Newbie looking at 6040 (China CNC) for polypropylene 15mm sheet

[JOGARA]

One important thing to look for (and the cheaper stepper motors available online often fail this criterion) is inductance. High inductance may give high torque, but it slows the rate of rise of current through the motor coils which means that the rate of torque increase is also slower. That means that they are OK at slower speeds but with higher speeds/faster pulse rates, the torque drops off. The motors I'm using are 8-wire so that the coils can be wired in series or parallel. Series means lower current but poorer high-speed performance; parallel means higher current draw but better high-speed performance. This is all a bit of a simplification but it's broadly true and why you don't want high-inductance motors if you want to run fast. Does mean bigger PSU and drivers to suit the higher current.

I'm using the Zapp 3Nm NEMA23 motors on a 1500x750 cutting area router. Fairly heavy gantry (maybe 75kg?) driven by two motors and 5mm pitch ballscrews. I'm limited to about 5000mm/min by whip in the ballscrews (I should have used 10mm pitch) but those motors seem to drive that load without problem. I'm also using EM806 drives (from Zapp). I wanted newer digital drives, even though I had some appropriate rating older analogue drives from the Mk1 router, because, apart from generally better performance, they have stall detection. With a dual-motor master/slave axis drive on X, you really, really, don't want one motor to stall while the other keeps running. That could get very messy. I have wired the fault detect signal from the drives back to my motion controller so that if one drive trips, the machine stops very quickly. While setting up and tuning, this happened a couple of times which gives me some reassurance that the system works. I run on about 68V and have wound the motor max current setting to a point that it seems to run reliably on load without overheating the motors. The EM806s are well within their ratings although I have a couple of fans blowing a gentle draught across them.

For motion control, I went for Mach3 and a CSMIO IP/M ethernet controller. It's probably about the best controller around (based on general feedback and reputation) unless you go for its big brother the IP/S which costs about twice as much. The IP/M is not the cheapest option, although once you add in the fact that with "lesser" motion controllers you also need a breakout board, and a decent one that includes spindle speed control is not cheap, it's not that bad. It also uses 24V for signalling which gives better noise and interference rejection compared with 5V systems, and has differential outputs to drive the stepper drivers - again, this is an unusual feature but gives better interference rejection. I fitted mine, wired it all up, and it just worked first time, no messing about. The down side is that the IP/M can drive a master-and-slave axis machine like mine, but it cannot properly home the two axes. In practice, I am finding that this is not a problem and I have a simple manual workaround for this. If I were starting again today (I bought the electronics a couple of years ago), I might consider the UCCNC UC300ETH instead which is a cheaper option and getting a fairly good write-up in forums like this one. Haven't played with one myself though. You can save money by not needing Mach3 and using the UCCNC software which is also getting good feedback. All the same, I'm pretty happy with what I have.

But there are as many opinions in this area as there are CNC builders, so take all my comments as one man's view!

Thanks for all the info.

Looking at the steppers on Zapp, http://www.zappautomation.co.uk/elec...ription_tabbed
These ones are (what I believe) you are talking about?
Parallel with 3.2 inductance and 3Nm holding torque at 4.2A.


Can I ask what power solution you are using to get 68v?


I took a look at those controllers but they are way out of my price range.
Currently the steppers and drivers are costing me £300.
With the added power draw this is another big wedge and means ill have to forfeit the controller with the £30 one off eBay.

I get that it is better to spend more on a CNC router but at a point it starts to run over budget :p

[Zeeflyboy]

I'm guessing something like this http://www.zappautomation.co.uk/elec...er-supply.html


Yeah these things can snowball, one more expensive item leads to another and so on... reality is most of us are working to a budget so you need to figure out what you are willing to spend and what will be sufficient for your needs.

If budget is starting to pinch, I would also take a look at what areas it's best to put your money into initially. Might be an idea to go for the better controller (e.g. the CSMIO IP/M mentioned above) and just make do with the cheaper steppers until you feel the need to upgrade.

Ultimately of course you end up spending more by buying cheap then replacing, but reality is it gets you up and running in the mean time.

[JOGARA]

I'm guessing something like this http://www.zappautomation.co.uk/elec...er-supply.html


Yeah these things can snowball, one more expensive item leads to another and so on... reality is most of us are working to a budget so you need to figure out what you are willing to spend and what will be sufficient for your needs.

If budget is starting to pinch, I would also take a look at what areas it's best to put your money into initially. Might be an idea to go for the better controller (e.g. the CSMIO IP/M mentioned above) and just make do with the cheaper steppers until you feel the need to upgrade.

Ultimately of course you end up spending more by buying cheap then replacing, but reality is it gets you up and running in the mean time.

Yea, I am thinking around £1,500 max.

Probably will go for these switching power supplies at first and upgrade later to the better power.
Would allow me to then have the nice steppers and drivers.
But I would also be using the cheap Chinese controller.

That will probably get me started for now. If I then need to upgrade in a few months at least I have done this project and hopefully have another one where I can spend a few more quid on nicer things if they are needed.

I would really just avoid those unsupported gantries like the plague... yes they may be ok with plastics and wood but they still limit how fast you can push it and will limit you in the future as well if you look to do some harder materials. It is not an area to cut costs imo as it's extremely difficult to upgrade or improve it later without just buying a new machine (which is what I ended up doing).

What is your time scale? I'm probably building myself a new bigger CNC over the next couple of months and the barebones X6-2200L mechanics would be up for grabs once I've done the machining I need to do for you to go to town on with your own electronics. That's like your generic 6040 but with proper profile HG20 type linear rails.

Looking at the parts on the one I listed; https://www.aliexpress.com/item/6040...999.277.umjtYe
Isn't the Y rail supported underneath?
I know it is not linear rails but should be better than the rods just floating?

The X axis ones are floating by the looks of it.

[Clive S]

Can I ask what power solution you are using to get 68v?

A toroidal transformer 24-0-24v in series with one rectifier and two caps

[Neale]

A toroidal transformer 24-0-24v in series with one rectifier and two caps

Actually, I'm using a 2x45V toroidal with both windings strapped in parallel to give a single 650W supply. Same thing, really!

My first router used LinuxCNC (cheap - nothing cheaper, in fact) and a parallel port to a cheap breakout board. No spindle (speed or start/stop) control. Old analogue drivers. It worked. Not ideal in many ways, but you don't always need "the best". But you do need something that works for you, and it does need to be reasonably reliable. Best thing, I guess, is to try to understand what compromises you are making by going cheaper and deciding if you can accept that for the time being. The other thing to keep in mind is, "Can I easily upgrade it later?" For example, changing a motion controller or stepper drivers is not too invasive. But changing ballscrews for leadscrews, or supported rails for profile rails, might be more difficult later.

I have probable spent around £2500 on my steel-framed, ballscrewed, profile railed, motion-controlled, 1500x750 router. That's probably typical.

[JOGARA]

Would something like one of this work?
http://www.airlinktransformers.com/c...Filter+Results

They have 70+70V so would mean 2 sets of 70V?
From what I know, you can connect these in parallel though you have to be careful to get the phases the correct way round?

As for the rating, thinking 2000VA?

As for caps, 110v and as big as i'd like?

[Clive S]

Would something like one of this work?
http://www.airlinktransformers.com/c...Filter+Results

They have 70+70V so would mean 2 sets of 70V?
From what I know, you can connect these in parallel though you have to be careful to get the phases the correct way round?

As for the rating, thinking 2000VA?

As for caps, 110v and as big as i'd like?

Ok what DC voltage to you want to end up with. What steppers are you using and how many.

Read #31 again 650VA should be more than enough try and get caps that are 100V

http://www.airlinktransformers.com/c...Filter+Results

[JOGARA]

Ok what DC voltage to you want to end up with. What steppers are you using and how many.

Read #31 again 650VA should be more than enough try and get caps that are 100V

http://www.airlinktransformers.com/c...Filter+Results

Going off what people said, higher voltage the better? So close to the max of the drivers.

As for the drivers, http://www.zappautomation.co.uk/elec...ion/em806.html (buying direct from manufacturer in China)
Steppers, http://www.zappautomation.co.uk/elec...ion/em806.html

[Neale]

Going off what people said, higher voltage the better? So close to the max of the drivers.

...which is what you will get if you use a lower voltage transformer. Yes, I know it doesn't sound right, but in practice a 45V or so transformer will end up giving you around 68V DC across the smoothing capacitor(s). This also gives a bit of allowance for the fact that the mains input voltage will vary, and the transformer will probably give you about 5% over the rated voltage under light load to allow for a drop when on full load.

EM806 are good drivers.

[Clive S]

Going off what people said, higher voltage the better? So close to the max of the drivers.

As for the drivers, http://www.zappautomation.co.uk/elec...ion/em806.html (buying direct from manufacturer in China)
Steppers, http://www.zappautomation.co.uk/elec...ion/em806.html

Those are 80V drives so run them at about 68V to allow for the back emf. 24-24 v in series = 48 = about 68V dc when rectified.

AM882 drives would be less dosh and just as good.