Ebay CNC motor kits? Any good?

[gr8fun]

Hi All

I'm new to this CNC building lark, so I've not much clue when it come to specifications of kit. I'm hoping to learn a little from those who have already trodden my path.
My plan is to build a reasonably light weight, 4x4 plasma table. Based on belts and pullets for the X&Y and a screw thread, probably donated by a "G" cramp for the Z

I've been researching motors\drivers etc and the cheapest I can find are on Ebay at £157.19.
Value CNC Kit 3Axis Stepper Driver Board + Nema23 1.86Nm Motor + 24V15A PSU + CD | eBay

While the location is claiming Middlesex, I'm a little dubious as the price looks to be conversion from another currency - I'm guessing China.

The spec is
Package includes:

• 1 x New 3 Axis TB6560 Driver Controller Board 1/16Microstep 12-36V, 1.5A-3A
• 3 x New 57BYGH76-401A Single-Shaft Stepper Motors 1.89Nm/263oz-in 2.8A
• 1 x 24V 15A DC power supply

Toshiba TB6560AHQ chip - High power, maximum 3.5A drive current chipset !
For TB6560AHQ Datasheet, Please click here.
1-1/16 microstep setting - Higher accuracy and smoother operation than standard 1, 1/2 step!
Adjustable 1.5A-3A drive current settings for each axis - 25%,50%,75%,100% of full current can be set for different stepper motors
Overload, over-current and over-temperature safety - Full protection for your computer and peripheral equipment !
On board current switching - Power output can be set according to specific user requirement !
Full closed-type optical isolation to protect the user's computer and equipment
Relay spindle interface - Outputs Max. 36V 7.5A for spindle motors or coolant pump (only one device can be powered by this output!)
4 channel inputs interface- Can be used for XYZ limit and emergency stop !
Professional design - Two stage signal processing with super anti-jamming !
Bipolar constant current chopper drive with non-resonant region - Controls motors smoothly through range without creep effect !
Four control inputs (divided into pairs of knives) - Allows setting of limit and emergency stop !
Universal architecture - Supports most parallel software MACH3,KCAM4 etc!

I have established the in the CNC would , plasma should be light and fast compared to perhaps a router that needs to more rigid and slower.

So, what should I be looking for?
Will this kit be OK?
Are there better alternatives (at a sensible price)? Being my first attempt at building a CNC I'm doing this on a tight budget so my mistakes will not hurt too much...
Any advice greatly received!!

Thanks chaps

Danny

[njhussey]

Hi Danny! Most of the advice you will get will tell you to steer well clear of the cheap Chinese TB6560 drivers as you can only run them at 24V absolute max which them limits the speed of the steppers. I bought one before joining the forum and I will use it but in a machine that will only be cutting balsa.

[Shinobiwan]

From what I've read on here. In the grand scheme of things its shite really and even with gearing the speed would be limited because of the low volts.

The real kits start at about £300 and upwards I believe.

BTW I see you mention your on a tight budget so your mistakes won't hurt as much but throwing money away on cheap components will still hurt non the less!

[njhussey]

Danny, the thing to do is to design your frame, gantry etc and then once you know lengths, weights etc have a look at this thread as you can put in the variables and what steppers you plan to use and it tells you if it's ok. Then once you've got your results you go away and re-design it again for the umpteenth time ;)

http://www.mycncuk.com/forums/showthread.php?t=1524

[gr8fun]

Cheers chaps. I think that could have been a disappointing purchase had it not been for you.
Much appreciated. If you get chance would one of you (or someone) explain the "limited speed" bit, briefly, I incorrectly, assumed it was the driver that governed the speed.

So, based on the information you chaps have given, this
Driver Kit Two (Three axis)
would be a much better investment?
3Nm, 50v motors..

thanks for your help

Danny

[martin54]

Danny, I would forget about purchasing the electronics until you have a design sorted out, budget for them but don't actually purchase them. Not always best to buy a kit either, doubt there is anything wrong with the kit you linked to but the power supply is only 36v so you have already limited both your drivers & your motors, there are some useful sticky posts that help explain some of this if you have a look through the forum.
METAL & WOOD WORKING - FAQ's, Problems & Solutions

Have a look through the sticky posts as some of the things you need to know are covered.

[Tom]

Cheers chaps. I think that could have been a disappointing purchase had it not been for you.
Much appreciated. If you get chance would one of you (or someone) explain the "limited speed" bit, briefly, I incorrectly, assumed it was the driver that governed the speed.

So, based on the information you chaps have given, this
Driver Kit Two (Three axis)
would be a much better investment?
3Nm, 50v motors..

thanks for your help

Danny

In layman's terms (I'm a layman, and someone correct me if I go off the rails... ):

Voltage governs top speed
Current governs torque

The drivers limit your maximum voltage. You can run them at less than max voltage, but the motors won't achieve the same top speed. If you put too much voltage on the drivers, they will burn out.

The drivers in that kit are good (I have some). I couldn't find where the kit's power supply voltage is mentioned, but if it's only 36v its a shame. The drivers would be underpowered and motors slower than they could be. I run the same drivers at 47v, which is a bit too close to 50, but no problems so far.

It's good advice to wait on the electronics until you have something to bolt the motors too...

[Lee Roberts]

I cant confirm the PSU voltage but the 408 in the title dose suggest that it could be 36v.

.Me