Not sure what to do...

Hello,

So I would like a CnC router, I would like rough cutting dimensions to be around 30x30x10cm, and I would like to mill PCBs using a 0.2mm bit diameter for TQFP components. Other than PCB it would mainly be wood and plastic, though if it could cut Al (even at very slow rates) that would be a nice to have bonus.
As in terms of budget I guess £4-500 is about right 700 ish max. The problem is I dont have any precision building/drilling tools which makes it kind of difficult, so im trying to build it to rely on the precision of the Al extrusion as much as possible...

So im thinking either I buy a kit - for example the Shapeoko 2 or I build from scratch from extruded aluminium, but not being much of a mechanical engineer or any experience in this field it would be a lot of guesswork - hence why i'm here.

I am leaning more towards the DIY route as I dont really like the timing-belt pulley system of the shapeoko 2 much and do like a challenge.

I have started to knock together a concept but obviously I haven't got far as I really dont know what im doing!
http://i12.photobucket.com/albums/a2...zz/cncMill.png

If I could give an overview of a concept and if you could give me some advice that would be great!

Shopping list:

Spindle: Makita RT0700C
Machine base: 20x20mm Al extrusion (or should I use 30x30 or 40x40?)
Gantry: undecided
Y axis: SBR12 (or should I use 16?)
X axis: SK16 (or SK20?)
Z axis: SK16 (or SK20?)

Motors: Nema 23 (1*X, 2*Y, 1*Z)
Ball nuts and lead screws: Undecided.


So, do you think I should just keep it simple and buy a kit? Or seen any similar DIY plans that I could use / get advice from?



Cheers!
Dom

Take a look through these build logs and see if you can borrow ideas to make your own machine; http://www.mycncuk.com/forums/253-DI...ter-Build-Logs
I don't think you will find a kit but the obvious choice is something like this from ebay; http://www.ebay.co.uk/itm/CNC-3040-R...item3cc034136d
Some people buy these as a first machine to get themselves up to speed on using a cnc machine, then they know what is required if they decide to build one.
It's going to be difficult if you don't have the gear and facilities to build, plus the cost will quickly rise if you have to pay to get stuff made.
Anything for sale here ? http://www.mycncuk.com/forums/188-Items-For-Sale

Your budget is not enough to be useful.! . . . I've seen this time and time again and the outcome is nearly always the same.? Weak Under performing machine that is unreliable that ends up with 1 of 3 outcomes.
#1 It's scraped and started again so the your budget is the price of learning(hardway)
#2 It's modded and upgeaded etc ending up with a machine that is still a compromise and cost twice the price of doing correct first time.
#3 It's frustrated the hell out of you to the point of giving up completley putting off CNC forever.

My advise is wait save up £1000-1200 minimum and do it correctly first time. In the mean time while saving plan and check out every thread then start your own thread asking about anything that your unsure about or can't find in other threads.
If you do this you'll get a nice reliable usable working machine much quicker than rushing in and frustrating the hell out of you.

Good luck.

Your picture seems to show you trying to create a floppy rectangular base from aluminium section and then bolting two supported rails on the top.

I had a quick look on ebay and found a piece of aluminium 600x400x12 for £86 and I wasn't really trying.

Thanks I appreciate the Comments!
I reckon for my first machine I might take EddyCurrents advice and go for the 3040 off ebay, though the 0.05mm repeatability is 25% of my target 0.2mm accuracy which is a bit worrying, but I hope it will be good to get my started?

Many thanks again
Dom

Quote:

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Originally Posted by DMW

. . .though the 0.05mm repeatability is 25% of my target 0.2mm accuracy which is a bit worrying, but I hope it will be good to get my started?

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No, it's 4 times more accurate than your target

Quote:

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Originally Posted by DMW

Thanks I appreciate the Comments!
I reckon for my first machine I might take EddyCurrents advice and go for the 3040 off ebay, though the 0.05mm repeatability is 25% of my target 0.2mm accuracy which is a bit worrying, but I hope it will be good to get my started?

Many thanks again
Dom

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Quote:

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Originally Posted by EddyCurrent

No, it's 4 times more accurate than your target

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But don't believe everything you read on eBay either..... suggest you trawl threads here for 3040 owners and ask what they actually get...

surely it means that it will cut at 0.2mm+/-0.05mm
Which means two cuts that are supposed to be 0.2mm apart could be worst case 0.1mm as each cut can be 0.05mm in the wrong direction?

Maybe, or perhaps I've supped too much Grassmoor Dark Ale ? brain not fully functional

With regard to Irving's post have a read here; http://www.mycncuk.com/threads/6981-...3042#post53042

Low budget machines could lead only to frustration, i believe.

The Alu profiles are expensive for a build.

For me the cheapest CNC should have the following things as a must and then around them build the rest:

-water cooled spindle and VFD.
-reliable breakout board
-reliable motor drivers
-supported rails

Save some more money and buy a mini mill, at least you will definitely return your money producing some quality things.

All these 3040 and so are toys.

Sad but true.