HDPE/Acrylic/Nylon/RG1000

[Redirect Left]

So i'm currently designing my first featherweight, and a little stuck on the right sort of material.

Originally I was going to use Acrylic, as i thought a clear bot would be rather neat looking, and I know from experience it's rather strong at a decent thickness, however a little research showed it was quite hard to work with compared to other stuff, you can't angle grind through it without risk of shattering, drilling can chip and weaken the structure considerably, a screw being a little too tight can crack it deeply, etc.
So I looked a littler further on the plastics website (directplastics.co.uk is what i'm using), and came across HDPE, Nylon & RG1000. HDPE & Nylon I know already are fairly common choices, although I personally don't know the strength differences between the two.
RG1000 is entirely new to me, I don't know the ins and outs of it, and googling for it doesn't seem to bring up much.

Price wise, lots of difference, all include VAT (all taken from the website noted above)
1000x500(mm) RG1000 = £53 (8mm)
1000x500(mm) Acrylic = £46 (8mm)
1000x500(mm) Nylon = £87 (6mm) (they don't do this in 8mm)
1000x500(mm) HDPE = £32 (8mm)
The thickness is just a reference, I've not decided end thickness of everything yet

Does anyone know these plastics, and the ins and outs of them compared to each other? I'd be greatly appreciative if anyone can take the time to help me worm through the plastics to find a suitable one for my need
I might still use a tad of acrylic for the top, if it proves strong enough at a certain thickness to withstand featherweight hammers and similar

[maddox10]

Acrylic doesn't have any function in robot wars. It's as brittle as glass.
If you want something to see trough, and up to the task, go for 6-10mm of Macrolon/Lexan/polycarbonate.

[Redirect Left]

Acrylic doesn't have any function in robot wars. It's as brittle as glass.

I wonder if my previous experience with acrylic was infact, not acrylic at all then. That took a huge whollop with a hammer numerous times in the exact same place, and only then did it fail entirely, instead of a crack or anything it rather spectacularly went into hundreds of bits.

I'm mostly looking for opinions on the HDPE/RG1000/Nylon anyway.

[Roboteernat]

If your 'acrylic' took a huge wallop, and you only think its acrylic as it was a clear plastic, then your probably thinking about Polycarbonate.

Polycarbonate, or PC, is used in police riot shields, Beta (Killerhurtz) chasis, bus stops panneling, public stands, displays and more importantly, Robot wars and robot fighting arena walls.

It takes a huge beating, and due to its properties is expensive.
Although it can be easily cut and drilled, it is more expensive than the others.
I bought some 4mm for an antweight arena (Swindon makerspace) and it cost £150 for some large sections, but it was only 4mm. you would need 6-8mm depending on what you are planning. - i bought this from http://www.cutplasticsheeting.co.uk/

[lowndsy]

Was the "acrylic" flat on a surface, or unsupported?

[Roboteernat]

RG1000 is a denser version of hdpe (in very basic terms) Machining on lathe is difficult due to its long molecular structures causing the chips to stretch as apposed to chipping off.
When milling or cutting with a hacksaw it is comparable to hdpe.

being denser RG1000 weighs more, but need to check.

[Maxamuslead]

taken from Direct Plastics


About RG1000 Sheet

Advantages

RG1000 is odourless, tasteless, and nontoxic.
More economical than virgin grade
It has extremely low moisture absorption and a very low coefficient of friction,
Its self-lubricating, and is highly resistant to abrasion.
It is also very resistant to water, moisture, most chemicals,
Resistant to UV radiation and micro-organisms.

Disadvantages

RG1000 Sheet has a maximum operating temperature of 90°C
A short term operating temperature of 120°C, and a melting point of around 135°C.
Not probably suited to high tensile applications
Since it is a recycled version of UHMWPE its not compatible in every respect.
Its not FDA approved as there is no white/natural grade

[Redirect Left]

I've looked at that sort of stuff Maxamuslead. They don't actually give me anything of real value in the descriptions, such as real world strength compared to X, weight, etc.

Was the "acrylic" flat on a surface, or unsupported?

Flat surface, concrete pavement to be specific.

If your 'acrylic' took a huge wallop, and you only think its acrylic as it was a clear plastic, then your probably thinking about Polycarbonate.

I assumed acrylic as it was dirt cheap, £5 for a 1000/500(mm) @ 5mm thickness rectangle, which seems an impossible price for polycarbonate. Unless the person I bought it from was just as clueless over it, possible considering it was from a secondhand and overstock fair, the item wasn't labelled as any specific plastic, just a price on the tag.

[lowndsy]

Flat surface, concrete pavement to be specific.

That would spread the shock of the impact - Perspex would stand up to a few whacks with a hammer like that.

[Maxamuslead]

I've looked at that sort of stuff Maxamuslead. They don't actually give me anything of real value in the descriptions, such as real world strength compared to X, weight, etc.

fair enough, the UHMWPE data sheet might help more then

http://www.directplastics.co.uk/pdf/...ta%20Sheet.pdf


PS The density is 0.945 (g/cm3)

[Redirect Left]

I was more hoping that people would be able to give me their experience with things, how easy it was to work with, how it performed against certain weapons, except acrylic as we've already ripped that one to shreds.

[Roboteernat]

HDPE is cheaper than RG1000 (reground UHMWPE) about 3rd - 5th cheaper. good impact properties - used to make rubbish chutes on building sites - those yellow tube things.
The main property benefit is that its a better bearing surface, low friction coefficient, which in our game is not a necessity.
We don't have water issues... yet... so this is a null point.
They both have great impact properties, albe it HDPE iis softer therefore will take the force better than shocking, but could lead to dents.

The only real difference is do you mind eventual dents - HDPE
You want to pay less - HDPE
less dents - RG1000
Green material - RG1000
White or black - HDPE or RG1000

trying to confirm the stat about the chute material, I see both HDPE and UHMWPE are both used to make the chutes.

[Henry Nourse]

UHMWPE is also super slippery, more so than HDPE, so it can be a lot harder to machine as a result and I imagine that would carry over to RG1000. I've heard tell that this can be useful for avoiding getting grabbed or for getting out of tight corners but I'm doubtful it makes too much difference.

We've used HDPE so I can talk a bit about our experience with it when it comes to working with it (it never went into the arena!). It's a nightmare to cut, or rather it can be, but you can do it with either a jigsaw or a bench saw so long as you have the appropriate blades for the job. You'll need to cut at a low speed to avoid it melting mind, that caught us out even at medium speeds! Get that right and it's easy, but it took us quite a few goes to get it figured. Flood-cooling would probably help a lot but I can't say for sure. It's a pain to clamp down or mark on too since it's so slippery and as such nothing really holds it and ink can come right off. Drilling was fine, again just use low speed and make sure you have a good grip on the drill as it sometimes pulls and makes nasty hourglass shaped holes! You can shave corners with a knife quite easily which is handy for rounding things off without a load of filing too, plus 5mm or smaller bits can be cut using just a knife with a few passes but things like 8 or 10mm will eat up a lot of punishment.

Like I say, I haven't used it in the arena but it does seem to take hits pretty well from what I've seen. A lot of gouges and not a lot of actual damage seems to be quite common. There's actually a thread in the Beatleweight section about the advantages of HDPE against UHMWPE, so that might be a good place to look.

[Liftoff]

Treat HDPE as if you're working wood, if you have wood working tools such as a planer thicknesser, crosscut, handplane etc you'll be able to cut it and achieve a very good finish as well. Avoid sanding and abrasives as the finish will not be so good, you'll be better off with a handplane. Be ready for a big mess tho!

[Redirect Left]

As none of you mention it, i'm guessing my original plan of angle grinding the HDPE down to size isn't advisable or will otherwise produce not too good of a cut?
Jigsaws aren't too expensive, although I need to buy (or just build) a work bench still before construction fully gets underway, motors & battery arrived today, so literally only thing left to do is figure out how to work the HDPE I bought (2000mm/500mm/10mm) in the best manner. Will need to buy some thicker stuff for key areas i know.