh liquid resin to rush in, then moves down for the next layer of resin to attach to the last layer as the UV light sets it.

That means – more variables!  And you thought you had it cracked!

We can actually set the speed that the base plate raises the resin print off the FEP release plastic.  And oddly, this is one area where I believe (thanks to the wisdom of many much more experienced 3d printers) that the default values you are given (for the Elegoo Mars Pro at least) are basically totally wrong.

If you set the lift values to go very slowly (40mm/min) then then plate very gently retracts, and this tends to work very well, especially for detailed prints.  You can go the other way with “Vroom Speed”, and set it to around 240mm/min and then the plate goes quite quickly with a comparatively sharp yank.

The default values of 90 or 100mm/min are actually terrible.  They go fast enough to put force onto the build, but slow enough to extend out the period that force is applied for.  Going as fast as possible gets the pull off the plate done quickly.  Going as gently as possibly minimises the stresses.  This middle of the road setting?  It’s the worst one to pull minis or parts of supports, or have supports not reach key pieces.

I generally use Vroom speeds for 0.05mm layer standard quality prints, and very slow 40mm/min speeds for 0.03mm layer high quality prints, and I find that works well for me.

This is something I haven’t found very well documented online, and came across chatting in 3D printing chats with people who do this professionally.  It makes sense to me and has definitely given me more reliable and better prints.

Learning curve, eh?

The Joys of 3D Printing – The Learning Curve 1 – Exposure Times!

So, we have all of our safety equipment in line, and we know w’re doing this for fun and to create our own wacky bits and pieces rather than looking for cheap replacements to existing minis.  Pour some resin in the tank, and hit print, right? (And note, I am again just talking about Resin Printers, not Filament Printers here!)

Oh no.  This is nowhere near that simple.

First, every resin printer screen produces different amounts of UV light.  That means the length of time you need to expose each layer of the print will vary depending on your printer, and the condition of the screen.  Mono UV printers produce a much stronger light, speeding the prints up considerably. 

Next, each brand, type and even colour of resin requires different amounts of UV exposure to set as well.  We instantly have two factors affecting the exposure times!

But … it doesn’t end there.  Resin printers generally offer a range of quality.  Most default to a layer height of 0.05mm.  That’s pretty damn good.  But most can go to 0.03 or even 0.02.  My Elegoo Mars Pro can go to 0.02, but I don’t really see any improvement beyond 0.03.  Of course – if you have less resin in a single layer, what does that mean?  Yes, the exposure time for each layer needs to be altered again.

So what does the exposure time effect?  

Over exposure means that you’ve exposed the resin to the UV light for too long.  How can that be a problem?  Well, if any UV light bleeds around the edges of the print, you’ll find additional resin at least partially sets too, making parts a little larger than anticipated and losing detail.  

Under exposure means that you haven’t exposed the resin to the UV light for long enough!  What does that mean?  Well, small details may be smaller than expected, or absent entirely, as the entire piece may not have set.  You’re also more likely to see layers not sticking to each other properly, as the resin hasn’t fully hardened on the existing parts of the model.

You need to dial your printer in to the right settings for the printer, the layer height, and the specific resin.  For very precise work, you might even need to dial it in for batches of the _same_ resin!

Test prints exist – the Ameralabs Town being the best I’m aware of, with a whole slew of guidelines here to help you tweak your printer exposure settings based on printing this cracking wee model.  There are other test pieces, but this is particularly good to illustrate a wide range of possible results.

You can also generally get recommended PDFs of exposure times for various resins for a standard 0.05 layer thickness from the resin manufacturers and printer manufacturers, like these for the Elegoo here.

To get up and running, using the standard layer height with the recommended settings from the manufacturer will get you working.  It won’t be the best quality you can get, but it’ll work, and get you started.  But to move off the defaults, you have to really start learning how to work with test prints.  Like the article title says – its a learning curve!

The Joys of 3D Printing – Safety!

First, lets just highlight this refers to Resin printers, not filament printers.  I’m sure there are safety issues there as, well, but this is just what I’ve learned from getting a Resin Printer from Xmas, and learning both the hard way and through frantic research how to do it without dying horribly.

So, lets be very clear – the big issue with resin printers?  The resin.  UV sensitive resin is, frankly, absolutely horrible stuff.  Potentially carcinogenic, organic dangerous fumes, can cause increasing allergic reactions over time to the point of very serious burns.  Some resin is worse than others, but it is a hazardous material and needs to be treated very serious.

What does that mean?  Resin doesn’t go down the drain.  All waste resin needs to be UV cured for safety before disposal – the supports, any wiped up on paper towels, and any resin washed off models in alcohol or water.  IPA evaporates off fairly easily – water is more onerous.  Once the resin in the water is cured, though, it can be poured away reasonably safely through a filter and all the resin disposed of.  That’s the key.  You need to make sure _everything_ gets cured by UV exposure.

If you are using more resin, you need to be careful with the alcohol too!  That’s also a dangerous chemical!  I’ve gone very heavily for water washable resins, so I haven’t really got as much experience here.  Some people prefer it as the alcohol reminds them to take it all seriously – water washable leads some people to take risks.

In terms of you – you really want a mask rated for organic compounds.  You are dealing with fumes, not particles.  You want a printer with built in air filters, and a well ventilated space, even if its just a convenient window to air a room out.  You really don’t want to be touching the stuff.  Disposable nitrile gloves are generally the way forward, and they aren’t the cheapest.  If you have reusable gloves – you need to be careful of how you wash and dry them in terms of the waste resin too.

I use a big 20 litre transparent tub for waste water I store outside in the sun, which serves to cure the resin for disposal, and use a smaller tub for cleaning the minis, that then gets dumped into the larger tub.  It is a pain, but you really don’t want raw resin getting into the environment.

You definitely want some portable UV lights to be able to cure minis and the stuff for disposal in a range of locations depending on size.

Resin printing is not for the faint hearted, and if you have kids, you need to make sure they understand just how dangerous the stuff is.

Once cured the resin is pretty safe.  I still wouldn’t use it for anything to do with food – don’t print cookie cutters or that sort of thing! Just remember – when its liquid, its dangerous.

The Joys of 3D Printing – The Costs!

Well, I got a fantastic Christmas present – a 3D printer.  Its an Elegoo Mars Pro (around £200), and I have been having the most tremendous fun with it since.  It has been a very steep learning curve though, and you have to be very careful – you are working with very dangerous chemicals if you are working with a resin printer.  Since I felt I had to start almost from scratch and work out a heck of a lot of the safety process and techniques around the printer itself, I thought it might be worth noting down (and updating) what I learnt.  This is all about SLA Resin Printers – I haven’t tried any filament printers.

First off, if you think 3D printing is a good way of getting cheap models?  Forget it, really.  It is not.  There are a lot of costs even in successful prints beyond just the raw materials.  3D printing is tremendously fun, and lets you create miniatures no one else in the world owns.  But it is a hobby in its own right at this point, and isn’t cheap.

Why?  Well, every time you do a print, you’ll need to handle partially cured resin.  Vinyl or Latex gloves won’t work – you’ll need Nitrile gloves.  At around £20 for 100, thats 40p for 2 for every print used up. (Note – this is at the start of 2021 when gloves have gone up in price quite a lot – you used to be able to bulk buy much cheaper).

Every time you do a print, you’ll need the resin to actually print with!  That’s around £40 for 1kg of resin.  You’ll be able to print quite a lot for that, of course!  A normal single mini will be just a few grams, maybe 20?  But you will have failed prints, and every print needs supports.  Its still not a lot per mini, but it does clock up!

Every time you do a print, you’ll need to clean the resin.  You can get water washable resin (which is a bit dearer itself).  Most resin requires cleaning with alcohol.  Which you’ll need to buy and look after safely.  More cost.  If you use water washable resin – the water can’t go down the plug.  You need to store all the water, and cure that either in natural sunlight outside or with UV lights, then filter out the resin for disposal in a bin before pouring the water away.  So that’s a big selection of large transparent tubs and filters.  Alcohol (IPA normally) can’t go down the plug either, but its normally easier to just evaporate that off outside.

But the costs don’t end there!  The resin tanks use a transparent piece of plastic at the base (known as FEP) that allows the screen to shine UV light through.  This gets worn and damaged over time and has to be replaced.  Fortunately, you can replace just this film – but its not easy to do right, and of course you have to buy the film! (£20 for 5 sheets).  Its not needed often, but it something you really need to have on hand!

And the screen itself burns out!  I have one of the older style printers that doesn’t use a mono screen.  The estimate is 150 hours of reliable printing from a screen, which is a disposable part.  That sounds like loads.  A high quality large print can take 15 hours (of which not all is screen time, of course, but moving build plates up and down too).  3 months printing if you are lucky – and that’s certainly all that’s guaranteed on the £27 parts.  Newer printers use mono screens which do generally last much longer – but will still burn out and will need to be replaced.

And finally, of course, there’s your own time and risk!  You’ll be working with hazardous chemicals – its not too risky if you are careful, but it is still a risk to your health.  A decent organic chemical rated mask is recommended, and they aren’t cheap.  Every print will take hours.  You’ll be spending electricity on the printer.  You’ll have to spend your time prepping the images on a computer (and you’ll need the PC or Mac to handle the 3d studio preparation).  All of your time spent cleaning the print, curing the print (you’ll probably need either a UV light and turntable, or a dedicated cleaning and curing booth), and at the end of it you’ll have a model you’ll probably need to assemble – just starting at the point you got home from the shops.

It may sound as if I’m very down on the whole process, and nothing could be further from the truth.  I AM ENAMOURED!!!  But it is a new hobby in its own right, and the costs and time you need to put in are something to be aware of.  It’s not like buying a paper printer, and having it work after turning it on.  You need to spend a lot of time on safety, on computer programs planning the print, in 3d software designing models, cleaning and safely disposing of resin.  If you go into this expecting to click a button and get cheap minis, you will be throwing your money away.

If you want to see something you put together on a screen appear magically in real life, then everything I’ve just mentioned is totally worth it.

My next article will probably be focussed on safety, and the steps and processes I’m doing to keep myself safe while doing these prints.