Team Coolspeedbot: first feather weight robot

[Coolspeedbot]

I see, well looks like I made everything 0.5mm too big from you guys have said.

[overkill]

Like Andy says, clearance around holes is a must. A 0.5mm oversize hole is pretty standard (that's just 0.25mm clearance) for drilled holes and for laser or waterjet cut holes, as much as 0.75. Small waterjetted holes are often not particularly round and I like to clean them up using a Dremel with a tungsten cutter.

[Andy]

To be extra safe I normally make most holes 0.5 bigger than needed on 4mm parts, but for some holes where strength is important I have gone to 0.3 oversize through 10mm thick hardox (higher taper) and they have mostly been ok after a small amount of work with a needle file, for your design id say go 0.4mm or 0.5mm the intended size and it should be fine.

[Coolspeedbot]

Yes. It's a huuuuuge pain when you have to enlarge the holes yourself.

thats why I wanted to be sure.

[R9000]

Yes. It's a huuuuuge pain when you have to enlarge the holes yourself.

[Coolspeedbot]

After another bit of Maths and some tweaks with the CAD I think I got a bot that should be possible to make. with the bot using 4mm hardox instead of 5mm it can free up weight. Now I have emailed K-cut about cut tolerances and got a response, but I wanted to check with people here.

Should holes be made lightly bigger then I need them to be and add a millimetre or two around the parts to insure they are not cut too small?

Screen Shot 2017-05-26 at 18.56.14.png

[shakesc]

you wont get 1mm or 2mm hardox
SSAB did a run of 2mm but that was it, really just beetleweight stuff

[maddox10]

The thinnest Hardox 450 I have worked with is 1/8" or 3.2mm.

I heard about thinner stuff, but never had the pleasure to see it.

[Coolspeedbot]

Hummm, might look into it but I can only go 1 or 2mm thiner at best.

[R9000]

You could always try thinner hardox. 5mm is really quite thick for a featherweight, especially all over. Carbide has 5mm hardox side armour and a 3mm raex base, and that's a heavyweight.

[Coolspeedbot]

Ok so I did the Maths and looks I might have to use HPDE in select places instead of Hardox. I knew this might have been the case but still a little disappointed.

[Coolspeedbot]

thanks Rory

[R9000]

About 970 kg/m^3, just less than water.

[Coolspeedbot]

you wouldn't happen to know the density of HPDE?

[R9000]

No worries! Sorry if some of that was elementary to you, I just find it quite useful, especially that last bit, for when you're working with equations you've never used before.