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Cobey3289
25-01-2018, 10:12 AM
Hi guys,
Need some help, the size of wire required for cnc is confusing me!
I am going to be running nema 23's 425oz drawing 3amps. However, I am undecided as to whether to use individual wires so I can match up the motor colours all the way through to the drivers. Or, use a 4 core wire to the control box and individual wires within.
So my question is what size wire do I require? I can find suitable rated amp wire but I then get confused with the 0.5,0.75, 1.0 etc.
I have read different things about wire size in respect of using 18awg or 22awg, but most listings for wire I have seen refer to the 0.5 etc.
Is automotive wire ok?
I know I will be using proper rated cable for the actual power supply. I just need to sort out motors and peripherals.
Thanks in advance
Mick

Desertboy
25-01-2018, 11:16 AM
0.75mm 4 core CY cable, you need CY normal 4 core is a big No due to interference. Wire colour is irrelevant and you'll find CY you get 3 blacks wires and an earth. It's very easy to work the wiring out it doesn;t matter how you wire it to the motor the end you wire to the drivers twist 2 wires and try to turn you ballscrew if you feel resistence you have matched pair if not try a different combination. When you have a matched pair the other pair must be matched wire them to the drivers. If the motors go the worng way invert the pin in Mach3/linuxcnc.

https://www.ebay.co.uk/itm/ALL-CY-CABLE-0-75MM-16MM-2-CORE-5-CORE-CY-CONTROL-FLEXIBLE-CABLE-PER-METRE/171352110328?hash=item27e561b4f8:m:mDC3qW60lEdeT99 1FfFPUNw

Search for companies local to you it's not hard to source cheaper than this.

Neale
25-01-2018, 07:25 PM
The CY cable I have used has the three black cores numbered along their length so you can identify which core is which at both ends. The third core could be used for an earth but it works fine as one of the four connections for the steppers - electricity doesn't care what colour wire it runs in!

Talking about awg and oz-in motors suggests that you have been looking at US sites. Europe and European suppliers tend to talk about cross-sectional area (0.75, etc) and Nm. It doesn't really matter which system you use but that's why some people use one set of units and some another.

Cobey3289
25-01-2018, 09:07 PM
Thanks guys, it seems to make a bit more sense.
In my research, I've just watched a video of a guy wiring his steppers with
Cy cable. He used a 4 core plus earth and didn't use the earth. He did however expose the wires in his control box and connected them to the side of the metal box to earth them. I'm planning on building a Perspex box, so do I still need to earth the cable or can I just use the 3core and earth as my 4 wires?
Thanks
Mick

Clive S
25-01-2018, 09:20 PM
Thanks guys, it seems to make a bit more sense.
In my research, I've just watched a video of a guy wiring his steppers with
Cy cable. He used a 4 core plus earth and didn't use the earth. He did however expose the wires in his control box and connected them to the side of the metal box to earth them. I'm planning on building a Perspex box, so do I still need to earth the cable or can I just use the 3core and earth as my 4 wires?
Thanks
Mick

You need 4 cores to connect the motor to the driver in the control box and use use the screen to connect to the ground star point. Also a plastic box is not suitable it is better with a metal box that can be earthed as it will help with the screening.

You will also need CY cable for the spindle

Cobey3289
25-01-2018, 09:52 PM
Quite agree, it seems the more you research, the more questions that end up needing answers!

JAZZCNC
25-01-2018, 10:09 PM
Quite agree, it seems the more you research, the more questions that end up needing answers!

Which is exactly why you should never buy anything until you know 100% it's correct for your needs. So don't be afraid to ask.

Regards wiring then it basicly boils down to this for CNC.

Anything which carries signals Ie: Motor wires, Control signal wires, Limit switch, E-stop, require shielded or twisted pair cables. With the Shield going back to Single Earth point " Star point".

Other wires which carry power to components Ie: From PSU to drives, power for control, power fro relays etc can all use normal single core cable often called Tri-rated cable. The cable must be sized according to load it will carry but often people will use one size, that being rated for highest load they'll use. 1.5mm/2 will work for most things.

If using VFD for the spindle then they require special treatment in that shielded cable must be used between VFD and spindle even thou not carrying signals. This is because of the high frequencys they use which can creat lots of electrical interference(noise).

Cobey3289
26-01-2018, 10:46 AM
Thanks for that jazz.
Stepper drivers and psu's.
I'm going to be running nema 23's 425oz 3amp. What stepper driver should I use? Some are rated up to 3amp and some more and then they are rated voltage wise. Until I decide on steppers I'm assuming I should hold off on psu's.
I see some people use 2 psu's driving two motors each. Can I just use one for the motors and a 5v supply, or is it best to use one for motors, another lower rated for fans etc and a 5v for the board?

Mick

JAZZCNC
27-01-2018, 01:07 AM
Thanks for that jazz.
Stepper drivers and psu's.
I'm going to be running nema 23's 425oz 3amp. What stepper driver should I use? Some are rated up to 3amp and some more and then they are rated voltage wise. Until I decide on steppers I'm assuming I should hold off on psu's.
I see some people use 2 psu's driving two motors each. Can I just use one for the motors and a 5v supply, or is it best to use one for motors, another lower rated for fans etc and a 5v for the board?

Mick

Well it's little more complex than just amps.?
Not all steppers are equal and even thou may be rated same size doesn't mean they will perform the same. Inductance rating of the motor is very important to how well stepper will perform with a given voltage.

For instance, motor with high inductance will spin much slower than one with low inductance using the same voltage.
So if the steppers you buy have high inductance it will mean you'll need to run them with much higher voltage to get the same speed as Low inductance motor.

Then you have how the motor phases are wired. Steppers tend to come in two flavors. 4 wire and 8 wire.
4 Wire motors are less flexible because their phases are predefined at the factory. Often their phases will be series wired.
This means they will require much more voltage to achieve high speeds. Parallel wired motors, on the other hand, will reach same speeds with less voltage.
Often you'll find Series wired motors on Mills or machines which require high torque but less speed. This is because they produce higher torque lower down the rpm range but quickly lose torque as RPM's rise.

Parallel wired phases, on the other hand, give less low down torque but carry more torque higher up the rpm range. This is why parallel is preferred for routers.

8 wire motors allow Either series or parallel phases so again are preferred and easier to find than 4 wire parallel wound motors.

Voltage is the key to getting speed from stepper but at same time too much voltage can lead to over heating and resonance issues.
So this brings us back to inductance and why it's important. Lower inductance means higher speeds can be got with less volts and less volts equals less motor heating, less resonance etc.

So to answer your question about Drives and PSU will require knowing more about the motors. Would also help to know more about the machine spec and what you intend to do with it.

However if you want proven setup which works with most small to medium sized routers then the spec below works great.

Nema 23 3.1Nm 4.2Amp 8 wire motor wired parallel. Ideally with Inductance around 3mh or less.
Digital drives with voltage between 70-80V. Leadshine AM882 are great drive.
PSU with 60-68Vdc output depending on drive voltage. Current will depend on #motors and PSU type.

Now the Psu is little more involved because several types but the best solution by far is unregulated Toroidal PSU. It's gets little involved to why best but trust me this is the best setup for stepper motors. If really want to know why I will explain.

The reason you have probably seen people use 2 psu's is because they have bought off the shelf units which have limited current output so not enough to power 4 motors.
However the best solution is to build your own PSU which is very easy to do and doesn't require degree in electronics. We can help you with whats needed and will say if you can't wire this then you can't wire any of the machine it's that simple.
This way you get exactly what you need in terms of voltage and current in one setup and will work out cheaper than buying off the shelf units.

You will need a separate linear PSU for the Control etc and these are best bought off the shelf and cheap enough not bother building.

Hope this helps.

Desertboy
27-01-2018, 08:25 AM
Regulated or Unregulated Power Supply
Both regulated and unregulated power supplies can be used to supply the drive. However,
unregulated power supplies are preferred due to their ability to withstand current surge. If regulated
power supplies (such as most switching supplies.) are indeed used, it is important to have large
current output rating to avoid problems like current clamp, for example using 4A supply for 3A
motor-drive operation. On the other hand, if unregulated supply is used, one may use a power supply
of lower current rating than that of motor (typically 50%~70% of motor current). The reason is that
the drive draws current from the power supply capacitor of the unregulated supply only during the
ON duration of the PWM cycle, but not during the OFF duration. Therefore, the average current
withdrawn from power supply is considerably less than motor current. For example, two 3A motors
can be well supplied by one power supply of 4A rating.
Multiple Drives
It is recommended to have multiple drives to share one power supply to reduce cost, if the supply has
enough capacity. To avoid cross interference, DO NOT daisy-chain the power supply input pins of
the drives. Instead, please connect them to power supply separately.

Selecting Supply Voltage
The power MOSFETS inside the AM882 can actually operate within +20 ~ +80VDC, including
power input fluctuation and back EMF voltage generated by motor coils during motor shaft
deceleration. Higher supply voltage can increase motor torque at higher speeds, thus helpful for
avoiding losing steps. However, higher voltage may cause bigger motor vibration at lower speed, and
it may also cause over-voltage protection or even drive damage. Therefore, it is suggested to choose
only sufficiently high supply voltage for intended applications, and it is suggested to use power
supplies with theoretical output voltage of +20 ~ +72VDC, leaving room for power fluctuation and
back-EMF.

http://www.leadshine.com/UploadFile/Down/AM882m.pdf

Cobey3289
27-01-2018, 09:47 AM
Thanks guys, the wealth of knowledge on here is great.
My cnc is going to be 100cm x 75cm c beam construction. I intend to cut wood, acrylic and some aluminium with it. At this stage, the aluminium cutting will be to cut bulking blocks for the stickmaking world. Anything else will be ideas that come into my head at a later date.
As stated it will be run by nema 23's 425 oz 3amp motors x4 with8mm threaded rod. I can't say it's going to have a hard life, but that's just my thoughts at the moment. Once built and working, my thoughts and practices may change.
I plan to use a MacBook as my computer for the cnc. This I think will necessitate using a USB breakout board. Are there any particular boards suited to the USB side of things and as I'm heading for USB, was looking at chilli pepper as opposed to Mach 3/4.

Thanks
Mick

Clive S
27-01-2018, 09:52 AM
As stated it will be run by nema 23's 425 oz 3amp motors x4 with8mm threaded rod.

Threaded rod and cutting ally don't go together very well:thumbdown:

Cobey3289
27-01-2018, 09:55 AM
What would you suggest, as that's what come with the mechanical build. I thought at least that's a step up from the belt system!
Mick

Desertboy
27-01-2018, 09:56 AM
Thanks guys, the wealth of knowledge on here is great.
My cnc is going to be 100cm x 75cm c beam construction. I intend to cut wood, acrylic and some aluminium with it. At this stage, the aluminium cutting will be to cut bulking blocks for the stickmaking world. Anything else will be ideas that come into my head at a later date.
As stated it will be run by nema 23's 425 oz 3amp motors x4 with8mm threaded rod. I can't say it's going to have a hard life, but that's just my thoughts at the moment. Once built and working, my thoughts and practices may change.
I plan to use a MacBook as my computer for the cnc. This I think will necessitate using a USB breakout board. Are there any particular boards suited to the USB side of things and as I'm heading for USB, was looking at chilli pepper as opposed to Mach 3/4.

Thanks
Mick

8mm threaded rod, NO, NO, NO, NO!!!!! My reprap used that for a drive lol this is not reprap territory.

get ballscrews, get a free PC with a parallel port ask on forums and then you can use a 5 breakout board and linuxcnc with the money saved you pay for the ballscrews.

it'll cost ~250 for 4 ballscrews and fittings for this size.

I think you're better off belt driving than threaded rod, you can do a belt and pinion setup which will be a lot better I'm sure. Just google it there's a few setups out there.

Cobey3289
27-01-2018, 10:06 AM
Hi Clive,
That's tr8 lead screws not threaded rod, my mistake.
Mick

Desertboy
27-01-2018, 10:14 AM
Hi Clive,
That's tr8 lead screws not threaded rod, my mistake.
Mick

still lead screws are only 50% efficient ballscrews 95%

That means 50% of energy is lost to friction! It just doesn't make sense anymore to use them for our application.

Where they work well is using really big ones for lathes, etc. Where ballscrew prices are prohibitive.

JAZZCNC
27-01-2018, 10:33 AM
Hi Clive,
That's tr8 lead screws not threaded rod, my mistake.
Mick

Mick starting to appear you are a classic case of the internet searching leading you up the wrong path.
In the early days of DIY CNC components like ball screws and good off the shelf drives etc cost lot of money. Things have changed massively and now the cost is down to sensible figures we can afford.

Now it's very easy and we see it all the time that new builders find old build's which used components like Tr8 and even threaded rod and all sorts of DIY methods and follow this route. Unfortunatly often they are sadly dissapointed and waste lot of money.

So my advice is to take a step back do little more research and ask any questions you may have no matter how stupid you think it may be.
UNDER NO CIRCUMSTANCES BUY ANYTHING Until your sure it's correct for your build.

For instance, all the previous info regards Voltages drives etc to achieve best speeds is mostly irrelevant because the limiting factor to speed will most likely be the Tr8 and everything that comes with it not the voltage. So you would have wasted money building PSU etc that's much more than needed.
Said this many times that machine is only as good as it's the weakest link and for a great machine you need components which are well matched to give balanced machine.
Trying to save money only costs you money when comes to CNC, so don't try cutting corners because will only regret it.

Suggest you start build thread if you haven't already which shows your design. Then ask any questions there. If we can see what you have in mind it's easier to advise the correct components or approach.

Cobey3289
27-01-2018, 12:13 PM
Hi jazz,
Seems like a total re-think is in order.
Just off the bat then, having already purchased the nemas and drivers (already en route)! What would you recommend for the rest of the kit to complete my 750x1000mm . I have c beams already, may need to add to this to adapt to ball screws etc.
Thanks
Mick

Cobey3289
27-01-2018, 12:17 PM
Where do you guys get your kit from, as it seems like ooznest is the most popular place for purchases?
Mick

Neale
27-01-2018, 12:30 PM
Definitely a rethink needed! I doubt if many people on this forum buy anything from Ooznest, for example. I don't want to sound as if I'm knocking anyone, and I'm sure that the Ooznest machines will do most of what is claimed for them (i.e. allowing for all advertising hype!). However, whether they will do it particularly accurately, fast, with a decent surface finish, or for very long without frequent adjustment, is more open to question.

A couple of UK suppliers of the more specialised kit for CNC building are CNC4YOU and Zapp Automation, both of which sell decent quality kit with a decent level of service as well. People like KJN will sell aluminium extrusion for frame building, and you can use rather better quality guide rails and drive systems from the first two I mention. However, a lot of people go direct to China, e.g. via AliExpress, but you do have to know a bit more about what you are looking for. That's where help from folks on this forum can help immmensely, so you buy the right stuff first time.

As suggested, post a proposed design as a build log, and wait for comments. Don't be too upset if you are told to start again - it will be advice based on past experience, and will help avoid disappointment. For a bit of background, read Desertboy's build log as he has significantly changed direction since he started based on advice from here, and will have a much better machine as a result.

Good luck - people genuinely want you to succeed, and we all had to start somewhere.

JAZZCNC
27-01-2018, 01:35 PM
Hi jazz,
Seems like a total re-think is in order.
Just off the bat then, having already purchased the nemas and drivers (already en route)! What would you recommend for the rest of the kit to complete my 750x1000mm . I have c beams already, may need to add to this to adapt to ball screws etc.
Thanks
Mick

Mick Neil says it all really but straight off the bat I can tell your design is probably working along the wrong lines for good machine because you mention C beams. This type of beam isn't often used because of it's weak flexy nature.

This is why we ask new builders to start a thread and give some idea of the design. Even if it's just picture of fag packet sketch.
Like any structure you start at the foundations and if these are flawed then the whole structure fails. The Machine design then leads you to what components are required.

Building a good CNC machine is done in orderly stages and nearly all those that shoot off buying components before the design is finalized waste money.

Start a Build thread mate.