Have to keep an eye out on eBay... there are several new for under £1000 with a 200 x 300mm work area (3020T) or 275 x 385 (3040T), but it might still be worth shelling out for an A3 or A2 size unit.
Often a used one comes up, like this 3020T, just listed: CNC ROUTER / MILLING MACHINE / ENGRAVER | eBay
The Following User Says Thank You to irving2008 For This Useful Post:
Thankyou, i would definately shell out the extra for a bigger workspace, are there any pointers you could give me in reccomending what i should be looking for in a good CNC (one that will do the jobs i want it to anyway)
out of interest would something like that be aapable of doing say 100-200 letters a week? and also ability to do freestanding letters?
Thanks for your help!
I'm sure Jazz and others will leap in with their thoughts shortly... but here's mine.
The key things to look for in a CNC machine are (in no particular order)
Work area - is it big enough for what you need? Obviously a 200 x 300mm machine will cut out 150mm high letters, but a machine with a 600 x 1200 bed will take a 1/4 sheet of mdf and can cut 15 or so in one pass, saving setup time, as well as handling those bigger jobs. So you need to take a view on what would be the ideal size for your set up - not forgetting room for the machine, a 600 x 1200 machine needs a working footprint of 1800 x 2000 or so.
Work height - tricky one this. Ideally the minimum you can get away with because a large work height (z-axis) means the machine is less rigid unless constructed of heavier duty materials, and therefore in turn is heavier and more costly to get the same speed. So consider what you might want to cut... just MDF? 30mm work height is more than enough. putting some decor on the base of a wooden box? you might need 100mm or so depending how big the box. Its areas like this that you might, in time, consider 2 machines.. a large one with low work height for sheet work and a smaller one with a larger work height for those more complex but physically bulky jobs.
Rigidity - cutting MDF is easy... but what else might you want to cut? hardwoods, light metals (aluminium, copper, ?). The harder the material the more rigid and physically heavy the machine needs to be.
Traverse speeds - there is a trade off between cutting speed, spindle (cutter) power and rapids speed (the speed the machine can traverse when not cutting). Faster = more expensive. If your letter is a simple A 150mm high and 100mm wide it has a cutting path of roughly 700mm . So a machine capable of 1000mm/min cutting speed will take around 5 minutes or so to cut that out depending on the number of passes (e.g. 5 passes @ 2mm depth). That may be fast enough, but add some decoration to the surface and some twiddly font bits and suddenly you could be looking at 20min to cut it. Is that fast enough? Only you can say. Obviously the bigger the machine the faster you want it to go, but bigger often means slower unless you throw money at it. So try and assess what sort of speed you need.
Spindle speed and power - this determines how big a cutter you can use and how fast it cuts. A high traverse speed needs a powerful and fast spindle motor to avoid burning/scorching the wood due to rubbing rather than cutting. Many larger MDF cutting machines use conventional wood routers but recently the trend is to lowish cost variable speed water cooled spindles using high performance motors derived from the very high power/low weight motors designed for model aircraft and the like. They have the advantage of being (relatively) quiet and have high-duty cycles (how long they can run for before needing to be left to cool down), some exceeding cutting times of 20hours or so. Low end machines will use spindles based on hobby pencil cutter tools like Dremel or Kress; these are quite effective but very noisy and wont stand much abuse.
Quality of components - cheap routers use unsupported rails and trapezoidal screws; speed and rigidity suffer. that doesnt mean they cant be used, but you need to know the limitations of the machine, generally cheaper machines will do the job but at the expense of needing much lighter cuts at slower speeds... A quality machine will have ballscrews and supported rails.
Once you have the machine, you need a PC to drive it (probably not your main work PC else you'll get nothing else done). CNC needs a dedicated PC but it only needs a relatively low spec machine. Pick up a cheap Pentium 4 circa 2007/8 running windows XP on eBay for £50 and it'll easily do the job.
Then you need the software. There are three stages - design, tool path generation and machine control. Theres lots of free software that will do the job. In the design software you lay out your shape and turn it into a set of vectors, usually in some standard drawing file format such as DXF or DWG files. The toolpath generation software works out the coordinates/paths that the cutter needs to traverse and their sequence, allowing for the size of the cutter, machine speed, depth of cut, etc. It works out when to raise the cutter and put it down again to cut out internal bits. It generates a G-code file - a sequence of machine commands of speed and direction. Finally the machine control software takes the G-code file and drives the machine to perform the cut. It is generally the last bit that runs on the dedicated PC.
I dont know about font generation but I'm sure someone will... I guess its a case of having the fonts in an appropriate vector format so they can be imported into whatever design software you use so they can be manipulated and positioned.
Hope that helps a bit. Any more questions just ask, no question is too stupid.
I saw this tonight on ebay , you may get a bargain but it looks like the kind of think for doing the mdf .. wood letters
CNC ROUTER / MILLING MACHINE / ENGRAVER | eBay
Hope it helps sorry if I'm way off :)
The Following User Says Thank You to Fivetide For This Useful Post:
I think you should seriously consider a machine big enough to cut a reasonable number of letters from one sheet since, unless cutting letters from identically sized pieces is the sole purpose of the machine (in which case you use a jig to speed up the process), you could well find set-up time to be greater than the time taken to actually cut the part.
The Following User Says Thank You to Jonathan For This Useful Post:
i will mainly be cutting MDF wood but possibly up to 18" for free stading letters, obviosusly if i have a machine capable of other woods i would look to use them, bt this is not a top priority on things i would like.
then it comes to cutting speed, up to 20 mins per letter is quite long, i would obviously like something quicker if i can, the picture than was put for an item on ebay looks like it would do a good job for me, only the working area is very small, this may have to be my compromise to stop having to pay silly money.
with all that taken into account, roughly how much am i looking at needing to save up, my business turnover is around 5k net profit per year (it would certainly be more if i wasnt restrictied im sure) i could fork out 3-4 grand at hthe end of hte tax year if i had to, to get something i want but then i have to look at how long it would take for me to recoup that money...a long time i would think
Thanks again all :)
Last edited by kemo_2002; 29-08-2012 at 08:11 AM.
1. you're looking at this from the wrong angle... 5k net profit means you are paying ~£1.25k pa in tax? Any capital expenditure you make in the tax year is deductable against taxable income (see here for more info, it differ depending on whether you are a sole trader, partnership or a limited company) so at least some if not all of the cost of the equipment can be offset against tax. If you are careful you can do it across two tax years as well...
2. Investing 25% of your income into extending the business isnt unreasonable, so putting £1k+ a year back into the business to increase its turnover and profitability is sound planning
On that basis (and you need to do the numbers more appropriately for your actual situation - or get your accountant to) a £4k+ spend seems perfectly reasonable.... and the ROI is probably better than you think...
If you are using cut pieces of wood as opposed to say 1/2 sheets [ read expensive machine ] think about nesting the letters seriously.
I don't mean nesting as in doing J's as spoons but see about getting thinner letters to go at the side of wide sloping letters.
Something like a J upside down, then an A followed by a A upside down and finally another J or L right way up will use virtually the same amount of wood as the two A's.
You also want a CAM program that can leave tabs like Vcarve so all the letters stay in the parent material until broken out and the tabs sanded off. This way it stops damage to the letters and tooling.John S -
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