Feedback request for upcoming FDM Quality Guidelines

[Perry_1]

@cobnut

Thanks for that, that is pretty good! I would have printed that part, and it would have been off by 25% of the width of the hole in my nozzle, on each side!

[cobnut]

Sorry, I had an attack of Friday afternoon mischief As it happens I’m doing an order now where the customer needs very accurate dimensions. One print had an X of 117mm and it came out (in ABS) as 116.68mm. Pretty happy with that but an going to reprint at 100.4% to see if I can get closer.

[Perry_1]

I did not know remember that in the FAQ, and sure enough, you therefore have every right to expect it. It really is a bad term to use for complaint resolution. Wow, that needs to be a different phrase.

As for your price point, that is exactly the key. Realistic expectations for the technology, and thus realistic expectations for the price.

There are more perfect ways to 3d print, and less perfect ways to 3d print, but there are probably no perfect ways to 3d print.

But sometimes the customer is looking for that perfect price point, in which it is likely FDM will be more perfect!

[Jackson_Moody]

Great! That makes perfect sense! Thanks!

[Odense3DPrint]

@Robin3D

also that is on an ultimaker… but maybe 3dhubs does not care what printer is in use?

[Enza3D]

I do want to add that guaranteeing dimensional accuracy is a bit of a point of concern for me. I am not concerned by my ability to meet it, I am concerned by customers potentially misinterpreting what that means. Guaranteeing dimensional accuracy does not make any difference if the part is poorly designed; i.e. the design of the part does not take into account tolerancing for mating parts and such. This is the classic example of making a 2 mm hole for a 2 mm rod; even if the hole is perfect, the rod will never fit into that hole, because the hole does not take into account dimensional variations that will occur in the rod. It will need to be made explicitly clear to customers that this guaranteed dimensional accuracy is based off of the model they provide, not what they intend it for. If a part is provided that is 2"x2"x2", then it is only the Hubs responsibility to make sure that the print is within your set dimensional variation.

My other concern with this is that it’s a royal pain in the butt to get dimensions from STL files as that is not really their intention; STL files just contain information about the geometry of the surface but contain no data about dimensions. If 3D Hubs is going to implement dimensional accuracy requirements, either the customer needs to provide the dimensions (such as via a drawing or by filling out a form), or Hubs needs to require uploads of parametric models instead of/along with STLs. I do not want to be held responsible for a dimension being wrong because I more or less need to guess as to what the dimension should be. Just my 2 cents on it.

[PepCo_Parker]

This raises a good point, a customer may ask for money back on a part that is according to them dimensionally inaccurate as it doesn’t fit into other parts, when in reality the issue may be the part design itself. This would be very hard for 3D hubs to gauge when siding with disputes. Almost impossible I would think in fact.

[Enza3D]

If the issue is with the part design, then it is the fault of the customer if the final print does not work as expected. Tolerancing is a core tenet of mechanical design; if you brought a poorly designed part to any prototyping shop, it’s on you if things don’t work once manufacturing is done. If a print is within the allowable accuracy range (1 mm or 1%) then it’s not the Hubs fault.

Shapeways and any other larger print shop is very much what you see is what you get; as long as they deem a part printable, they will print it but that’s it. If it was printed how it was supposed to, they do not care if the design itself was incorrect.

[PepCo_Parker]

Yes but let’s say two parts were designed to fit each other, but we’re designed improper via a hole or gap being a mm too small or too large. Diagnosing these issues before printing is nearly impossible, and the customer could argue they don’t fit due to tolerances of the hub being poor. Both of these sides of argument are hard to prove unless you are there in person. With the way 3D hubs handles refunds I could forsee it being an issue

[Enza3D]

That improper design will show up in the model, and that is why I suggested also requiring either a form/drawings or parametric models. If the feature in question is in the model, there is no argument about who’s at fault and parametric models display all this information with a couple clicks. It is not the job of a Hub to comb through a model and find problems, that is the job of the designer to prevent in the first place. If a feature is designed to be 10.5 mm wide, and the Hub produces it with a 10.1 mm width it’s correct by 3D Hubs definition. I know each Hub handles this differently, but this is the reason my Hub does not guarantee pieces will fit together unless we designed them. It is on the customer to make sure the design is correct, we just make what they give us. If we design it, it is designed with appropriate tolerancing for any mating features and I have no issue guaranteeing it will work because I made it and know what I am doing and the tendencies of my printers.

This is also why I think implementing a guideline like this will cause problems, and I agree with you there.

[Odense3DPrint]

@Robin3D has an “official” test piece been made?

i want to be on this “wagon” since it will indeed ensure somewhat a minimum level of print quality

Also how will you verify this? i could imagine that the hub print the test bit an use a caliper and photo document that it can be printed right.

Just like that you have to print a marvin when you create a hub

And while at it i think that there should be an option to reverify this… ie when hub rebuilds printer etc

[Joerg_4]

Good points, you are absolutely right!

Hopefully one of the 3D Hubs officials will reply to your post, may be @Robin3D

Cheers,

Joerg

[Robin3D]

Hi @Boelle,

That’s correct, the FDM Quality Guidelines will be the same for all FDM printers. We can’t expect every customer to know what kind of quality they can expect from a specific printer model/brand so that’s why these guidelines will set a standard for all FDM printers.

Best,
Robin - 3D Hubs

[Perry_1]

@Enza3D you are so smart.

Yes, there is no way, outside of the dimensions of the final X,Y,Z part, that a tolerance can be checked, in any realistic way, without donating hours to each model.

I would assume we are not being asked to load some software, put the model in, check the size of all the various features, check the tolerances on each, etc., and make sure they are all within spec.

SO, this dimensional accuracy should always be on the final XYZ measurement, as the tolerance “guarantee” if you will. The size that is displayed on the 3dhub page, or in the slicer software as bounding box size, if you will.

[Robin3D]

@Enza3D, @Joerg_4, @PepCo_Parker, @Perry_1

Hey guys!

Thank you all for expressing your concerns and giving me your feedback. I really appreciate it. The reason that we have to set guidelines on dimensional accuracy is because we have to draw the line somewhere and we thought setting a 1 mm tolerance would be a reasonable first step.

I completely agree with the fact that you, as Hubs, cannot know the application of your customer if they do not communicate it. Ofcourse in some cases you will have an idea by looking at the design that it’s part of an assembly and in this case you can double check with your customer if a 1 mm tolerance is sufficient.

But in most cases this is not the case and also, not your responsibility. If you receive a model from a customer and you print it within the guidelines that we as 3D Hubs set, you will be paid out for the job no matter what.

When a customer is not happy because the print does not exactly fit, we will ask them to take a photograph of the print next to a measuring device such as a digital caliper to show the exact size of the print. Of course we do want to keep our customers happy but this is not always the responsibility of the Hubs.

Feel free to reach out to the 3D Hubs admins (such as myself) at any point if you have a situation where the customer is not happy with the result but you printed the part according to the guidelines, we’ll definitely be able to help you resolve such a situation.

Best,
Robin - 3D Hubs

[PepCo_Parker]

Hello again Robin, So to me this means hubs will have to start watching our backs by taking photos our selves of parts with calipers next to them, it wouldn’t be hard to fake photos to make it seem like parts aren’t the right sizes when they really are. This would be the only way to insure people aren’t cheating us out of good parts, but even then now we have to charge for our time photographing and setting all that up

[Enza3D]

My costs are definitely going to go up because of this; even if the verification is for my own insurance, it’s now another step I have to do for every print and that will be reflected in my prices. Because you’re right, there’s no way to prove it is correct unless I have already verified it myself and have pictures of it.

The problem is, how do I know if a dimension is right or not? Unless I have a parametric model file, or the customer explicitly specifies the dimension of a feature, I have no way of knowing (other than guessing from the STL) if it is correct.

[PlastiPrint3D]

My issue with these guidelines is quite simply the policing of them. Are you going to ask the customer to send you the 3D print so you can verify the dimensions yourself and make a ruling on it? Not every customer will have a set of calipers and even if they do, use them correctly to get an accurate reading.

Also this requires that I record how each model has been orientated in the slicer as your tolerances are in the X,Y and Z axis however that’s not to say that I printed a model along these axis. What if it’s a curved model that was printed at 45 degrees so that while the length of the curve is beyond the 1mm tolerance, the actual readings in the X,Y and Z axis weren’t?

And lets get something else right here, these guidelines aren’t designed to make my life as a hub easier, they are designed to make 3Dhubs job easier. I am now going to have to record, document and photograph more details of a print before sending it out.

[PepCo_Parker]

That’s exactly my point. How could someone say what the customer shows tolerance wise is correct? It could very easily be wrong or misleading. In reality, 3D Hubs up until this point has in my opinion been running a great part just on mutual trust. If a customer requires a specific tolerance, as far as my experience goes they would specifically address this before I accepted the order, and I could respond accordingly. Same procedure as asking about infill, layerheight, material, and colour. Has tolerances become such an issue suddenly or is this merely a non existent problem being fixed. ‘Don’t fix it if it ain’t broken’. All I have to say is this is definitely going to impact customers who may have preferred just a cheap part and didn’t need tolerances greatly. It will certainly force us hubs to constantly watch our back now as an unruly customer can backlash quite easily and request an unfair refund. And I don’t mean to be Curt, but don’t respond saying all disputes are handled fairly. I have had situations before where I should not have lost money on jobs, but had to accept as 3D hubs heavily pushes for the side of the consumers. As well a fight in that situation would most likely have lead to a poor review and hurt my hub greatly. We are already at the will of the consumer, this is just giving them even more un necessary power. If a customer specifically needs a certain tolerance then I don’t see why they can’t just request this, why does 3D hubs specifically have to get involved?

[Enza3D]

To keep it even somewhat fair, Hubs would have to physically measure the part themselves. A customer could easily take the pictures at a skewed angle to warp how the print looks or improperly calibrate calipers so that the device measures incorrectly. If a Hub hadn’t measured the part themselves, they have no defense in the dispute and I don’t think this thinking is being paranoid either. It’d be a quick way for a customer to get prints completed for free, and for larger jobs, I can see this happening quite a bit. It’s very easy to edit photos, and I will not accept that as the only way 3D Hubs decides if a print order was completed correctly or not.

If Hubs wants to implement dimensional accuracy requirements, then that’s fine but you have to be able to implement it/police it fairly and provide your Hubs with the tools they need as well. I feel like a broken record here, but getting dimensions from an STL file is inaccurate and inefficient; if I need to verify dimensions are correct (which now I do), then I need to know what they are in the first place. I can only do that if the customer tells me what they are in a drawing, or if I have the parametric model. I can ask a customer for the file, but if they don’t have it and can’t clearly communicate what dimensions are required, these new guidelines will force me to turn them away. The risk is too high otherwise.