Thread: Hello fellow handy people :)
I thought it best I show my face amidst my reading of the forum.
Little about me I guess; I'm an engineer working in the automotive industry, automatic transmissions specifically. My background is in mechatronics (link for anyone who want's to know what it is) which is pretty handy for stuff like this. My favourite colour is blue.
I've been thinking about building a CNC machine of some sort for... Oooh a very long time. I remember a fair while back I made a plotter out of mindstorms Lego, that counts right? I'm now at the point where I have put enough other projects to the side so I can crack on with this, also other projects I want to do next require parts that would ideally need CNC machining.
The journey so far been; figuring out a lot of it on my own, then doing a lot of research, then being overwhelmed with information and choices, now breaking the whole process down into distinct parts I need to design & build. I know everything can be built from scratch, but I also know some bits are best just bought in to keep momentum in a project. This is what I've figured so far.
Goals: 3 axis, bed size maybe half metre square(ish), to mostly machine aluminium (always good to be ambitious), have good repeatability, have good accuracy.
Frame/bed: Design and make it myself. I'm tempted with doing it out of steel/iron instead of aluminium just because I always enjoy building things more solid than they need to be. From what I understand in terms of the frame, solid is a good thing. Should I just go for aluminium or would a hybrid of materials potentially be an idea?
Locomotion (mechanical): I see that one of the best options is to use a ball screw for this and after some reading it does indeed make a whole heap of sense. Like any sane person I want to keep cost down and I noticed these things aren't cheap, I may have also noticed that there may be a supplier you guys use for this ;) Any info appreciated.
Locomotion (electrical), Control (electronic): Although I'm perfectly capable of making all the required parts for the driver boards etc from a set of plans, I just want to go for a hassle free electrical side of things. To this end I have been looking at getting matched steppers, drivers and control board such as one from here: CNC Systems the only catch here is the different choices out there. I know the "which one is best" question is always a dangerous one on forums but I'd like to ask: Are there any very well known, tried and tested systems people commonly use including steppers? NB: I'm aware that i'll likely need a 4th stepper to give one per side on the bed.
Control computer: I have various scrap computer components including motherboards laying around, I'm sure I can cobble together a control computer with a parallel port on it, either that or i'll just build a dirt cheap one.
Spindle: I've looked at the various choices and accompanying problems people have with different spindles. I also looked at what would be required with my target material (aluminium) and it seems that a lower and potentially variable RPM would be better. I checked out the RPM's of different off the shelf tools to get an idea of what's out there and found drills to be way too slow and routers to be way too fast. I'l like to be doing more than just engraving so I want something with a bit of grunt behind it too. This lead me to think about getting a nice motor and rigging it up myself, the only catch is that I'm not really sure on the chuck attachment side of things. And... it's a lot more work that could bog the project down. Any ideas of a good off the shelf spindle to fit my needs?
Sorry for the wall of text. Hello again and thank you in advance for any help you give, I'll return to reading the build threads now :)
Hi,and wellcome. I am not one of the experts, but if you really intend to cut mainly ally or perhaps even I think you should seriously consider going for a fixed gantry moving table design. This would probably mean that you only need to use one ballscrew centrally to move the table if everything is "beefy" enough on a
500mm x 500mm working area. Anyway good luck with your design. G.
Welcome Husky. I'm not one of the experts either, but if you want to be doing mostly metalwork with your machine you might be best of with a moving table design. If you keep your eyes on ebay or engineering auction sites a cast iron surface plate might make a good solid table and a fixed gantry of thick steel or epoxy granite should let you take decent chunks out of aluminium with ease. If the epoxy route is too expensive, heavily reinforced concrete will do the job but the structure will shrink for 6 months before it becomes stable.
For the matched motors/drivers if you want cheap and don't have any issues with China wantmotor.com have lots of kits, they seem to be the same guys that manufacture most of the motors on ebay. A few people have purchased from them and are perfectly happy but there are also a fair number of negative comments on the web, everybody makes their own judgements about price vs perceived quality.
Can't argue with the price though. ;)
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