Page 8 of 13 FirstFirst ... 345678910111213 LastLast
Results 106 to 120 of 184
  1. #106
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    No problem, we're all here to learn and it's always nice to see somebody share when they've found out something new.

    AutoCAD went parametric in 2010 I believe. The thing with parametric is it doesn't just change the dimension, it maintains the relationship with the things around it (if it's been constrained in that way). That's the whole key to being able to modify designs. It's been years since I used AutoCAD, but your memory probably isn't failing you. IIRC you can specify and change the length of a line, but it didn't maintain that relationship with the other geometry around it. It was essentially a fancy pencil.

    I think there are probably quite a few people on the forum who have absolutely no idea what this is all about, and may even be scared off CAD by the whole discussion. It's really not that difficult in reality and whether something is parametric or Paralympic really doesn't matter. It's just a matter of sitting down with a CAD program and going through free tutorials. You start by drawing a line, then two, and so it goes on. It doesn't take long before you're drawing objects, and away you go.

    When deciding on CAD software you'll want to do your homework and decide whether it's right for you. I don't think there's any right or wrong here, and we all think differently. But to simplify things a lot, there's basically two ways to model, either solid modelling or modelling from sketches. Neither of those descriptions is a technical definition BTW, just the way I personally try to describe it (as technically it's all solid modelling). With CAD programs geared more toward modelling in solid, think of it like working with lumps of plasticine. You add and remove plasticine to get the model you want, and can push and pull it in to various ways to change the shape. The latter is arguably why it's favoured by those with a more artistic and organic mindset as the model lends itself to being manipulated to what looks like a pleasing shape to the eye for example. I personally found it quite clumsy to work with basic shapes that we would want to machine traditionally. In contrast, programs like SW and F360 you typically start from a 2D sketch, then "constrain" it by inserting the parameters you want (dimensions, angles, etc), finally you extrude it to become a solid. It's the way I prefer to model, but again, no right or wrong here. F360 can certainly then manipulate the solid, but that's not normally how most people use it.

    For those singing along at home who may still be interested, here's a couple of short videos by Autodesk that help explain it a little better. I must admit I wasn't overly wrapped in the example they used in the first video, but it should still be useful. The second video helps explain what is meant by "design intent", what is parametric modelling, and how constraints fit in to this whole thing.

    https://knowledge.autodesk.com/suppo...C60F0-htm.html

    The second video mentions "dimensions and constraints", which is how we would think about it when sketching, but for those new to the field it's probably important to remember a dimension is also a "constraint". Any time you're specifying anything about a line when drawing it (dimension, angle, relationship to other lines, etc) you're "constraining" it, and will prevent it being modified in some way if the model is modified. It's a really important thing to get one's head around, both to ensure the model maintains its "design intent" when modified and also to ensure you don't over-constrain the model. The latter will prevent you making changes you may want to ... and also provides really REALLY annoying error messages that will cause you to use rude words. I really like this video as I think it sums up what this whole thing is about, how parametric modelling works, and why selecting the appropriate constraint is so important (not necessarily difficult, just important).

    https://knowledge.autodesk.com/suppo...BAB73-htm.html

    Hopefully that helps un-muddy the water

  2. #107
    Join Date
    Aug 2012
    Location
    Australia
    Posts
    645

    Default

    Quote Originally Posted by Pete F View Post
    Wow, you're doing some awesome work there, you should be justifiably proud of the stuff you've put up. Sorry if I missed it, but what type of plastic did you print the arm in?
    The DRO arm was printed in PLA. It was just a hatchet job test print with no tweaking. It was printed off the first draft. I wanted to test out the honeycomb in-fill and test the fit.

    I have been playing with TPE over the last couple of nights. It started off with the bottom layer being pretty rough. I pushed up the heat incrementally, tweaked the flow and speed and after 10 test prints I got a good print at 260c. It's amazingly strong stuff.

    Tonight I have been printing more test cubes. I have been testing different heats and infills. I can highly recommend TPE from a fun factor. It prints straight onto glass (adhesion is great at 60c) and leaves no mess behind. Simply peel it off and there is no cleanup. It also has no smell at all. I can get really flexible through to quite rigid (for a rubber) that flexes but always springs back to its shape. The other surprising thing is that even at low temperatures (200), I cannot rip the layers apart. It's much stronger than I thought it would be.

  3. #108
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    I thought this video was good to sum up a few points that were raised in this thread.

    What can you print? Well pretty much anything, and it's just limited by your imagination. That wasn't a 1 1/2 HP British Seagull engine they used, so it goes to show that the plastics can be used and have actual engineering strength. Before someone wades in and tries to start an argument based on a pedantic point about propellors, how long the test was etc, this was clearly just a demonstration, and no, you probably don't want to use a printed propellor on your boat before sailing across the Pacific! But if you were stuck in the middle and lost a prop, you could probably get home if your boat happened to have a 3D printer, even if you had to print a new one each day.

    This demonstrates my comments about the so called "carbon fibre" filament. It's just PLA with CF particles in it. The specialty CF printers I mentioned are completely different and lay down actual CF strands. The reaction to CF filament is typical of the video, people assume it will be very strong, but I've been completely underwhelmed by it. I've heard the CF filament is also abrasive so can screw up your nozzle, I've never personally tried it so don't know. The CF printers on the other hand are amazing, and the parts are super strong.

    They made comments about not being able to demonstrate nylon due to the support removal. For those who aren't aware, these printers can't print on air, and they need something on which to lay down subsequent layers. You'll try to orientate the part so support isn't needed, but sometimes there's no way around it. The slicer will generate the support, and Simplify 3D is a slicer that's particularly good at that. The support uses the same plastic as the model, but produces a transition point between the support and the model that's weak and can break away easily. Think of support a bit like scaffolding in building. Since nylon bonds so well to itself, it can be difficult to remove the support. I have no doubt the nylon prop would have survived their demo, but what may not have been obvious is the prop inefficiency. Nylon is relatively flexible, and I would have expected the blades to flex under load. I've printed some nylon parts that haven't been useful in practice, as they needed to be more rigid and nylon doesn't offer that.

    The ABS failure most likely demonstrated one of the considerations with printed parts using this technology, and that's the inter-layer strength. When you're designing a part to be printed (and it needs strength) it's important to consider that the printed plastic behaves much like fibres of wood. So it will be very strong along the grain and relatively weak across the grain. The "grain" in printed parts is the layers of plastic. Even though you may have relatively good layer adhesion, the part still won't be as strong across the layers. ABS is significant in this area as it shrinks considerably when cooled and can even crack or delaminate. That part may have survived better if the prop was printed at an angle. Knowing when to do that type of thing will just come with experience, but should be kept in mind. This prop also demonstrated what vapour polishing looks like.

    Printed parts can be machined and refinished just like any other plastic, and apart from vapour polishing they mentioned sanding and sealing the wood prop. That's something to keep in mind, and I will sometimes machine printed parts to further improve the tolerance, or make them look better. We mentioned earlier being able to insert metal components, magnets, etc during the print, but another thing that can be done is to "hot stake" a metal part in. I can't recall ever having done that personally, but there's no reason I can see that it shouldn't be done. So for example on those propellors you may be able to have the centre as a simple undersize bore in solid plastic and hot stake a splined insert in there to provide better wear/strength/etc

    Finally, they mentioned 3D scanners. I've seen them demonstrated and they're pretty good these days. In the video they highlighted the limitations of not being able to see properly inside parts. I've seen printers with the scanner inbuilt, and they are the equivalent of "replicators" of sci-fi movies. You put the original part in, push a button, and come back in a few hours to remove the clone of the original. Probably a bit of a gimmick if used by that, but again, it's really only limited by one's imagination, and scanning a part can probably save some CAD time.

    Anyway, I hope this provides a bit of entertainment if nothing else. I think the Kiwi mates did a good job of it.


  4. #109
    Join Date
    Jun 2008
    Location
    Victoria, Australia
    Age
    74
    Posts
    5,080

    Default

    Thanks for that video, polycarbonate is pretty good stuff eh?

    I have a job coming up using polycarbonate, I'm almost convinced to buy a 3D printer to make some of the prototype parts. I just need to find one that has a heated enclosure.

  5. #110
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    Yes there are quite a number of engineering plastics available now, but I'm afraid I'm lagging behind the cutting edge of what's available in regard what I personally use. I've been flat out with work and other projects, and the 3D printer is typically tied in with workshop stuff, so it's been sitting there mainly idle lately. I use TPE (flexible rubber type material), PLA, ABS, and nylon, but haven't tried any of the more engineering type plastics. Some of the filaments available that you'd possibly be interested in Ray would be PETG and PC, also some of the recent nylon alloys. The nylon I use is a relatively basic alloy, and there's been a lot of work done in that area to come up with better alloys.

    Unfortunately you won't find a 3D printer with a genuinely heated "build chamber", well you will, but you'll be buying a commercial printer. The patent for that is owned by Stratasys and I understand they protect the patent aggressively. There's some technicalities in regard the patent and what it actually covers, so some manufacturers are basically able to get around it, but that's really not important. It seems plenty of people are printing in PC without it anyway, but you'd need to do some research on that as it's not something I have personal experience with.

    This is a guy I follow on Youtube, not so much now as he's scratch building his own 3D printer, but he had some good info when I was first starting with my printer. The printer frame is exactly how I would have done it, and it looks good, but I haven't followed it. Anyway here's a video of him testing PC he printed on a printer not dissimilar to mine (ie no heated chamber).

    https://www.youtube.com/watch?v=kZRkiSso1Rk

    This video is testing PETG
    https://www.youtube.com/watch?v=x8XaUfVZEP4

    The thing to watch out for if buying a 3D printer is that it has an all metal hot end. Some of these more advanced plastics require printing at much higher temperatures, and not all printers are able to do that.

  6. #111
    Join Date
    Jun 2008
    Location
    Victoria, Australia
    Age
    74
    Posts
    5,080

    Default

    Quote Originally Posted by Pete F View Post

    The thing to watch out for if buying a 3D printer is that it has an all metal hot end. Some of these more advanced plastics require printing at much higher temperatures, and not all printers are able to do that.
    The printer I'll be using is a Mankati XT Full Size I think the currently installed head has a teflon insert, but my son spends his life building print heads, and it's his machine, so he knows what to do.

    The thing that's pushing me over the edge is the ability to 3D print tooling for injection molding. The job eventually will end up on an Engel Injection molding machine, but prototype runs might be doable with 3D tooling.

    These guys seem to have figured out how to do it.


  7. #112
    Join Date
    Oct 2011
    Location
    Norwood-ish, Adelaide
    Age
    59
    Posts
    6,541

    Default

    The video says all printing was done on an Up Box. Still $3k though.

    Michael

  8. #113
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    Quote Originally Posted by Michael G View Post
    The video says all printing was done on an Up Box. Still $3k though.

    Michael
    There are literally hundreds of different 3D printers out there, thousands if you count one-offs that people build themselves. As such virtually nobody could keep up with the different manufacturers, it would be a full-time job for several people to review and test all the alternatives. I am not at all familiar with that brand, but have taken a quick look.

    I'm not trying to take anything away from this brand, I know nothing about it, it's probably an excellent printer and my opinion is purely a generalisation about FFF printers in general. But FWIW my opinion is to B.O.B. (Beware of Bull $%^&!)

    At the end of the day an FFF printer is a very simple device. It has a very simple motion control system that moves a heated nozzle around, and an extruder to push the plastic through it. That's it. That's NOT to say that all printers are the same, and there is a bit to get that all running tickety-boo, but when you read the blurb, B.O.B. Things like fancy lights on the front ain't gunna get you better prints. "100 micron" may sound impressive, but that's 0.1 mm. Whoopee, that's standard these days. An enclosed chamber MAY get you better prints, it depends on what plastic you use. It's unlikely to hurt anyway.

    What you DO need are things like a heated bed. That should be standard. You need a full metal hotend, and some can claim "oh but it's got ... and that's just as good". Whatever. You NEED a full metal hotend if you're going to print high temp plastics. Some would say it should be open source so it doesn't turn into a pumpkin later down the track. Pete shares that opinion. You need the build volume you're interested in. It's probably not as large as you may expect, but if you REALLY need to print big objects in one go and can't possibly join them together because of some bizarre reason physics hasn't thought of yet, then there's no point in buying a weeny printer. Otherwise what you need is just the ability to do those simple things well. That's basically what you're paying for, and the confidence that when you take it out of the box it will do so. But when evaluating one over the other, B-O-B!!! Because some companies seem to trowel it on by the tonne! It's very difficult for companies to differentiate themselves in this market and the market is becoming ridiculously crowded. So when you're evaluating a printer, ask why this one costs $5K, $3K, $50K, 500 bucks or whatever. What does it do (or what doesn't it do) that causes it to be able to justify that price.

    In regard uses for the finished prints, I'd suggest that mainly comes down to the plastic used and not what squirted it out. These are THERMO plastics, which means they need to be heated and extruded. If it needs to be heated to a high temperature then you need a hot end that can handle those temperatures. End of story there. Conversely if the use of the print is above its melting temperature of the plastic you've chosen it will melt. No great surprise there. So if anyone is claiming anything different then I'd suggest they're being generous with the truth ... or defying physics. One or the other, but I know which my money is on.

    Edit: just for the record to illustrate the other end of the scale, I bought a very cheap kit directly from China. A lot of the things looked ok, but in fact were either counterfeit (the hotend was counterfeit E3D. That's how I got to know the guys at E3D), crap, or both. The feed tube for the filament was nylon instead of teflon. how do you reckon having a tube shoved in the hot end with a lower glass transition temperature than the plastic you're trying to print is going to work out! So it goes on. What you should be paying for with a more expensive brand is, well firstly getting what they say it is. Mainly the R&D is done for you and it should pretty much just work. If you buy a cheap printer you become the R&D department and will need to get it working.

  9. #114
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

    Default

    I see you can get a ABS plastic. Cool, will be able to print new brake rotors for my car, then I will have ABS brakes as well.
    Gold, the colour of choice for the discerning person.

  10. #115
    Join Date
    Jun 2008
    Location
    Victoria, Australia
    Age
    74
    Posts
    5,080

    Default

    Quote Originally Posted by .RC. View Post
    I see you can get a ABS plastic. Cool, will be able to print new brake rotors for my car, then I will have ABS brakes as well.
    You can get ABS in 2 weeks with no exercise, (that's what the ad said) you don't need to be 3d printing them. I think they come in a 6 pack?

  11. #116
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

    Default

    Is this the Torwell plastic au distributor?

    https://www.torwell3d.com.au/collections/all-filaments
    Gold, the colour of choice for the discerning person.

  12. #117
    Join Date
    Aug 2012
    Location
    Australia
    Posts
    645

    Default

    Quote Originally Posted by .RC. View Post
    Is this the Torwell plastic au distributor?

    https://www.torwell3d.com.au/collections/all-filaments
    Frankly I'm not sure. I have purchased from that lot on Ebay. There is also a few other Australian suppliers. Torwell happily sell direct from China. You can get a few rolls of each type to test. It works out about half the price. I buy locally at times when I just want a single spool.

  13. #118
    Join Date
    Sep 2009
    Location
    Newcastle
    Posts
    341

    Default

    Can you recall the shipping price for Torwell (the 8 rolls min from China)?

    I've ordered a PETG and PLA from that Australian mob. PETG was out of stock, but they are expecting within days and emailed me within hours of placing order.

    I hope PETG will replace ABS with less warping, for permanent objects. PLA has never sounded good for functional objects to me - I've bought a roll to try it out, but mainly considering making objects for slip casting (ceramics).

  14. #119
    Join Date
    Oct 2007
    Location
    Sydney
    Posts
    3,112

    Default

    I think PLA often gets a bad wrap, it's often fine for many applications. One of the things to watch for in the application is the low glass transition temp, so you wouldn't want to intend to use it where it was getting hot (eg in a car interior in summer)

    For those who print in "wood", how does it compare to real wood in terms of refinishing? I've always thought of that filament as a bit of a gimmick (though nor as bad as the coffee filament), but then wondered about printing patterns for example and refinishing them. Is it any easier in this filament compared to plain PLA?

  15. #120
    Join Date
    Jun 2008
    Location
    Victoria, Australia
    Age
    74
    Posts
    5,080

    Default

    I was wondering why 3D printers use filament and not conventional beads that most other plastic processes use, I see only a few and they don't appear to be very well developed. Strange?

    Most plastics can be had for $1 to $2 per kg, filament seems to be 10x that. Seems like a good argument to build the extruder head directly into the printer.

Similar Threads

  1. Parts Wanted for Align Rapid Traverse Unit
    By colnjulia in forum METALWORK GENERAL
    Replies: 4
    Last Post: 12th May 2015, 11:00 AM
  2. finally a forge for a Rapid blower
    By AndrewOC in forum THE SMITHY
    Replies: 0
    Last Post: 20th Dec 2013, 10:01 PM
  3. printing of threads
    By eskimo in forum METALWORK GENERAL
    Replies: 7
    Last Post: 25th Jul 2012, 09:25 PM
  4. Printing out an Arc-Welding Tutorial...
    By Batpig in forum WELDING
    Replies: 10
    Last Post: 24th Feb 2009, 07:42 AM
  5. 3D printing to make pattern?
    By neksmerj in forum METALWORK GENERAL
    Replies: 2
    Last Post: 25th Jun 2008, 08:44 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •