[GreenLead]

Having been bitten by the CNC bug ever since this, I'm interested in having a go at putting together a small general-purpose CNC mill.

Basically, I'm here to seek help on finding the general direction to getting started.

The mill is to have 200-300mm of X-Y travel, and 100-150mm Z travel, with 1/20000" resolution; the spindle is to be mounted on a moving gantry. I'm leaning towards building the frame out of extruded aluminium sections.

The machine is intended for cutting small aluminium or epoxy molds for injection molding of plastics, plus other things like milling gears and such like.

As I am a university student I will be working on quite a tight budget.

I have experimented with EMC2 and the Allegro UCN5804B Unipolar Stepper ICs, although the result was less than satisfactory (I may need a chopper driver)

Here are some issues I have so far:

1) As EMC2 seems to be the only free control software around, I've decided to go with it. The sim-axis setup looks sweet, but now I'm wondering how I would convert a 3D design from PTC's Pro/Desktop to the required gcode.

2) Referring to a CNC retrofit of a TAIG2108 for mold-cutting, my colleague told me he used NEMA23 276oz-in steppers, and the mill had 1/2"-20 ballscrews. What sort of controller (and motors) should I go for that will meet the above specs and not break the bank in the process?

Any help/advice/pointers would be gladly appreciated.

[Harryman]

What's your budget? No point in anyone suggesting stuff you can't buy.

[shadrag]

Well, "CNC Mill" and "shoestring budget" can not be put in the same sentence. Also, you specified 1/20000" which is 0.00005" resolution which is not something you are going to find within 1000 miles of "inexpensive".

[scrapman]

I don't think you're likely to find a machine of the desired resolution on a university student's income. Not meaning to rain on your parade, but most of your mid-range ($60K-$100K)industrial machines only have .0002 unrepeatability, and it's quite a leap to go from university student to toolmaker/die-sinker. Unless you have a solid background in machining and machine theory, you're setting yourself up for a big disappointment.

[cadmonkey]

I have to agree with the previous posters - you're asking for a LOT for very little. A stepper machine won't do that kind of resolution without extreme gear reduction which limits speed hut that wouldn't matter for the size you're looking at. As for G-Code - that's something you're best to contact the manufacturer about. EMC can handle any standard G-Code thrown at it, and has some features in it that some other packages don't - I hand code most of my own work but I don't do, or should say I haven't done any relief milling. To even come close to the accuracy you want, regardless of stepper vs servo you're looking at HIGH DOLLAR ground screws and my bet is you'd need HIGH DOLLAR glass scales for position feedback. Even at short lengths they won't be cheap. EMC can handle all of that, but the mechanics are going to be pricey.

If you do manage to prove us wrong - do tell and brag to the heavens! (and patent anything that isn't already covered and then start manufacturing these cheap high precision units and selling them to payback your school loans).

[Stepper Monkey]

If you are bitten by the CNC bug, starting out by trying to make a mill from scratch is just not the way to go. Learn to be a machinist first. Without a CNC mill already at hand to make many of the parts required, a good manual lathe, and a few other more mundane goodies of a well stocked shop like a bandsaw and the like, it is going to be a pretty lost cause anyway (at least making one that performs better and/or is cheaper than just buying one).
Even more importantly, without experience and a background actually doing machining - not just for the actual manufacture of the machine but the design parameters you need to specify - designing a machine is not going to work. It is not at all trivial, even for engineers.
Even if you were to make a machine appear out of thin air right now to your imagined design, it still likely wouldn't do what you wanted it to as you likely don't have enough knowledge base now to even know what to specify in the design.

From what I see from the link you posted, nothing even close to what you specified may even be necessary though. Even a basic used Sherline or Taig setup will handily manage that sort of work without issue, either cutting the actual pieces or the molds for making them, and those mills are at the very bottom range for as cheap and light as CNC gets and still function adequately.
Try something like one of those and get your feet wet. Then determine what you need. That may be all you ever need, maybe not. When I needed more accuracy I eventually built my own machine using a beater stock Taig that held an order of magnitude less tolerance than that machine I built from it. If you really want to tackle building a machine you'll need to collect a lot of other tools that cost more than a small mill package anyway. Get your feet wet, learn, and once you collect the whole set maybe you'll be ready for a build. Or maybe you will find you won't need to and can be happy with modding the one you have. In any case, building first is not the answer.

[sansbury]

Stepper Monkey has some very sound advice. I will throw out a slightly different idea, which is to start by building a small (~120mm X/Y/Z) router around a Dremel-type rotary tool. This will allow you to learn all about steppers, drivers, CAM, etc. without spending too much money. I started this way spending less than $300 total for absolutely everything.

The routers can be built from hardware store parts with ordinary home shop tools and a lot of the parts and all of the knowhow can grow with you into a larger machine. Also you should see if you can get access to a machine shop through your school. If you can, that opens a lot of doors in terms of being able to fabricate parts as well as hooking up with people who can help you succeed.

[tmarks11]

for the type of thing you want to make, I would second the recommendation of a cnc router. Take a look at the stuff built by widgitmaster (he may have one of his mini-routers available as an almost ready-to-go option). Doesn't look like you really need much room in the XYZ axis, and his stuff would be perfect.

http://www.cnczone.com/forums/showpo...9&postcount=10

Also look at some of the other build logs in the cnc router forum.

[GreenLead]

Hey guys, thanks for the response(s).

I was aiming for something with equivalent specs to this, although obviously I must've gone ahead of myself.

My budget is around NZD$600-700 (USD$450-550). Obviously, not even enough to even get a Sherline or a TAIG, or even one of these.

Had a look a widgetmaster's setup - something along the lines of what I might need, but his units are pretty pricey at USD$1050, and I'll have to get the steppers, controller and dremel myself.

It's very difficult trying to do just about anything in New Zealand, considering the lack of resources.

Yeah, I'll look again at the Sherlines and stuff. Thanks guys - will keep you posted.

[bones]

Hi,
I agree with most of the guys. Good luck with builting one for that price.
You will be lucky to but he motors and drivers with that budget.
I CNC'ed a Hafco AL-50G Lathe and it cost me about $1200 AUD for the parts.
And that was getting alot of them cheap.
I also did a small mill. $300 for the mill $120 for a new compound table, ballscrews and you've hit your budget already.
And if I didn't have a mate that had a mill, saw etc there was no way I could of built them.

Personally I wouldn't muck around with electronics, buy a board already done! And electronics is my trade!
They are cheap and work straight away.
Xylotex board and their motor package will get you started.
http://www.xylotex.com/3AxSysKit.htm
$372USD shipped to you. That's your motors and drivers done.

As for resource in NZ, you don't need them.
I hardly buy anything from Australia. Too bloody expensive.
It's cheaper to buy it from the US and pay $50 shipping than it is to buy it here.

A router machine is the go, as the guys said. Use a small 30K rpm router.
They are cheap. Use acme threads (oops I swore) as they are cheap and you can can replace he nuts cheaply when they wear.
But ballscrew are heaps better if you can get them cheap.

Built it strong. re-enforce stuff where ever you can.
Rigitity is the key for a good machine.

Best way it to buy stuff bit by bit.

And make it pay for itself. Do some wooden carvings and go sell them.
Wooden signs for the front of peoples house's.
eg. DIDYOUBRINGYOUROWNGROGALONG

You can sell then to family members and mates.
Then buy a proper mill with maybe an ballscrew kit to suit.

Easy money.

Cheers
Rodney

[darkith]

Hey guys, thanks for the response(s).

I was aiming for something with equivalent specs to this, although obviously I must've gone ahead of myself.

Heh, the Taig's resolution of .0005" is 1/2000, not 1/20,000 as you originally spec'ced. That's a good part of the confusion cleared up.

D.

[sansbury]

Look at the Mcwire design on Instructables:

http://www.instructables.com/id/Easy...lling-Machine/

This is a good basic outline for a cheap but minimally functional machine. If you haven't done this before and don't have a big pile of scrap and parts you will spend twice as much as you plan so with this design I'd give you a good chance of staying at or under $500USD

[cob]

hellow greenlead,
I was in the same situation your in about 3 months ago i did not have the slightes idea of how to build a cnc but I knew I wanted one just to practice. how to use a cam system. and finnally I decided to purchase a used sherline for 350 bucks, then I retrofitted with knew motors and controllers for another 300 bucks I am using mach3 the demo version which is free which is good enough for know. and I am using my laptop to run the machine but from what I hear laptops only throw out 3.5volts and maybe thats why I am loosing steps so that means I have to buy a pc I seen one for 200 bucks. ass you can see know i am at 850 bucks total. so you might try looking for some thing used and retrofited. if you whant to go the cheap way.
anyways good luck and do some reseach

[draughted]

looking at those minute guns i couldn't stop my self thinking of the mill that got me interested in cnc , the proxxon mf70. it sure looks the right size. now i didnt buy one, it didn't fit the bill, but it could suit your purpouse
and start off on a cool career.
its cheap and many people have used them for similar things

just a suggestion!

[GreenLead]

Okay, now that I've had some time to think things through.

sansbury: I've seen those tutorials before. Parts, even scraps, are very difficult to get in NZ. I'm trying to see if I can get stuff from local importers. Hardware store parts are pretty much useless here.

cob: the only used mills in NZ cost tens of thousands of dollars.

draughted: I'm not too sure about freight and handling. Besides, as I have stated, I'm a university student, not a machinist, so it would be highly unlikely to retrofit the manual mill.


A few days ago I changed track and began looking at the possibility of buying a hobby-sized setup to cut aluminium. I had initially considered the Unimat MetalLine CNC, however it turned out it was little more than a very expensive "toy" that barely manages to dent aluminium. The controller itself costs 900 Euros (NZ $1900 w/ shipping)

Sherlines would have fitted my requirements perfectly, but complete CNC setups cost $2500 (NZ $3000+)

And needless to say, I have absolutely no experience with refitting anything.

So now, instead of trying to scratch build a moldcutting mill, I'm struggling to even find an affordable one to use here in NZ!

Here are my revised specs:

- approx. 200mm travel in XYZ directions
- can easily work aluminium for short-run moldmaking
- at least 1/100mm step resolution

Any help would be greatly appreciated

[jalessi]

http://tinyurl.com/63glwe

[cob]

greanlead
you should not get discurish someone will have one for sale. I didnt know nothing about building a cnc at all. thank god for this site theres alot of good and talented people that can help you step by step on retrofiting one you just have to be patiant and it will take time to understand it. at least for me it did.
by the way can you look at ebay in new zealand.:cheers:

[Jason3]

GreenLead - did you get anywhere with your CNC mill idea?

I have a spare ballscrew you can have to get you started if you want it - it's a ground NSK unit, 16 mm dia, 2 mm pitch, only 100 mm travel but might do for your Z axis even if you chuck it out later & put in a longer/better one. I would say it's pretty worn, but hey, it's free

Regards,

Jason

[GreenLead]

Again, thanks for all the help so far!

I've been quite keen on getting my hands on a HobbyCNC EZ kit for the stepper control portion. I wanted to join the Yahoo group to ask around and see if it will fit my needs...alas, Dave only allows people who have actually bought his stuff to register

I have a spare ballscrew you can have to get you started if you want it - it's a ground NSK unit, 16 mm dia, 2 mm pitch, only 100 mm travel but might do for your Z axis even if you chuck it out later & put in a longer/better one. I would say it's pretty worn, but hey, it's free

Thanks for the (very generous) offer. However, now that I'm gone from the ridiculous goal of scratch building a mill, to the more reasonable goal of buying a hobby one and retrofitting it, I don't know if I'll get to use it.

you should not get discurish someone will have one for sale. I didnt know nothing about building a cnc at all. thank god for this site theres alot of good and talented people that can help you step by step on retrofiting one you just have to be patiant and it will take time to understand it. at least for me it did.
by the way can you look at ebay in new zealand.

I asked around quite a bit, dealers and distributors and all. Most were stuff you would find in large machine shops, way out of the hobbyists' range.

I checked ebay NZ as suggested (as well as its more popular local counterpart, TradeMe). Both turned out irrelevant stuff..."CNCed mag wheels", and such like.

I asked my boss at work about the Sherlines, and he told me it was "another expensive toy." Of course, he advised me to start by being a machinist rather than a computer whizz...although as a full-time engineering student, that's quite difficult.

I guess now that I'm stumped, I'll need to redefine my requirements:

- Require a hobby cnc setup for making small injection molding molds to make plastic toy accessories like Will Chapman's LEGO-compatible BrickArms (www.brickarms.com)

- Budget of around NZD$2000~3500 (Emphasis on NZD)

- Possibly using the HobbyCNC EZ board, 3 axis.

- Possibly >270oz steppers

- work with most materials, including aluminium (I'm only doing short runs, so worn molds aren't too big a deal for me)

- Run via parallel port on a Linux PC with EMC2

- (Additional info) I'm using PTC's Pro/Desktop to draft my CAD designs, so I'll need a way of converting the DXF files to g-code for EMC2 to machine from.

So yeah. Any pointers please?

Thanks in advance.

[PoolQ]

When I started into this I bought a Hobby CNC drive, it is still sitting on my desk, my lathe uses gecko drives. I got zero support with my first choice.

Just something to think about