Practical prints and printing materials

[danzen 0]

Hi all,

I've decided to purchase the entire kit (needed to "persuade" significant other).

But before I do, I just wanted to clear a few things up.

I've seen plenty of beautiful prints (thanks to the collection at Durant's blog).

But, aside from looks, is the Ultimaker good for printing practical stuff? Things that actually work reasonably well?

Like for example, properly meshing gears or Lego blocks that assemble together nicely.

I'm concerned about the repeatability as well as the printing material.

Of course, I'm not expecting the quality of a proper commercially manufactured product, that would be unreasonable.

I have some experience with a commercial ABS printer, and even though the best layer thickness I can get out of the machine was about 0.2 mm, I was very happy with the usability of the prints.

Given the resolution of the Ultimaker, I'm guessing accuracy shouldn't be much of an issue, but how repeatable is it?

Using Lego as an example, if the prints are not reasonably repeatable some blocks are going to fit too tight while others too loose.

I love how strong ABS is, especially when the the model is designed carefully and printed in the optimal orientation.

Correct me if I'm wrong but Ultimaker prints best using PLA. I don't have anything against this material but I'm not really familiar with its mechanical properties.

Using gears as an example, will PLA gears disintegrate under load? Reasonable load that is, I'm not going to print myself a gearbox for the car I drive to work but maybe one for an RC car. I'm not expecting the gears to work forever (there will be wear and tear) but at the very least work well for a few months under frequent use.

So can anyone share their experience with practical prints and how PLA compares to ABS? Some pics or even videos would be nice.

Am I expecting too much from a DIY 3D printer? I would still be happy with merely "good looking" prints though, but "working" prints would be so much better.

Thanks guys.

[owen 19]

Repeatability is no problem except where warping happens or if you starting at a different height.

The initial accuracy may not be there but you can adapt your model to suit.

For example printing holes turn out smaller than intended and so you may have to make the holes bigger in your model to get them right.

As long as you don't change certain things after this, like recalibrating or printing at a different speed etc., it should repeat the same print.

You may find ABS better for Gears at it is less brittle. Gears would be OK if they weren't too small in PLA I think.

There are plenty of gears printed and used on Thingiverse. http://www.thingiverse.com/tag:gears

[danzen 0]

Hi Owen, thanks for replying.

I'm aware of the initial accuracy and adapting the model to suit, which is why I'm not concerned with accuracy at all.

You make a good point about not changing things when printing.

It's starting to sound very promising.

Yeah, I had the impression that PLA is more brittle, which is a cause for concern since practical prints would typically need to support loads in one way or another. I'm just curious as to how brittle it really is. Will PLA shatter when dropped on a hard surface? Maybe similar to acrylic?

I've seen some of those pics before. But seeing pictures doesn't really tell me how well they work, which is why I was hoping someone with personal experience can share their opinions on this.

Going off topic for a bit, has anyone tried polishing PLA prints before? I'm thinking that if all goes well for me, I may want to DIY a vibrating tumbler to polish parts. Probably will need some experimenting with slightly over-sized prints to account for material loss if I need accuracy.

[owen 19]

Yeah, I had the impression that PLA is more brittle, which is a cause for concern since practical prints would typically need to support loads in one way or another. I'm just curious as to how brittle it really is. Will PLA shatter when dropped on a hard surface? Maybe similar to acrylic?

No it's not that brittle. Big pieces are very strong. It depends on how much it is filled. When a part gives way it usually breaks apart between layers. All parts strength depends on there thickness, fill and shape. Tube shapes are very strong. Sometimes certain thicknesses don't fill as well as others. I did some experimenting using Netfabb and found for a vertical wall 1.6mm thickness filled well and 2.6mm and thicker filled very well but between these 2 thicknesses there was much hollow space and no where near the strength of the 2.6mm thickness. Of course this can change if using something other than Netfabb or if using Netfabb it would depend on what style you were using as well as you could create your own style with different fill characteristics.

The other thing I didn't mention is heat. Although PLA doesn't start to melt till 140C or something is gets soft at a much lower temperature than that. So that could be a problem in your RC car.

[danzen 0]

I'm aware that bonds between layers aren't as strong, which is where careful design and print orientation comes into play.

So it all comes down to the fill? I haven't looked into Netfabb, but I assume it can do solid fill so long as I have the time and materials?

Thanks for mentioning heat. Can't believe I forgot to consider that.

Guess I'll have to be more careful when printing things like motor mounts or brackets.

Thanks for the insight. I can't wait to get my kit.

[Daid 306]

PLA starts to become soft around 70C not very soft, but if heated at 70C for a long time it will be deformed.

As for PLA vs ABS. I've never used ABS, but from what I've read ABS is flexible and PLA is very rigid. PLA breaks before it bends, making snap together items hard to print. Strength between layers becomes much better if you print smaller layers. My 0.3mm prints are much weaker then my 0.2mm prints. So far I've zero 0.2mm prints breaking on layer bonds, and quite a few breaks on layers at 0.3mm.

I have a 0.2mm PLA print without infill, only 3 outlines, and it's really strong. I always throw it at people when they ask how strong prints are, just to show them that I feel like it won't break.

[somerwil 0]

Hi Danzen (RC friend ;-)),

as a long time RC cars racer in Holland and multiple times Dutch national champion in electric off-road I would really not recommend PLA for the gears. Sure, it depends on the rc-model you're running but in my cars only the most optimized plastics will do the job. When the wrong material is chosen for the gears they wear too quickly. In some cases resulting in worn gears after 4-5 battery packs... Normally my plastic gears wear out after some 20-30 battery packs depending on surface. The power of the car itself is obviously also a big aspect in gearing load.

PLA will work fine for gearbox cases, battery bars, servo mounts etcetera. A-arms, shocktowers and such might be possible but testing is needed. Very precise parts like gearing will not be good enough. ABS will probably work somewhat better but still not good enough.

Just my $0,02

[danzen 0]

Hi Daid,

Wow, thanks for the tips, it will surely come in handy. I'm curious though, what's the logic/physics behind thinner layers having stronger bonds?

Hmmm... that means PLA is better for some applications while ABS is better for others, not exactly a drop in replacement. I hope someone comes up with a mod to improve ABS printing on the Ultimaker. I would definitely like to be able to print in both PLA and ABS.

Hi Somerwil,

Sorry to disappoint but I'm no hardcore RC geek. Not at all competitive, just very light recreational entertainment.

Probably giving the example of RC gears isn't quite appropriate as some, such as yourself, immediately think of high performance gears.

I will most probably be using the Ultimaker to print parts for robots, and that includes custom gears that one simply cannot find anywhere. So high performance and reliability aren't exactly necessary.

The examples you gave of what PLA works fine for is definitely encouraging. But I noticed you did not mention motor mounts or brackets. Would that mean PLA simply cannot handle the heat? I do understand that the motors you're using probably heats up quite a bit, but what about something less intense?

As for precision, I think from all the pics that I have seen, it doesn't seem to much of a problem for the Ultimaker provided that it is tuned and calibrated well. It certainly has much higher resolution than the commercial printers I've used before.

Thanks for the replies guys.

[somerwil 0]

Hi Danzen,

Brackets will do fine in most situation but I personnaly don't even consider my motor mount in PLA. The motors I use in my cars get up to 800-100 degrees Celsius at which PLA gets 'fluffy' again. I tried this with a printed cup and filling it with hot water to make a cup of tea resulting in a melted cup. Not melting in such a way that the cup was gone but feeling like chewing gum style. I can't find an english word for that tbh...

The printed gears will work very well with robots. On the Mendels some gears are used on the extruder. These seem to work fine!

Conclusion: It really depends on the application of the gears.

[danzen 0]

Hi Somerwil,

Thanks for the input.

I think the word 'fluffy' works pretty well.

Guess I'll be able find out personally what works when I get my kit.

[danzen 0]

I've just placed my order! Now all I need is patience... lot's of it...

Anyways, I'm looking to get some materials and the "flexible" PLA from the UM shop seems really interesting but unfortunately it's out of stock.

RepRapWiki lists two other suppliers with "soft" PLA which I assume is the same thing. The problem is, both sources are from Germany and the shipping to Australia is way too expensive. Does anyone know a reliable source of "flexible" or "soft" PLA that doesn't cost a fortune to ship to Australia?

p.s. Anyone else find it extremely annoying that you can't find all the colors you want/need in stock from a single supplier?

[somerwil 0]

I've seen some prints in the flexible PLA. These looked really nice! It has some sort of rubber feel to it.

 

p.s. Anyone else find it extremely annoying that you can't find all the colors you want/need in stock from a single supplier?

I completely agree! There are quiet a few shops but none of them seem to able to deal with the demand. Faberdashery has really nice packages at affordable prices. Just a tip: you can print a lot with a kilo of PLA/ ABS. The 2,3 - 3 kilo spools are enough for more than a year of printing. My advice: go with the smaller packages and try out the different materials before buying these bigger spools.

M

[danzen 0]

My advice: go with the smaller packages and try out the different materials before buying these bigger spools.

Yeah, that's exactly what I'm aiming for in my very first material purchase.

Wow, there are some really nice colors at Faberdashery (I think the naming helps, being fancy and all). It's making me drool...

Also great that I get to choose exactly how much I want.

Damn, if only they had flexible PLA. I wouldn't think twice if they did.

Btw, the PLA that comes with the UM kit, how much do I get and is it a random color?

[Daid 306]

The 2,3 - 3 kilo spools are enough for more than a year of printing.

I've started with a 2.3KG black PLA spool when I got my ultimaker, and I'm about half way trough it. I got my printer half September. But I'm not printing large things or lots of things. If I would print every day I would be using my 2nd spool already.

The "start with small spools" tip is very good. The 2.3kg spools are heavy and bulky, while the 0.75kg spools are easy to handle.

You get 0.75kg with the printer, in the color they got in overstock I guess. I didn't get it with my printer (they forgot to package it) so I got to choose the color and they shipped it to me afterwards. (+1 for customer service!)

EDIT: Oh, and I also want the flexible PLA. Sounds like a fun material, in a none sex-toy way

[danzen 0]

The 2,3 - 3 kilo spools are enough for more than a year of printing.

 

I've started with a 2.3KG black PLA spool when I got my ultimaker, and I'm about half way trough it. I got my printer half September. But I'm not printing large things or lots of things. If I would print every day I would be using my 2nd spool already.

There seems to be quite a difference here. So basically 2.3 kg could last at best more than a year and at worst less than 3 months?

 

EDIT: Oh, and I also want the flexible PLA. Sounds like a fun material, in a none sex-toy way

Ooooh....maybe ice trays in naughty shapes...that would be fun and hilarious to serve to guests. Imagining their reactions got me giggling a bit. I wonder how flexible PLA fairs in the freezer.