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Calulate rapid prototyping stl build time

  1. Apr 18, 2015 #1
    I am not sure where this goes , if this is the wrong place sorry.

    The question is asking for
    Time required to build the part.


    The 4 is the total length of the part.

    It also says the scanning speed is 80ft/min
    the spot size is 0.010 in
    delay time is 7 sec/layer

    The formula that is given


    Ti= time to complete layer
    Ai=area of the layer
    v= average scanning speed of the laser beam at the surface
    D= diameter of the spot size
    Td= delay time between layers to re position the worktable

    I want to know the steps of this forumla.
  2. jcsd
  3. Apr 18, 2015 #2


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    Are you familiar with how a 3D printer works?
    If you put units into the formula and it should become clear.

    Time taken = (area to be covered / (speed of print head * width of printed line) + time to reposition for next layer
    Seconds = m^2 / (m/s * m) + Seconds

    If you know the layer thickness you can expand the formula to give a total time to make the part.

    Of course most parts are not printed with 100% infill so actual time may be significantly shorter.
    The actual time is difficult to calculate accurately (by hand) as it depends on the part shape, the slicing method, infill shape x, y, z max acceleration etc etc
    Most slicer programs can calculate it for you.
  4. Apr 20, 2015 #3

    Yes, I am familiar how 3D printing works. I have printed a few parts. I know that the printer will calculate the time, but the question is asking to caclulate manually .

    So when I calculate the time

    (I am choose the bottom surface)

    Ai=3*4 = 12

    When I enter it in the formula I get

    82 seconds

    82 seconds gave me the time to build 1 layer

    The question is asking how long will it take to build the whole part.

  5. Apr 20, 2015 #4


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    Science Advisor

    If the part is prismatic then each layer takes the same time so clearly:
    total time = #layers * (time/layer)
    To calc. #layers you need this information:

    If the part is not prismatic, you'll need to derive an expression for area as a function of height. Then maybe a bit of integration.

    Your formula assumes infinite acceleration of the print heat & 100% infill - not a realistic model and will give poor results.

    Is this homework? If it isn't, why not just use the printers software? Or upload your STL to an on-line print calculator? Anything else will not be accurate.
  6. Apr 22, 2015 #5
    This was a question from a exam where you have to calculate the time it takes. I know printers can calculate the time, but what can I do.

    When you calculate the time which was 82 seconds

    You divide the thickness/height by the layer thickness. The layer thickness can be any reasonable number.

    So in this case 1/0.02 = 50

    So 50*82 = 4100 seconds to make the bottom part

    Do the same thing on the top part.
  7. Apr 22, 2015 #6


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    Science Advisor

    Yes, that's right. If you choose a better (ie prismatic) orientation you'll get the answer faster.
    Let your image be the plan view/layer shape then layer area is constant and you have more time for other exam questions.
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