As I mentioned before: greater is misleading, as I don´t think the dimension is meant, but the accuracy.
Robin must reformulate the sentence, as it leaves room for interpretation.
bye, Tibor
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The greater refers to the dimension (i.e. +/- 1mm or 1%) and not the accuracy. It is common statement in engineering at least.
The below text is from the original quidelines draft text from 3DHUBS
FDM parts need to be produced within an accuracy of +/- 1mm or 1% depending on which is greater.
For example, in the case of a 40mm cube, a 1% accuracy requirement would result in a max of 0.4mm deviation. As this is below 1mm, the 1mm is leading and determines the maximum. A printed part of 40.6 x 39.4 x 39.3mm would be acceptable as the deviations are within this 1mm. Printing a cube that is 38.8 x 39.4 x 39.4mm would not pass the dimensional accuracy requirements as the width deviates more than 1 mm.
@Vienna3DPrint hmm, good point, I’m now wondering if I’ve read it the right way (as a native English speaker!). A better (but not necessarily ideal) sentence would be either of:
“FDM parts need to be produced within an accuracy of +/- 1mm or +/- 1%, whichever is the lesser inaccuracy.”
(so the 20mm cube should be produced to within 0.2mm, because 1% is less inaccurate)
or
“FDM parts need to be produced within an accuracy of +/- 1mm or +/- 1%, whichever is the greater inaccuracy.”
(so the 20mm cube should be produced to within 1mm, because that is the greater inaccuracy)
depending upon which meaning 3DHubs are actually looking for, and the 1% should be +/- as well. @Robin3D ?
edit (just noticed the doc does include examples)
Also with example it makes no sense.
40mm=2,5% (1mm), 400mm=1% (4mm) Why should the tolerance be bigger at smaller objects ?
40mm=1% (0.4mm), 400mm=0,25% (1mm) would be more accurate.
Maybe more understandable would be: Accuracy can be expected within 1mm deviation in any direction for objects below 100mm expansion and 1% deviation in any direction for objects above 100mm expansion.
But ok. Shall it be. I´ll pass on any questions to 3DHubs. It´s their guidelines, it´s their explanation.
bye, Tibor
Sorry @Georgei but your comment has made me think of this episode of Doctor Who: I can just see all the staff at 3DHubs fighting their way past mounds of 30mm cubes (to within 1% accuracy, of course).
Exactly…We try to solve a problem. Not create more.
Maybe to help quell the “uprising” support can pick top performing hubs, have them try the new rules out on a few orders and see how it goes… I feel like hub reputation is something people are forgetting plays a role here! If you consistently do garbage prints then that weighs different than if you do good work consistently. In the end I feel like we can sit and bicker but till we TRY the new rules we can worry ourselves bald over them… but till we begin to use them we can’t really say much.
@Joerg_4 on a serious note, the problem with approval by file (apart from the one given by @Georgei ) is that it’s a single instance of proof. Marvin suffers from the same problem; I can take a photo of a lovely Marvin and upload it, but there’s no actual proof it was printed by me, not a friend with a lot more experience and/or a better printer. If we were to use a test print for dimensional accuracy, ignoring the problem of the 3DHubs offices being overrun with thousands of prints, there would still be no proof that you were responsible for that accuracy or if it was your print, that you would continue to deliver such accuracy for all your clients.
Quality standards need to be something that can be checked by the Hub, the customer and, if necessary, 3DHubs for any print carried out, not something that’s done once (without any real proof) and then never assessed again.
From my own experience, you guys always side with the customer for obvious reasons, and as a hub you can’t do much to argue. Complain or call out the customer, and you’ve got a rubbish review that could ruin your hub, let it slide and people are quickly taking advantage of you. Honestly as I’ve said in the past, these new guidelines seem to be adding needless power to our customers over us and for what reason?
I strongly agree with this view. Obviously, if the guidelines don’t work we will not pursue
For 2. I fear the comments below touch on some good points.
I like the idea in 1. If the guidelines work (test) we can expand with this kind of finetuning (or if necessary to work). Will put the on the list with the experts (@Robin3D)