Hi everyone!

Misaligned expectations between a Hub and their customer is one of the biggest pain points for FDM 3D printing. In order to set the expectations of customers, standardized quality expectations need to be set and communicated upfront. With the help of some of our most active users we’ve set up these guidelines that every Hub will have to accept and follow when joining the platform. We think this will improve the overall customer experience on the network and the image of FDM printing in general. On top of that, we expect these changes to significantly increase returning customers and help them make an informed purchase decision.

A little while ago I introduced this idea on Talk and received great feedback. Since then, we created a first iteration and I’d love for you to give me your feedback as well.

FDM Quality Guidelines [DRAFT]

***Next to these guidelines we will also update the checkout flow of FDM orders to inform customers on the limitations of FDM printing***

***We will also update the General Purpose Plastics material page***

The goal of the FDM quality guidelines is to improve FDM printing standards globally. This will lead to the following:

  • FDM printing as a reliable option for professional customers, leading to more business
  • We’ll be directing customers to Hubs that print their orders according to these standards
  • Fair price/quality comparison between Hubs

These guidelines reflect the part quality you should be able to obtain using a well-tuned machine and post-processing.

GUIDELINES

1. DIMENSIONAL ACCURACY

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 1mm.

If you cannot meet this dimensional accuracy guideline with a certain material, the material in question might not be able to meet a customer’s expectations and should not be offered.

For example, if you are not able to prevent a part from warping while printing with ABS, you should discuss with your customer and either switch to another material that is less prone to warp (such as PLA) or the order should be cancelled so your customer can switch.

2. SURFACE QUALITY

  • Consistent Surfaces. The final print shouldn’t have any inconsistent surfaces. Small unavoidable inconsistencies such as retraction marks and a layer changing ‘seam’ are still ok.
  • No delamination. The layers should be firmly attached, resulting in a print without gaps or cracks.
  • Small details. Details larger than 0.8mm in the model should be well discernible in the print. If details on the customer’s model are (too) small, inform your customer of the result he can expect.

Please review the appendix for examples of what we consider poor surface quality.

3. FINISHING/POST-PROCESSING

The customer should always be informed during the “Hub Review” step when one or more models in an order require support material and which parts of the model will have support traces.

If additional costs are required, they should be added during the Hub Review step.

All support material must be removed and brought down to a level where the surface is continuous. Small traces of support material are often unavoidable and acceptable (see image)

IMAGE 1 Depicting a good print, support removed but not very well, traces still clearly visible.

EXCEPTIONS

These guidelines apply to all FDM orders on 3D Hubs and can only be deviated from when specifically discussed and agreed upon between Hub and customer in the comments section on the order page.

DISPUTES

If a customer raises a dispute, prints are reviewed against these quality guidelines. If the print doesn’t meet the guidelines, the customer has the right to be refunded under the 3D Hubs Buyer’s Protection.

APPENDIX

The appendix will contain a number of example of prints that do and do not meet the FDM Quality Guidelines. These photographs are still a work in progress.

Thank you in advance for your feedback!

Best,

Robin - 3D Hubs

22 Likes

Hi Robin, the support part interests me; unless printing with a soluble material (such as HIPS) using a dual extruder and set to 0 distance, I think it’s virtually impossible to get a good smooth surface on top of support material at anything approaching parallel to the bed (compared to the sort of surface you’ll get from the bed, or from a good top layer). For example, if you had a disk on a spindle, printing with the disc parallel to the bed, the underside of the disk is going to be uneven compared to the top side, or to how a disc would look printed directly upon the bed.

I’d be interested in your image of this problem, and your recommendations.

7 Likes

Hi @cobnut, thank you for your reply. We definitely realize that the surface area’s connected to support material can never be as continuous as a top layer or the ones directly on the bed. That’s why we mentioned: “Small traces of support material are often unavoidable and acceptable (see image)”.

We’ll also take a precise photographs of a part printed with with support and how it should look after it’s been removed. Here’s a preview of the part being printed at 3D Hubs.

If it’s important that a complex part has a similar surface finish both on the top as well as on the bottom (support) side, we highly recommend that you inform your customer that they should expect this in the final print. Alternatively, they should be guided to another 3D printing method such as SLS which requires no support material.

I hope this gives a good answer to the problem.

2 Likes

I think these guidelines are fair! My motto always has been (and always will be!) to discuss potential problems with a customer BEFORE we proceed with an order. last thing I want is the client to think their print is going to turn out like something off a polyjet machine when in reality… that was not the case. Best to discuss stuff now than get a lousy hub review.

Given the advances in slicers/printers you would be pretty hard pressed in my opinion to NOT meet the requirements listed but its good to see that you guys are laying out a set of standards to check your prints against. As for the supports usually a little work with sandpaper can do wonders for cleaning up a slightly rough surface… since most machines are same material supports there is only so much one can do to make a surface smooth, although a little slicer tweaking & post process work can work WONDERS!

3 Likes

I really like that the tolerances are taken into account. Plastic changes shape slightly once it cools, plus slicers, gears and motors all have tolerance limits on them so CNC accuracy just isn’t practical on FDM. Also kudos to the 3D Hubs team for working hard to bring changes and improve the platform.

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This all sounds great! All of your points were definitely valid, and I hope this can be implemented! My one concern is the dimensional accuracy. A 1mm deviation can be nothing or everything to the customer. Especially if they are printing a part with many moving pieces, they may desire greater accuracy. I guess it really depends on the customer… Other than that, though, this sounds great!

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Hi @Robin3D that image doesn’t really show how the finished surface will look… I think there should be photos comparing the top surface and “supported” surface of the same object once the supports are removed, although it’s a good idea to include the photo showing what’s meant by “supports” as it’s useful for the customer to understand the process.

3 Likes

I think a hub and customer would discuss that if something is say a device with “print in place” elements… usually the tolerances on those are somewhat large to accommodate for things printing weirdly if you will! That said it falls under the “reviewing an order initially” side of stuff :). If your not sure about your printer being able to handle stuff like that… then you may want to find some stuff on Thingiverse and test to make sure!

Is anyone else having the issue of not seeing any images on this post? The only image I can see is one down here in comments that’s supposedly showing how support material should look after a print, but is showing a part still being printed with the support material still on it.

Hi @PepCo_Parker, the images are still in progress. We’re currently printing the same part again and again to show different print qualities, which are acceptable and which are not. The picture in my comment was just a quick snapshot I took with my phone while printing.

That’s exactly right, these guidelines are set to that both Hub and customer have default expectations of a 3D print. If a customer needs the parts with higher dimensional accuracy, it should be indicated and this is what we’ll add during the order flow so customers are aware of what they can expect.

Hi,

Some comments on the guidelines:

1% dimentional accuracy is not good enough for me. I print loudspeaker cabinets at roughly 300mm x 200mm x 300mm scale. 1% would mean that a accuracy of 2.9mm is acceptabe. I cannot load drivers into the cabinets with this level of accuracy and would not be able to rely on prints adhering to these guidlines.

I don’t understand what a layer changing ‘seam’ means. I have received prints where there is a step in the surface and i would suggest that this is not perfect and therefore should not be allowed. I cannot sell products which have a step in the surface and i think this should be included in the guidelines. The guidelines need to have clear definitions (the photos will probably help!)

Disputes were previoulsy on the basis of prints being ‘perfect’. These guidelines seem to water that down in some areas.

I’d also like to suggest some content on infill. Infill has caused me all sorts of problems, not least because it is quite poorly defined. I asked two hubs to print identical stl’s (actually they were mirrored) and without any comms (because i was at this point completely in the dark about the concept of infill) one printed with triple wall thickness and infill of 20% on a 7mm thick enclusure wall (3mm solid - 1mm 20% - 3mm solid), the other printed with 1.2mm wall thickness and 15% infill (1.2mm solid - 4.6mm 20% - 1.2mm solid). One was 40% density, the other nearly 80% density. The difference was huge, and both were within the rules before the guideliness and would be within the rules of these guidelines. As such I think something needs to be included in the guidelines about infill. Or maybe on the ordering page.

In gereral supportive the the initiative.

Thanks

Chris

Hi @chrislloyd I think we’re talking about guidelines here for the majority of print jobs, rather than rules that define what a customer must accept from a Hub in a printed object. If you need better than 1% accuracy on your prints, you can specify that with the Hub, ditto infill and perimeter settings etc.

At the end of the day, a good Hub should make sure they know what the client wants and needs and discuss the project until both sides are happy. I think these guidelines are merely to help manage both customer expectations and Hub requirements, not necessarily to say prints that meet these guidelines are always “OK”, if you see what I mean.

Hi @cobnut Yeah that makes sense in terms of the general nature of the guidelines. And I agree that it remains down to me to specify what I need, but it is difficult to do that at first and I think some people may get put off by the difficult entry barriers. However, in the spirit of pushing the industry forward, in terms of quality and applicability of end use, I would stick with the need for dimensional accuracy and perfect finish. If I am a minority in this, then clearly they don’t need to go into the guideliness.

I guess there are two streams here, one which is focussing on low cost prototyping where these things don’t matter so much and the other is expanding into the production of finished parts. I see a bigger future for the industry in the latter stream.

Hi Chris, first of all, I should point out that these guidelines are for FDM only, and FDM has specific issues that don’t apply to SLA or other print methods. If you need “perfect” quality, it’s possible that FDM isn’t the most appropriate technology (although of course, some FDM prints can be very fine indeed).

I don’t think you’re necessarily in the minority, I think you’re right that broadly speaking there are two types of print being made here; prototypes and “finished parts” (and, of course, both these categories can be split down further). I (try to remember!) to always ask customers what the print is for but even if it’s a prototype I don’t see that as a reason to compromise on quality and things like dimensional accuracy can be just as important for prototypes (after all, a prototype is often used to test fit, etc.).

Where it can be an issue is where supports are necessary. As we’ve discussed earlier in this thread, supports can often leave an uneven surface - it’s simply the nature of FDM printing; it’s virtually impossible to get as smooth a surface on top of supports as on a surface printed directly onto the bed or as a top layer. If the print is for a finished product, this could be a problem (depending upon whether the surface is actually visible (sometimes they’re parts that are built in such a way that this surface isn’t external), but for a prototype it may be no issue at all.

@chrislloyd
Thank you for those comments. They perfectly illustrate why guidelines, setting expectations, and good solid communications are important to this issue.

It is my understanding that one of your prints did in fact fall below the current rules of 3dhubs.

Prints are supposed to have a minimum of 20% infill on 3dhubs.

In the case of walls, or shells as we call it in FDM printing, the rule I believe is 3 shells. So in both cases, the hub did both OK.

As for the layer changing seam, this is an important thing to point out as a difference between FDM and other forms of printing.

Primarily, what should be explained to the customer is they should have some expectation of seams.
It was mentioned in the previous thread that one of the common complaints from customers is that they were expecting the part to be fully smooth. That is, they were unaware that FDM is printed via hot threaded plastic drooling from a hot nozzle in tiny oval threads a layer at a time, resulting in noticeable layer changes. Thus, an explanation that there are in fact noticeable layers on the print is needed.

As for expecting “perfect prints” from such a technology, I think it depends on what one might define as perfect. I would never do an FDM print for a customer that was asking for “perfection.” In fact, I am not sure I would do an SLA print for someone that had an expectation of “perfection.” This is an unrealistic expectation in almost all disciplines of manufacturing, but definitely something that may be unattainable as you might define it, in 3d printing.

If you expect your print to have no shrinkage, no layers, no retraction marks, etc., then I suggest that you are a perfect prospect for the pre-order guidelines being discussed in advance of an order, so that your expectations can be brought inline with your perceptions of what FDM can deliver.

This is where a good solid relationship with a singular hub can be beneficial to you. Working with the same printer, same material, same brand, same color, same software, etc. can allow you to develop models that best match your expectations. That is, if your models need to be at perfect tolerances, you can then work with that hub to get to exact results. IF the PLA always shrinks at say .5%, you can always make your models .5% bigger, and get good fits.

I am not saying your expectations are too high, just that most customers need to be informed that FDM is the lowest cost, fastest solution for 3d printing, and as such, should be aware that if they need perfection, they should be notified of other options, that may take longer and cost more.

1 Like

Sorry, @Perry_1 I really, really, hate to do this, but the pedant in me simply can’t let it lie… If printing results in a 0.5% shrink, i.e. a 100mm wide part becomes 99.5mm when printed, then the model will need to be 0.5025% larger, not 0.5% larger. Sorry, I’ll go away now… :slight_smile:

1 Like

Hi,

Yeah I appreciate ‘perfect’ is not a completely helpful term in this sense. Although the reason I used it is because it is used in the FAQ of 3D hubs quite freely and used in terms of what would happen in the event of a dispute between printer and customer. 3D hubs have an expectation that a print will be perfect, otherwise a refund is available. As such, it needs to be dealt with in the guidelines or removed from the FAQ.

Understand on seams (these were layers in my mind) I’m slowly getting up to speed with the terminology. My concern was for steps in the seams, where the print is misaligned.

I would love to move to other techniques, but realistically, at my price point i’m only interested in FDM.

It would be nice if 3dhubs did not have to do this. This should really be handled by the hub. I know this is not happening, and this is why 3dhubs is trying to fix the customer expectation every time, because the number of complaints is too high, which costs them and the hub revenues when resolved. I know I am a prolific communicator on every order, and have even had customers exasperatedly declare to “just print it!” This is worth it, every time. I have had good luck with my reviews, and almost always it is about typing a lot up front!

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Support marring is a complicated issue, and needs a lot of explanation. For a small thin overhang that requires a little support, the print should show little marring. For a larger, wider, longer, flatter section that requires support, I tell the customer they should expect a very rough, marred surface.

This is because on a such a supported area, the surface is mostly bridged across the support material, and will sag minutely as it is printed across that area. The more of this that occurs, the less perfect that surface will be.

Additionally, support material across long surfaces also means that section of the print is being printed on less stable terra firma, and is thus going to be subject to a little more “wiggle” as the print is occurring, resulting is much messier surfaces on long, wide, flat surfaces held up by support materials.
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As for warping, shrinking, and corner curling with high shrinkage materials such as ABS, the customer should always be told this is a possibility or expectation. I always communicate this to a customer who has a print with large, long, flat models. I don’t have the issue usually, but I tell the customer it can happen, because I do not want to do a 10 hour print that the customer is expecting the next day, without them understanding that it COULD happen.

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Infill expectations I usually do not have to communicate. But it should be stated by 3dhubs, as it is unclear to many hubs what the minimum infill is supposed to be. I see many hubs that say they print 15%, but 20% is the minimum for 3dhubs, I believe.

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It would be easy for a large ABS print to shrink outside this tolerance of 1%, and I mention it as a possibility when ordering a print in ABS. ABS is a material used for injection molding, because it shrinks away from the mold so well!

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Additional expectations should be communicated to the customer when they order, by the 3d hub. Sometimes I can see the use of the model right away, and can see there will be no problem. A bust of Ceaser is all good with a little shrinkage. A phone case could easily shrink to the point of not being usable with ABS. Small holes in the objects are going to be the wrong size, almost always! So I always discuss these tolerances when I see them in a model.
A 10mm hole in one model, and a 10mm post that goes in that hole on the other model; I can almost always be sure there is going to be an issue. We are printing in a smashed hot thread with FDM, and it is going to smash outwards a little. If this is the case, I need to discuss it with the customer.

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I always type a lot before I accept an order. It takes time, but it is always worth it. It is all about looking at the model, material, etc., and discerning the use of the final print, or asking questions when that is not discernable. I ALWAYS want the customer to get what they want, not necessarily what they think they want.

I just did a quick review of some of my comments with customers, these are real:

-the posts on the thingiverse raspberry pi case will be very weak, and will likely break off if they are not careful

-some ABS orders should be printed in PLA

-gold PLA will not look like gold, it will look like plastic.

-get the drill bits out, because it will not work without it

-support material is going to leave your model unrecognizable, lol

-white will look better than black

-using it for cosplay, and going to paint it grey, it should be printed in grey, so that when it chips, it will be less noticable

-I cannot accept the laptop stand you designed, because it is so weak it will simply collapse

I am never shy about adding costs to the order for things the customer needs, like stronger infill, more shells, or better resolution. I offer .4mm layer height, because some customers just want a quick, cheap prototype. But I get orders from customers at that layer height, and I have to tell them not to do it! And I have had 3 orders where I told the customer to get it done with SLA, even though it will cost more and possibly take longer.

This is all key to a good experience for both parties. I have even told customers to get the order in PLA, and if it did not work out, I would reprint it again in ABS for free, to get them to switch away from a shrink prone disaster. I have never had a customer get it reprinted.

6 Likes

@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!