Ebay CNC Motor/Driver Kit - Please recommend one

Hi, I am building a Solsylva Router - its my first build. The SOlsylva plans leave you on your own to choose and assemble your own electronics and he recommends buying a kit. Being my first build the learning curve has been steep so I would welcome a reasonably easy solution.

I need...

3 axis Nema 23 kit - around the 425 oz/in end of the scale. Complete with drivers, breakout board, parallel cable - the lot!

The machine is aluminium construction - 600 x 1200 cutting area and I will mostly be cutting wood and occasionally aluminium sheet

I have seen loads on ebay UK but I wonder if some are better quality than others and if some are easier to setup than others - ease of use is vital to me since a working system is better than a drawer full of parts and a broken dream LOL

Here's just a couple I have been looking it - how do they compare other than price?

http://www.ebay.co.uk/itm/Free-DE-sh...item3a94c868ff

http://www.ebay.co.uk/itm/From-UK-Fr...item4632730bc6

Thanks in advance for your help - excuse the crudity of my simplistic understanding of things at this stage.

Glyn

Hi,

The kits sold on fleabay tend to have high inductance motors so you don't get as much performance. My router is about the same size as yours (a little smaller) and I'm using the below bits...

Most people go for these steppers (or equivalent): http://www.cnc4you.co.uk/Stepper-Mot...x-3-60BYGH301B

These drivers: http://www.zappautomation.co.uk/elec...ion/em806.html

BOB.....various ones, take your pick really depending on whether you're doing twin X axis ballscrews or not. Best to use are CS labs CSMIO series but they're pricey but you can use PDMX, Planet CNC, Pure Logic and many more.

Parallel cables are 10 a penny on fleabay....

Power supply, lots on here make their own (my next job...) although you can buy 68V 6A ready made ones...http://www.zappautomation.co.uk/elec...er-supply.html

IMO whilst the ebay kits are cheap and do work you'll not be getting the best performance and when (not if!!) you build your second router you'll be able to transfer the electronics over and get good performance with a better router.

Hope this helps, I'm sure someone else will be along in a minute to comment...

Thank you Neil, that seems like sound advice, being very new to this, I assumed that I had to buy them all as a kit or run the risk of them not being compatible with each other. I am not sure of what particular metrics/ratings I need to be aware of to judge compatibility. My plan was to get a kit simply to avoid those hassle as the mechanical elements have been challenge enough. I do like the idea of upgrading the motors but those stepper drivers seem awfully expensive - are they really worth it?

Would something like this kit from cnc4you be a big step up from the ebay kits then? or just a very slight improvement?

http://www.cnc4you.co.uk/CNC-Kits/St...3.1Nm-x-3-Axis

If I did go for buying things separately, is there a halfway house with slightly more affordable drivers? I do think the motors from cnc4you are a definite upgrade and I am sold on that but are they not worth it without the expensive drivers? Also the BOB list you suggested, are you suggesting that any of those will work? Are they fairly universal?

Thanks for your input - much appreciated

It's a better kit but to get the best out of those Stepper motors you need to run them at as high a voltage as possible, 80V drivers would be best. To do this you need better drivers. The leadshine steppers are digital ones and will drive the motors much more smoothly than the analogue ones. At the end of the day it's up to you and will depend on your budget but it really doesn't do to scrimp on the electronics.

BOB's are fairly universal in that you can connect almost anyone's drivers to them as all they are doing is taking a signal from whatever program you're using to drive the machine (Mach, LinuxCNC etc...) and doing their stuff to it and passing it on the the steppers.

Hopefully someone more experienced than me will be along to explaing more fully.....

Ok well first neil is correct about ebay kits they are best avoided.

Problem with kits in general is that they are miss-matched and often your getting inferior something or other.
The CNC4YOU kit for instance has 36v PSU which is too low voltage for any decent speed from the motors supplied. Those motors will easily take 65-70V but the drives they supply are only rated 50V max. They are lower quality analog drives and so they supply 36v PSU because they don't want you pushing them too close to there Max voltage rating where they may blow up.

You'll find many suppliers doing this and this is why those who know and do there home work realise or get advised to buy Decent drives and if want to save money build your own PSU thats perfectly matched to your needs.

Cuttting corners on the electronics is THE most common mistake made with DIY CNC. The Heart of the machine is the Electronics and Cheap stuff just cripples any machine.
Steppers get there speed and To some degree torque from the voltage you put into them. They also produce electricity when de-accelerating. This means that you need drives with some overhead on there Max rating, typicly 10%.
Now to get good performance with 3Nm you really want to be running them over 50V with 65 -70Vdc being ideal voltage running on 75-80Vdc Max drives.
Running 50Vdc max drives will mean using 40-44Vdc max voltage which means the motors will be running roughly 30% below what there capable off.

Now people often build there own Toroidal PSU because correct size PSU's are hard to find or expensive. So building your own means they can get exactly the voltage and current they need at sensible money.! . . . Scary shit your probably thinking.!! But it's really not and very easy really when explained so don't be put off this option.

Honestly don't cut corners on the electroincs you 100% will regret it if you do.

Quote:

---

Originally Posted by njhussey

BOB's are fairly universal in that you can connect almost anyone's drivers to them as all they are doing is taking a signal from whatever program you're using to drive the machine (Mach, LinuxCNC etc...) and doing their stuff to it and passing it on the the steppers.

---

NO NO NO another big mistake often made is thinking BOB's are simple things so cheap will do.!! . . . They handle all the signals all the Data passes thru them and good stable CNC machine is all about the quality of the signals feed to it. So no matter how good the signals going in if those signals get corrupted by cheap nasty BOB they will come out fuzzy wuzzy and the Machine will perform Fuzzy wuzzy.!!

Many many hours, days,weeks and not mention Hair have been lost to poor quality BOB's.

Hi Glyn,

There a lot to be said for safety in numbers when it comes to buying electronics ) Especially when it comes to ordering the various component parts. It can sound like you are being presented with a narrow path, but its not, its sound advice that will save you time and money.

If you have not already done so, it is worth scanning/reading through the Mach 3 product manuals. They have useful things to say about the relative importance of the electronics you chose and how everything fits together.

Should you find the time, I would recommend scanning through this document - just the relevant bit towards the start:

http://www.automation.com/pmd/Motion...hineDesign.pdf

You may not plan to complete the machine with a motion control card in place, but it is worthwhile planning the purchase of your BOB with one in mind - IMHO. It all looks a bit daunting at the start, but honestly, it doesn't take long before you will be looking at those Ebay deals in a different light.