View Full Version : Help With a number of build issues & uncertaintities
20-09-2014, 02:30 PM
Hi Guys I’m in need of a bit of help & advice here I have been building an OX machine I got from Robocutters 4 axis 1200mm x 1200mm mounting a Makita Router – I intend to use the CNC to cut wood & cardboard, I’ve bought a special Donek Tools dragknife tool, from the states but I’m also interested in doing carving.
After a bit of a long protracted build with the ‘kit’ I got the mechanics tested had a smoking board ! that has burnt out the A axis diodes & capacitors. After some trawling of forums I’ve decided the controller was cheap rubbish and have endevoured to invest in some better controllers, drivers & if necessary motors. I have a number of Q’s
Mechanics – is the machine robust enough for what I want to use it for ? I planning to build a vacuum bed http://donektools.com/cnc-basics-tutorials/ Which I assume will provide a pretty stable work surface when clamped to the OX rails. but any advice on clamping the CNC and work pieces down would be most welcome as I have little experience of this
Electronics & motors – any advice or even just a nudge in the right direction to controller, drivers & motors – From trawling forums again £6-700 pounds would appear to be realistically what one has to spend
Computer hardware – I managed to get the burnt out controller running on A virtual 32bit version of Windows 7 on a macbookpro using a UC100 usb adapter – this is ideal – I’m prepared to invest in this as well ideally a laptop & USB any advice here ? I’m running a licenced v of Mach 3 – I’ve had varying advice on using LPT ports/ usb adapters
Anyone live in & around north oxfordshire I could really do with a buddy for this !
20-09-2014, 10:18 PM
Ok well sorry to say this but that gantry and Z axis isn't really upto the job of cuttung anything harder than cardboard. To be honest the whole machine is flimsy and I'd say only any good for very light work or plasma/laser cutting.
To cut wood properly with correct feeds and DOC then it will need to be beefed up considerably. Same goes for the Z axis it will struggle with heavy router hanging on the end and this will show in the quality of finish.
The base frame is also less than ideal with those long thin flimsy sides with no support or bracing from Bed to support them. Unfortunatly this design doesn't lend it's self to cutting anything hard so really IMO it's not much more than plotter or drag knife type machine.
Regards electronics then my advice is to buy Digital drives as they are so much better than analog drives at handling resonance and give much smoother motors. Can't accurately advise which without knowing more about motors you have and the voltage run intend to run them at.?
Also don't buy a cheap Break out board(BOB) as BOB's are one of the single biggest sources of trouble and hair pulling.!!
I can say that based on the light weight of the machine that most 50Vdc drives run with approx 2nm motors around 42-44Vdc would easily be enough.
If you want upgrade abilty then look to drives capable of 75-80Vdc and 3nm motors running around 68-70Vdc. These will suilt most machines upto 4 x4 with moderate sized gantry very nicely.
With Motion control then while USB is much better than parallel port Ethernet is better still and much more immune from noise and some of the power issues USB can suffer from. Devices powered from USB are pain for dropping signal due to power losses and they really should be run from an external PSU not the 5v provided by USB.
Don't try using USB to PP adaptors with Mach3 they won't work correctly causing all sorts of timing issues at best with high chance they won't work at all.
Also be aware the Mach3 parallel port drive doesn't work with Win7 64bit and the PP driver doesn't like running on laptops so only do this if your using an external motion control card.! . . .. Ethernet is by far the best IMO.
So sorry to be hard on the machine frame but I'm not known for blowing smoke up anyones arse and your best knowing sooner rather than later.
21-09-2014, 12:51 AM
This machine should be in the "Hall Of Shame". But don't worry, so has to be the first machine i have bought, i learned on it and its still making me money.
The biggest problem with such creations is that you will spend more time thinking how to better it instead of using it. Unless you are very organised and start right away using it to reinforce it.
But the inherent problem using this type of bearings will remain for the life of the machine.
Aluminum is out of the question, more than 0.8kw spindle is out of question. Thats a real problem cause it makes it unsuitable to upgrade it self by making new pieces.
The wisest thing will be to make it plasma cutting machine. And meanwhile make money with it and cut pieces for a proper machine. I know it hurts but believe me it will hurt more when you invest more in it and one day you get it clear that to upgrade it will be more effort than to build a new one, that the drives and the motors and what ever you buy now is the stuff of any value in it, and so on.
Forget the upgrades, digital drivers and wasting money in it. Buy the Gecko g540 which will be ideal for it. Make it plasma, use it or sell it.
21-09-2014, 02:20 PM
I was going to make a comment when i first saw it but try not to offend if possible, regrettably if you don't do your research you waste your cash.
Cracking shed though.
21-09-2014, 03:15 PM
I was going to make a comment when i first saw it but try not to offend if possible
It's a matter of perspective suppose because I don't see it has being offensive I see it as being honest and helping someone avoid wasting money and disappointment.!! . . . . It's more offensive to me for someone to know something is Bad or wrong and not say anything.! . . . .But that's just my view and perspective.
24-09-2014, 02:10 PM
Thanks for the advice guys I'm not in the least offended just a bit pissed - I've decided to sell this on as a plasma cutter or similar & have contacted cnc4you.co.uk regarding components for a new build
24-09-2014, 02:19 PM
Please do not buy any components yet, get a design together ask for comments and the guys will make sure you don't order anything unsuitable, if you can possibly stretch to profile rail this will make a far superior build, there is a company called FSA that trade on ebay that sell second hand rails and Jazz for one has had good results using that kit.
Good luck on whatever you decide.
24-09-2014, 03:54 PM
Yes don't buy anything yet, It's the worst thing you can do and classic mistake.
Another thing is don't rely on the sellers to advise because they will only try to sell you what they have in stock or need shut of. Often this or some of it isn't the best for your needs so just hang fire and check with us here before ordering.
Start with design and then work from there. Motors and drives sat on a bench are just wasting warrenty and you can bet your last dollar they will be out of date by time machines built and cutting.
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