for 3d printing to be fast enough for rapid prototyping and strong enough to be mechanically useful the use and placement of material must be optimized. more material in structural regions and
strength of 3d printed parts, less material in areas that are mainly cosmetic. given a solid model, the placement of material is controlled by slicing software and they don't always
make good choices. until we have better slicing software available, let's look at a couple of methods for helping to control the placement material in 3d prints. our example is the base of a hummingbird feeder. the original has deteriorated in the sun and now leaks. the base screws onto a glass jar that holds nectar and then a perch attaches
to the bottom with a screw. besides being watertight, we need some basic rigidity between the areas holding the perch and the glass jar and when the screw is inserted into the bottom we can't create a leak. so we want a good amount material in this region but a minimal amount material at the edges. here's the final 3d printed part. because
the threads are part of a complete cylinder the jar is actually held more securely than with the original base. i originally planed to use heatset inserts to receive a screw for the perch but these screws are quicker to install. they're used in computers for securing fans to the case and thread into soft plastic nicely.
this is the first solid model that my wife designed and she did so using a caliper, fusion360 (#fusion360) and tutorials from autodesk site and nyc cnc's (#nyccnc) youtube channel. she did a great job on a complex first part. the thread in the the center was the most challenging and that was printed separately for test fitting. our replacement part differs only slightly
from the original. the sides are much thicker at the bottom to enable 3d printing versus the injection molding of the original. also our replacement allows the glass jar the recess further hopefully keeping wasps out of the nectar. looking at a cross-sectional view these areas are solid and thick. if insufficient material is allocated, especially to
overhangs, a print can fail quickly. to export the model for 3d printing select the 3d print button and then select the model body to create an stl file. the tessellation process takes a few seconds even for small bodies. the stl file is then loaded into simplify3d a commercial 3d printing package. a slicer configuration in simplify3d
is called a process. let's start with a default slicing configuration which uses 10% infill. i've had good success with simplify3d on an original makerbot and taz 5 3d printers and it has saved me enough time to justify the cost. i've also had success with the makerbot software and cura but simplify3d gives me a
consistent interface to different printers again saving time. in preparation for printing we can examine the slicing layer by layer. solid layers are marked in green and in filled layers are marked with orange. we can see the entire part including the base uses minimal material. the infill pattern reduces material usage and is pretty but
the top layers will never bridge the infill wall nor will this print be watertight. to make the base watertight will make the base solid in simplify3d. we can define multiple processes and toggle between them based on layer height. we'll begin by creating two processes, one for the base and the other for everything else.
the base is within the first 3.5 millimeters, so the first three and a half millimeters will be sliced by the first process with 100% infill the second process will begin at three and a half millimeter and have 10% infill. we name the processes to reflect their configuration. because each process is only valid
for a certain range of layers we must select both processes to slice the complete part. this approach works okay and helps to make the base solid while saving material on the sides however the center above three and a half millimeters is still sparse. we need more control over slicing than simply specifying a range of layers. in
fusion360 we can partition the original parts into two bodies where one body has 10% infill and the other body has 100% infill. to partition the part, we will use the slice body command. first we'll create a copy of the body just for reference if we need it. using slice body, select the copied body and then an element to slice with.
this operation created more than the two bodies that we wanted but we can combine the extra bodies. now we export each body to its own stl file. we again import the part, now consisting of two stl files. import them together or one at a time. if imported together they will appear side by side but if imported separately they will probably
overlap but be placed on the build platform. regardless of the import method, use be sure to select the align selected model origin so the two bodies are correctly aligned to each other. we again use two processes but without layer ranges. instead of layer ranges, we associate each body with the appropriate process.
the base body is assigned to the 100% infill process, and the side body is assigned to the 10% infill process. because the side body continues from the base body there is no need for bottom layers in the side process. now we prepare the part for printing, selecting both processes. examining the generated slices we see 100% infill is used for the base and the entire center
region and 10% infill is used for the sides. there are also no extra bottom layers between the side and the base bodies. before ending this video i'd like to show an additional example that's maybe more generic. this is a shelled cube in fusion360 with a series of small holes on one side and slightly larger holes in the adjacent side. we
want to use minimum material for the cube while stiffening the holes with 100% infill. we start by making a copy of the body which will shortly become our tooling to create the stiffeners using a constructive solid geometry cut operation. material is now removed from where the stiffeners will later be. this backward approach may take some getting
used to. for additional variety with the larger holes we'll create a single stiffener that binds all of the holes together. with the stiffening region defined it's cut from the tooling. with the csg tooling now defined we can create another copy of the box that will become our stiffeners.
with the target and tuning bodies defined we use the combine bodies cut operation to create the stiffeners. this operation removes from the target body all material that overlaps in the tooling body. for convenience, a new group is created to contain all of the stiffeners. now we can easily toggle the visibility
of the group of stiffener bodies and the box body. with either of these enabled independently we go to the top of the browser tree and select save to stl. this is a shortcut to the 3d print option. finally we repeat this process for the stiffeners. by having them organized as a group that allows us to export all the
stiffeners on single stl file. back in simplify3d we import both the box and the stiffeners. next we align them to their common model origin. because the models need to be rotated and we want to rotate them as a unit we combine them together into a group. after rotating, the group is aligned and centered on the build
platform. just like the previous example two build processes are created, one for the stiffeners with 100% infill and one for the box with minimal infill. the fun part is always reviewing how the slicer has interpreted the model. in this case we have two overlapping bodies with different processes. the box is receiving minimal material inside except for
around the stiffeners where 100% infill is being used. i included this additional example because it feels more generic. the stiffeners are being built into the vertical wall instead of up from the build platform. they're also defined using sketches which means that you could have arbitrary shapes and these shapes could actually be embedded within
the object. it's also possible to review the bodies independently. simply select only the process associated with that body. given the advantages that we've seen from integrated cad and cam in fusion360 and the growth of 3d printing someday we'll be able to guide the slicer using tools inside a cad. there the designer could pass their intention
along to the slicer. combine this with generative design and simulation and the software package would be a next generation design tool. i always struggle to balance print time and part strength the approaches we've looked at provide some basic tools for optimizing. if you have any ideas or suggestions please share
them and let's learn from each other.
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