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craftcadet
26-08-2010, 05:30 PM
Hi Everyone

My Name Tony and I in live in Tunbridge Wells, Kent. I am a complete novice when it comes to cnc and hope to learn a great deal here. I begining to build my first cnc machine. I have built this driver circuit -

http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/?&sort=NEWEST&limit=40&offset=480

and have succesfuly got it working, now to build the machine!

I am a keen craftsman and excited about learning new skills. I work in a theatre where I make Jewellery and Headresses for opera and ballet.

Looking forward to this cnc thing

Cheers
Tony

Lee Roberts
26-08-2010, 05:45 PM
Hi welcome to the site, your membership has been accepted.

Regards,
Lee

irving2008
27-08-2010, 12:51 PM
Hi Tony and welcome.

Dont wish to dampen your enthusiasm but have you got any thoughts about the size/capability of the machine you are going to build? The unipolar drivers you mention are fine for a very small machine, maybe thats what you want for jewellery, but will quickly run out of capability for anything larger...

craftcadet
27-08-2010, 01:24 PM
Hi Tony and welcome.

Dont wish to dampen your enthusiasm but have you got any thoughts about the size/capability of the machine you are going to build? The unipolar drivers you mention are fine for a very small machine, maybe thats what you want for jewellery, but will quickly run out of capability for anything larger...

Thanks fo the welcome

I have been reading though the forum and am beginning to realise that i may be going down the many roads that lead to dead ends that many others and stumbled upon. Ok thankfully I have not as yet built the machine so can start smaller. Here is what i intended to build :-

Mill for Wood and aluminum

X axis = 600mm
y axis = 600mm
z axis = 300mm

I have bought these motors Astrosyn MY103H702 (they are in the post I hope). I read you have a set and were going to test them, did you get round to it? I was going to post a question about them on the original thread. I need to figure out the power supply for them, can you help?

so that is the basic outline. My hobby budget is very limited and I am happy to change my plans just get my teeth into cnc.

Too big an idea for my driver? could you suggest axis dimensions?

Thanks for your interest and knowledge

Tony

GeorgeD
27-08-2010, 02:11 PM
Welcome Tony.

Have you got these axis lengths right? Y is a bit on the high side?

X axis = 600mm
y axis = 600mm
z axis = 300mm

craftcadet
27-08-2010, 02:19 PM
Welcome Tony.

Have you got these axis lengths right? Y is a bit on the high side?

X axis = 600mm
y axis = 600mm
z axis = 300mm
Did you mean my Z axis. I know it seems high, I just thought i would like to carve tallish things one day :)

irving2008
27-08-2010, 02:44 PM
Tony,

The Astrosyn steppers are OK and fine for a small router for wood, pcb, plastic but you might struggle with aluminium. You won't get more than 0.8Nm and 300rpm out of them on a unipolar driver. The size you have suggested is possible, will depend on the design. The power supply will depend on your driver... but you probably dont want to go above 12v. Depends on the current limit resistor (light bulb) you've used...

craftcadet
27-08-2010, 03:01 PM
Few! thanks Irving thats a relief.

I'm thinking of using a reclaimed PC power supply so 12V with a possible 3A should be ok. I need to work out the current limit resistor (light bulb) combintation with a bit of testing when the motors get here.

irving2008
27-08-2010, 03:54 PM
well those steppers need 1A/phase so a 3A supply will be fine. The motors are 6.2v so need a 5.8ohm resistance on 12v, which is 5.8W so try a 6V 6W motorcycle tail/side light bulb to start, this will limit current to about 0.9A. A pair of 12V 15W bulbs in parallel will increase the current to about 1.2A, on a 12v supply.

GeorgeD
27-08-2010, 04:12 PM
Hi Tony

You have to allow some leeway for two axis so if you want those figures?allow another 50 mm to each axis,ie...

650 X axis
350 Z axis

This extra 50mm is end to end components and then will give a full 600//300 distance but still will be short due to the Y axis plate and spindle.
So think on size before you constuct and think about what you want to cut when its up and running.

The X axis could be longer in my view ie 450 at the very least.

craftcadet
27-08-2010, 04:12 PM
Thats extremely useful information. thank you very much. I'll report back when I have everything to experiment with. I'm interested in the formulars you have used to calculate these values. I completely self taught with electronics and have built many circuits but only published ones. I have never designed my own so the math is a learning curve of mine.

craftcadet
27-08-2010, 04:30 PM
Thanks GeorgeD. My sizes are not so critical at the moment but will take into consideration what you have said

irving2008
27-08-2010, 04:49 PM
On a low budget you're going to be limited to 10x2 or 12x3 trapezoid leadscrews with a delrin nut. With 300rpm and a 12x3 the maximum traverse rate is 900mm/min for rapids, maybe 1/2 that for cutting. A 600mm axis will take 1.5min to traverse.... so this isnt going to be a fast machine! You may wish to make it smaller as a starter machine...

craftcadet
27-08-2010, 05:04 PM
thanks Irving this will need rethinking


....Goes off to ponder

irving2008
27-08-2010, 06:21 PM
My starter machine for milling PCBs used TR10x2 screws and those motors with 30v drivers. It was all made from MDF and the overall work area was 500 x 300 x 150 but I actually rarely cut a PCB bigger than 140 x 100 and even that took a while. The limiting factor on PCB size/complexity was how long I could run the spindle (a modded DeWalt die grinder) before terminal deafness set in on anyone within 100m radius.. Think about your spindle (Kress or similar?) and where you will run it and for how long (a 6hr run isnt unlikely) - that gives you a clue to the speeds you need - and what work area you could accomodate within some sort of soundproofing environment....

pavlo
27-08-2010, 09:24 PM
Hi craftcadet, I have built a machine that is only a bit bigger than the one you are planning. I'm not too far from you so if you want to come and see it running you are very welcome.

craftcadet
28-08-2010, 11:37 AM
Thats a great offer thanks pavlo I would like to see one running. where abouts are you, pm me if you prefer not to disclose to all who read this.

cheers

Tony

craftcadet
28-08-2010, 11:43 AM
Some great pointers for me to consider. I think I may go a bit smaller just to start ( I tell my self). I like most people want to run before i can walk, but i know I'm going to have fun learning to crawl.

Soundproofing seems an issue. How do cnc machinists get around that?

irving2008
28-08-2010, 12:27 PM
Tony,

You'll get better results if you pose questions in the main forum, in 'General Discussion (http://www.mycncuk.com/forums/forumdisplay.php?15-General-Discussion)' or 'Problems and Solutions (http://www.mycncuk.com/forums/forumdisplay.php?99-Problems-and-Solutions)' than on the 'New Members' forum