First steel diy CNC router build

**Jonathan** · 21-05-2014

Just remember to compensate when the material you're making the thread in is different to the nut - e.g. for aluminium you want (very roughly) twice as long thread depth.

**ivars211** · 24-05-2014

I have got some 0.5mm^2 4 core shielded cable at home, would the wire thickness be enough for ~3m 36V supply and 4A stepper? Stepper should get around 35.3V at the end. I know 1mm^2 would be much better, but I would like to use what I have on hand already, perhaps I can run two cables in parallel?

Thanks

**Neale** · 24-05-2014

Personally, I wouldn't bother. I doubt that your power supply is accurate to that level anyway, and it wouldn't make much difference if it were. It takes a bit of mind-adjustment but with these kinds of drivers and motors, the actual voltage as such isn't that important. The driver limits the motor current to whatever you have set, whatever the supply voltage, and the reason for wanting a higher voltage is that it allows the current to rise more quickly to the set value, taking into account motor inductance (which is why the experts on this forum bang on so much about low-inductance motors - it's just so that the current rise is quicker for a given supply voltage and it's the current that makes the motor go faster). Having a slightly lower voltage across the terminals means that the current rise will be very slightly slower but you ain't going to notice the difference in practice; for most of the stepper pulse the driver will be regulating the terminal voltage to less than this anyway.

**JAZZCNC** · 24-05-2014

Originally Posted by Neale

It takes a bit of mind-adjustment but with these kinds of drivers and motors, the actual voltage as such isn't that important.

Actually voltage to a stepper is very important but I agree the difference 35 and 36V won't be noticed. That cable will easily handle the amps you'll be pulling so yes get it used.

**ivars211** · 10-06-2014

I am at a point, where pretty much everything mechanic is finished.
I am building my CNC in garage, and I only just realised that there is no earth wire coming from electric box, there are only phase and neutral. Now I am quite stuck, do I have to dig in some peace of metal (quite impossible in that location), or do I just leave earth wires from spindle and PSUs untouched? Would it cause safety issues? The thing I am struggling the most, is where to connect common earth from all of the shields to? Any ideas how to approach this?
On the side note - how big fuses are you using for VFD+2.2kw Spindle and motors/drivers? I am planning to go 15A for spindle and 10A for drivers/steppers?

**Clive S** · 10-06-2014

Originally Posted by ivars211

I am at a point, where pretty much everything mechanic is finished.
I am building my CNC in garage, and I only just realised that there is no earth wire coming from electric box, there are only phase and neutral. Now I am quite stuck, do I have to dig in some peace of metal (quite impossible in that location), or do I just leave earth wires from spindle and PSUs untouched? Would it cause safety issues? The thing I am struggling the most, is where to connect common earth from all of the shields to? Any ideas how to approach this?
On the side note - how big fuses are you using for VFD+2.2kw Spindle and motors/drivers? I am planning to go 15A for spindle and 10A for drivers/steppers?

You do need an earth in your garage you will need to hammer an earth rod in the ground and connect it to and RCD type consumer unit this will then trip at 30mA and give you protection. An electrician would do this for you. The spindle will run from a 13A plug and the drivers from say 10A.

All the shields and earths in the control box should be connected to one point called a star point and then that point should be connected to the earth. The shields are generally connected at one end only, at the control box. Hope this helps ..Clive

**ivars211** · 13-06-2014

OK guys, just finished my electric installation, got all the wires connected, everything seems to work, except FVD, nothing happens when power is applied. So my question is, am I doing something wrong or do I have faulty FVD?
I connected mains to FVD like this: http://www.mycncuk.com/attachment.ph...5&d=1381658518
but did not connect spindle yet. I would think that it should power up (at least LED showing power or something) even if spindle is not connected.
My FVD and spindle: http://www.ebay.com/itm/250952872638...84.m1439.l2649

Any comments will be much appreciated!

**Clive S** · 13-06-2014

Have you checked to see if you have mains voltage at the terminal in the VFD? With a meter or test lamp. (be careful) ..Clive

**Lee Roberts** · 13-06-2014

I could be wrong but isn't there a system on these that stop it coming on if there is no spindle attached, i'm sure I read somewhere that you shouldn't power them on with no spindle connected as it can damage them, I could have my wires crossed however.

.Me

**Jonathan** · 13-06-2014

Originally Posted by Lee Roberts

I could be wrong but isn't there a system on these that stop it coming on if there is no spindle attached

I'm not aware of such a system - I would recommend putting the settings in the VFD with no spindle attached, in case you accidently press 'run' before it's ready.