[Sevenmead]

Just finished my schematic yesterday. I would appreciate anyone pointing out anything they think is off. Thanks.

http://www.cnczone.com/forums/attach...d=300438&stc=1

image is also hosted here..

http://openbuilds.com/media/router-schematic.50/full

[dharmic]

Four things jump out.

1. The earthing - I'd be looking to run earth from the input socket to a point on the casework, then separate earths from that point to the spindle controller, each of the power supplies and shields out to the spindle and steppers.
2. The e-stop relies on the computer or the BOB receiving a stop signal and doing something with it. I'd feel a lot more comfortable if the e-stop were sitting on the mains input. Hit that button and EVERYTHING stops, straightaway, regardless of whether software or switching components on the BOB have failed.
3. The homing switches in series like that mean you have no idea which switch has triggered - which can be really helpful if one switch jams and needs fixing, or if you start a homing cycle with one axis already at the stop after an overrun and shutdown. I'd personally look at another BOB that had more inputs if you can't get one that has six already there.
4. Fuses? I'd have separate fuses or fast blow breakers mounted in your case that run from the active line to the inputs of the spindle controller and the two power supplies. Just in case something goes awry. And if they're case mounted it means you can replace easily.

Hope this is of some use to you.

[aarggh]

As the other poster pointed out, I reckon star earthing is probably the most important aspect with builds to deal with noise issues.

Bring the earth to one point only from the mains input, and then from that point to all other devices, otherwise you create earth loops, which can have voltage differentials and cause all kinds of erratic behavour and noise issues. This is the number one cause of most VFD/Spindle issues.

cheers, Ian

[A_Camera]

Four things jump out.

1. The earthing - I'd be looking to run earth from the input socket to a point on the casework, then separate earths from that point to the spindle controller, each of the power supplies and shields out to the spindle and steppers.
2. The e-stop relies on the computer or the BOB receiving a stop signal and doing something with it. I'd feel a lot more comfortable if the e-stop were sitting on the mains input. Hit that button and EVERYTHING stops, straightaway, regardless of whether software or switching components on the BOB have failed.
3. The homing switches in series like that mean you have no idea which switch has triggered - which can be really helpful if one switch jams and needs fixing, or if you start a homing cycle with one axis already at the stop after an overrun and shutdown. I'd personally look at another BOB that had more inputs if you can't get one that has six already there.
4. Fuses? I'd have separate fuses or fast blow breakers mounted in your case that run from the active line to the inputs of the spindle controller and the two power supplies. Just in case something goes awry. And if they're case mounted it means you can replace easily.

Hope this is of some use to you.

Some comments from me:

1. Earthing. I chose a different route. My power supply is 100% electrically isolated from the metal frame and I chose NOT to connect the machine frame to the mains earth. I think it is MUCH safer this way for several reasons, one is that the electrical system in my home is different from that in the USA and I also have an earth leakage circuit breaker on every circuit in my home, providing protection against residual-currents. I don't think that is standard all over the globe yet, not even in Sweden. So, in regard of earthing, I think he should consult a local electrician who can inspect the machine for electrical safety. That is far more important than advising on connecting everything to one common point.

2. E-Stop. I agree to 100%, it is a good idea to have a REAL emergency breaker, not just one which is dependent on electronics and that the computer can handle the input. That philosophy is quite dangerous. However, I chose partially a similar solution to his, which the exception that I also have a REAL emergency switch as well. In my opinion it is good to have an E-Stop which is controlling the software because there are situations when you want to quickly stop the machine without destroying the software running sequence so that you can resume the work when whatever caused the the reason to stop is fixed. Of course, if a disaster is happening than it doesn't matter and you should quickly stop everything, breaking the mains power. A real emergency stop button can be a life saver or can save the machine from being destroyed, which is far more important than an end mill or a work piece, or even the table. This is why I initially only implemented a real e-stop, and first after I realized the need of being able to continue some times after a stop I implemented even a software controlled e-stop as well.

3. Homing switches. My solution is the same as his. I have all my limit switches AND the E-Stop connected in series to the same port. I don't need any real home switch, mechanical switches are inaccurate unless they are very expensive, and even so, inertia makes homing fairly inaccurate so I decided that I don't care about homing. I set up the home position different every time anyway, so having a fixed home position is pretty pointless in my opinion, unless one uses ATC I can see no use for homing position in a small machine. Limit switches are different, their purpose is to protect the machine (sort of) and preventing it from serious damages. Of course, they can't provide 100% protection, but definitely saved me a lot of headache more than once. On the other hand, I have no need for the information about which limit switch was hit, I can see that with my own eyes if the machine stops, and the override limit switch command will override any switch, so I can jog back to normal and fix the issue.

4. Fuses. Again, I think that is up to local regulations and perhaps depends on his mains plug. Some countries have individual fuses in every wall socket or plug (UK is an example), some homes have very good circuit divisions and protection (mine definitely), and also some power supplies have built in fuses. Never the less, it is a good idea to have a built in fuse or a fast blow breaker, but it is important that it is faster and dimensioned below the one on the mains plug, otherwise it will not provide any protection at all. So if the main socket circuit has a 10A fuse than the machine should have one which is less than that.

[Sevenmead]

Four things jump out.

1. The earthing - I'd be looking to run earth from the input socket to a point on the casework, then separate earths from that point to the spindle controller, each of the power supplies and shields out to the spindle and steppers.
2. The e-stop relies on the computer or the BOB receiving a stop signal and doing something with it. I'd feel a lot more comfortable if the e-stop were sitting on the mains input. Hit that button and EVERYTHING stops, straightaway, regardless of whether software or switching components on the BOB have failed.
3. The homing switches in series like that mean you have no idea which switch has triggered - which can be really helpful if one switch jams and needs fixing, or if you start a homing cycle with one axis already at the stop after an overrun and shutdown. I'd personally look at another BOB that had more inputs if you can't get one that has six already there.
4. Fuses? I'd have separate fuses or fast blow breakers mounted in your case that run from the active line to the inputs of the spindle controller and the two power supplies. Just in case something goes awry. And if they're case mounted it means you can replace easily.

Hope this is of some use to you.

First Question.. Where would this e-stop be connected? How is this different that the main power switch? You use the term "mains input". I am not familiar with that.

Earthing. This is all contained in a wood box. Non of the other components have and obvious places to attach an earth ground. please advise.

At this point a different BOB is not an option but quite possibly in the future. Either way I have watched a bunch of videos on limit switches and I am comfortable with them for now.

I had originally planed on having a fuse block but it didn't happen mostly due to oversight. I will see about getting some in line fuses... or at least a main fuse.

[aarggh]

Some comments from me:

1. Earthing. I chose a different route. My power supply is 100% electrically isolated from the metal frame and I chose NOT to connect the machine frame to the mains earth. I think it is MUCH safer this way for several reasons, one is that the electrical system in my home is different from that in the USA and I also have an earth leakage circuit breaker on every circuit in my home, providing protection against residual-currents. I don't think that is standard all over the globe yet, not even in Sweden. So, in regard of earthing, I think he should consult a local electrician who can inspect the machine for electrical safety. That is far more important than advising on connecting everything to one common point.
.

So if your spindle develops a short (this is a lot more common than people would think), and your touching the frame of the machine, what do you think happens? Just because the power supply may be isolated from the machine, doesn't mean any other parts aren't in most cases. And if everything is isolated from each other, you then have a bunch of mains powered gear at floating earths.

The setup you have may work for you with your equipment and mains supply configuration, but I still see no reason why in general you wouldn't adhere to the standard industry practice of star earthing to avoid voltage differentials and ground loops.

cheers, Ian

[A_Camera]

So if your spindle develops a short (this is a lot more common than people would think), and your touching the frame of the machine, what do you think happens?

To start with, I described how MY CONFIGURATION is. I also advised to consult a local electrician to inspect his machine for safety.

To continue, since it is MY CONFIGURATION and that's what you are asking about, so in my case, if there would be a short in my spindle, for whatever reason I can not imagine, I can tell you what would happen... basically NOTHING. My spindle is low voltage spindle, and there may be some smoke maybe, but I would not be the one getting smoked... Also, I would guess that in that situation there would be a current surge and at least one circuit breaker or fuse would be blown.

To continue further, if I would use a mains powered spindle then it would almost certainly trip the earth leakage circuit breaker, so once again, nothing serious would happen. Like I said, it is not a world standard, but it is installed in my home and you can also buy portable ones for small machines. It really works, even if you would have a leaking current, not enough to trip the circuit breaker, if you touch that leak the earth leakage circuit breaker will trip, breaking the current flow so you will not get smoked.

Never the less, what is most important is that you check what is necessary or needed in your own country. Following Internet advises and not having enough knowledge is really dangerous.

Just because the power supply may be isolated from the machine, doesn't mean any other parts aren't in most cases.

I don't understand that sentence. Sorry, it isn't clear, at least not to me.

If the power supply is isolated from everything else then you only have low voltage on the other side, isn't it? I mean, this discussion is about the schematics, and in that I see no other mains powered units, his spindle looks like being driven from a separate power supply which doesn't have an earth terminal, so what else is there to be careful about? Remember that if you connect the frame to earth then you better be careful about your low voltage stuff and NOT connect GND to the frame anywhere because then you might fry your electronics connected to the CNC, including your computer. Forget about using simple passive touch plates if you have everything earthed...

And if everything is isolated from each other, you then have a bunch of mains powered gear at floating earths.

Right and wrong. Actually, in my home I have many things which are not earthed. Vacuum cleaner is one of those things, mains powered drill machines are some other, just like desk lamps with metal frames. In other words, not everything metal is earthed and it would be pure dangerous to connect everything to earth just because it is metal. But... I have never heard the expression of "floating earth", perhaps you could explain what you mean by that. "Floating earth" would mean to me an earth wire not connected. There is no "floating earth" in my machine, my power supply is connected connected to earth, just as it supposed to be, only that the frame of the power supply is isolated from the CNC frame, so even if there would be an issue with it, nothing would happen.

The setup you have may work for you with your equipment and mains supply configuration, but I still see no reason why in general you wouldn't adhere to the standard industry practice of star earthing to avoid voltage differentials and ground loops.

The setup I have DEFINITELY works for me. Yes, the industry standard is a star earthing, but not unreserved everything. That might create a really dangerous situation. Besides, like I said, different countries, different standards. What you can do in Australia may be illegal in Sweden or USA, and what is today standard in EVERY newly build homes in Sweden is NOT a world standard, at least not yet. Remember how it was with safety belts? Volvo introduced it and it took many years and a lot of arguments to convince the world. Can you buy a car today without a safety belt factory installed? Maybe one day no homes will be built without an earth leakage circuit breaker as well, but in the meantime, follow the local laws and regulations.

[UA_Iron]

Some comments from me:

1. Earthing. I chose a different route. My power supply is 100% electrically isolated from the metal frame and I chose NOT to connect the machine frame to the mains earth. I think it is MUCH safer this way for several reasons, one is that the electrical system in my home is different from that in the USA and I also have an earth leakage circuit breaker on every circuit in my home, providing protection against residual-currents. I don't think that is standard all over the globe yet, not even in Sweden. So, in regard of earthing, I think he should consult a local electrician who can inspect the machine for electrical safety. That is far more important than advising on connecting everything to one common point.

A limitation of the earth leakage circuit breaker is that it can be tripped by external voltages/currents from something connected to even metal pipes - in your situation, and to avoid nuisance trips, you were probably right to do this. The rest of the world will most likely not adopt this methodology as they have already gone to a newer GFI/GFCI type of circuit interrupt.

This was especially annoying when installing medical devices in france and getting the nuisance trips from even the lowest of leakage currents from things like input power filters.

3. Homing switches. My solution is the same as his. I have all my limit switches AND the E-Stop connected in series to the same port. I don't need any real home switch, mechanical switches are inaccurate unless they are very expensive, and even so, inertia makes homing fairly inaccurate so I decided that I don't care about homing. I set up the home position different every time anyway, so having a fixed home position is pretty pointless in my opinion, unless one uses ATC I can see no use for homing position in a small machine. Limit switches are different, their purpose is to protect the machine (sort of) and preventing it from serious damages. Of course, they can't provide 100% protection, but definitely saved me a lot of headache more than once. On the other hand, I have no need for the information about which limit switch was hit, I can see that with my own eyes if the machine stops, and the override limit switch command will override any switch, so I can jog back to normal and fix the issue.

You should be able to get better than 0.1mm with an inductive proximity sensor and a proper home routine. All kinds of sensors are capable of 0.01mm repeatability or better, even 0.005mm repeatability (N-MSTKG-A?Contact Switches- L-Shaped Cylinder Type With LED?MISUMI?MISUMI USA). The limitation would be your mechanics and if you're using a stepper motor, actually being able to rotate to that precise position. Even then, homing with axes is well understood and super repeatable.

Often times motor drivers/controllers will allow for setting of soft limits with encoder feedback as well, so, as an additional protection to a limit switch, a programmable boundary can be set.