Belt Grinder 2x72" and 50x2000 mm

[JAZZCNC]

Needless to say that the experience from building CNCs till the moment helped in in such way that the only error till now was just 1 spot weld not at the right place.

Erm I'd say the error was the spot welding.! . . . Doesn't look good or strong. Great for proto typing but not for real thing. It needs proper welds to give it credabilty as industrial strength tool.!

[Boyan Silyavski]

Erm I'd say the error was the spot welding.! . . . Doesn't look good or strong. Great for proto typing but not for real thing. It needs proper welds to give it credabilty as industrial strength tool.!

I feel that too. Nothing will go out from here that could be broken by hand and a hammer. And you are absolutely right, now i could take the hammer and certain pieces could be broken apart for seconds. When all belts are spinning and i see everything is working correctly there would be proper welds where necessary. The other thing i will do is blacken all bare steel heating it with the gas torch to 315C.

[toomast]

...The other thing i will do is blacken all bare steel heating it with the gas torch to 315C.

What do you mean by that?

[Boyan Silyavski]

What do you mean by that?

There is a way to treat low carb steel / mild steel/ . You heat it at 315C, keep it there a couple of minutes, thin oxide layer forms in black, then you brush it with some oil and it goes even blacker. Result is much tougher part, even if not a high carbon steel. Black oxide layer is not real anti rust though it gives some protection


bellow you could compare bare cold drawn steel bar and treated.

[toomast]

There is a way to treat low carb steel / mild steel/ . You heat it at 315C, keep it there a couple of minutes, thin oxide layer forms in black, then you brush it with some oil and it goes even blacker. Result is much tougher part, even if not a high carbon steel. Black oxide layer is not real anti rust though it gives some protection


bellow you could compare bare cold drawn steel bar and treated.

Interesting. What is the "official" name of this process?

[JAZZCNC]

When all belts are spinning and i see everything is working correctly there would be proper welds where necessary.

Well next time do your self a favor and grind Chamfers on the edges will give stronger nicer welds. Created your self lot of grinding now or ugly proud welds.

[Boyan Silyavski]

Well next time do your self a favor and grind Chamfers on the edges will give stronger nicer welds. Created your self lot of grinding now or ugly proud welds.

Where was important and i was sure that will not need to break it apart its done like you say. The machine is still not finished.

[njhussey]

Instead of heating and quenching why don't you chemically black the steel? It doesn't add any hardening but does add a bit of rustproofing, not much but some!

[Boyan Silyavski]

Instead of heating and quenching why don't you chemically black the steel? It doesn't add any hardening but does add a bit of rustproofing, not much but some!

Cause it seems a bit expensive to buy the kit for blackening at the moment. The torch is easy,cheap and toughens the material. No quenching, air cooling. But that would be the next logical step



Now about Power.
Motor power. I was lead to believe / from forums/ that you need at least 1hp per inch belt, so i decided the machine to have 1.5kw motor. Mean while i had
made my self a 12" sander. 3 phase 0.75kw motor that run on 230VAC using capacitor, no VFD. The disc was easy to stop. See video below. So i decided to invest in a VFd cause i wanted to run it from 0-3000RPM depends what i am doing. I connected it yesterday. Man, i could not stop it in any way, its brutally strong combo. And only 0.75kw.

So i am starting to believe there is some misconception here. Cause belt is not wider than portion of disc i used for grinding yesterday.And as i said, i couldnt stop it pushing hard using steel bar. So i started to think thats the pulley mass is to blame. while all pulleys i designed are very much big bored and so they are light, the motor wheel is a whopping 1.6kg at 120mm. I started redrawing it recessed in the middle but could not lower the mass less than 1.1kg. So i went further and made all walls 8mm only. Weight dropped to 680g.

So in short i start to think that this could be driven using 0.75kw motor combined with VFD instead of the over sized 1.5kw, when pulleys weight is made minimum. yet to prove on next machine. of course i will see how much i need that low revs where is a small loss of power


Below video of the 0.75kw motor when runs on capacitor on 2 phase line






And video of same motor that runs on VFD again 2 phase line. I could not stop it pushing very hard against it a 40x10mm steel bar.Trying seriously to abuse it . The disc itself is a very thick diamond cut disc and the blue sanding disc thats glued, is a 60 grit zirconia. So you judge what a beast it is now with the VFD connected.

Its very interesting to me if sb has a similar machine, 12" disc sander using 1400RPM mono phase motor, no VFD and if it could be stopped pushing hard against it?????


PS. Black lines on disc are from sharpening my pencils. Disc is new otherwise. First i run it at half speed and then at full speed at 100hz. It was scary to hold thebar with only one hand.

[Clive S]

Boyan I think you have answered your own question you can't compare using a 3 phase motor on single phase with caps against the VFD. You won't get the torque with the caps especially if they are not big enough.