Small Parts Test Kit

    A test assembly "kit" was made up of various part models and printed in one run.  Due to the overall size and complexity the run was a bit over 8 hrs.  Starting at the top in the left view the two "C" shaped parts are trailing truck spring saddles, between them at the top are four small front saddle mounts.  Below those are four rod shaped front trailing truck spring pull rods.  The two rectangles at the left with an "X" in the middle are frame spacers used on the front and middle frame assemblies.  At the right of those are a pair of spring "A" and "B" parts, "A" at left.  Below the frame spacers are two brake hangers that go on the front and middle frame assemblies.  Below those are four bearing assemblies for the front and back driver axles that interface with the frame and driver springs.  At the right of those are another set of trailing truck spring "A" and "B", "A" at left.  Surrounding and below the parts in translucent clear PLA is the green ABS raft and support structure.  Much of the time was spent building the ABS portion.  That portion is sacrificial and facilitates build and support during build of the PLA parts.

    At left is a close up of the four bearing parts that clearly shows the surrounding green ABS supports and the green ABS raft below.

    The two frame spacers did not require supports for overhangs and rest directly on the green ABS raft.

    The raft and supports did not always build properly.  At left is shown one of the two trailing truck spring saddles and above left one of the four front mount for the saddle is lifted.  The saddle is separated and distorted.  Above the right side of the saddle are three of the trailing truck spring front pull rods.

    The four pull rods are shown in position on the raft at left.  Some ABS supports were used to make the build.

    Two of the four front saddle mounts are distorted. This is due to the delamination of the raft structure.  The information provided by the manufacturer indicate that ABS will distort when structures over 100mm are built.  That is the case here, so the raft delamination is somewhat expected.

    The picture at left shows the other "C" shaped trailing  truck spring saddle.  This one came out good.  The green ABS material nearly surrounds portions of the model, however, it was readily removed by pulling the material away using fingers.

    Spring parts "A" and "B" came out fairly well, however, insufficient separation between the leaves resulted to permit the two structures to be interleaved.  Both portions operated as springs quite well and it appears that a design change using a modified "A" version will work quite well.  The "A" spring is at top with the round pin mount at left.

    The other spring "A" section did not come out well.  The PLA material was spread around near the top and leaves were distorted.

    The view at left shows the good spring saddle and saddle front mounts and pull rods above it.

    At left is another view of the four front-back driver bearing assemblies illustrating the extensive amount of support material used to deal with the overhangs present on the model.

    The driver brake hangers that attach to the front and middle frames are shown at left middle.  They also have extensive amounts of ABS support structure surrounding the parts.

    The view at left shows the parts at right after separation and at left the residue of the support and raft structure.  The green material is ABS while the white translucent parts are PLA.

    Overall the results were fairly promising indicating that small parts can be built successfully, particularly in PLA.  The small front saddle mounts are about 1/4" X 1/2" and have six bolt details, which are present.  The detail fidelity of the bolts is not very high, but they are recognizable as round objects and in the minds eye they are either bolts or rivets.
    The dimensional tolerance is similar to other models previously made, IDs tend to be undersized as do some outer dimensions.  Some are over sized, particularly outer dimensions of small objects.  These parts will be measured and compared to design values as part of an accuracy study.  The results should provide rules of thumb for size adjustment of design dimensions to result in somewhat better fit between mating parts.