budget diy cnc controller question

[dangerousdave]

Money in the bank will be spent up I would need to purchase bits monthly to do it. I would go down the ball screw route if it were possible.. or necessary I have searched through other build threads and they are not greatly detailed nor do I want to spend a grand on electrics I would have liked to got electrics all sorted for 2-300 quid including motors and psu. What would you recomend for me? I dont need anything mega quick but would like repeatability and fairly decent accuracy

cheers for your input its all greatly appreciated

[irving2008]

Money in the bank will be spent up I would need to purchase bits monthly to do it. I would go down the ball screw route if it were possible.. or necessary I have searched through other build threads and they are not greatly detailed nor do I want to spend a grand on electrics I would have liked to got electrics all sorted for 2-300 quid including motors and psu. What would you recomend for me? I dont need anything mega quick but would like repeatability and fairly decent accuracy

cheers for your input its all greatly appreciated

Dave,

It's not like me to be blunt (I usually leave that to Jazz or JohnS lol) but, with all respect, if you don't have the willpower and focus to put the money aside in a separate account then you're unlikely to have the determination and focus to ever finish a project of this scale; an 8 x 4 machine is not a light undertaking, ask those few who have done it successfully.

Your question about motors and PSU re repeatability/accuracy suggests you have a huge learning curve to go through to understand the basics before you're ready to purchase anything.

The build logs have a wealth of detail but they need to be used as part of a learning process; they are not, and never can be, a step-by-step hand-holding guide. No two machines are the same, especially at that size.

Also consider this: this is a year-long project, if you buy the electronics now they will be out of warranty by the time you come to use them so you'd better budget for replacing them because if you buy that cheap crap you're almost guaranteed to need to do so. So save the money now and buy the right stuff when you need it.

The members on this site have a huge amount of expertise; you are well advised to listen to them if you don't want to throw money away.

Off-topic, but relevant; for putting money aside, if you're in the UK, I suggest premium bonds as a saving vehicle; ok you get no interest but it's sufficient hassle to get the money out to keep it safe and you might win something!

[EddyCurrent]

nor do I want to spend a grand on electrics I would have liked to got electrics all sorted for 2-300 quid including motors and psu. What would you recomend for me?

A rethink !

Im by trade a qualified engineer albiet a cnc turner thats never worked with wood but cant be that hard

I've found that the softer the material the harder to get good tolerence. You just have to compare hand cutting dovetails in hardwood and softwood to see that hardwood is much easier.

[dangerousdave]

I really dont think this is a huge project. Im by trade a qualified engineer albiet a cnc turner thats never worked with wood but cant be that hard :p.. but thats why im asking about the electronics side of this. The router bed is for me the easier bit. People keep saying them boards are crap but have offered no alternative? I know there cheap crap thats why im here to get opinions and learn more about what others are using. Im sure not everyone is using expensive gekodrives? Surely someone uses some alternative? As far as a time scale goes maybe 6 months would be a realistic one.

[Clive S]

Dave. I don't normally respond to new builds as I am a newboy myself that has been guided through the maze of do's and don'ts of building and buying different parts for the machine and now after a year of hard work I have succeeded in building a router 1600x1000 that I am happy with. I have only been able to achieve this without wasting a lot of money and time with the help of Dean (Jazcnc) and Jonathan form this forum. They have given there time freely you cannot buy that sort of experience.

Why don't you start with a drawing in something like Sketchup (its free) and post it on here and then the good people will evaluate it and give you good honest feedback as you develop it into a working drawing and then a machine.

As you are doing this they will advise on the type of motors, drives and rails etc that will work with your setup.

It would also help others if you said what you would like to cut and to what tolerances. Please take this with the spirit it is intended and good luck with the build. ..Clive

[Jonathan]

People keep saying them boards are crap but have offered no alternative? I know there cheap crap thats why im here to get opinions and learn more about what others are using.

I bet you can't find a finished build log on this forum which doesn't show/tell which drivers they used.

Your question is like asking someone 'what engine should I buy for a 2.5m long van?' Nobody is going to tell you to get a specific engine because we don't know anywhere near enough about the van. Granted, a lot of people use the same drivers and similar motors, so we could mention one of those - but aside from being an argumentum ad populum, that would be irresponsible since you'll very likely end up with a poorly matched system. Don't think that just wanting to cut MDF and plywood makes things easier, as it's actually optimal to use the highest feedrates for cutting those materials.

Pick a few of the build logs from this forum at random and read them:
Gantry/Router Build Logs
Also read some for smaller machines so you can see the important differences you must consider for your relatively large machine.

Edited to add:
What are you prepared to pay for the whole system? As a rough guess I'd say minimum £2k to make something good enough, but good enough is the enemy of the best...

[JAZZCNC]

I really dont think this is a huge project.

Mistake No1 Assumption is the Mother of all Fuck UP's

Im by trade a qualified engineer albiet a cnc turner thats never worked with wood but cant be that hard :p..

Means Nothing I've helped every type of person with CNC from Engineers to Doctors and I can tell you the ones who build the fastest and have the least hassle are usually the ones who wear the Suits.!!. . . . .Because they Admit they know nothing and Listen then Act.!!. . . . . Those that waste money or fail do it the other way around.!!

but thats why im asking about the electronics side of this. The router bed is for me the easier bit. People keep saying them boards are crap but have offered no alternative? I know there cheap crap thats why im here to get opinions and learn more about what others are using. Im sure not everyone is using expensive gekodrives? Surely someone uses some alternative? As far as a time scale goes maybe 6 months would be a realistic one.

Sorry Dave but you didn't ask advice on what to use you asked about that specific board and got a reply, it's not our fault if it's not what you wanted to hear.

Regards what to use then Jonathan Van engine example is correct but it's worse than that. . . . . What your actually saying is your planning to use R&P with possibly 4Nm motors for cutting wood.!! Fair enough you'd think.??

But back to the Van, What your actually saying is you'd like to know what MAKE of electronics to run 4ltr engine on to get 8000MPH but without telling us the MAKE of the vehicle, WEIGHT of the vehicle or what FUEL your planning on using what size WHEELS and how many GEARS it will have.???

MAKE = Materials to be constructed from.
WEIGHT = Mass to move IE gantry etc
FUEL = Voltage running motors at.
WHEELS = Pinion Size
GEARS = Ratios

Now you can't give us this information because you don't know it your self because you haven't designed or planned the machine. So therefore we can't possibly tell you what to buy.

I could offer suggestions now but that would be wrong at this stage and exactly why I offered the advise I did when I did.
If you choose not to follow any of our advise then more fool you and I'll wish you good luck. . . . But I and many others on here don't suffer Fools lightly, We will suffer Insults and even the Odd Idiot no problem but Fools will get very little response back and absolutely NONE from ME. . . . . . DONT BE A FOOL . . . and take the advise in good faith.!!

[dangerousdave]

Hi Clive thanks for your responce. In terms of design I have dfx files for a mechmate but am reluctant to go down that path I want to build something simlar using welded steel box section

I only really want to cut mdf and ply sheets if the machine is capable I may make a few bits for my rc car out of alloy but thats not important as I dont need to if I cant

As for tolerance id like repeatability withing 0.5mm and accuracy of the same over a meter span. Its not overly imporant over the distance of the table

do you think im beong unrealistic?

[GEOFFREY]

Hi. if you follow the advice from some of our more experienced members, you will find it difficult to build anything that ever could be as inaccurate as your current requirements!!! In practice I feel sure that when you have a machine that performs really well, you will end up doing taking on work that would benefit from greater precision. PLEASE, listen to what Irving, the "3 J's and others tell you and you will end up with a machine that performs well and will save you some of your hard earned cash. Good luck with your project. G.

[m_c]

I'll answer the why are those controllers crap?
They use a very common, but failure prone stepper driver chip, especially if you try pushing them anywhere near thier limits. Which given the size of machine you're planning on building, you would have to do to get even moderate performance.
Individual leadshine drives (be that older M452s? or the newer digital drives) will allow for far more powerful motors, and far better performance. These cheap combined controllers/drives seem like a bargain, but when one of the axis goes pop, which they are renowned for, unless you're good with a soldering iron, the whole lot is junk. And you'll soon regret the purchase when watching your machine crawl doing rapids, as the drives just aren't capable of reliably moving it any quicker.