Shapeways issue

[cboath]

Ok, so I make a model, and upload it. Price is say, $300. OK, fine, I get it. Not a problem. I then realize that I could hollow bits of this piece out, so i do. I hollow it out to the point of reducing the model volume by about 30%. I upload that one to shapeways and it tells me the cost is $301. How exactly does THAT happen? If they're pricing by amount of material used, shouldn't I be at about $210?

 

[Angelus Lupus]

Price also takes into account the complexity of the shape?

 

[cboath]

Complexity is a non-factor. Says so on their site. Doesn't take any more effort to print a complex shape. Just if you design it wrong, it may not be strong enough to support it's own weight.

Apparently the kicker is, when you hollow it out, in some shapes, it requires you punch the hole through to the outside world. The outside access can be small (2mm min) but has to be there - in some cases. Not something I would have guessed. Came across that tidbit a few minutes ago when digging in their site for pricing information.

Thing is I did a saber a few months ago where I simply hollowed out the internal area. It had no outside access and it dropped the price substantially. Live and learn I guess

 

[8 perf]

I had never heard that before. Could you post a link to that bit on the "2 mm" access hole to be punched out, from their site. I have done 2 versions of my lid for the clock of Ages and have not run into this yet. The second one was indeed cheaper, so I am interested in seeing their changes.

 

[madmanmoe64]

The access hole is to do with the way they print things, if you already know how an SLS printer works, go ahead and ignore this.

The way it is done is that the machine lays down a thin layer of powder and then lasers only the portion it wants to make solid. It continues to do this until you have a giant box full of powder, then they fish around in there and pull out your model.

If you designed (for example) a hollow ball, then all the un-sintered powder would be trapped inside, you have to have a hole so that the excess powder can be removed.

They do say you don't have to put in an access hole if you don't mind your model being filled with powder, but they collect and reuse any un-sintered powder so I imagine this would push the price up.

this video shows them removing a model from a block of powder and collecting the excess.

 

[cboath]

Shapeways | creating hollow objects

The specific quote:
If you want your object to be truly hollow (i.e.: containing air, not plastic), you'll need to add a few holes in the object wall. These holes will allow us to remove the support or excess material. They should be at least 2mm wide and I recommend you add two or three - more if you have a complex shape that could be more difficult to clean. (The hole in the next image has been exaggerated for clarity)



Now, like I said, I hollowed the piece and without the hole, the price was the same as if I did it solid. I have a saber up there i'm trying to convice myself to print ($125) that I did hollow out, but have no holes and the price dropped by over 100. Somewhere I saw it say that it's an issue with more complex pieces...Regardless, access hole equals big price reduction was all I needed to know

 

[T2SF]

I hate volume issues as well. My issue was that the origin points in solidworks were off. Basically it was counting the space around the object. Make sure the TOP/FRONT/BACK is flush with your model, otherwise that space will be counted and throw stuff off.

 

[exoray]

I hate volume issues as well. My issue was that the origin points in solidworks were off. Basically it was counting the space around the object. Make sure the TOP/FRONT/BACK is flush with your model, otherwise that space will be counted and throw stuff off.

I have not experienced or noticed this, what version of Solidworks? I know I had a bunch of issues exporting to a Shapeways friendly model with the older versions like 2007, Shapeways seemed to always complain about something no matter how it was exported... But, with 2010 and forward those issues are all resolved...

 

[8 perf]

Out of curiosity, have you run the 2 files through different types of plastic options to see if the problem still exists and is not confined to the one type of RP method you have chosen?

 

[aron42486]

Are you certain that your piece is registering as hollow? I designed something and didn't realize I had some intersecting interior faces. Because of this, shapeways defaulted my piece to solid which I could see causing confusion.

They do not really have anything that lets you check if your piece is hollow.

I'd go back to your model and check for any overlapping faces, vertices, etc. just to be sure. Beyond that, I'm not sure what it could be.

 

[KitSmasher]

There's a number of factors involved in SLA/SLS/Rapid prototyping. Most places that do it are charging you for machine time. Material cost is not so much a factor as time on the machine.

For instance, if you were growing a six inch cube, the time on the machine would be the same if it were solid or hollow, because it's still the same build volume (space in the machine).

And then there's support material. For instance, a sphere is an expensive shape to grow, because of the support material needed to keep it from tipping over in the machine while it's growing.

If you can slice your part in half, and keep it hollow, you might see a price difference.

 

[madmanmoe64]

They do not really have anything that lets you check if your piece is hollow.

I think it was Shapeways that put me on to a great little program called 'Netfabb' .
Free to download and it will run a test on any .stl file inspecting it for inverted faces and intersecting geometry as well as useful things like calculating volume. Most of the time it will even repair it for you automatically.

I always give my models the once over in Netfabb before uploading.

This is Shapeways' quick guide to checking and repairing a model in Netfabb

I found it really useful.