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  1. #1

    What constrains quality on a 3d print?

    Instead of going all out and doing a custom build, I'm going to see what I can learn putting together a Prusa i3. I am wavering between buying a kit and piecing all the items together for the full BOM myself. I

    I don't know that I'll save money piecing an i3 together, but I'm hoping to increase quality.

    So, in terms someone who has never 3d printed could understand, what limits the quality of a 3d print? Stepper resolution? Pre-print settings? Temperature control? Frame stability?

    On the note of temperature control: I've gathered that a heated bed is important/essential, especially with ABS. What about after the layer has been printed? What if were to rig up a controlled flow of heat around the item as it's being printed in an effort to maintain (reasonably) consistent temperature for all layers throughout the duration of the print.

    I do plan on setting up some tilt correction. Any advice on what to go for there?

    What do I need to spend a few more dollars on to get better overall performance? I don't want to send a tremendous amount of money, but I would appreciate any tips on where I should spend some extra money.

    Thanks for your time.

  2. #2
    Staff Engineer printbus's Avatar
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    All the things you mention can affect print quality.

    FOLLOWUP COMMENT: The resolution of the stepper motors themselves is pretty standard (200 full steps per revolution). What matters is the amount of microstepping applied (typically ranging from 1/2 to 1/16), and the nature of any gearing between rotation of the motor and linear movement of an axis.

    If you're sold on a Prusa i3, I'd suggest taking a look at the i3v series printer kits from MakerFarm - they are a variation of the Prusa i3 that utilize a combination of a veneered MDF frame and aluminum v-rails, with delrin wheels that ride in the v-rail channels for all movements. This combination leads to a rigid frame with very smooth movements.

    The MakerFarm subforum here contains a lot of user input on build help, printer mods, and even implementing automatic bed leveling/compensation.
    Last edited by printbus; 01-17-2015 at 10:12 PM.

  3. #3
    Super Moderator old man emu's Avatar
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    Quote Originally Posted by printbus View Post
    All the things you mention can affect print quality.
    That's the whole crux of learning how to 3D print. You can't just download a file from any of the numerous sites that offer them, nor use the file of an object you have created using your CAD or modeling software and shoot it to a printer expecting a perfect object to be printed. The big step between design and physical object is the generation of the code to create the object. This code is a standardized one that is used by computers to control the movement of machines.

    In general, the code is called G-code because the movement commands consist of the letter "G" and a number which relates to a particular movement. If you consider the ANSI code for letters and numbers used elsewhere in computing, you'll get the idea. There is also a sub-set called M-code and its commands are used to control ancillary functions such as turning on fans and other things not directly related to movement.

    The code is generated by special software called slicing software. This software is used to compute the number of layers required to create the object, based on the thickness of each layer which the operator sets. Then it interprets the operator's inputs regarding the type of infill required; speed of various movements, thickness of filament and a whole lot of other inputs until it produces a file of instructions which can be fed to the printer to create the object.

    If you are starting off, building and setting up your printer is the simplest part of creating an object. It is getting the experience of selecting the correct slicing inputs that is the difference between a novice and an expert 3D printer.

    I agree that the MakerFarm i3v is a solid foundation for learning about printer design and construction. It is not a plug'n'play printer, but is not difficult to assemble and there is scads of backup from both the manufacturer and the users.
    Old Man Emu
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    But you won't outlast me!

  4. #4
    Thanks again for the replies.

    In respect to the setup:
    Are there any pitfalls to setting layer height somewhere around the capability of the machine? I'm assuming that this will create a smoother part.
    Next, is this calculation for the capability of the machine's minimum layer height correct:
    M5x1.5 lead screw = 1.5mm for one full revolution.
    1.8 degree steps = 200 steps per revolution
    1.5mm / 200 = 7.5 micron z axis resolution ???

    Even giving it room for slop, the .1 mm or 100 micro layer thickness I've seen recommended for higher quality prints seems too large. Is it within the realm of possibility to print at say 40 or 50 micron layers?

    The extruder I bought came with a .4 mm nozzle. I also bought a .2mm and .3mm nozzle. I'll probably start with the .4mm and work my way down as I learn. What problems might I experience?

  5. #5
    Staff Engineer printbus's Avatar
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    I can't answer all of your questions, but note that standard M5 threaded rod has a pitch of 0.8mm, not 1.5mm. Printers will often also use microstepping, which increases the theoretical resolution even more. Various other factors come into play, however. For example, backlash in the threaded rod drive will create a positioning error. Also note that even though you might be able to mechanically position to an ultra small resolution, you also have to look at what the firmware and the extruder hardware have to do in order to extrude the right amount of filament for that layer height. The printers I'm aware of don't have as much resolution in the X and Y axis, so is there much to be gained by having an ultra fine layer height, especially when it increases the print time?

  6. #6
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    From the site Microstepping: Myths and Realities
    "In summary, although Microstepping gives the designer more resolution, improved accuracy is not realized. Reduction in mechanical and electromagnetically induced noise is, however, a real benefit."
    Which was news to me...

  7. #7
    Thanks for the correction on the rod pitch. Excellent point on the x & y resolution.

  8. #8
    Technician -willy-'s Avatar
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    Also remember filament storage plays a part in quality of prints. If your storing the filament out in the open you will find water issues and endless clogging. General consesus about how to store is a container from a fish tank to some type of plastic container. There is usually some form of water absorbent material. Some people are using clay type kitty litter, rice, I myself will be getting a reusable dessicant from Amazon. The dessicant I will be using costs about $7 that I will attach to the inside of the container. The dessicant changes color when it needs to be recharged. Recharging is nothing more than placing it in a oven at 150F for a couple of hours.

    Here is a vid of some one that was having water issues with their printer.

  9. #9
    Engineer-in-Training
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    Or use PET filament, which does not absorb moisture.

  10. #10
    Quality should be the main concern of any business. You are thinkg about to enhance the quality of your printing is definitely give you a lot benefits. Don't think mush about it. If you will serve quality work, you will definitely get good from it.

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