I am going to build a CNC machine, What do I buy?

[Hood]

Well, the controller breakout board magic thingy has arrived.Paid for Monday, arrived this afternoon. From Poland:

View attachment 266911

Very nicely packaged and presented.
All I need to do now is work out which drivers to buy, still not decided.

Did another search this evening and no sign of the toroidal.
The cap is yours if you want it for the price of posting, I only do UPS or post office nowadays or if you want to arrange for Hermes or whoever to collect from me that is fine.

 

[eSCHEn]

Did another search this evening and no sign of the toroidal.

So I thought to myself last night that I'd check today (Wed) and see if I definitely don't have it but I promptly forgot So I've just ventured into Narnia and checked everywhere and 100% don't have it, sorry!

 

[Hood]

I have it in the back of my mind that someone got it or bought it or... Weird, I can usually remember these things, must be senility setting in

 

[northwest]

Well, having looked at all the options, this is what I have decided to go for:

https://www.automationshop.co.uk/ps408-12-linear-power-supply-7.html

it is this power supply:

with the added bonus of a 12volt out. Going to have to double up on one of the power outs for the 4th axis driver but that isn't the end of the world I don't think (will use the Y axis) but as always I welcome your comments.

 

[northwest]

As is always the way, I didn't get past reading the manual but it gave me a real insight as to why @m_c has a piece of wire for an emergency stop!

Apparently I need ONE OF THESE to wire up the emergency stop? The PNOZ X7 24VAC/DC Safety Relay at a very reasonable £168.18 pence, plus the vodka. Would anyone have a few alternatives?

 

[MCKDAVID]

Safety relay is probably over the top, I just use a big standard relay and it works fine. Ok the safety team could argue that theoretically it could fail and that a safety relay tested to n million cycles is safer, and they'd be right in the absolute.. however taking into account the function of the machine and its use I made an executive decision that a standard relay was fine. Have box of AC relays here if you want one... Pm me an address and I'll send you one

 

[Hood]

It is a stepper system so ...
I personally have safety relays on my CNCs, well 3 out of the 4 as the Beaver doesn't have one but I did make up a relay board that does the same thing. I got my safety relays for free in a big box of bits and that is why I used them, if I had been paying then likely I wouldn't have them..

 

[northwest]

Pm me an address and I'll send you one

That is very kind of you David, if I understand you correctly then, substituting the £XXX Safety Relay for an alternative AC one you end up with the same (okay, not tested to the Nth degree) function?

 

[m_c]

That piece of wire is where an E-stop button should be wired in. It's just that I've never got around to mounting one. That machine you can stall just by holding it, and it doesn't have a cutter, so I'm not too concerned about it having one as it's only me that uses it.
All my other machines that cut materials, the E-stop is something that gets fitted first.

The whole safety relay thing you can argue either way.
The main thing a safety relay prevents, is the relay failing to open due to a welded contact. Safety relays monitor themselves, and should they detect a fault such as a welded contact, they'll fail to activate.

The chances of welding a contact is pretty slim, provided the rest of the system is designed correctly, and you're not pushing the E-Stop relay to the limit of it's current switching capability.

 

[northwest]

That piece of wire is where an E-stop button should be wired in. It's just that I've never got around to mounting one. That machine you can

I did get that, I wasn't casting aspersions, I was pulling your leg @-)

 

[northwest]

I thought it might be helpful if people saw where I am with the Mill right now as you can see where I am trying to get to. This is the current Power Supply:



This is the controller box:



So you see, I am getting into Ferrari territory here, presently have a Morris Minor.

 

[m_c]

13.8V?
That must currently have the performance of a robin reliant with a couple cylinders down, let alone a morris minor!

 

[MCKDAVID]

That is very kind of you David, if I understand you correctly then, substituting the £XXX Safety Relay for an alternative AC one you end up with the same (okay, not tested to the Nth degree) function?

Exactly, safety relays are generally used in safety critical functions, like fire detection, safety circuit controls etc.. I'm the only one using my system, and I'll accept my responsibility for myself.. a relay is only a coil with contacts a safety version is just a more reliable with monitoring version, but fundamentally works the same way. The relay I've used is 10amp switch capacity, but is only actually carrying about two tenths of naff all current, so nowhere near electric capacity. Agreed it could mechanically stick, but the way I shut down the system is the last thing to close is that relay so it's tested every time I use it. I'm happy enough to use a standard relay. Everyone needs to decide for themselves which model is best for them.

 

[northwest]

13.8V?
That must currently have the performance of a robin reliant with a couple cylinders down, let alone a morris minor!

I think you now have a grip of the situation :-)

 

[northwest]

Well, having looked at all the options, this is what I have decided to go for:

https://www.automationshop.co.uk/ps408-12-linear-power-supply-7.html

it is this power supply:

with the added bonus of a 12volt out. Going to have to double up on one of the power outs for the 4th axis driver but that isn't the end of the world I don't think (will use the Y axis) but as always I welcome your comments.

Well, that isn't going to work, there are none and Gary tells me they are not going to arrive anytime soon. He suggests I use two of these instead: https://www.automationshop.co.uk/catalog/product/view/id/59580 It is a 42volt 280 watt unregulated switched power supply with 7Amps continuous current, I am not convinced. Looks like I am back on building one again.

 

[m_c]

Those would work, but they are an expensive option. I would say you'd probably get away with just one though.

 

[northwest]

Those would work, but they are an expensive option. I would say you'd probably get away with just one though.

That's what I thought, there has to be a different (better) option. We are back to your suggestion of RS part no 671-9148 is 21.39+vat for a 120VA, or a 160V unit at just slightly more.

With EM542 drives, you could possibly get away with a 30VAC secondary, but you'd have to build it and check how high the DC voltage is. Theoretically it would give you about 41-42VDC, but by the time you factor in mains voltage fluctuations (you need to add about 9% for the upper UK voltage limit above the rated 230V), and load regulation of the transformer it may be closer to 50V than you'd like

Which if I am not mistaken is exactly where the 42volt unregulated transformer from automationshp.co.uk puts me with voltage surge? The DIY option is starting to look really attractive.

 

[mtt.tr]

If just use a 6a din contactor

 

[northwest]

Well, relentless I am. These turned up today, 4 off:



then I discovered the data sheet for the stepper driver so it is this one:

 

[northwest]

Just seeking a bit more guidance here.
I was going to buy a couple of rolls of .5 or .75 cable for my panel build, do you think I am going a bit light on the cross section?

https://chaloncomponents.co.uk/product-category/cable-management/tri-rated-cable/

but then I was going to buy some terminal blocks, what a minefield:

https://chaloncomponents.co.uk/product-category/terminals/entrelec-terminals/

Can anyone just give me a bit of guidance on this, I figure 30 would probably do it, I can always order more.