Newbee looking for advice

hi everyone out there.

i have delved into the world of electronics by means of an arduino board and a couple of stepper motors i ripped out of a printer - i am now THE expert in cnc!

HA

the reality is im embarking on my first garage cnc - nothing elaborate just 1000 x 500 maybe, constructed of steel to run a router and/or plasma cutter.

so im asking for advice or can someone point me in the right direction

what i am thinking is........


twin x axis steppers with ball screws, these will run along the shorter length
trapeziodal screw and nut on Y and Z beacause theyre much cheaper.
nema 23s all round for the sake of simplicity and affordability

now id really love to carve up some inch thick birch or something in one pass, but that will be depending on the motors so ive realised will probably require a couple of passes with the smaller motors, also i would like the benefit of power for routing and also the requirement of speed with plasma cutting.

imnot sure what software i will be using but thats a date not set in my schedule but have been looking at easel from the inventables website. largely because ive seen a setup using it.


SO any advice firstly on my grand idea ^^^^^^^^or is this just a pipe dream for the first time CNCer or any websites or posts i can reflect on.
1. what sort of torque or power will the motors need to rip half inch wood at a reasonable speed while leaving room to re-purpose as speedy motors for plasma - any suggestions please
2. id rather buy a kit form motor/driver set for the four axis like you see on ebay, but thats why they're on ebay right?
3. the lead screws or ballscrews is a definite advisory item which i am told that will lend efficiency to the motors?


i should mention my design does not allow for a traditional center placed x axis leadscrew underneath the cutting table hence the twin x axis motor concept.


any advice greatly appreciated

thanks all

andy

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Originally Posted by dandy

1. what sort of torque or power will the motors need to rip half inch wood at a reasonable speed while leaving room to re-purpose as speedy motors for plasma - any suggestions please
2. id rather buy a kit form motor/driver set for the four axis like you see on ebay, but thats why they're on ebay right?
3. the lead screws or ballscrews is a definite advisory item which i am told that will lend efficiency to the motors?

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#1 3nm motor stepper motor will do everything you need for machien this size but that's not what will limit your DOC it's the spindle and the strength of the machine. Also Chip clearence is required for large depth of cut else you'll get burning and excess tool wear.
Also there's more to stepper than just Nm size. Drive quality and Voltage they are run plays huge part in performance.

#2 Waste of money. For good machine you need balanced system and these kits don't offer this. There more than just power to consider when buying steppers. The spec of the stepper affects the Voltage required. Motors with high inductance will require much higher voltage to get the same speed and torque as lower inductance motors.
Voltage plays key part in the speed and to some degree torque you'll get from motor. These kits have Crap drives with low voltage supplies with high inductance motors. Hence why there cheap.!

#3 Forget lead screw they will be nothing but hassle. Ballscrews from china are cheap and easy got so not worth not buying. There's no comparison between them it's no brainer.

#4 I know there's no 4 but i'll throw this in for free.
Don't use twin motors drive the screws with belt drive connecting them together. Saves on money and much more reliable, completely removes any chance of racking.

hey jazzcnc thanks for your input

i am keen to get started with my project so will ask some more advice,

do you know a supplier for ballscrews, like you say china is cheap maybe you have used someone there? also some advice on the drivers, i was looking to gt seperate drivers rather than a single board because when i burn one i can replace one as opposed to 3 or 4.

your suggestion on the belt driven x axis is interesting, didnt really consider this becuse im afraid of getting it wrapped around my fingers or even my face! also the design scope doesnt allow for this unless i change direction using pulleys at 90degrees directly below the screws which incidently will take care of the belt timing.


again thanks jazz

There are many on Ali express but Fred Lee at BST automation is the one I'd recommend and use often.

Drives then you want Digital drives the ones I'd recommend are Leadshine AM882 but if your on Budget then Leadshine DM856 are ok drives. Both are 80V drives which means you can run motors safely around 65Vdc without stressing the drives or heating the motors excessively.

Regards the belt drive then your fears are easily solved.? Keep fingers and face out of the buggers.!! However sensible idea is to cover them. Also they will normaly be at the rear so your not likely to get in your face or fingers.

Regards fitting then can't say unless you show the design. Not sure what your meaning or thinking by belt timing.? There is no timing invloved.

yeah your right jazz, its hard to visualize your dead right there, so im gonna get some drawing program and get it down on paper.
looking at your recommendations has given me a bit of a reality check, its gonna cost more than 50 bucks and a few lengths of steel anit it!!!

well someone gotta keep them in business.

drawings to follow up........

soon........
ish........

Attachment 19238

how do i get this picture big enough to see???????????

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Originally Posted by dandy

how do i get this picture big enough to see???????????

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it is big enough to see if you double click on it. What are you going to use this for?

ho right its a thumbnail so just click on it.........


so the trasparent like boxes were my original thought of twin motors driving the screws, but as pointed out by jazzcnc a single motor with a belt running the two screws would be a better option. Now looking at it i would need a few extra pulleys because i want this belt outta the way hidden in the box section, nice and neat, like a pro who knows exactly what needs doing right!!!!
........any comments greatly appreciated as its my first build.

the gantry will be riding along the x supported by bearings i have lying around which will be driven by the screws through slots in the x(in red in the thumby thing for the feckless incompetent wannabees who keep asking for constant advice and inspiration and general nappy changing) , now the footprint for the gantry isnt quite complete, infact scale is out the window here its just concept like a guy in his shed out of earshot from the missus and nothing to do but build (or try to) (or think to try to) a cnc system.

im still thinking on leads for the x purely so i can weld straight to the nuts, no fuss with the bare minimum expense just to prove test, after which i can replace with suggested ballscrews and use said leadscrews for shelf supports............... pictures to follow

of course the z is missing as its far beyond comprehension right now.

the reason it is designed like this is because i want it to drop into slots i am yet to cut out of my bench and clamp into place, the bench coincidentally doubles up as a table saw, but you dont want to go there..... no yet.......not with a 24" blade,

the question really is does the belt fit the design?


so TIA for any comments or questions,

im hoping to get this to slot into my bench when needed, do a bit of routing, like signs and name plates and house numbers and so on, and when its in the way i can take it out, put it on the shelf - or in the bin and be done with it. TBH if im really honest i dont really know. but i want to build a cnc

Your wasting your time with this design and approach. It's doomed to fail. Far too complicated for no gain and woe fully under built to be any use for cutting anything but chocolate.
I suggest you take step back look around the forum at other builds to get an idea of whats required for good machine.

The simple truth is there is no quick cheap way to build CNC and trying to cut corners will just cost you more money in long run, Happens time n time again. Theres also no point trying to reinvent the wheel or waste time and money with proof of concept. Only so many ways to build router so just look around find what looks and works good then copy or use it for base of your design.

Get looking and do some serious research. DONT BUY ANYTHING other wise 99% chance you'll waste money.

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TBH if im really honest i dont really know. but i want to build a cnc

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Ok but if you are really serious you need to get some proper drawing done but first look through some of the build logs on here to get ideas as the the one you have put up I don't think will even ice a cake. Please don't let this put you off. So decide on a cutting size you want and then half it. To build a decent machine you will need a budget of around £1500 - £2000 using decent drive, motors, screws rails etc. Also the golden rule is don't buy any electronic stuff until you have the frame designed and sorted. Good luck with the build. My first one took me about 10 months from start to making chips and all knowledge was gleaned from this forum.

And there I was getting ready for the Queens prize for engineering, bought the tie aswell, you really took the jam out of my donut there jazz!! But on a serious note the sketch was just to show what I was thinking with the belt. It looks like I better start with a stand alone system to begin with. Done a bit of research last night and hats off to jazz,Clive s and a few others, pointers and advice coming from all directions so keep up the good work, this place is nothing without your help

I want my jam back.....

Attachment 19241

heres my first attempt of the bed. made from 50x50x2 box section for the main frame and the bed will be 40x20x2. i will have A-frames under the centre of each beam and get rid of the uprights. this will also allow for ball screw option for the x axis.

i cant help thinking here that 50x50 isnt stiff enough but with A frames should be ok

the actual size is not determined yet, im just hoping im barking up the right tree here but probably looking at 1100y 900x

hiwin or similar rail for the x, not round i just dont like it.

big question ???? how accurate or square do the x axis members need to be with regards to setting up the rails? i suppose i mean if theres a slight twist in the box section.

must do more research

Hi Dandy
welcome to the forum
Please do as instructed, and have a look @ some build logs, you will learn what is involved in constructing something that is going to be rigid enough to do what is asked of it.
your gantry wants to span the narrowest part (ie width) of your frame to keep it as rigid as possible.
Time to do research.
Regardes
Mike

just for information ive read this on geckodrive and it makes some interesting points, although cant help some of the figures are plucked from obscurity, but nonetheless makes good in roads to figuring out the basis of a a machine

link here http://www.geckodrive.com/support/st...or-basics.html


ta to everyone for comments and advice

Hi guys,

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