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Hi
I'm Russ from Manchester.
After messing around with a desktop cnc (ox) I'd like to add an 8x4 to my joinery shop, mainly for cutting sheet material for cabinets, templates etc.
I've been thinking of building an Avid style cnc but have been offered a second hand machine (awaiting details) for not much more than it would cost to build my own. I'm confident in the build but not so with the electronics. Anyone got any advice on build or buy, assuming the buy is in good working order?
Thanks
After researching and designing my machine from the best spindle down to the last bolt length for my specific needs, finding decent suppliers at a good price and shipping them, was in retrospect the "simple" part. Building my machine hardware accurately without a CNC, purely with hand tools, drillpress, tablesaw and handheld router to mill aluminium was another "simple" part. Then came troubleshooting the electronics and safety systems to all talk to each other and work properly, the hardest and most frustrating part, and then learning the cad/cam/cnc software, calibrating the machine and how to use it, not too simple either, I came to a single conclusion:
Next time pm Jazz on this forum and get him to build me a decent machine and I will spend my time just learning how to use it! :hysterical:
Jokes aside, I have learned so much valuable information that I wouldn't do it any other way. I knew nothing of electricity and electronics before I started, but it was a hard and frustrating road for me personally. So many easy mistakes to make. Case in point is I still have my spindle tripping the limit switches randomly. I have everything star grounded including cables, EMI filter on VFD, all electronics in separate cabinet but it still happens. I am beginning to wonder if it is the quality of limit switch and just going Pepperl-Fuchs. So many little things can and do go wrong. I see now why so many home builds take years or end in failure.
If you dont have oodles of time, patience and want to get up and running quickly I would buy a decent build with good electronics. As Jazz has said, good electronics make the machine, I will second that.
W
So what electronics do you have? Maybe other forum members can help you.Quote:
Originally Posted by handles
You might want to start a thread of your own rather than end up hijacking this one.
Kit
You have a commercial shop. Get a professionally designed and built machine. Not only will it be easier to run, but easier to maintain as well.
If you are doing CNC as a hobby and like fiddling with things and optimising tensions on belts, etc, then the reverse applies. Because overcoming the build problems are part of the fun. It's like art - if you want to see the image, buy a painting rather than a jigsaw....
What are you smoking, brah? The man asked for an opinion on whether to build or buy, which I duly gave. How is that hijacking a thread?Quote:
Originally Posted by Kitwn
A custom machine by someone who does it for a living, or a good commercial is optimized. The problems that you haven't even thought of as a newbie are all ironed out.
A homebuild contains all the errors and mistakes from someone doing it for the first time. Therefore that will require tinkering at best, or rebuilding from scratch at worst.
As DG said, if you want to tinker because it is fun, build it yourself. If you want to run it as part of your commercial operation buy a custom made or a commercially built one.
Hi all
Thanks for the replies
The reason I asked was I've been thinking of building one for a while but fear it could be one of those projects that never get finished! Plus I've been offered a Chinese made 8x4, almost new, for less than the cost of building.
I do general joinery, doors/windows etc but I'm looking to focus more on cabinets and thought a cnc might be beneficial.
Anyone got any experience with chinese machines? I don't need a workhorse as there'll be days/weeks where its not used but at the same time will want it to run properly when needed.
Thank again
Russ
You mentioned that you still have your spindle tripping your limit switches randomly, I was referring to that. Apologies for not being clear.Quote:
Originally Posted by handles
Kit
No worries, Kit, I was just giving the OP an example that you can do the research and all the "right things", and still hit problems if your electronics are too cheap. They are the only cheap electronics on my machine and I will be upgrading them soon, so all good.Quote:
Originally Posted by Kitwn
Sorry, cant help you with experience on Chinese machines. If you do decide to build your own, however, I built an Avid replica and can give you a lot of useful info on this to fast-track you.Quote:
Originally Posted by Russjp
Been there, done that, got tears all over the T-shirt. There's quite a saga in the archive here of problems I've had with the spindle causing spurious tripping of limit switches when using a cheap Chinese BoB and LinuxCNC via a parallel port. I'm still not entirely sure where in the chain from BoB input to PC motherboard the problem really was. The shiny new AXBB-E controller and UCCNC software installation running via Ethernet have been faultless so far.Quote:
Originally Posted by handles
Kit
Russ You might be lucky. But I would post some pics or maybe a link to it. its a minefield out there.Quote:
Originally Posted by Russjp
If you are coming at this as a complete novice,do you need to gain proficiency with some form of CAD first?There can be quite a lot of learning needed for a total novice,just to get a sensible CAD file with all the entities joined at the part boundary and holes in the correct locations.Then you need to learn how to use a program to convert it to Gcode and load it on a machine that will carry out the instructions.Learning how to build and calibrate the machine is another significant step and none of the processes are trivial.
I've seen a few Chinese/Taiwanese machines and they are not all identical.Those built to the lowest achievable price point don't have much in common with the more sophisticated machines but any of them will get you producing parts a lot sooner than building a machine yourself.Not to mention that even the most basic will seem like a quantum leap forward for a man used to working with panel saws,jigsaws and hand routers.What it won't do is produce at the rate of a bigger and more expensive machine or for as long before wear and tear sets in.If you look at a few of the promoted machines online you may well notice that a lot have the same anatomy and a different colour coat of paint and label.
Chinese machines are like a box of chocolates without the lid and no sell-by date.? You never know what you are going to get and often leave a sour taste in your wallet.Quote:
Originally Posted by Russjp
I have retrofit several Chinese machines and have many customers who went the Chinese route only to regret it. Now I'm not saying all Chinese-made machines are bad news but you really need to know what you are looking at because you can easily be buying trouble.
If it's the type that uses what's called a DSP pendant rather than a PC or dedicated controller with a screen and keypad to control the machine then I find these are bad news. Often the pedants break down and start doing crazy things usually within 18months of new, when this happens better to rip it out and retrofit it with a better control system.
With these DSP type controllers, I find it often goes hand in hand that the drives which control the motors (usually steppers) are cheap nasty units that need replacing and the wiring leaves a lot to be desired in terms of safety. It's very common that the wiring is shoddy and wire routing is poor, the quality of the wire is also very poor so between this and bad routing it's common to get wires break which can lead to days of downtime tracking down exactly which wire broke and where.? Often it's quicker and easier to just start again than wasting days tracking it down only for another wire to break somewhere else.
My advice is to be weary and take someone who knows what they are looking at.
My local Men's Shed here in Tasmania bought a Chinese machine a couple of years back (before I joined I might add) which has exactly the kind of DSP controller Dean describes. After using 'proper' controllers, first LinuxCNC and more recently UCCNC I find the DSP device hopelessly inadequate and frustrating to use. The machine has hardly been used by the shed members and I think this is one of the reasons. I find it confusing and I already ( sort of) know what I'm doing. Mechanically the machine seems reasonable but I'm hoping to convince the shed to upgrade the controller to something better at some point in the future (that'll be some point when I have the time to do the refit and setting up myself).
If you do consider buying such a machine, my advice would be to budget in an immediate replacement of the controller rather than waste time learning how to use something you will not keep long term.
Kit
Thanks.Quote:
Originally Posted by Clive S
I've got no pics at the moment. Its a friend of a friend who's offered it to me. He bought it new 2 years ago, says he's had no problems with it but has had to downsize premises due to the lockdowns. I've not seen it yet as its a 4 hour drive away. All I know so far is single phase, has a vacuum bed, runs with nc studio and he added a 4.5kw water cooled spindle.
I've no real experience with a large cnc, just my desktop OX using vcarve Pro.
I might try to find time to get down there to have a look but, apart from seeing it running, I'm not sure what I need to be looking for!
Thanks for the offer, I might take you up on that depending on what I decideQuote:
Originally Posted by handles
That is one of the reasons I built mine to be configurable, and with rack and pinion . I have a 1.6m wide gantry X axis by 1m Y axis. I can extend it along the Y another 2m simply adding more rack and linear rail to another ally extrusion table and bolting them together.Quote:
Originally Posted by Russjp
I haven't needed to do that as I just use my assembly table as an extension, which is the same height, and just slide full sheets along onto the CNC bed.