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  1. #1
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    Default 3D Printing - My rapid prototyping

    I know many around here have thought about getting a 3D printer. I personally felt like they were toys for quite a long time. Build volume was pretty small and the surface finish was usually garbage. A while back Pete F posted on PM about a kickstarter printer called the BigBox. It seemed to have a lot of promise. Large format, high quality and zero compromise was the promise.

    After reading the warnings about it not being a "first printer" and designed for people with experience in 3d printers (not me! I had never even seen one in the flesh) - I thought I would try my hand to "meccano" a 3d printer during the cold winter nights when I could not be bothered freezing in the garage... So against my better judgement I took the plunge.

    It arrived about 4 or 5 months later in a big box with many small boxes within. It took me about 2.5 weeks of around 4 hours a night to assemble the beast. It was fiddly, irritating and I had the dreaded thought I might be one of a growing list of people that
    did not get theirs together to an acceptable standard.

    IMG_3089.jpg IMG_3154.jpg IMG_3161.jpg

    All those negative thoughts disappeared when I clicked print. I started out printing a toy boat. It's a fancy "3d benchmark" that came with the printer. I would have been happy with any steaming pile of plastic at that point. The printing had me completely mesmerized. The first one printed shockingly well.

    IMG_4475.jpg IMG_4476.jpg

    After messing with a few settings I got it printing consistently well. I convinced myself to stop stuffing around and start printing real things. PDW had told me he was not convinced they were much more than a toy. He had seen the "benchy boat" at that point. So I printed a prototype supercharger mount for my car..

    IMG_4502.jpg IMG_4503.jpg

    After printing the supercharger mount I had a comment "I wonder if it could print a decent foundry pattern". So I set about making them. I first printed a few squares as that was PDW's next casting project. The squares were printed and PDW dropped them off at the foundry before Christmas. I'm really looking forward to seeing the cast items!

    IMG_4559.jpg IMG_4574.jpg IMG_4603.jpg

    After the square I went back to my main project (one of many!) - a 12 inch water brake dyno pattern. Because the pattern is so big and complicated it takes a heck of a long time to print out. Each piece was about 30 hours. I had it deliberately printing slow to get reasonable surface finish. This one is now all glued together and ready for the foundry.

    IMG_4719.jpg IMG_4721.jpg IMG_4979.jpg IMG_4974.jpg

    When I received my Kearns "ho-bo" it arrived with a broken handle on the tail stock. Whilst I was waiting for people to arrive on Christmas day, I spent half an hour in CAD and kicked off a print before anyone arrived..

    IMG_5099.jpg

    Next up I'm likely going to convert the printer to have 2 independent print heads. There is a prototype for the BigBox floating around. I'm waiting for an announcement out of E3D of a "kit". This will allow me to print anything I want in high quality without compromise. 3D printers struggle with overhangs (printing on air). A second independent head can print a different material as a stable platform for the base material to print on. This is then washed away - which means I can print manifold patterns etc that have complicated shapes and overhangs without having to compromise or get a poor surface finish from supports in the same material.

    For the observant - yes my printer has dual print heads. But they are not independent and far too difficult to level and align them on the same carriage. Then you have the issue of the second head dragging and possibly oozing material over the freshly printed surface. Independently moving heads are the way to go. One does its work and docks, then the other does its part etc. No dragging, oozing or having to align them perfectly to one another.

  2. #2
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    Great it worked out for you. The prints look excellent.

    Yes the days of 3D printers being toys are long gone. Of course they can be, and for many people that's all they are, but their uses are limited only by one's imagination. The key is to learn a CAD system so you can design your own work, and consider them a pair; the printer translates the imagined into something real and tangible. If somebody was to rely on only downloaded models designed by somebody else it's likely to remain just a toy. With a good CAD program it becomes another workshop tool.

    As far as the soluble supports, I would look further in to this and be sure that's the way you want to go. The soluble filament is relatively expensive and I've personally never seen a need.

    As you say, a printer like this can't print on air, however a good slicer will generate supports from the plastic you're printing in, and these can be broken away easily after the print is completed. Likewise for a raft if you have a job that needs that. I can recommend Simplify3D as a slicer. It is a paid app, and isn't exactly cheap, but as with a lot of things in life, you get what you pay for. It may seem crazy to pay for a slicer when there are free alternatives, but having tried them all, I would still recommend Simplify. It came highly recommended by geeks in this field, however I was reluctant to pay for it at first. In a moment of weakness I caved in, bought it, and then understood what they were talking about. Supports for example are one thing it does very well.

  3. #3
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    Thanks for dropping by Pete. I agree that CAD goes hand in hand. It would be a massive mistake for one to buy a 3d printer without being willing to spend the time to learn CAD. I did CAD in school 20 years ago and fortunately learned a few things. I was at the crucial cross-over from pen and paper with a slide rule to Mac's with MiniCAD. I was never much good at it in school but knew the power of the beast. These days I really like working in CAD. Once one gets the hang of things you can go from concept in your mind to a 3D model in no time.

    Fortunately Simplify3D was part of the package with my BigBox. When I placed the order for the machine I had no great idea of what a slicer did. I have played with a lot of the settings in Simplify3D. My profiles are now such that I can get consistently good prints without any failures.

    I generally use Torwell PLA - which can be purchased direct for ~$10 per kg (although minimum order applies). It prints exceptionally well and completely consistent - even if let sit without vacuum bagging. If you have not tried it out you should. It has printed better for me than any other brand.

    As for supports, I have printed quite a few in PLA. They break away perfectly but the surface finish on the part leaves a lot to be desired. I have it in my mind that it's because the base layer can't get enough "squish" happening to give a nice flat layer. No idea if that's really the deal. I probably need to spend more time on it to really know why the layer is not nice and smooth directly above the support. It could well be a setting in the slicer.

    I found it hard to get inspiration from the little guy with so many toys being printed... I did come across a thread over on performance forums where people were printing full-scale mockups of suspension parts prior to putting them in the big VMC's. The rationale is it's much more cost effective to test the fit with $2 worth of plastic VS $50 worth of aluminum billet. It all makes too much sense and is the reason I wanted a printer - to make real prototypes ready to test fit before I spend hours making them in metal.

  4. #4
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    Nice example of practical applications for a 3d printer, the 3d printing world is evolving rapidly. Have you thought of using something like the supercharger mount to make a silicon master, which is then used to cast a wax version for investment casting in something like aluminium?

    My son has been working with 3d printing for a few years now, he also has a laser cutter that can do acrylics, by combining 3d printing with laser cut parts you can prototype almost anything.

    Ray

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    Not wishing to rain on the parade, but it looks like that pattern has an undercut on it
    IMG_4979uc.jpg
    Or have I got my draw angles confused?

    A few months ago I went to a high school and saw their 3D printing. Although basic, I thought it quite interesting how they were integrating it with their tech studies program. A few weeks later I then visited one of the Universities where they are printing titanium, including items for medical applications. One of their show pieces was a jet turbine engine all of around 50mm long. I'm trying to get back there for a longer tour. If I do I'll see if I can take a camera.

    Michael

  6. #6
    BobL is offline Member: Blue and white apron brigade
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    My son is also into 3D printing. His day job is as Penetration Tester for IT systems (i.e. White hat hacker) but he also dabbles in physical security. A few months ago he demonstrated how easy it is to copy and print standard pin/tumbler type lock keys. The keys printed would not stand up to repeated use but they last more than long enough to do some mischief.

    At the Uni where I used to work they have a prototype 3D printing lab with a bunch of different printer types. The one that caught my eye uses a liquid bath in which a print head focuses a Blue laser and partially sets the liquid. This machine can print objects with minimal hard support because the rest of the liquid helps supports the set material. After the object is printed the object is placed in a chamber where it is exposed to intense UV so that it sets hard. The finish is extremely good and it makes the plastic filament method look average.

  7. #7
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    Quote Originally Posted by Michael G View Post
    Not wishing to rain on the parade, but it looks like that pattern has an undercut on it
    IMG_4979uc.jpg
    Or have I got my draw angles confused?
    Michael, thanks for the note. I have 3 degrees of draft on all the surfaces. It's set up for the pull direction. I ran some solid model analysis and it was showing the draft to all be correct.

    My idea is that it will be placed in a core box and have the outer rim face down onto a flat board. Sand will be pounded to make the outside shape up to the top of the rim with the drafts enabling it to be removed. The pattern will then be flipped over, remaining in the core box. A top core box will then be attached and the sand pounded in to make the scalloped inner core. The drafts are setup to allow the sand core to be removed from the printed mold without any overhangs and the like. The idea in my mind is it will cast like you would if you were to cast a piece of channel.

    Let me know if you think I'm missing something here.

    I will find out for sure when I take it to the foundry. PDW mentioned that the foundry wanted to make a modification to the squares. I can't remember what that modification was though. We certainly had no problem with them doing whatever they deemed appropriate. They also had 3 or 4 degrees of draft and were mirrored patterns.

    Edit: I just spotted your little red arrow. That step is a bit of an optical illusion. The step is at the top of the scallop. The pull direction is upwards. The inner rim drafts from the step outwards. Hopefully the following photo shows the step a bit better:

    IMG_4954.jpg

  8. #8
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    Ah yes I forgot that printer shipped with Simplify. I remember at the time thinking they clearly wanted that to be a project that sets the person up for success in the task, instead of it becoming a hobby in itself.

    You're often correct about the area above supports not printing perfectly. I normally try to orientate parts so supports either aren't needed at all, or are minimal. The only suggestion I can offer there is to think outside the box, literally. In other words the orientation may be at an odd angle instead of horizontal + vertical. It's sometimes a compromise, as having things at an angle may lead to issues elsewhere.

    In regard finish quality, don't be afraid to refinish the plastic either by sanding/machining etc or by filling and painting. I've never bothered with the latter, but if I were making a mould that's possibly what I'd do just depending on the finish required. The finish I get is normally quite good, and any residual just a function of the process much like milling leaves machining marks, grinding leaves grinding marks, etc. Obviously the layers are more noticeable than, say, grinding marks, but you get the idea. Some people are critical of the process because of the artefacts of the technology, but at the end of the day it's an additive process that relies on building up layers. It's a bit like walking up to an old CRT television and criticising it because if you look closely you'll see lines and pixels. While absolutely true most of us are more interested in watching the movie and seeing the big picture! Yes there are other technologies like SLA as Bob mentioned and in that case they are very easy to home construct with a simple video projector and Z axis movement. But every technology has advantages and disadvantages. Laser sintering metal powder is great for example, but I don't think many home shops can afford the 1/4 million bucks for a laser sintering printer, so I'd definitely list that as a disadvantage!

    Some commercial printers use dissolving supports but outside them I haven't heard many good reports. I'll be interested to hear how that all goes for you if you do go down that path.

    I too will often model and print a part in plastic before cutting metal. It's much better to sort out problems at that stage than approaching the end of the build to discover there's some fundamental error! That and making jigs are what it gets mostly used for. Not that I've been using it much lately, but that's another story!!!

  9. #9
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    That looks more the part. Thanks for clarifying.

    Michael

  10. #10
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    Quote Originally Posted by RayG View Post
    Nice example of practical applications for a 3d printer, the 3d printing world is evolving rapidly. Have you thought of using something like the supercharger mount to make a silicon master, which is then used to cast a wax version for investment casting in something like aluminium?
    Do you mean like this Ray

    IMG_4744.jpg IMG_4769.jpg IMG_2134.jpg IMG_2130.jpg IMG_4969.jpg IMG_2157.jpg IMG_5008.jpg

    In the end I realised that I could not get the detail I wanted in the casting with wax. I really needed a spin casting machine or the like. I also found that as much as I wanted to be a sculptor, a master pattern maker, my ambition well and truly hit the wall with my ability. Tail between my legs I headed off to think about alternatives and there it sat for 3 years until my 3D printer arrived with the express purpose of getting the supercharger mount completed to a high standard whilst retaining a period look.

    Interestingly some people use PLA for investment casting. Apparently the burn-out is not great though. There are manufacturers now making filament out of wax. This type of filament is made specifically for investment casting. I will either go down that road or split my final pattern in CAD for standard sand casting.

    I'm really only getting started in my journey with 3D printing. Bob mentioned SLA printing which uses a bath and resin. It gets great results, but the catch is that it has a tiny build area unless one spends stratospheric amounts of money.

  11. #11
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    That's interesting about the burnout, I hadn't heard that, thanks. If you do go for a dissolvable plastic I wonder if that could be used? Alternatively use another plastic that can be dissolved with solvent? Way outside anything I've done, so just throwing it out there.

    Actually the SLA printers are really cheap and easy to make. The resins harden with exposure to a video projector so you just need a Z movement to lower the build tray into the vat. The resin needs oxygen to harden so this type only harden the top layer. The downside used to be the cost of the resin, and with this technology you need enough resin for the build volume, as the model is lowered down as it builds. However a couple of years ago the resin formula/patent/whatever was released and the prices dropped a lot. They still don't exactly give it away, but it's realistic and just needs topping up, so consider the initial tank fill part of the build cost. I don't believe the resin lasts indefinitely however, but I don't know too many details about all tha. There's yet another technology that pulls the model out of a saucer of resin and builds from the bottom up. That is harder to DIY, but freaky to see. Like something from science fiction!

    SLA is fast (say 10 seconds per layer) but I'm not sure just how strong these resins are. I've never tried ripping a model apart, and figured the people who have shown them to me probably would have a sense of humour failure if I tried, so I'm not super convinced. The resolution is superb however. The resin stinks and is apparently not really the type of thing you want to be breathing, so it's not like it's something you want in a home study sitting on the end of your desk.

    Like I said, there's no one perfect solution in all this.

  12. #12
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    Quote Originally Posted by Pete F View Post
    You're often correct about the area above supports not printing perfectly. I normally try to orientate parts so supports either aren't needed at all, or are minimal. The only suggestion I can offer there is to think outside the box, literally. In other words the orientation may be at an odd angle instead of horizontal + vertical. It's sometimes a compromise, as having things at an angle may lead to issues elsewhere.

    In regard finish quality, don't be afraid to refinish the plastic either by sanding/machining etc or by filling and painting. I've never bothered with the latter, but if I were making a mould that's possibly what I'd do just depending on the finish required.
    ..
    But every technology has advantages and disadvantages. Laser sintering metal powder is great for example, but I don't think many home shops can afford the 1/4 million bucks for a laser sintering printer, so I'd definitely list that as a disadvantage!
    I have been learning fast about part orientation when printing and designing parts for 3D printing. I had heard some chatter about designing for 3D printing before I purchased the printer but had no real idea of what it all meant. In reality I now put angles on parts and design realistic overhangs where possible instead of requiring supports. My initial water brake design had a square flange, that I redesigned into an angled flange after printing a 1/4 scale test. The overhang ended in a birds nest. The angle was the compromise and something that can be milled away without issue in the cast part.

    Funnily enough I purchased some SmoothOn finishing compound a month ago. I had been attacking a few of my prints with a needle file and some sand paper, but for the water brake I wanted a better finish in some areas. This stuff is some kind of 2 part lacquer. Hopefully I will test it out soon and be able to report back. Apparently it smooths to a point of removing print layer lines and is easily sandable to a high shine. I will be testing it out on one of my test prints first however!

    One thing I tend to do these days is design a 0.5mm radius on the edge of my prints. It turns a sharp edge into something rather nice. The difference is amazing to hold in your hand. Just another one of those design things that I picked up when making a DRO mounting extension arm for the Kearns.

    As far as strength goes, some of my prints are unbreakable by hand. I picked up that an increased wall thickness makes a big difference, as does solid layers every so often between support layers. A fairly dense infill and honeycomb structure tends to give great strength without going overboard.

    Laser sintering is interesting, as are the discussions around price. Every time I excitedly read news of some start-up aiming to bring down the cost, we are still talking 50k+. Not an economic proposition for a few prints here and there. Not to mention the cost of consumables. I don't want to assume - but I don't expect them to be cheap.

  13. #13
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    Quote Originally Posted by variant22 View Post
    Do you mean like this Ray
    .
    Yep, I should have guessed.

    The 3D printer we used in Austria a few years back had a support material that dissolved in dilute Caustic Soda, then we would wash the parts again after the support removal. I guess they have better support material these days.

    The 3d metal stuff my son has done ( mostly silver jewelry ) was done by shapeways, you just upload your model and they will print it in any number of materials. Shapeways - 3D Printing Service and Marketplace

    It would be interesting to see what someone like shapeways would quote for that Supercharger support in Aluminium.

  14. #14
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    Good tip on the radius, thanks I'll try that.

    I've done some nylon parts and tested them to destruction and they literally are unbreakable. Eventually they do get kind of "mushed up" but don't ever really break like other plastics do. When I get more time I want to try some of the newer filaments coming out that are extremely strong plus rigid. The issue with nylon is always it's flexibility. Mostly however I just come back to PLA as it's easy to print, the finish is good, and is generally strong enough. If a part really needs to be strong, the print will be a part of a pathway to something else.

    Some aircraft parts are printed now and that has double benefits. As you mentioned the parts can be extremely light and very strong as a result of an internal structure that would otherwise be unmachinable. Allied with that is that they can achieve closer to theoretically ideal geometry. That's the other side of designing for printing that sometimes needs some rethinking. It's probably no big deal to somebody like an artist who thinks in abstract form, but for people like myself who came from a more practical background, it's learning to let go of traditional constraints. There is now no cost to complexity in form, so whereas previously you may just have a flat surface to make it easier to actually make, now it can be any shape and the printer doesn't care. It's something I probably need to work more on, and still design in straight lines.

    I noticed some facets on your pattern's circumference, is that a result of your CAD software?

  15. #15
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    Having a wet day today I did some googling and youtubing and it is astonishing what usable mechanical objects you can build these days with these printers.

    It would be great for projects for kids to get them into STEM subjects.
    Gold, the colour of choice for the discerning person.

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