How to create a HDPE Truss

I have created a HDPE Truss by milling parts of the truss and combing them with bolts and nuts. I would like to share my experience with everyone so that if you are interested you can try it out yourself!

Now the first thing that pops in your head when you hear a HDPE truss is, what is it ? A truss is basically an arrangement or framework of 3 or more bars which support structures like bridges, long span roofs, electric towers, space structures etc. and HDPE is the plastic material that it is made of.

Here is a video that I made demonstrating how to operate the Othermill and mill one of the members of the HDPE Truss.

The materials that you would need to make this are :

  • 2 HDPE pieces (4’’X5’’X0.12’’)
  • 4 M4X20 bolts
  • 1 M4X16 bolt

So the first thing that you would need to do in order to start the milling process is design the members. I had modelled the members of the truss on Fusion 360 in the MODEL mode.

Here is a figure showing the dimensions that I used to model them,

Where,

A,B,C,D are joints of the truss and all the members AB,AC,BC,CD and BD are pin connected.

Member AB is attached to the supports (A to a roller and B to a pin). It has a length of 30mm and a thickness of 2mm.

Member AC has a length of 30mm and thickness of 1mm.

Member BC has a length of 42.43mm and thickness of 2mm.

Member BD has a length of 60mm and thickness of 2mm.

Member CD has a length of 42.43mm and thickness of 0.5mm.

The above parts can be modelled from scratch or can also be found on the Bantam tools website (link mentioned below).

http://resources.bantamtools.com/truss?__hstc=226706562.e7728c1e99e058ce5bcd548e8c440213.1504705058149.1505742045326.1505764208800.12&__hssc=226706562.30.1505764208800&__hsfp=3069822152

Once the modelling part is done, the part that I found the most tricky begins. This part is the selection of toolpaths that carry out the milling operation on the othermill. If you select a wrong toolpath like I did way too many times than I would like to admit, you will end up milling a different pattern.

The selection of toolpaths is done in the CAM mode on Fusion 360. The various toolpaths that are provided by the software are shown in the figure below:

 

The toolpaths that finally worked for me are :

  • Bore for circular milling the holes of the members
  • Ramp for milling the sides of the members

One of the wrong toolpaths that I had chosen during the selection process was the Adaptive Clearing toolpath, which resulted in only clearing the extra material around the area of the members (shown in the figure below)

After selecting the appropriate toolpaths, the members are exported using the Postprocess option to a software called Otherplan. After exporting the members on to Otherplan, the Othermill is used as shown in the video right at the start.

The members are milled with a 1/16’’ flat endmill bit (shown below) .

Once all the members are milled, they are assembled with M4X40 and M4X16 bolts and you will have your very own mini support system !

 

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