View Full Version : NEW MEMBER: Anybody here from Midlands?

02-10-2012, 02:38 PM
hi all.

just a quick hi to all you like minded souls. Very impressed with this site. Especially keen on the 'show off your work' area.

Software developer by trade, however evening workshop retreater, quite capable in eletronics and am fortunate enought to have a
reasonably equiped workshop the fact I work for an international industrial tool supplier I have no shortage of tooling.

Over the years I have achieved many 'home builds' ive done gas bottle log burners, internal combustion engines, hydraulic log splitters,
go carts, rip saws and no end of classic cars.

I came across the idea of building my own cnc many years ago when I made a plotter.

So in recent months, I have saved / sold begged and borrowed to build up a stash of cash to buy the necessary parts to build a cnc machine.

It seems a common experience that people have an idea in their head, they find this site read some of the existing build threads and then see
how that 'mental image' changes!. Im trying to build something with a workable area of around 1mx1mxabout 300m Id got it all weighed up in my
head and a few sketches on sketchup and I was just about to order. But now im questioning the use of unsupported rails...

What I havent been able to find, is decent recommendations for suppliers for buying this stuff.

I have seen this for example
ebay item:310398333862

from a company called merchant dice

which is like a kit... a kit for three axis.. looks brilliant. but is this good?

I think I can answer my own question. I wish to cut aluminum so therefore, I assume a 1m span of unsupported rail will flex and therefore
this isnt a good idea?

can anybody recommend any places to buy linear kit from? maybe a good place for supported linear rail?

ive got the electronics already... nema 23's

where do you buy aluminum, think its called 'excursion' or 't channel' looks quite a popular material to actually build these machines with
ive looked but with no sucess for a supplier.

Anybody here from Leicester / Rugby / Birmingham way, would be nice to meet up with local like minded souls. none of my mates are / or have
any inclination for this type of thing.


02-10-2012, 03:20 PM
That kit is very poor mainly, as you said, because it includes long unsupported rails which are not suitable for a machine to cut aluminium. It also doesn't use ballscrews.

The place almost everyone here uses is linearmotionbearings2008 on eBay. His prices are much lower than anywhere in England and he will cut the rails and ballscrews to whatever lengths you require.

linearmotionbearings2008 | eBay (http://www.ebay.co.uk/sch/m.html?_nkw=&_sacat=0&_odkw=spindle&_osacat=0&_ssn=linearmotionbearings2008)

Which motors and drivers did you get exactly?

If you search 'aluminium extrusion supplier' on this forum you'll find some, but I would seriously consider using steel box section as it should be far cheaper or stronger for the same money.

I live near Leicester so I'm probably quite close...happy to meet and discuss things if you want to.

02-10-2012, 04:23 PM
Hi Jonathion

excellant. thanks for the nudge. that supplier has just what im looking for...

evil laugh

ebay: 250482515891

Think il buy that? recon its up to it?

I have the steppers (bought for another project) can you recommend power supply / breakout board / stepper controllers etc?

im in Stoney Stanton...


02-10-2012, 06:57 PM
Welcome to the forum Matt from another newbie, learnt quite a bit already by reading build logs & asking questions. From what I have seen in the short time I have been a member you are in very capable hands if Jonathan has offered assistance.
They will need to know what motors you have, nema 23 is not enough detail. Without a bit more detail they won't be able to recommend drivers & power supplies.

Best of luck with the build

02-10-2012, 11:25 PM
Nonooo.. too early to buy things! You should get the design done and do a lot of research first to avoid mistakes.

That set is very mismatched. The lengths of the rails implies it is intended for a machine with, roughly, 1000x1550 travel however only the Z-axis ballscrew is the most optimal size. The problem is the critical speed of the screw, which is the rotational speed at which the screw will start whipping/vibrating excessively, imposes a lower limit on the diameter of ballscrew you can use for a given length. Short answer is up to about 600mm use RM1605 and up to 1500mm use RM1610. The reason for that is using the 10mm pitch screw instead of 5mm means the rpm for a given feedrate is halved, so if you are limited by the critical speed, this doubles the possible feedrate.

03-10-2012, 08:23 AM
Your right. Il get some drawings of my intentions done, and take it from there. Ready your comments it appears I have a lot to learn, and shouldnt rush in.

I should perhaps start an actual build thread rather than continue this one also. Il do this when I have some drawings

In response to martin (and anybody else who can make any recommendations on drivers / breakouts / power supplies the steppers Ive bought are as follows

Nema23 3.1Nm High torque Stepper Motor 1.8 Deg, Dual shaft

full spec sheet http://cnc4you.co.uk/resources/60BYGH301B.PDF

03-10-2012, 02:17 PM
The 3Nm stepper motors are used on most builds as they are good value for money, so that's a good buy. Did you get 3 or 4 motors? For the size of machine you're planning on 4 would be best so you can have two ballscrews on the axis that moves the gantry, or you can link the axes with a long timing belt so that only one motor is required.

The torque from a stepper motor is proportional to the phase current. Therefore the torque reduces as the motor speed increases since the inductance of the coils limits how high the current can reach before the next step. To combat this you need to run the motors on a higher voltage, since this increases the rate of change of current. The motors you have chosen can be run on up to about 75V, so it's best to choose drivers rated for at least that. Currently there's plenty of 80V drivers available on eBay, such as these:
Cnc 7.8A,80V,256 Mirco digital Nema34 step motor driver | eBay (http://www.ebay.co.uk/itm/Cnc-7-8A-80V-256-Mirco-digital-Nema34-step-motor-driver-/130769266767?pt=LH_DefaultDomain_0&hash=item1e7274a84f#ht_2107wt_1271)
CNC Micro-Stepping Stepper Motor Driver 2M982 24~80V 7.8A Controller | eBay (http://www.ebay.co.uk/itm/CNC-Micro-Stepping-Stepper-Motor-Driver-2M982-24-80V-7-8A-Controller-/120957619741?pt=LH_DefaultDomain_0&hash=item1c29a2ce1d#ht_4087wt_1037)

I bought quite a few of the DQ860MA and found them to be a little better than the m752's I have.

Next question will probably be what power supply do you need? Getting a toroidal transformer and making it yourself is the best option and there's a few discussions in other threads about how to do this and why. Or I can show you...