Update Design Specifications

As the title says. I have had a few different models rejected because of, well apparently no reason at all. Most recently, it was with this particular file:



The material is FUD, and after waiting 3 weeks, I receive a message that that was rejected. The highlighted spot is a wire used for connecting the real parts together and exceeds the 0.3 mm limit by 16%.

I have had others print with no problems with diameters of less than that, and I have had some reject with diameters all the way up to 0.5 mm. There doesn't seem to be any form of consistency in the process.

Is there any chance that you guys will be able to actually provide real numbers that will pass the test every time? I don't want to have to use 1 mm wires to support everything just to get the prints to pass.

I believe the issue is that your support is over 10mm in length and under .6mm as stated in the design rules

Supported Wires

< 0.3mm thickness: not allowed
0.3mm-0.6mm wire thickness: keep under 10mm wire length
0.6mm-1mm: keep under 50mm length
1mm+: should be fine at anything length

In this case it is a "supporting wire" I think, which states:

https://www.shapeways.com/design-rules/frosted-detail

As to the late notice, it is a busy holiday season, so that might account for the delay in rejection. Or perhaps it mistakenly pasted inspection but failed during print.

And sometimes it happens that these things do get through and do get printed, but might be rejected a next time if they fail to meet the rules.

So following the design rules to the letter is your best bet at getting the model you want in one piece.

Cheers

There in lies the problem - it isn't a supporting wire (at least as I understand them).

For me, a supporting wire would be like the shaft on a model helicopter between the helicopter body and the rotor. The shaft is integral to the model.

Further, if it is a supporting wire:

or

or

All from the page linked (which I have seen - but it doesn't actually clarify things). Typo aside, it isn't actually in agreement with anything else on the page.

In particular if it is a supported wire, this wire is not an unsupported span of 14.67 mm. If you look at the image, there is a second brace which connects that wire to the box above it (which also has wires connecting it to other objects). Since that is the case, the actual length between supports of the wire would be 7 mm.

Using a sprue wire that is 0.6 mm to connect into a wall that is 0.3 mm thick would risk the wall being damaged during shipment, I don't care if the wire breaks - I do care if the wire snaps a hole in the wall.

I did not notice the bar in the middle, so in my eyes, you would be following the rules. I'd ask support about what you can do to make it printable, and explain that there is another support attached keeping it below the 10mm. Maybe they'll say submit again and it will work?

As far as support or not, I wouldn't want someone else deciding if a bar is needed or not, and currently there is no way to say you don't care if it breaks.

I agree the page could use some work, it is a bit of mismatch.

But from your info:
"The highlighted spot is a wire used for connecting the real parts together"
So that would make it a supporting I think.

For which I think this is leading :
< 0.5mm thickness: not allowed
0.5mm-0.8mm wire thickness: should support minimal weight
0.8mm-1mm wire thickness: should be under 3mm wire length
1mm+: should be ok

With regard to connecting thick sprues to thin walls, all I can advice is : don't

Part of the problem. Would be nice to have a Shapeways file format that allows you to specify such things, granted in this design - it is fairly apparent that those exist simply to collect the actual model parts for the Shapeways people to fish out of the printer.

Which is problematic on so many levels. I agree - you should not. However, when you have thin walls (one of the virtues of FUD) and you can not use thin sprues (if your interpretation is the one being used this week). Then you have no choice...other than of course to not go forward with the design at all.

However, I interpreted this as a supported wire (since it is supported at multiple points - not holding a single object as their test prints illustrate), I believed I was following there guidelines.

The test on the "supporting wires" is also a bit wonky. While 100 grams doesn't seem like much - it is significant when it comes to a lightweight plastic that weighs just over 1 gram per cubic centimeter. For a 1 cubic centimeter object to experience that force - it would need to fall from 10 meters high (and not be cushioned at all in any sort of packaging). For a more reasonable height - say 2 meters...the top of a really high loading dock or so, you would need to have a 5 cubic centimeter object. Now supporting that much bulk on the top of a single 0.35 mm wire would be asking for a bit much...but I don't think it is a problem that would arise very often.

Looking at the graphic of your piece all the wires supporting the individual components ate too thin. I can't see any way that it could be picked without the wires breaking an the chance of components being lost. How pieces break in instructive These two pieces have both have 1mm square sprues the first breaks up in the post, sometimes breaking the components, while the second hasn't broken yet.

https://www.shapeways.com/model/362383/br_conflat.html?key=69 e502b882f9c47a3cb6c4ff01235ed9
https://www.shapeways.com/model/22601/bwk0512.html?key=06ba51 837cd4f55a235687b76a4ce078

Ingeneral I would advocate placing your components freely into a rigid supporting framework so that any stress on the framework is not transmitted to the work pieces, for instance

https://www.shapeways.com/model/385476/small_bike.html?key=e6 d29e36bea12db0e05789ce0a683807
https://www.shapeways.com/model/263992/small_luggage_barrow.h tml?key=583f16b4153b73e016a05472adecd5d5

If that is what it takes - than that is what should be in the specifications.

I just need to know, adding frames and cages when they aren't needed is a waist of resources (both for Shapeways printing them, and for me paying for them to be printed).

An extensive frame like you suggest would easily double the cost of this particular item.

I know that any wire (no matter how large) has the chance to break - that is why I prefer the wires to be thin. If stresses are applied to break them - they fail first. With the larger wires (especially wires thicker than the parts themselves) you run a greater chance of the breaking wire actually breaking the part.

The connection point also comes into play. When I am looking to free the parts from the wire frame, I don't want to have a bunch of huge stubs to deal with. Bigger (and 1 mm is HUGE) normally require sanding at the contact point - even with a good quality pair of flush cutters. Thinner wires can be shaved flush with a sharp knife.

As to how they should be picked up - same way I do when I get the package...very carefully.

0.3mm for walls is thin, trust me, I've poked holes in prints just by cleaning them.

0.35mm for supporting wires again is too thin... yes, your wires are supporting, they're holding together much larger stuff, essentially they're sprues and 0.35mm for sprues is too thin.

The solution?
TBH, I'm not sure. The model looks like some sort of horse drawn carriage? Is there a way of re-positioning the parts to make the model more cube-like so that more parts are supported?

It is also worth remembering that with sprues/wires, they form part of the complete model file, Shapeways have no way of knowing what constitues a part made with redundancy in mind (e.g. sprue) or a part that is essential to the design (e.g. wheel spoke)

Frustrating as it can be, we all often face these little challenges and have to figure out a workaround.

Paul

We actually attempted this one but the wires snapped during post processing.

Keep this in mind:
Supporting = structures that has extra weight applied as compared with if the structure was just free form

Supported = structures whose weight is distributed or lifted by other parts of the model

While there is a wire in the middle of the long wire, that wire is attached to large structures and when you place it flat.. it supports the (much) larger structures. That wire is also 0.34mm and does not satisfy the supported wire rules. Because that wire puts put on the longer wire, it's hard to qualify the longer wire as supported because there is weight placed on the wire.

A few more suggestions:
- the obvious one: thicken the wire, this should be OK to your end model especially if the wires are used as throw away parts

- you can also place the two "plates" side by side as opposed to on top of each other. That is actually better for production as well. Just make sure there's not a lot of space between the parts--this makes production easier and makes your wires less likely to break.

That is unfortunate, both that the wires snapped during post and that the order was rejected. At this point, I am still testing the material to see how it handles different designs. For my purposes breaks tell me more than a complete model does.

Perhaps a tag/flag that can be applied to the model to let you guys know that we don't care what the result of the print job is would be handy.

Unfortunately, I am not too sure if that is as simple of a solution. The large plate that the wire connects to is also very thin. Connecting to the side (as opposed to the large flat surface) makes removal of the wire easier). There is only so much that you can thicken the wire before it is thicker than the part that it is supporting.

A solution might be to use an oval or rectangular wire. This would allow an increased cross section (with an increased strength) - however, I am not sure if you will allow that to pass your checks.

An oval with a major axis of 0.9 and a minor axis of 0.3 would have a cross section of 0.212 - a bit larger than a simple circle with a diameter of 0.5 mm. The thinner wire would make it easier to connect to the thinner parts - even though it is wider as well.

That will work, I actually figured that it would be easier to do the layouts with a more cube like shape than it would be with a large flat area of parts. If large and flat is the way to go - I can arrange my parts in that manner.