Advice on this parts list please.

I am going to build my own CNC router. I will only be cutting wood. I figured I would pass this by some others who know better than I do just to see if there are any glaring issues or unreputable sites in my list. Anything major I might be missing?

Linear motion, X & Y axis:
2x set of 2 linear rails and 1 ball screw w/ mounts. (2000mm)
https://www.amazon.com/Joomen-suppor...st_bbp_dp&th=1

1x ball screw w/ mounts
https://www.amazon.com/Joomen-Machin...st_bbp_dp&th=1

This gives me a total of 4 linear rails and 3 ball screws. One rail will be unused, but they don't sell them in singles. I would use a screw and rail for both sides of the X axis, then a screw and rail for the Y.



Z axis:
1x Ball screw w/ mounts (200mm)
https://www.banggood.com/SFU1605-200...r_warehouse=CN
+
2x Linear rail (200mm)
https://www.banggood.com/200mm-Linea...r_warehouse=CN
+
2x Ball screw nut housing
https://www.banggood.com/Ballscrew-N...r_warehouse=CN



Table:
40 series extruded aluminum to build the table from the ground up.
https://parco-inc.com/product/40mm-x...cut-to-length/
Should I go with the 80mm ones though?

40 series 45 degree angle 160mm supports
https://8020.net/40-2578.html

Joining plates also.
https://parco-inc.com/product/40-s-5...joining-plate/

Double T-nuts
https://parco-inc.com/product/40-s-m...economy-t-nut/



Router:
2.2 KW router, inverter, clamp
https://www.amazon.com/gp/product/B0...1e1b33ccb22a36
I have seen spindles without inverters. Do I really need one? I've also seen people slap a DeWalt in and go. Trying to cut costs if possible. I'll only be cutting wood.
I also saw one setup where it was hooked up to a transformer, but another setup where it looked like they just hooked into the wall.
This part of my project I understand the least about.



Stepper motor + driver kit: (566oz, Nema 24, encoder, 5A motor, 55mA driver)
4x https://www.omc-stepperonline.com/cl...nd-driver.html

Power supplies, 36V (36 recommended in motor specs), 6A (taking a guess here!):
4x https://www.amazon.com/Utini-Power-S...c&sr=1-29&th=1

I haven't gotten around to the smaller brackets and such that most things would be attached to, but that will be easy.

Thank you!

For running that spindle, yes, you'll need an inverter, also called a Variable Frequency Drive. It produces 3-phase power from the single-phase power you've likely got, and feeds it to the motor at varying frequencies that determine its speed (but in a narrow range; these motors can't run slowly). You can use a regular hand router, but they're noisy and don't last long in this application; 3-phase motors are more powerful for their size, quieter, and just keep going.

For those motors, I'd think a higher-voltage power supply would be better. The motors want 51 volts to run optimally, and the drivers say they'll take 50v, so a 48v power supply would probably be safe.

If you're cutting wood, save some money in your budget for a good dust collection system; these things make prodigious amounts of dust.

Thanks for the info. The inverter was definitely something I was wanting to know more about before I pull the trigger on this. I will also look for a higher voltage power supply for the stepper motors. It's looking like it will be in the range of about $2000, but that's way cheaper than buying one retail.

if your looking for T slot extrusion i came across this company and used them for the small amount i got. tnutz.com they have a sale right now so depending on what you need it might be worth checking into? i have used 80/20 in the past and this stuff was just as good and cheaper even without the sale.

You'll want to use 1610 ballscrews. The machine will be very slow with those motors and 1605 screws.

Thanks for all the great info. Machinedude, I will check that site out. ger21, I have found a 1610 and will use that. I found a useful video that explained the numbering. All is starting to make sense now.

ger21, I was reading some of the other threads about builds and saw some of your posts about torque curves at different rpm's and the importance of inductance. I watched a video that explained what inductance was in stepper motors, so I understand what it is, but I'm not making the connection as to how high inductance is bad for stepper motors doing CNC. Would you mind explaining just so I can understand it properly? Thanks.

Quote:

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ger21, I was reading some of the other threads about builds and saw some of your posts about torque curves at different rpm's and the importance of inductance. I watched a video that explained what inductance was in stepper motors, so I understand what it is, but I'm not making the connection as to how high inductance is bad for stepper motors doing CNC. Would you mind explaining just so I can understand it properly? Thanks.

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As a stepper motor's rpm increases, inductance slows the current flowing through the motor, reducing torque. The higher the inductance, the faster the torque drops off.
When a stepper powered machine is accelerating, it requires a constant force, from a standing start up to full speed. So, you can only accelerate with the force you have at your max speed. If you look at the torque curve for that motor, with a 48V power supply, it only has about 110oz of torque at 1000 rpm. This means that your acceleration rate will be limited to whatever rate you can get with 110oz-in of torque.

A motor with lower inductance would have more torque at any given speed.

Hi,
Gerry is so right about inductance, the less inductance the faster the stepper can go.

All stepper motor manufacturers make high torque steppers but with commensurately high inductance. They do this because they can do it cheaply
and first time buyers don't know any better and they assume high torque must be the best.

The same manufacturers will also make steppers, maybe the same size as their higher torqued siblings with lower torque but also much lower inductance.

For instance you could buy a 600oz.in stepper but with inductance of 6mH. At 1000rpm the stepper may have as little as 60oz.in torque. Another, identical
sized stepper might have only 400oz.in holding torque but because it has only 1mH inductance will have 150oz.in torque at 1000rpm. Thus the apparently
weaker, lower torque stepper will be better overall than the high torque unit.

Another area where stepper manufacturers are making money from people new to CNC is closed loop stepper control. The manufacturers claim they are more
powerful and faster......they are not. Its a line of BS they are feeding you to sell their products.

ALL steppers lose torque the faster they go, closing a control loop does nothing to change that.

There are some advantages about having closed loop but way WAY less than the manufacturers claim. In the first instance look for low, very low inductance.
A low inductance open loop stepper of adequate spec will outperform any closed loop high inductance stepper.

With a 23 sized stepper look for 1-2mH, 1mH preferred and reject anything over 2mH.
With a 34 sized stepper look for 2-4mH, 2mH preferred and reject anything over 4mH.

Use the highest possible voltage power supply your stepper drivers can handle, to as best as possible, overcome the loss of torque at speed.

Craig

i had to look up "prodigious"

I'm going to add that in conversation

Thanks

That makes sense. The more I read around, the more people say that the bigger motors are just overkill, too. I'm seeing many CNC routers run on 23's and 24's just fine. I was thinking about how the ballscrew is so ingenious for moving things, if you think about it, the leverage used to rotate it isn't far away from the shaft of a motor. It's right there in the center. So when considering torque, it is very efficient it would seem and you would get a lot out of your motor. I imagined how easy it would be to physically rotate a rod underneath a large load - you probably don't need that many ounces per inch of torque, and doing the math, motors in the many hundreds of torque does seem like overkill.

Like I said, I feel like this is 90% research and will be 10% building. I am trying to watch and read everything, looking at examples, charts, specs, etc. One thing I discovered was that a 500W spindle only requires 110VAC outlets, while the 1,5kW one I was hoping to get requires 220VAC outlets. I noticed three different Teco VFDs on Amazon and couldn't tell the difference. I saw one guy's video where he was wiring a VFD and saw that his was a 203 instead of a 101. Looked it up and saw that it was a voltage difference and thought, hmm why would that matter. Well, it's what you're hooking up to it that matters and I would be hooking the spindle up to it obviously. And so I saw that the 1.5 kW one was 220v.

Anyway, point is that I don't have a free 220v outlet in my house. Watched more videos and discovered you could make 220 from two 110 outlets if they are opposite frequencies. You join their hots together. Read in a random comment of that video that they sell a retail product called quick 220 that does it for you. Only catch is that it says in the product description that for power tools, you need 3-4x the wattage to account for spikes or the fuse might blow. That means I would have to buy the 5000W one - $175. Ouch. To afraid to rig wires together to do that on my own. Don't know how I'd deal with wattage spikes.

By the way, thanks again for the answers and info. I'm sure all the users on this site really appreciate having people who are willing to take time out of their day to shed light on the issues we have questions about. It helps a lot.

Hi,
in New Zealand our single phase domestic supply is 230V, so I cannot claim familiarity with 110V supplies, having said that combining
two phases to get 220V is not rocket science.

You do not connect the two 'hots' together, but rather the two neutrals and your load is connected to the phases. If you are uncomfortable
then by all means employ an electrician to show you......messing with what you don't understand could be dangerous. A little help
and you be fine.

Most VFDs will run on 110V, but it means that the max output voltage of the three phase output will be about 100-105V_rms,
and that will limit the speed that a spindle can attain. In order to achieve full speed you will have to find a spindle that is rated for 110V,
entirely possible but a much reduced selection than spindles rated for 230V_rms.

I would suggest get an electrician around home to investigate whether indeed you have two phases available....that will influence your
choice considerably.

Craig

Thanks for all the replies. I feel like I have made a mistake purchasing a Nema 24 stepper motor. I cannot seem to find any mounting brackets for them. Are 23's supposed to usually work for them?

Hi,
'23 size' refers to an NEMA (National Electrical Manufacturers Association) standard, namely a motor with a square flange 2.3 inches across the flats.
NEMA in a US based association and the standard dimensions are inches.

In metric; 2.3 inch = 57mm. As a consequence many metric based countries, China is the obvious example, make steppers with a 57mm square flange
which are intended to be a drop in replacement for NEMA 23's. You will often see part numbers with 57 in them, HS57CD, for example, and you can be
assured that it will fit a NEMA23 mount.

57mm is an unusual size if you are accustomed to metric manufactured parts and so many manufacturers have chosen to make steppers with 60mm
flanges, so just a little larger than the NEMA23 equivalent. There is now a semi-official designation NEMA24 which reflects equivalence to 60mm.

If you cant find either 60mm or NEMA24 mounts you will, with a little work with a rats tail file, be able to enlarge the holes of a NEMA23 or 57mm mount
to make it fit.

Craig

I think all the holes are the same on Nema23 & 24. Just the flange is different.