Designing a leaf spring assembly

    The trailing truck spring along with driver springs are leaf springs with many thin layers.  The limitations of the 3D printer and a desire for approximate prototype operation of the springs was pondered for quite awhile.  The 3D printer can print x and y lateral dimensions in quite small increments, however, the manufacturer indicates that vertical walls must be 25/1000 inch (0.025") or greater limiting the minimum size of z features in x and y dimensions.

    Each leaf spring is composed of many thin spring leaves layered in a holding band.  Considering the limitations for printing each spring assembly is designed as an assembly of alternating spring leaves 25 thousandths thick spaced 30 thousandths between leaves.   During printing the part will be on it's side so that each leaf is built as a thin wall across the width of the spring.  The positioning accuracy of the 3D printer should provide the ability to build the individual leaves .  Finally the spring strap is added on the top of the walls forming the spring leaves providing a means to hold the assembly together.






    The alternate half is designed in a similar fashion such that the leaves fall between those of the first half nearly filling the gaps between the leaves of the first part.

    

    The two parts are then interleaved to result in a series of 25 thousandths thick leaves spaced 5 thousandths apart.   The spring assembly is bonded together at the spring strap area to finish the overall assemly.

    In principle these parts should be producible on the 3D printer and when combined provide a working leaf spring assembly.  The spring constant of the ABS plastic will allow some spring action of the assembly, although it may be overly stiff considering the rather low weight of the ABS plastic model.