# Questions about working with plastics.

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#### Triode

##### Active Member
For building robots around the size of an RC car or a desktop computer, I am trying to learn what kinds of plastic would be practical to work with at home. And which methods people here find easiest. Using legos, wood and cardboard are getting old and I can't weld in my apartment.

John

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#### Triode

##### Active Member
It sounds like for my purposes using either PVC or polystrene for the parts requiring more strenth, such as the sides of an arm, or the chassis of a car, and Coroplast for larger parts and ones that would be curved, like body panels. So the solvent for Polystyrene and PVC is inexpensive? That makes sense, I just though earlier you said that the preperation costs were high, I wasn't sure what you meant by that.

#### arhi

##### Member
Triode .. you can also think about plexyglass (ACRYLICS). It is light and "strong", very good for base / holders, it can withstand much more heat then PVC/ABS..

Now, it is more brittle then PVC/ABS but IMHO much better. You can easily get the "plates" of different thickness (1mm - 20mm with 1mm step is available in shop near me for example in tables up to 2m x 6m).

Bonding acrylic is
- nuts & bolts - this is my preference way of bonding acrylic as it can be disassembled quickly and easy
- liquid acrylic - this is 2 component glue, one part is honey like mass and the other is powder that solidify it. You can both use liquid acrylic as a glue to weld/glue two pieces of acrylic or you can pour that into a mould to get a piece you want. After it sets (few hours but depends on the hardener) it becomes just like any other acrylic so very hard. 1Kg of liquid acrylic in local store is ~10US\$ so I'd not say the price should be the problem, and I recon it should be cheaper in USA then in this god forsaken land.

Working with acrylic is very easy, sands nice, you can cut it using dremel disks or with a saw... you cannot use the nibbler for the holes (it will break) and you have to pay attention when drilling holes as you cannot drill big holes from the first go .. you have to drill small holes first - also you need lot of rpm but dremel should handle it with no problem.

of course acrylic being available in transparent + many (semi transparent to transparent) colors is additional bonus

#### Hero999

##### Banned
A bit off topic but beware that mixing polystyrene with petrol makes napalm which is very dangerous if ignited.

#### Mr RB

##### Well-Known Member
It sounds like for my purposes using either PVC or polystrene for the parts requiring more strenth, such as the sides of an arm, or the chassis of a car, and Coroplast for larger parts and ones that would be curved, like body panels. So the solvent for Polystyrene and PVC is inexpensive? That makes sense, I just though earlier you said that the preperation costs were high, I wasn't sure what you meant by that.

Sounds like you need vacuforming, look up "DIY vacuforming press" or similar. That will make your body panels, and maybe chassis parts too since once the thin sheet is formed into curved/bucket type shapes it gets very strong.

#### arhi

##### Member
hero, we agreed not to give terrorist tips on the forum

Mr RB, not sure how feasible vacuforming press is for "home builders" as I did not see any vacuforming press you can use in house, you really need a real workshop area for that.
On top of that - in order to vacuform he need to make a mold first .. it can get fairly expensive at the end ...

#### Triode

##### Active Member
I've read about vacuforming, but for now I'm just planning on making frames and housings by cutting plastic sheets into shapes, bending them in places, then welding them via some method. I will also drill holes in it and use bolts in places, but almost all plastics allow for that. I'm trying to keep this practical and fairly cheap. I don't have a huge amount of room or a garage, so vaccuforming isn't a good option for me, and right now I don't think its necesary to make the kinds of things I'm thinking of. Likewise, while I would like to make a CNC cutter some time, that also requires a good amount of space and resources. I'm limited not just by room, but that in an apartment you cant do work that makes a lot of noise, makes a big mess, emits a lot of fumes, or uses flame and gas. If I could do that stuff I'd just get some angle iron, a chop saw and a welder and make whatever I like So thats the reason that for now I'm thinking some plastic housings that are simply cut, bent and fused with heat or solvent, would be a nice quiet relativly clean way to build some things, that I could do on the craft table next to my workbench.

#### arhi

##### Member
planning on making frames and housings by cutting plastic sheets into shapes, bending them in places, then welding them via some method. I will also drill holes in it and use bolts in places, but almost all plastics allow for that.

Check what is the easiest plastic to get near you. You can find sheets of plastic, different thickness in many stores ... the most common is PP, HDPE and Acrylics. PP is cheapest, HDPE is stronger then PP and more resistant to high temperatures, Acrylics is lighter and stronger the PP and HDPE but is very brittle so not as easy to work with as PP & HDPE. ABS is great for extruding but for working with sheets, I advice PP or HDPE or Acrylic depending on what you need. You can mix them of course.

I'm trying to keep this practical and fairly cheap. I don't have a huge amount of room or a garage

That's why I mentioned RapMan:

video:

does not take too much space, no fumes, no gas, no vapours ... you can see on this guy video how big it is and how it works ... the only problem is price .. if you want to get a full kit it will set you back some 700GBP ... if you make it yourself, you can go much cheaper (~300E)

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