Stepper/Driver Advice (I'm new, but have done some research.)

[Manicalistical]

Hi, I've been lurking around for the past couple of weeks trying to get my head around some of the concepts related to building my own machine. I'm sort of in need of advice to decide on what driver I should use for my build. Initially I plan to start out with a 3 axis machine, though I am designing with a later upgrade to 4 axes in mind. I plan to use EMC2 which I have sorted out on an refitted old pc (decent latency of about 40 000nS) and a frame made from some huge steel I beam and channel I have lying about in the yard (I'll be splitting that lengthways to decrease the overkill.)

That is about all I have actually accomplished so far, now for my targets; 3 then 4 axes, precision, able to machine mild steel. Having an really fast machine isn't really an issue, I'd prefer it to be precise and reliable.

I figured that with what I have already the best step would be now to decide on a stepper driver. I know that gecko pretty much meet my criteria perfectly, but I'm a student and can't really afford it. The other options I have narrowed it down to are:

• MECHATRONICS 4 axis: www.easy-cnc.com * Your best option in driver boards for CNC machines
• Pro Chopper kit from: HobbyCNC PRO Chopper Driver Board Kit | HobbyCNC
• FET-4 from: Stepperworld FET3 controller circuit board
• CNC5AIXS4 from: 4 AXIS (TA8435) CNC STEP MOTOR DRIVER 4 AXIS CNC STEP MOTOR DRIVER [CNC5AIXS4] - $109.90 : CNC Driver ARM Ulink 5-axis BDM Keil Mill - CNCGeeker.com Univelop Tech. LLC, CNC

Are these good options or would I be better off using a breakout board and separate drivers? I was leaning towards the first two until this afternoon, especially the MECHATRONICS one, though apparently the Chopper kit has a good reputation here.

Also I think I would like to use lead screws (that is ACME and things right?) so what would be the approximate size steppers I should be using? I was thinking the Nema 23 frame size variety, but what sort of price would one expect to find them at in Australia. they seem to vary considerably and I'm unsure of the quality a lot of sellers provide.

Any suggestions or advide would be very much appreciated...

[AssassinXCV]

Well, think im in the SOLVED position of your position, being a student as well, i have a low budget.

I'm ordering the Hobby CNC Pro 4 Axis kit. You have to put it together yourself, but i think it's worth it to save the $50+ that you would have spent with the Mechatronics board. The Mechatronics board is Bipolar(4Wire) and HCNCPro is Unipolar(6Wire), so if you already have stepper motors; if they have 4Wires, get the mechatronics board, if you have 6Wires you can get either one of them since you can wire the 6Wire motors in a way to act like 4Wire motors

The Stepperworld boards; hoss2006 and H500 stated that they are weak board since they can only be powered with 12v, while the HCNCPro can go to 42max.

I have 125oz 3Amp Nema 23 Stepper Motors.

I too am using EMC2 as the CNC Controller software.

I'm planning on getting a Switching power supply that can provide at one setting, 24v and 12Amps, and the other settings around 32v and 16Amps. This is so that when running only 3 motors, i wont have too many Amps running through the board.

The 4 AXIS (TA8435) CNC STEP MOTOR DRIVER compared to the HCNCPro, the price is the same, but the HCNCPro is better quality because it's made in the USA, with the TA8435 chips are from China. The 4 AXIS (TA8435) CNC STEP MOTOR DRIVER is similar to the TB6560 boards, which some people have been having problems with losing steps.

The 4 AXIS (TA8435) CNC STEP MOTOR DRIVER also has a limit of 2.5Amps for the motors, while the HCNCPro offers 3Amps.

Hope this helps.

[Manicalistical]

Thanks Assassin, I just needed to hear someone else second it. I appreciate the breakdown a lot. A question though, you say that you are going to get a power supply with switching capabilities, I thought that the amperages stated for a power supply is the maximum that it can provide depending on the draw from the board/steppers impedance. Unless you are getting a power supply that had a fixed power output instead of fixed voltage i don't see the benefit of a switching one?

[AssassinXCV]

I'm not sure which power supply to get, i understand the voltage part; 24v is minimum, and the only difference when you have more voltage is that the steppers will drive faster; i've read people getting 36v power supplies.

The amperage part, i've read to get 10amp supplies, but then also 20amp supplies... my local electronics store where i got the 3Amp steppers said to get a 16amp supply, since 3amp x 4 = 12amps, and then that extra 4amps is for hte driver board chips and such to be powered.

That's why if i got a power supply that you can set everything, you can change the amperage if you're only using 3 motors;not all 4, you can set the amperage lower, since the draw is lower.

Please dont rely on that info, since i have very little experience with power consumption.

[Manicalistical]

Sorry my mistake, I misunderstood you and thought you were getting a power supply that had both a fixed voltage and current output rather than one that relied on the draw. I was just worried that you might of fried something with a fixed power supply. Anyway thank you again for your advice!

[AssassinXCV]

Okay, well i spent some time reading all of the posts in the HobbyCNC section of this forum,

One of the posts by HobbyCNC said to voltage/amps simple, to just get a 24v 10Amp board, and to not worry about the numbers from 4 steppers at 3Amps each.

[H500]

Simple power guidelines from Geckodrive:

1. Choose your supply voltage based on your motor's inductance:
Voltage = 32 * sqrt(Inductance in mH)

2. Choose current that can supply about 70% of the coil amperage. Any extra will be unused. Example: if 4 motors are rated at 3 amps each choose a supply that has 4x3x.7 = 8.4 amps. In all likelihood, you can get away with a supply rated as low as half that.

[Manicalistical]

Well thanks a heap for that feedback on the power requirements H500. I had no idea about the current requirements being that low, I was just basing it off the steppers in parallel. As for the voltages I'll just try to get the maximum I can for the board. Unfortunately as it's limited to 42V and I don't trust some of these cheap 40V chinese power supplies as far as I can throw them I'll just have to stick with 36Volts. So in that case I'd be looking for a stepper with an inductance of about 1mH, not very likely. I now understand why people fry the drivers and love the gecko's...

[H500]

Nema23 motors tend to start at 2mH. That means your drive need to be able to handle 45v or about 55v to allow for back emf. Many people go for bigger motors and then try to drive them with the tb6560 and 24v. That's a waste of a good motor.

[AssassinXCV]

So, just to make sure of everything, I have 3Amp Nema23s

The only difference between 24 volt power supply and 36 volt power supply is that the motors will run faster with the 36volts. But also, aren't the motors only rated for like 4volts? so why is the voltage so high??

The driver board and motors will only draw as much amps as it needs, so if i some how got my hands on a 24volt 2000Amp powersupply, my board wont blow up. With this fact, then that means that if i buy a power supply that supplies 20Amps, and another that supplies 16Amps, there will be no difference in performance since it can supply more than the motors will ever need, and, it there is no possibility of damage to driver board/motors; correct?

Meaning, all i need to do when buying a board is:

1. Make sure it's 24v but below 42. Magic number seems to be 36v to get the most power but not too dangerous?

2. Amperage needs to be 12amps or more, just to be safe, and there is no worries of having it capable of supplying more amps than that.

Sorry if this is getting repetative, i just dont want be sure that i'm not going to flush $120 down the drain.

[Manicalistical]

Well from what I understand from gecko's guidelines there is no way that hobbycnc driver can run any stepper at the correct voltage, actually it sort of indicates that gecko's are the only board that can run steppers.... I think I'll still be going with a 36 volt power supply anyway, I have much patience and in the end it's only at higher revs that the lack of current drops the torque, we're already going to be loosing out on the unipolar buisiness anyway. My reasoning is that the voltages required would be based upon the internal transistor layouts in the boards, this probably changes from supplier to supplier and so may not apply for hobby cnc.

To answer your question, a transistor circuit amplifies a low voltage signal using a another power source, whatever comes out of a parallel port will have a pretty tiny amperage and maybe insufficent.

Though I think it would be a very good idea if you take a look at this though: http://www.pcboard.ca/kits/hobbycnc/...iver_board.pdf

It's the assembly instructions for the board, at the end it mentions that that 4x2.5A steppers will require 20 Amps as as they have to run as unipolar. I don't really know what to think now.

Out of interest assassin what do you plan to use as a spindle/router, I nearly fell off my chair at somw of the prices.

[AssassinXCV]

Out of interest assassin what do you plan to use as a spindle/router, I nearly fell off my chair at somw of the prices.

Well, my cnc machine is teeny tiny desktop, with a floor space of 11" x 18". The Cutting area is 6" x 6" x 5 1/8". I built it wanting to make 3D parts more than anything, such as a 3D Face, Top half of a sphere, and such. I also have plan to add a 4th axis using one of these tiny 2" Diameter lathe chucks, but im not exactly sure how i will attach the motor to the chuck.

The spindle i'm using is a Dremel 4000. It ranges from 5000rpm - 35000rpm, and they boast that it is capable of not decreasing it's speed that much when cutting. It is the newest and most powerful of rotary tools that Dremel sells.

My machine isn't one of those huge bed machines meant for cutting up sheets of plywood or MDF, but is for cutting squre shaped blocks of wood, so i do not need a hand router.

Pictures

3 Axis...............................4 Axis..................5 Axis, possible, yet i'd only have 2" x 2" cutting area so it wouldn't be practicle.