Ready to pull the trigger and could really use some input.

[CLEFAVOUR]

[QUOTE=joeavaerage;2512696]Hi,

60VDC 600W would be adequate, but 80VDC and 1000W would be better. These large power supplies are expensive and most people buy switchmode supplies on the basis
of cost....but they are not the best choice. Linear supplies are far more rugged and forgiving of overload.

Craig, if you have the time and interest....would you mind elaborating on this subject a bit? How and Why are they more "rugged'? What makes them superior to a switching PS?

[ardenum]

electronics huh? I guess it's a question I'm gonna have to tackle at some point. I'm tarded when it comes to EE, been to university twice and failed it just the same, one day I solve the questions correctly the next not so much, and it can be the very same question and each time I get a different result. Thinking of buying a ready made control box myself like the

Complete control box 4Axis 5Amper max. with 2.2kW VFD - CNCdrive - webshop.

They have a schematic of their box so maybe it will be of some help to you if reading electrical hieroglyphs is a thing for you. I know its a different controller but I assume the wiring mindset is more or less the same regardless of which one you use.

[CLEFAVOUR]

Thank for the tip ardenum.
I've been designing a controller box and trying to get a schematic together, but I'm still just a dummy when it comes to the electronics. I am, however, learning a TON by just searching and reviewing what and why people have put certain components in their setup.
I have a pretty reliable source that is fairly local to me that has done some extensive work with automation electronics, so I'm optimistic that I'll get there one way or another. I'm hoping that once I have a diagram drawn up that I'll be able to share with him and the CNCZONE community to hopefully get things moving.

[joeavaerage]

Hi,
an linear supply has a transformer, a rectifier and a smoothing capacitor, that's it, very simple. Transformers are electrically very rugged but also
expensive and dominate the cost of a linear supply.

When a linear supply comes under heavy overload, the voltage may sag a few volts from normal and the ripple increase, but it just keeps on going.
Short term 2 x rated current is not ideal but a linear supply will do it whereas a switching supply would fault out.

Craig

[CLEFAVOUR]

So, I now have motors, drivers, and my controller in. Just waiting to order all of the other electrical components until I am absolutely confident that my setup will work. Right now I am working on power distribution and safety precautions for the machine. I have a crude diagram on how I think I want to have everything wired up, but I'm no electrician and would really appreciate some feedback.
This being my first machine, I'm sure there will be some changes down the road, but I just want to make sure that I'm being as safe as possible.
The machine will have a mains power switch, an on/off and e-stop for the contactor circuit, power button for the spindle pump and a power button for the VFD/Spindle.

I want to NOT be able to turn the spindle on without the pump being powered first, so I need to be sure that this wiring will function that way. ( This, of course, will be tested prior to final assembly)
I had planned to use 18AWG shielded wire for connecting the motors/drivers and encoders.
I am at a loss though when it comes to the sizing of my other main wires such as, main power from the AC to the busbars, bus bars to DC P.S. and so on.

So, what I'm needing help with is....

1) What size wiring and where? Why?

2) Do I put a breaker in this system anywhere? If so, where? And how do I calculate for that?

3) What size fuses for the drivers?( current/phase:4A # of phases: 2)

4) What line to fuse?(DC+ or GND)?

I'm really trying to figure this all out on my own, but these are just a few questions that I cannot find definitive answers on.
You guys have been so helpful with all of this and I truly appreciate all of the feedback.

So, please, by ALL means..... SCHOOL ME

Thanks
-Caleb

[ardenum]

Electrical people hate this type of diagrams, prepare to face their wraith!

[CLEFAVOUR]

Understandably... But, I'm no engineer, nor do I plan to be. This is what I have and it makes since to me.
Thanks for the 2 cents ardenum.

[joeavaerage]

Hi,

1) What size wiring and where? Why?

The stepper connections, being low(ish) voltage and high(ish) current will want to be substantial, 18AWG should be fine.
The 230VAC wiring will be at lower currents, but then you do not want any localised heating of those wires, the voltage is high enough to be dangerous, so I'd go with 18AWG also.

2) Do I put a breaker in this system anywhere? If so, where? And how do I calculate for that?

Its a good idea to have a breaker or fuse at the primary AC inlet. VFDs are notorious for drawing huge currents for very brief periods of time, and that makes calculating the breaker size hard.
Ordinary breakers, sometimes called C curve, tend to open with inrush currents so you'll size them bigger, say 20A or 25A, than D curve breakers which a specially for motors etc that draw big in-rush
currents, where 16A should be enough.

3) What size fuses for the drivers?( current/phase:4A # of phases: 2)

I wouldn't bother, it's not a bad idea, but a little over the top. I'd have just one fuse at the output of the DC power supply, either at rated output current or just over. Transformer power supplies can deliver
big currents in short duration bursts, and that's a capability that you have paid extra for, don't throttle that advantage by using to small a fuse.

4) What line to fuse?(DC+ or GND)?

All fusing should happen in the DCpos line. If you used a breaker and wanted to be 100% you'd use a dual pole breaker to open both DC and GND similtaneously.
In most jurisdictions its illegal to put a fuse in the Neutral, and certainly the GND of a 230VAC circuit, the fuse or breaker must be in the phase side, OR a double pole breaker.
I presume in NA where 230V is actually made up of two 115V phases then a dual pole breaker is mandatory, so that both phases open similtaneously.

I want to NOT be able to turn the spindle on without the pump being powered first, so I need to be sure that this wiring will function that way.

Unless it a life threatening failure for the spindle to start without the pump, then use your CNC software to ensure the pump is energised before, or at the same time as the spindle.

Craig

[CLEFAVOUR]

Thanks for the detailed response Craig. Lots of good info.
I've had to read through a few times but I think I'm understanding you correctly.

So, a dual pole with a rated voltage of at least 230VAC 20-25A(c-curve) or 16A (d-curve) between the mains plug and the mains switch would be fine?
And a dual pole with a rated voltage of at least 70VDC 16A between the 70V P.S. and the drivers?

Also, I'm not quite sure where these values are coming from.
Is the 16A based off of the max current that the 70V P.S. can draw from the mains(i.e. the 14.2A)?
And were the 20-25A just an estimate? or is this a formula of sorts?

Thanks for all of your help!
-Caleb

[joeavaerage]

Hi,

So, a dual pole with a rated voltage of at least 230VAC 20-25A(c-curve) or 16A (d-curve) between the mains plug and the mains switch would be fine?
And a dual pole with a rated voltage of at least 70VDC 16A between the 70V P.S. and the drivers?

Yes that sounds about right.

The vast majority of breakers are intended for AC service. Ordinary AC breakers perform poorly in DC situations. Given that the voltage is modest, only 70V, and with any sort of luck at
16A the breaker should hardly, if ever operate, then you'll get away with an AC breaker.

And were the 20-25A just an estimate? or is this a formula of sorts?

That was just an estimate. The spindle is by far and away the most significant load of your machine and the breaker will be sized to meet it. The power supply for the steppers will on
average draw a few amps at the very most, whereas the VFD/spindle could draw 10A or more for hours at a time.

VFDs are notorious for low power factor, the current distortion results in poor utilisation of the incoming energy, typically 0.5 to 0.6.

2200 /230 =9.56 A, but this assumes 100% utilisation of the current, if we assume a worse case scenario of 0.5 power factor:

9.56 / 0.5 = 19.13A

Therefore a 20A C curve, or better a 16A D curve breaker are a fair match.

Craig

[CLEFAVOUR]

Thank you so much for your help Craig.
I was a bit confused as to why you were Dividing the 9.56A by 0.5, but just so I know, this would essentially be the same as the 2200w divided by half of the 230V( i.e. 115v) to come to the 19.13A for a final estimate of the breaker size?
I'm sorry, probably a dumb question, but I just want to make sure that I am following you correctly.

VFDs are notorious for low power factor, the current distortion results in poor utilisation of the incoming energy, typically 0.5 to 0.6.

2200 /230 =9.56 A, but this assumes 100% utilisation of the current, if we assume a worse case scenario of 0.5 power factor:

9.56 / 0.5 = 19.13A

Therefore a 20A C curve, or better a 16A D curve breaker are a fair match.

Craig

Thanks again
-Caleb

[joeavaerage]

Hi,

I was a bit confused as to why you were Dividing the 9.56A by 0.5, but just so I know, this would essentially be the same as the 2200w divided by half of the 230V( i.e. 115v) to come to the 19.13A for a final estimate of the breaker size?

No, its called Power Factor. All real AC devices like motors and VFDs do not convert all the current going into them as useful work, and I don't just mean they get
hot, but rather the current gets 'reflected' back into the supply. Its called Reactive Current.

If a device has a Power Factor (PF) of 0.8, that means 80% of the current the device draws is converted into useful work. VFDs have a low PF, typically in the
range of 0.6 to 0.5.

Lets say a VFD is drawing 10A from a 23ovac supply and it has a PF of 0.6:

I_effective=I x PF
=10 x 0.6
=6A
So despite the VFD drawing 10A the 'real' current is 6A and therefore the reactive current is 4A. The power the VFD delivers to the motor is:

P_actual=V x I_effective
=230 x 6
=1380W

If you looked at the power utility power meter you would see:

P=V x I
=230 x 10
=2300W

So you are paying the power company for 2300W despite you only getting 1380W for your motor. It does not matter for little motors that we use but if you
had a huge VFD/motor in a factory and its running all day it would be expensive. There are means to correct the PF to closer to 1 (100% utilisation) but they
are expensive.

The calculation I did was I assumed a worst case PF of 0.5. Have a look in the technical specs of your VFD, it may specify the PF, but typically 0.5 to 0.6.
The better VFDs have a power factor correction circuit built-in, but usually you know because the manufacturer will trump it up loudly to counteract the much greater
cost of their VFD.

Craig

[CLEFAVOUR]

Thanks for the information Craig. You are definitely bringing up some information points that I, honestly, would have never considered.

[CLEFAVOUR]

So, I'm to the point where I have almost everything that I need to get the ball rolling on this build. I'm just in the process of deciding how I want the final machine to be laid out. In doing so, I noticed that one of my lead screws has a pretty significant bend in the machined side of the screw. The opposing side is not finished by any means and is WITHOUT any sort of support to keep the screw from "whipping" during rotation. The current screws are 16mm and the ones I'm looking at are 20mm.

I have found these ball screws
https://www.aliexpress.com/item/3256...8danBgypk&mp=1

The price point looks good and they have the BF support for the screw. The coupler included will also be ideal for my planned setup.

I haven't really done a lot of research on ball screws, but from what I can tell, these should be a suitable fix to my damaged lead screw?
I also figure that if I am replacing one, I might as well replace all 3 so that I KNOW what my machine is equipped with.

Is it common the have the same size and pitch ball screw on the Z axis as the X,Y axis'?

With the extra weight of the spindle on the Z axis, would I want to have a gear reduction or counterweight to make up for the extra work that the Z axis motor may experience?

Am I just overthinking this?

Thanks
-Caleb

[peteeng]

Hi Caleb - The spec of the screw is determined by what you want to do with it. Often the Z axis is a smaller pitch because it does not need to move as fast plus it needs to have more force for plunge loads. The X&Y may need rapid speed if the bed is big and your cutting ratio time to rapid time is small. So once you know what speeds and forces you need you can pitch your screw. Then after that you know the forces involved so you can calculate the buckling load of the screw and this determines your diameter. Then you check for whipping via its length and diameter. Hiwin publish the formulas for this in their site. Peter

Typical direct drive pitches are Z 5mm XY 10mm or Z10mm XY 20mm for a router cnc. There are coarser pitch solutions as well aimed at high speeds.

[CLEFAVOUR]

I had figured as much, just haven't put much time into the research yet. Thanks for the information Peter.

[peteeng]

Hi Caleb - Heres my screw calculator. Peter

[CLEFAVOUR]

Thanks for the calculator Peter.

[CLEFAVOUR]

So, in my spare time I've been mapping out the dimensions of my frame along with different ideas and modifications that I would like to do. I've been focusing quite a bit on my Z axis, as I'm just not very confident that the existing setup will be beefy enough to support the weight and load of the spindle while cutting. It's also WAY too far from the table to be able to mount the spindle and actually reach anything on the table with accuracy.
In the first picture, it shows the existing setup in a relatively neutral state. 3" travel in Z+, and 3" travel in the Z- (The magenta block is 1"x1"x3" for reference). The Z tower is bolted to the green plate via 3 5/16-18 SHCS and the plate and tower are then mounted to the main frame via an additional 3 5-16-18 SHCS and 2 10-32 SHCS on the back side for adjustments. Now, this frame is made of 3"x8" steel tube and is only about .150" thick.

This raises my first cause for concern. Everything that is mounted to this main frame is only threaded through the frame itself. Needless to say, any 5/16 size screw should have MUCH more than .150" worth of threads to hold onto.
So, I was considering using these...( https://www.amazon.com/dp/B010GQXPIQ...roduct_details ) to increase the thread count, but I've never used them before, so I'm not sure how they will hold up.

Another thing about the current setup is that the main frame will be in the way of the Z axis being able to drop beyond the green mounting plate.
So, a new Idea ensues... I've drawn up a game plan to bulk up the Z assembly and also drop it a few inches by cutting the main frame for clearance, and adding a 3 sided angle bracket for stiffness. All faces highlighted in MAGENTA are what mods need to be made along with new parts that I will have to make.

By moving the rails to the lower part of the Z assembly and by recessing it into the frame I would be able to mount the spindle with no concern and would also have plenty of reinforcement to sturdy the whole axis and adjust where needed.

So, a couple of questions that I have....

1) Does this seem like a good plan? I would love to hear any feedback as I am still VERY new to this.

2) With this whole frame being hollow, is there a go to "filler" of sorts? like cement, foam, or something to deaden the vibration? Right now its just a huge dinner bell...

3) Does anyone have any experience with the threaded rivets? Would they be a reliable enough to use for such a machine?

[peteeng]

Hi Galeb - The main issue with thread rivets is that you will not be able to pull up to the surface due to the rivet flange. if you are concerned about thread depth use a thicker tube. Doesn't hurt extra stiffness... forget about fillers just use thicker tube... Peter