FUD Part Count

I'd like to start this discussion - on behalf of Shapeways - on the topic of Part Counts.

I look at some of the models out in the shops, and I cringe when I see multiple, tiny, floating parts that have no cage or sprue around them. I can just imagine how hard it is to contain all of that during cleaning and packaging, and I can fully see why sometimes a customer wouldn't get ALL of a model that they order.

One of my first questions is.. I have "heard" that sometimes Shapeways adds a "Sinter Cage" around some of our models. If Shapeways sometimes has to build a Sinter Cage around a model to round up a bunch of small parts - why can't we work out some mechanism where that cage is just shipped with the model?

I have zero clue how to go about accomplishing this. If I as a designer add my own cage, then the customer is charged for the extra material. But, on the other hand, if I layout 20+ pieces and some portion of that has to be re-printed because of "Lost During Cleaning".. can't we come to a midpoint where the cage costs less than the main body of the model?

My latest attempt at this is this model: It's got 50 separate pieces inside - each 2mm by 3mm!


FYI.. the previous version of this model had a 1mm thick sprue thru the center and it [finally] was rejected because the barrels were breaking off. I asked the question, but didn't get a clear answer.. Is this acceptable for a Sinter Cage? The walls this time are 0.3mm thick - is that considered enough?

0.3mm thick walls, how wide are the 'wires'?

Paul

But, what shapeways does cleaning team really think about the cage?

This could make his work more difficult. I'm thinking on tiny barrels rotating into the cage but keeping all the powder-wax between them.

And, if the cage (or box) is the solution for take control of tiny parts for the cleaning team, don't you think they were doing it and recycling the cage after?

I get what you're trying to do, but I'm not convinced your cage geometry is the most ideal regarding volume/cost. (Are those barrels really only 2x3mm? Yikes!) Being loose in there, they could clump together and would be a challenge to de-wax, inviting the techie to poke around in there to clean them out.

We do need to make prints robust enough to survive cleaning and minimise the number of loose parts per model, lest we incur the wrath of SW and get smited with a "maximum number of shells" rule! I hadn't heard of them adding cages at their end - that would take labour and add to their overheads. And can they recycle used fused FUD? I thought it was a one-way trip, unlike styrene plastic that can be re-melted.

Personally I tend to sprue up or cage anything that could get lost, leaving only a few bigger lumps (say 20mm cubed min size) loose. That way my models don't exceed any reasonable tolerance for the cleaners. But I can see how spruing your barrels would be a problem - unless you attached them by short 1mm stalks to the "inside" of a more spidery cage so any "breaking" force wouldn't reach them? I'm thinking laterally, to a guy who transported delicate wargaming figures by attaching them to the insides of a metal box with magnets in their bases - they were "attached" at only one point (so no scuffed paint or breakage from rubbing against packaging), but were protected from the outside world by the box...

Well, shapeways always said that they couldn't send rejected-after-printed models to designers due to the material is directly recycled...

I fully agree that the cage above could be sub-optimal. That's why I created this discussion.
For clarity, I used have these same barrels on a sprue similiar to this:

With the older structure, they were telling me that the barrels were breaking off during cleaning.

With FUD, the support material is a wax-like substance, and it melts (evaporates?) away when the object is placed in a small kiln for a few minutes after printing. With the cage structure above, all (or a reasonable amount) of the wax (should) be able to flow out - no toothpicking required.

The issue here is what kind of cage to build. Obviously, it needs to contain the items such that they can't escape. I would prefer that the cage itself not get classified as "wires", so in this case, i made the pieces wider than they would have to be for containment, but kept them very thin to keep the price down.

My goal is to find the midpoint between containment and cost and avoiding rejections while keeping the overall PART count to one - such that the operator only has to touch one piece.... no lost tiny pieces, no 2nd and 3rd reprints to compensate for a broken sprue.

From my understanding, that's not applicable for FUD. For White/Strong/Flexible, yes, but not FUD. The "wax" perhaps could be recycled, but the cost to clean/filter it is likely prohibitive.

Parts being lost from a sprue system says to me that handling is not as good as it should be.
What do Shapeways operatives say?

Paul
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I remember one year ago when I uploaded my first model.

It was ten WSF anti tank hedgehogs linked with a clean sprue with beam look to be reused for dioraming... and all the ten hedgehogs came loose from the frame!

I removed the frame. Really is worthless to cleaning team.

Yes, indeed, what do they say? Like in the other posts on the forums, not much, it seems.

Say about what exactly?

A sprue breaking doesn't necessarily land on bad handling. If you put a marshmallow on each end of a toothpick, you can easily hold one of the marshmallows without breaking the toothpick. But if you put a larger heavier object on both ends, the toothpick will eventually bend, break, have the item slide off etc. Cages, handling, and sorting methods are being investigated continuously.

I haven't been commenting on this thread most because Stony started with "I'd like to start this discussion - on behalf of Shapeways - on the topic of Part Counts."

Mike,

If a model follows the 'guidelines' but gets rejected for a 'broken part' as such might happen with an item coming off of a sprue, then surely we designers, medellers modellers (UK English spelling) and shopowners who are the backbone of Shapeways business model deserve feedback as to the reality of what is possible not the theoretical-non possible outcome of a model.

It used to be that possible borderline models would be printed and shipped without any reported issues.

So yep, what is Shapeways' input regarding this matter is very valuable - Shapeways have a lot more experience at what some of us are trying to achieve, have achieved, but don't succeed due to whatever reason.

Luis - this is a discussion about FUD, not WSF, please don't confuse the two as the materials are different, so is the handling process.

Paul
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Ok, Paul, but boxes and sprues is applied to both materials.

Of course they do, this works in WSF but would not in FUD!

Paul

Indeed, insights from a SW techie would be very useful! I design little things (but bigger than Stony's micro-barrels!) and routinely use 1mm diameter sprue stubs to connect them to a frame. I've had one broken off in the zip-lock bag, and often need nothing more than light finger pressure to get the FUD to snap. So I can appreciate the fragility of an inherently brittle material when they are handling it at the factory. If the parts are big, I either add extra sprue attachments (to spread the forces) or use a bigger diameter. (A good way to reduce snapping stresses at the joint between sprue and parts is to flare the joint out so it isn't a right-angle.) I've used 1.2mm diameter sprues as "keychain"-style loops through the open centres of otherwise loose wheels with good effect!

My take is I know how the material behaves, so I intentionally design things to minimise exposure to "snapping" forces. Sometimes it means nesting parts within bigger ones, or arranging them so the attached parts all point inwards, with effectively a cage of sprue bars on the outside to take any impacts. If it don't stick out, it's less likely to break off...

One thing we could use is a "score" system on our "My Models" pages, showing info like "number of prints ordered", "number of prints attempted", "number of successful prints", number of successful cleans", "number of reprints" - that way I can see at a glance if a design is failing at cleaning stage even If SW decides to do a reprint and doesn't send a rejection note. Otherwise, how do we know what is troublesome? (Sure, rejected orders come with an email about the problem, but not the ones they ship after a lot of unmentioned agro in the factory.)

One thing we could use is a "score" system on our "My Models" pages, showing info like "number of prints ordered", "number of prints attempted", "number of successful prints", number of successful cleans", "number of reprints" - that way I can see at a glance if a design is failing at cleaning stage even If SW decides to do a reprint and doesn't send a rejection note. Otherwise, how do we know what is troublesome?

Yes to this.

Paul

He did indeed start this thread with those words. You'll have to ask him why he phrased it that way.

The issue is that non-SW people can discuss these things ad infinitum and that is fine up to a point but only SW can give definitive answers, or implement changes/create new rules. If SW does not do that, then many of these discussions become pointless.

Stony has raised some questions that have not been answered. And realistically, while others may have suggestions, only SW can answer them.