Disc Design

What do people think of this?

Weight: 1.4Kg
Thickness: 10mm
Max Diameter: 200mm
Material: Stainless Steel 304-HR

Can anyone see any issues?

Nice design but 304 stainless is no where near hard or tough enough, look into hardox

I can see a pretty major flaw. You have removed material where it is most important, around the edge. Scrap the pretty holes, they do nothing but remove material from the outer ring which is where you want all the material to be (in an ideal world)

Do you know any waterjet companies that do Hardox? I have asked 2 companies now and neither stock or will order in the material.

As for the holes... it was to bring the weight down to the 1.4kg I need and I did not want to take it out of the arms or the centre incase the arms bent but I know what you mean.

http://www.yorkshireprofiles.co.uk/materials.html

Quick search of google threw these guys up. Never used them so can't comment on how good they are.

Other way to do it is drop JL steel services an email and ask them to send you a plate of 10mm large enough. I wouldn't recommend getting them to machine it as they only have a plasma cutter with an accuracy of plus or minus 1mm at best (don't need to be hugely accurate making up digger buckets etc) and taking it to a water jet cutting company.

Regarding the circles, if you have to remove weight then it would be better to skim a mm or two off the inside of the rim than have the circles in place. Reason being is that that is closer to the center than the holes are (all about energy storage in a disc). Granted the difference will be marginal and you probably wouldn't notice but being an engineer I like to make everything as efficient as possible :)

How about making the disc out of something lighter and having steel inserts as teeth?

More difficult to make but could be worth it if you need the weight

Weights not an issue surprisingly, I reckon that I will come in at around 13.3Kg when finished. But given the CAD model says that it weighs 12Kg Its a good job I designed it under weight.

How much money do you have to spend on material? Ideally something like D2 would be better. Hardox is OK. If your going with hardox you want as hard a grade as possible, a hardox 450 disc with a sharp edge hitting another slab of hardox 450 with a flat edge wont do your teeth much good!

Look on google for local tool steel supplier's and see if they will sponsor you an offcut big enough. I'm sure someone would help you out :). Once it's water cut then get another loacal firm to harden it slightly (surface ideally).

I don't have a lot £50 max really, but I have been given 2 quotes for the disc, one was £70 in stainless steel and the other was £30 in Hardox, but I have no idea of the grades. Is D2 as steel? I still have not officially ordered it so I can change the material choice.

Getting the right material for a disc is quite difficult to get just right, but stainless steel will be too weak and the tips will fold over in a few hits. Hardox will be better, but against another robot with the same material the disc teeth is always going to get damaged.

D2 is a tool steel, often used in large power presses. I usually just call our local supplier and see what they recommend and see if they have any offcuts cheap of free.

Well hardox just get's blunted. You will rarely cut through anything anyway as most machines have heavy duty shells so I'd just go with hardox as it's a cheap easy option and if you are getting the whole thing for £30 then you could afford to swap it every couple of events :)

Well the disc doesn't exactly have a sharp edge, its 10mm thick so its more a hacking action rather than cutting. The company does Hardox 400. But I have tracked down a company that might be able to do it in D2.