Why CNC?

[tribbles]

Microstepping does do in-between steps, but you lose torque.

The controllers I'm using will (supposedly) allow the motors to be controlled to 0.036 degrees (10000 steps per revolution) from a 1.8 degree motor.

Normally you'd get half, quarter and eighth stepping (0.9, 0.45, 0.225 degree steps).

[saxonhawthorn]

Robin,

Er.... hrrumph! I have to live on a pension now, and our house rule is "If it costs money, we don't do it."
I just checked the price of an MSD542 from Motion Control Products (http://www.motioncontrolproducts.co....roducts_id=3): it's £47.12 presumably plus vat, and presumably I'd need one per motor (you're right that I'm new to CNC).

However I'm not new to electronics, and I have more oscillators, scopes, and logic analysers than I have benchtop real estate to put them on, and for me it's not a nightmare at all. I haven't yet designed or costed up making a multi-channel controller, but my instincts tell me that by the time I've bought four or five MSD542s I could have built many more myself and probably saved quite a few bob into the bargain.

But "He that putteth on his armour ought not to boast as he that putteth it off." I'll do it first, and then boast. :)

Ian

[irving2008]

Robin,

Er.... hrrumph! I have to live on a pension now, and our house rule is "If it costs money, we don't do it."
I just checked the price of an MSD542 from Motion Control Products (http://www.motioncontrolproducts.co....roducts_id=3): it's £47.12 presumably plus vat, and presumably I'd need one per motor (you're right that I'm new to CNC).

However I'm not new to electronics, and I have more oscillators, scopes, and logic analysers than I have benchtop real estate to put them on, and for me it's not a nightmare at all. I haven't yet designed or costed up making a multi-channel controller, but my instincts tell me that by the time I've bought four or five MSD542s I could have built many more myself and probably saved quite a few bob into the bargain.

But "He that putteth on his armour ought not to boast as he that putteth it off." I'll do it first, and then boast. :)

Ian

Ian,

As a hardware designer turned software engineer and one who much prefers to build rather than buy I would dearly love to agree with you. However unless your bits box is very deep you are unlikely to deliver something of the functionality of the MSD542 for the price. I built my stepper drivers based on a very long-toothed design using the L297/L298 chipset and the parts alone for 3 axes came to over £70. While arguably that was cheaper, I could have bought a DIYCNC System 3 for £90 for the same functionality and that doesn't come close to the capabilities of the MDS unit.

So I sadly have to agree with Robin, who I know to be no slouch for going down the "create your own" route (having seen the injection moulding rig he built, and his nearly finished plasma cutter - is that running yet?), that your limited funds are better applied elsewhere.

[Robin Hewitt]

I just checked the price of an MSD542 from Motion Control Products it's £47.12 presumably plus vat, and presumably I'd need one per motor

Gary has them for £33 + tax but I can see you feel driven to try :whistling:

It may look good on paper, but the 542 microcode is probably based on what actually works, rather than what should work. The best you can hope to make is the 542 prototype which probably ended up in the bin.

Confidence is that feeling you get just before you understand the problem :heehee:

I started out with home brew, then went to 542's, then fitted drivers that plugged straight in to the mains and rectified it. You can never have enough volts

[ptjw7uk]

saxonhawthorn I think you are in for a long long learning path as you have not yet arrived at the foot of the cliff.
My cnc conversion has almost been finished and now I am onto the software and that is just as hard as the mechanical side of things, there is just so much to learn.
The information on the subject is a bit thin on the ground and harder still i dont know what to look for in the books etc.
I like you like to do evrything but when I looked into the making of the stepper drivers I balked and bought a box already made so I could concentrate on my mill and oh boy was that a baptism of fire. The only machining I had done was the odd hobby done whilst at work but now I have to buy the tools myself and there are so many! and possibly more I havn't heard of yet.

Peter

[irving2008]

But then again, thats half the fun of it! I, like Ian, prefer to know exactly why something works, but I came to the conclusion some time ago its better to focus on the non-commodity stuff, on the grounds that enough people know about the other already...

Ian, if you go over to the CNCZone.com and look for threads from Mariss or about Gecko drivers there is a good, warts n all, thread documenting the development of a new driver from scratch through to a production item...its interesting but painful reading....

[saxonhawthorn]

Gentlemen,

"I think you are in for a long long learning path as you have not yet arrived at the foot of the cliff."

Of course, but that's exactly what I enjoy about engineering, and especially electronics and software. There's always new stuff to get my head into. Would you deny me the pleasure of doing what I enjoy most? (well, second most ;) I have spent years programming Intel processors, and if you can program Intel there's not much else in this vale of tears to terrify you. I have also had to decipher spec sheets in Japanese, and more recently Chinese. Where there's a will, there's usually a bored girl in a Chinese take-away who's happy to do a bit of translation over a plate of noodles.

Now, you're certainly right about all the tooling needed to turn out quality work on today's power tools; but this is just another argument for not spending what I don't have to on electronics. And there again: where I can make the tooling myself, I shall do so.

Irving, yes I have had a quick look at CNCZone and have seen the threads on Gecko. I'll read more at the week-end.

But I have to chuckle:- I entered this forum with people applauding the task of automating PCB manufacture. Now the roles have reversed, and you're all trying to disuade me from doing it!

Come on gentlemen! Where's the spirit that began the world's Industrial Revolution in England? Where's that can-do attitude that built the Empire? Ask an Aussie if he'd rather buy off the shelf or build his own? Nine times out of ten he'll roll up his sleeves and do it himself. (And incidentally, have you noticed that for several years now all the constructor articles in Practical Electronics have been written by Australians? It was a British magazine for decades, but it's now written by Aussies, and the online edition is distributed by a Brit living in America.)

If I were still employed in Industry I'd normally go for an off-the-shelf developped-and-debugged item every time, simply because the commercial environment almost never leaves time to re-invent the wheel. You just buy what's needed and cost it into the project, because the customer wants ten thousand off delivered at a thousand a month starting next Wednesday. But I'm not in that environment any longer. I'm a free man again; my time is my own to spend as I please; and it pleases me to learn about designing stepper drivers. There are not many areas I haven't explored yet, and in all my working life I have never met a technical problem I couldn't solve. Now I'm looking forward to doing this.

And I will.

Ian

[irving2008]

Ian,

I applaude your sentiments and your will-power... if I had the time I'd probably approach things a different way as well...

I look forward to your efforts with interest and I am happy to help where I can, as I know other will be too (not that I should think you will need it).

regards,
Irving...

[Tom]

Gentlemen,
Where's the spirit...

...in all my working life I have never met a technical problem I couldn't solve. Now I'm looking forward to doing this.
And I will.

Hear, hear....

It sounds like you will massively enjoy the project, and that's the only justification you need to start it. I won't be able to help with electronics, but I look forward to reading about it, and learning plenty... Bolt-together modular machines is what I (and many others on the forum) have done. It will be a refreshing change...

Onwards and upwards! - do keep us up to date with developments...

Now, you've made me thirsty for tea and English cake.... I'm going to boil the kettle.... :)

[Robin Hewitt]

But I have to chuckle:- I entered this forum with people applauding the task of automating PCB manufacture. Now the roles have reversed, and you're all trying to disuade me from doing it!

Au contraire, I'm totally selfish and want you to succeed with as few pre-conceived notions as possible.

I don't want you getting bogged down recreating things that are of no use to me, I want you to come up with novel solutions to old problems so I can pinch your ideas, fix your mistakes and make a better one :rofl: