New member intro & first question

Hello,

Long time peruser of this site, first time poster. My background is a combo of furniture manufacturing & computing / web development and i'm currently working on setting up my own furniture workshop. Would much rather build my own CNC(s) than buy one, mostly because I really really want to, and also because i want the flexibility in the future of modifying or extending them as the production processes evolve.

Starting off I want to build a gantry style router that can take boards up to 8x4', and realistically i think i'm really going to be wanting 5 axis (i.e z, a & c axes on the gantry head, if i'm getting my axis labels right) Which going by picture on the internet looks difficult but definitely doable?

I'm also thinking to build a smaller machine for milling metals, to be used mostly for stainless steel and aluminium. Haven't decided on the size or the style of machine so plenty of questions to follow on this one! Presumably building the smaller machine first makes more sense as then i can use it for any milling i want done for the second machine.

My main first question is about the frame / gantry: there seems to be a fair few steel framed examples on here and I'm thinking this is the way to go (especially for the milling machine); Mild steel is cheaper than aluminium and not particularly difficult to work with. Is there a particular steel type / extrusion process that i should be looking for in terms of size tolerance and rigidity etc? I know distorting is also an issue if i weld the components together so am I better to bolt joints as much as possible and weld in short bursts where i have to?

If some more experienced people on here could give me their blessing on this approach to the frame (or suggest a better one!) Then i'll go away and do some proper CAD models.

Thanks everyone in advance for your wisdom!

If you want your smaller machine to cope with stainless steel I wouldn't even think of making it yourself if your ideas are that it's a sort of gantry router. You could get a standard vertical mill of appropriate size and convert to CNC by adding ballscrews, steppers/servos and a controller. Such a mill would also be useful to build the larger machine, so you might want to reverse your order of construction!

I'm trying to work out what you mean by 5 axis for your gantry router that you want to cope with 8x4 sheets? Normally you have Z (up and down) and XY - leftright and forward backward - 3 axes. That will cope with cutting shapes out of large sheets. Other axes may be added but how useful they would be in what is basically a sheet-oriented machine I don't know - what are you trying to cut?

Hi John,

Thanks for the reply; Re. the gantry I'm only thinking to have this on the timber orientated machine. Thanks for the suggestion of buying a mill and converting - I have seen this thread on here: http://www.mycncuk.com/threads/7662-...-Scratch/page9
which looks to be a pretty solid mill built from scratch, though i've no idea what the price works out as vs buying & converting. On the whole though the construction of it seems pretty simple? Re tools I've got a good quality pillar drill, access to a tig welder, metal lathe and most other basic equipment.

Re. the 5 axis I need to be able to process sheets as a large proportion of the material being used comes in this form, so a basic xyz router would do fine for this. Beyond cutting out shapes though most of what i'm planning to make involves alot of angled edge cutting and egde boring. In the first manufacturers i worked at they had a 5-axis gantry style cnc with a pod rail set up which could do all sorts of angled cuts and edge drilling, and then when they needed to process sheet they would stick a vacuum board onto the boards and do standard nested cutting. I definitely won't be getting pods and rails but the principle is similar - I want to be able to do nested sheet cutting and also have the ability to do more advanced processing on the individual components afterwards. I've been to a few other workshops which used a gantry cnc router (3 axis) with an aggregate head on to provide 4th & 5th and it seemed to work pretty well..

Thanks,

Alex

Interesting thread that. But if you look at it in at least some of the pics he is machining parts on a large vertical mill. The table appears to be a billet of aluminium, machined all over, with a pocket in one face with ribs onto which are bolted machined steel strips to form tee slots, and the top surface is ground flat. Without access to certainly a mill, and a surface grinder as well, life would be quite hard building that. Also components like linear rails aren't that cheap, nor are large chunks of steel and ali. Apart from the time and potential frustration unless you really know what you are doing, it might well turn out cheaper to buy a mill, even a new one, and convert it rather than try to make your own.

I see your point about having rotational axes on the router head, sounds quite hard to make. Most people building routers seem to use off the shelf spindles, I guess one of those could be adapted by making a complex mounting for it. But does the rotation need to be computer controlled?

Hi John,

sorry for the slow reply; I've been looking at second hand mills online as well as totting up some inital costs. I'm definitely persuaded by your suggestion to start with an existing mill and convert; I hadn't considered that the ballscrews etc in the existing mill could be kept - for some reason i'd imagined replacing them. I think I can probably budget around £2000 for a used mill, which going by ebay looks like it may just be enough for something half decent, though maybe i'll need to splash a little more?

Re. the additional axes on the gantry the existing diy versions i've seen do look pretty complicated.. I think perhaps i'll treat this as a second project, i.e start out with a basic 3 axis and just bear it in mind when i'm doing the z axis that i'll probably want to build onto it at a later date. Manually setting the angle would certainly solve most of my issues for most of the parts I want to produce, so i think this could definitely be an ideal compromise.

Thank you for your guidance on this, it's very much appreciated! I'm working on putting together a proper spec of the components and some cad models, so will definitely be back on here for advice once i've got a more specified design.

Thanks again,

Alex