Plastic doesn't get tougher than this!
Updated: Sep 21, 2020
The Gladius beetleweight build is finally starting to reach it's conclusion!
It's been a while since my last update, partly due to some unexpected hiccups with the build, which I'm going to discuss in this post. One big sticking point was the top and bottom shields - I had naively assumed that accurately curving them to a large radius would be fairly easy. Unfortunately it turned out to be pretty tricky, and required several attempts to get right.
The instances of bent HDPE I've seen are for parts with a relatively small bend radius, and with a significant area of material surrounding the bend. This means that the builder can easily clamp or grab "cool" parts of the plastic in ways to manipulate the heated area. In this way, HDPE can be bent over the edge of a table, for example. In my case however, the whole shield must be heated, as the bend continues for the entire width and length of the part. This means there is no such "cool" area from which I can apply pressure to manipulate the form of the plastic. This issue, as well the fact that the part was larger than my vice, meant that clamping was out of the question.
I attempted to mount the shield directly to the chassis, and heated it up from that position, but it went, let's just say, a bit wrong. I then tried to find a round object, like an old bucket or something, that I could attach the plastic to, but unfortunately I didn't have anything suitable kicking about. So at that point I thought I may as well build a device, designed exactly to the dimensions that I wanted.
So I did!
Introducing the plastic-shield-bender-jig 3000!
As you can see from the images, the setup turned into a pretty bizarre contraption, and it took quite some time to get it sorted. The end result was pretty good, I think. There are some undulations in the bend which I am a bit unhappy about, and of course the little screws used to attach the part to the jig have left a series of holes. Both of these are pretty well masked over by the adhesive wooden textured wrap. All in all, not a bad job, but I regret not putting more thought into the manufacture of this part during the CAD stage. I'm not very experienced with bending HDPE so I suppose it's reasonable that I made an error like this, especially on a difficult part, but the lesson, to avoid underestimating the difficulty of this process, has definitely been learned!
With that out of the way, one chassis part remained: The polycarbonate rear! Prior to this build I hadn't really dealt with polycarb very much. Due to it's brittle characteristics, it has lost popularity amongst roboteers in favour of more durable plastics like HDPE and nylon. As I have found out, a result of these brittle properties is that polycarb hates having wood screws in it. I accidentally cracked one panel and snapped off a screw head, due to over-tightening. Another piece developed some pretty ugly surface scratches as well, but I can use it as a spare. I eventually got the hang of it though, and my third attempt turned out pretty well! All that for a part which will probably shatter if it gets hit hard enough. Should give the machine a really distinctive look though, and that's what Gladius is all about!
The chassis fits together nicely - here are some photos of what it looks like without the wood stickers. I will admit it doesn't look that great when its bare, which I think is mainly due to the shields.
I have started the decoration on a fully assembled robot, which I think really cleans up the look a lot more. This blog post has gone on long enough though, so you'll have to wait for the next one to see how that turns out ;)
Cheers for reading, and as always, take care.