1. Got a question or need help troubleshooting? Post to the troubleshooting forum or Search the forums!

Solved Model Tolerances

Discussion in 'General Questions' started by Ryan TeGantvoort, Jun 1, 2016.

?

Model Fit Tolerance?

  1. 1%

  2. 5%

  3. 10%

  4. 15%

  5. 20%

  6. 25%

Results are only viewable after voting.
  1. Ryan TeGantvoort

    Ryan TeGantvoort Active Member

    Joined:
    Mar 11, 2016
    Messages:
    343
    Likes Received:
    172
    Hi everyone!

    I have been working on building some Riser Feet and a Swivel Case for my Full Graphics LCD. Based mostly on Mike Kelly's XXL Swivel Case (http://www.thingiverse.com/thing:681887) with a few modifications. :)

    I printed out my first case for the Sainsmart LCD and I had a few minor fit/sizing issues. Everything basically fit too snug. I was able to make it work for now though. My Riser Feet were pretty good had to make a few minor changes, but I don't plan to reprint them.

    So I was curious to see what everyone else is using for Tolerances while developing models?
     

    Attached Files:

  2. 3D Printer Man

    Joined:
    May 21, 2016
    Messages:
    226
    Likes Received:
    57
    I did print the feet, before my printer died at 15 percent.
     
  3. Ryan TeGantvoort

    Ryan TeGantvoort Active Member

    Joined:
    Mar 11, 2016
    Messages:
    343
    Likes Received:
    172
    @3D Printing ROBO Make sure you reading the questions. It's asking for Model Tolerances not Infill %.
     
  4. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
    Staff Member

    Joined:
    Feb 18, 2015
    Messages:
    5,905
    Likes Received:
    3,593
    @Ryan TeGantvoort Here is the problem for us as makers. If you design a model in CAD you generally model it in the exact dimensions it should be. As a part designer the actual measurements are sacred and we don't mess with those. In my experience if a designer messes with the dimensions to 'make something fit' then I move on to something else, because I know that part is poorly modeled.

    Printing is different, we are not LEGO and do not have all the material scientists they have so we cannot account for all the aspects of material properties. We only make rash generalizations of how parts need to fit together as well as the print settings we need to get there. Depending on the output material we make minor adjustments to account for our specific printer precision. I am most familiar with PETG and my Robo so I can only speak to it specifically. I know that if I have a part that must be a very tight tolerance and dimensionally accurate I must take my model and in the slicer of choice enlarge it by 0.2% in the X/Y Axes (my printer is very accurate in the Z axis). In S3D you double click the model and uncheck Uniform Scaling then I put 100.2 in both the X and Y Scale (%) boxes. For ABS which I almost never use I recall the number was 100.8 for my printer. For PLA I leave it at 100. You will need to experiment until you find what scaling factor works best for your particular setup.

    If you plan to share your model with others please note that adjusting for your printer in the model will almost certainly make it the wrong size for the next person who tires to use it. If it is dimensionally accurate they can apply their own scaling factor and make it work for them.

    If you don't want to read the whole message the gist is, good modelers do not adjust the CAD model to make it fit.
     
  5. Ryan TeGantvoort

    Ryan TeGantvoort Active Member

    Joined:
    Mar 11, 2016
    Messages:
    343
    Likes Received:
    172
    Excellent write-up @WheresWaldo ! Very interesting hearing someone else's take on this. That makes a lot more sense to scale the model in S3D instead.

    For some reason, I trusted a Model I found of the Sainsmart Full Graphics LCD (http://www.thingiverse.com/thing:146379) which I used to model my Case without double checking my lcd dimensions, once I received it. Rookie mistake! So it may have simply been an issue where his Model was either wrong or slightly different than my LCD. I am going to model my LCD now and go from there. Tried to cut corners and ended up hurting in the long run.
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,479
    Likes Received:
    7,303
    @WheresWaldo is correct, that is the best approach.
    Since all of our models are for printing we have taken to allowing a certain leeway in sections where overlap or fitment is critical.. How much depends on the filament. For most of what we do (PLA) about a 1mm tolerance on the fitment areas is fine.

    This is going to be material, modeler, environment specific I would expect :)

    Materials other than PLA (Nylon,PET, PC, etc.) have their own adjustment factors since every one shrinks/swells when put down a little different. Find a number that works for you and test/Adjust.
     
    Geof and Ryan TeGantvoort like this.
  7. Ryan TeGantvoort

    Ryan TeGantvoort Active Member

    Joined:
    Mar 11, 2016
    Messages:
    343
    Likes Received:
    172
    Thanks for your input @mark tomlinson ! My first model of the LCD case had everything fitting exact which I knew was going to be trouble but I printed it anyway.

    I have found the best way to learn is to fail, but learn from your mistakes! Especially since 3D printing and modeling for 3D printing is all new for me. I have been working with Sheet Metal for the last 5 years or so. This is a whole new world, looks like I get to teach myself another trade/process!

    Now I have given myself a small tolerance in the model. For Example: For the LCD Front Screen Opening I gave it a 0.5mm offset on all sides. Or are you saying I should be trying a 1mm offset?

    I am going to try without these offsets and increase scale slightly as well to see what works best. Do you happen to know of any small tests for something like this? This Case took close to 20hrs to print the Front and Back.

    I have only printed in PLA so far. Gonna be getting to new materials shortly though!

    I just printed a 20x20x20 Cube to see if I have issues with calibration. After measuring, I got 20.15mm (X-axis) x 20.13mm (Y-asix) x 20.00mm (Z-axis)? So it seems I have a little Run-out on X-axis and Y-axis.
     
    mark tomlinson likes this.
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,479
    Likes Received:
    7,303
    This. If you are not failing you are not trying much ...
     
    Geof and Ryan TeGantvoort like this.
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,479
    Likes Received:
    7,303
    You will likely find that if you care to fine tune it the numbers you get will vary a bit from filament types.
    1mm works well for our stuff with PLA (most of the time). I would experiment and then dial it in using a small model.

    Create a smaller version of your model that contains just the elements you want to test (a hinge for example, or just the overlapping planes). Print just that portion. By small I don't mean scaled down, I mean just a portion of the entire model. You want something small so it doesn't take hours to test or a lot of filament either :)
     
    Ryan TeGantvoort likes this.
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,479
    Likes Received:
    7,303
    You could for example create a small dowel and a circular plate for it to fit through and keep tweaking the sizes and printing until you are satisfied with it.
     
    Ryan TeGantvoort likes this.
  11. Ryan TeGantvoort

    Ryan TeGantvoort Active Member

    Joined:
    Mar 11, 2016
    Messages:
    343
    Likes Received:
    172
    Thanks @mark tomlinson for the idea with the circular plate and dowel. I will give that a try and see what I come up with. Otherwise, I was going to print a section of the Case until I got the result I am looking for. Basically cut it down in SolidWorks and only print the problem area. The plate and dowel seems like a faster solution.
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,479
    Likes Received:
    7,303
    The plate and dowel will get you close. If you are a perfectionist (I know we are) then you may still want to use SW to extract the problematic section and do further testing/fine tuning. Eventually you will come up with some general 'fudge factors'that work for each filament type :)
     
    Ryan TeGantvoort likes this.
  13. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
    Staff Member

    Joined:
    Feb 18, 2015
    Messages:
    5,905
    Likes Received:
    3,593
    @Ryan TeGantvoort Sometimes if I am just testing fit, I might print the object with 2 perimeters and no top or bottom layers and a low percentage of infill. It will look funny but can print very fast. Sometimes I even cut the part and only print a section.
     
  14. KTMDirtFace

    KTMDirtFace Well-Known Member

    Joined:
    May 18, 2015
    Messages:
    1,247
    Likes Received:
    461
    I tend to not like to do the "scaling" in simplify3d. Not on parts that I want to fit anyway. I prefer to put the slop in the cad for myself.

    I don't want to scale everything on an axis normally sometimes its just one hole i want to enlarge or something.. so I like to fix it in the CAD model for my needs. If i'm making a random thing thats not a real life thing. I use about .2mm-.3mm slop for parts that should fit together.. but thats just works for me and sometimes it doesn't lol. who knows on anyone else.
     
    mark tomlinson likes this.
  15. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
    Staff Member

    Joined:
    Feb 18, 2015
    Messages:
    5,905
    Likes Received:
    3,593
    Here is why I like scaling in the slicer and not the actual model. We work with plastic and different plastics have different shrink rates, so you cannot use a universal model adjustment and make it work for every situation. Also what if you have someone that wants the model and will be using a CNC machine or some other disruptive manufacturing process (SLA, SLS, SHS). No CNC operator wants to mess with the model just because it was ADJUSTED in the CAD program. If you are building it only for yourself, then by all means do it however works. If you ever plan to share it, then do it better!
     
  16. KTMDirtFace

    KTMDirtFace Well-Known Member

    Joined:
    May 18, 2015
    Messages:
    1,247
    Likes Received:
    461
    Yea I get your point and it makes sense but I have never found scaling to work the way I want it to.

    I made this stupid thing on thingiverse, if I had put it up there with REAL dimensions I would have got a bunch of messages that it doesn't fit. So it has some slop built in. People want to print crap on thingiverse brainlessly not print then scale it after the fact until it does fit.

    http://www.thingiverse.com/thing:987937
     
  17. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
    Staff Member

    Joined:
    Feb 18, 2015
    Messages:
    5,905
    Likes Received:
    3,593
    If you put up a model with the correct dimensions and people complain just remind them to calibrate their printers better. I have had only one complaint regarding size on all my models. Told the guy to calibrate his printer precisely and never heard from him again. It is not your problem to fix other people's calibration issues.

    In the same token it is your responsibility not to add to calibration issues either. That is what you do when you share models that are not dimensionally accurate. That is also why I have started to share a STEP file with my models. If you don't like my measurements you can modify it yourself.

    Just my opinion.
     
  18. KTMDirtFace

    KTMDirtFace Well-Known Member

    Joined:
    May 18, 2015
    Messages:
    1,247
    Likes Received:
    461
    Well my own printers have never printed a lets say 3mm diameter hole at 3mm.. do yours? I don't think anyone's FDM printer can do that. Its close but its never 3mm.
     
  19. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
    Staff Member

    Joined:
    Feb 18, 2015
    Messages:
    5,905
    Likes Received:
    3,593
    Actually yes they do, in PLA.
    in PETG I need to scale a bit as I mentioned.
     
  20. KTMDirtFace

    KTMDirtFace Well-Known Member

    Joined:
    May 18, 2015
    Messages:
    1,247
    Likes Received:
    461
    Yea I don't know I haven't noticed much difference from PLA/PETG.

    Also its really hard to share "exact dimensions" in 3d printing when your making hodgepodged things to fit other things ( that you didn't design or even know the exact dimensions, measuring isn't good enough )

    But I do understand what your saying about sharing a CAD file with exact dimensions, yea if E3D or somone shared a cad file of their Extruder..it better be exact dimensions.

    I'm messing with this titan mount, i first measured it for that small stepper motor, but now that i'm trying to fit the stock motor on its slightly taller and wider from that one, not by much but it is diffrent.... so diffrent manufactures made diffrent sized motors slightly. I cannot account for that so I put slop into the cad. I can't just scale it because that would screw up other things in that currently fit. I havn't released the cad on thingiverse or anything though. But i'm just saying making 100% dimensionally accurate stuff in CAD for 3d printing.. unless its a 100% from scratch design... I dont see it being possible.
     
    #20 KTMDirtFace, Jun 1, 2016
    Last edited: Jun 1, 2016

Share This Page