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lanky_streak
14-09-2013, 11:20 AM
I'm an industrial designer looking to purchase my first CNC machine and would appreciate any advice on what's best suited to my requirements. The type of work I'll be looking for from this machine is for watch parts, namely dial engraving (aluminium / brass), watch bridge fabrication (brass) and ideally engraving stainless steel casebacks. Ideally it'd be capable of making aluminium watch cases, but that's not an essential requirement. I'm not against a DIY build, but as I know relatively little about CNC machines, I'd be more comfortable with an off-the-shelf solution / CNC machine 'kit'. To create watch bridges, I'll need to be acheiving +/-0.01mm accuracy in the X/Y axis - machining speed is relatively unimportant at the moment. My budget is a rather small 1-2k for the machine alone (I'd really like to keep it under 1500 if possible).

The options I'd considered so far are a converted Taig / Peatol mill with CNC conversion (and 4th axis), I've heard that an EMCO F1 would be more than capable if it can be found, and I'd also considered one of the CNC frame kits combined with C7 ballscrews / air-cooled spindle (Chinese with replacement VFD). I'm leaning towards the converted mill as I don't need a large working area, and these look like fairly 'solid' machines, but I'm also aware of just how little I know on the subject! If anybody with more experience has any suggestions, it'd be greatly appreciated. Thanks!

GEOFFREY
14-09-2013, 05:22 PM
Hi, wellcome to the forum. I think that you would be better with a small cnc mill. I think a Denford would be a good choice, although you would probably need to convert it to modern electronics and use mach 3. Good luck with whatever you decide to do. G.

EddyCurrent
14-09-2013, 06:21 PM
Way over budget but this has the accuracy you are looking for, so it says.
Buy Axminster SIEG KX3S CNC Mill from Axminster, fast delivery for the UK (http://www.axminster.co.uk/axminster-sieg-kx3s-cnc-mill-prod864995/)

More affordable, you could add cnc parts yourself maybe.
SIEG Milling Machines - Arc Euro Trade (http://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Milling-Machines)

Denford Novamill CNC Milling Machine With All Computer Programmes Ready To Use | eBay (http://www.ebay.co.uk/itm/Denford-Novamill-CNC-Milling-Machine-With-All-Computer-Programmes-Ready-To-Use-/281165020500?pt=UK_Home_Power_Tools&hash=item4176bdbd54)

JAZZCNC
14-09-2013, 06:51 PM
You'll defiantly be wanting a small mill or Purpose built sturdy Fixed gantry machine but with your requirements for engraving and aluminium work with tight tolerances plus relatively low budget when it comes to off the shelf CNC you'll struggle to find anything suitable.!!

You'll certainly find something available at your budget but they won't be ideal for your type of work because the spindle speeds are little on the low side with mini-mills and for a decent finish on aluminium/brass with small cutters you'll need 7-8Krpm speeds minimum and for good engraving you'll want 20Krpm minimum most mills will top out at 3Krpm.
Also chances are the mill spindles will have higher run-out and for fine engraving you'll need better than most cheap mills provide.

My suggestion is build a small sturdy fixed gantry machine out of steel so it's very strong, use profile linear rails on all axis with 5mm pitch ballscrews. Add to that Chinese WC spindle combined with Good quality digital drives and you'll have a very capable purpose built machine easily done within your budget. . . . . Any off the shelf machine equally equipped or capable will be 5K minimum.

birchy
14-09-2013, 07:06 PM
I'm afraid that as precision increases, so does the cost. I wouldn't look at anything less than a closed-loop drive system...ideally go for Servo drives rather than stepper motors. The main issue will be the mechanics...I'd suggest building a small machine using precision rails on such a tight budget.

lanky_streak
15-09-2013, 12:48 AM
Thanks for the replies, I really appreciate the detailed responses. I'll think I'll have to do a lot more research before deciding on building anything from the ground-up, but given the budget and the fact I'll need to get up to speed on how the machine works anyway, that's no bad thing.

One question on the closed loop system, is that something that can basically be added to any mill or are custom controllers / sensors required?

And for Jazzcnc, I've read a few comparisons (and still don't have an answer!), but is the watercooled spindle significantly better than the air cooled to warrant the additional complexity of a plumbed system?

The last CNC machine I had experience of was a Datron M8, and I see they do have an 'inline' mini-mill which looks great, but presumably as a 'POA' product, this isn't one for a hobbyist?!

JAZZCNC
15-09-2013, 02:21 AM
One question on the closed loop system, is that something that can basically be added to any mill or are custom controllers / sensors required?

Depends on the closed loop system, if your talking servo system then you'll need a controller that supports closed loop. Common DIY controller is MACH3 and that won't do closed loop.
If your talking about the Lead shine closed loop Hybrid stepper system then yes this will add to any machine has the drive takes care of the closing the loop so can work with any controller.


And for Jazzcnc, I've read a few comparisons (and still don't have an answer!), but is the watercooled spindle significantly better than the air cooled to warrant the additional complexity of a plumbed system?

It's mainly to do with Duty cycle, meaning how long it can run without rest. WC spindles are 100% duty cycle and can run for days none stop, i've run mine 34+ hrs without stopping. This can be important if your doing large or very detailed 3D work that have tiny depth of cut or tiny step over, often both if high quality finish is required.
They are also much quieter than air cooled has they don't have a noisy fan to do the cooling.


The last CNC machine I had experience of was a Datron M8, and I see they do have an 'inline' mini-mill which looks great, but presumably as a 'POA' product, this isn't one for a hobbyist?!

Ah ah ye bit out the DIY range we thinks.!! . . . . If you have used or experience on a Datron M8 then your going to be sick with the offerings 1500 will get you that's for sure.!!

lanky_streak
15-09-2013, 11:04 AM
Ah ah ye bit out the DIY range we thinks.!! . . . . If you have used or experience on a Datron M8 then your going to be sick with the offerings 1500 will get you that's for sure.!!

Ha ha - yeah, I'm well aware of the limitations of my budget! I think I was spoilt in the good ol' days when I could hand over a USB to the model maker to turn, mill or SLA whatever design I had in mind!

Thanks again for the advice - I think I'll respond to this post with any plans before I commit to purchasing anything. I'm currently having a look at other fixed gantry mills to get a feel for what is needed for this sort of project.

lanky_streak
16-09-2013, 08:18 PM
I also wondered if anybody had any experience of this type of Chinese machine: Ball Industrial CNC Slide Rail Guide Syetem Mill X-Y-Z Engraving machine Motor | eBay (http://www.ebay.co.uk/itm/Ball-Industrial-CNC-Slide-Rail-Guide-Syetem-Mill-XYZ-Engraving-machine-Motor-/261240944505)

...I've absolutely no intention of buying one as I don't want the risk involved with Chinese CNC quality control, but the size, component spec and claimed accuracy all look pretty good value for money. Coupled with a water-cooled spindle and decent electronics, it would make for quite a cheap build. I've searched the forums but couldn't find reference to this (only the 3020 / 6040 machines that are all over ebay) so wondered if anyone has any experience of these machines?

GEOFFREY
16-09-2013, 09:33 PM
Unsupported rails, no end bearings - I don't think Jazz will be too impressed!!! G.

price is low , but I expect you get what ou pay for.

lanky_streak
16-09-2013, 10:03 PM
Unsupported rails, no end bearings - I don't think Jazz will be too impressed!!! G.

price is low , but I expect you get what ou pay for.

Hmm - definetly need to do lots of reading up before embarking on this project, where's the 'Idiot's guide to CNC milling'?!

JAZZCNC
16-09-2013, 11:00 PM
Unsupported rails, no end bearings - I don't think Jazz will be too impressed!!! G.

Too right.!!. . . . .There'd be more chance I'd advise him to Dip is balls in sulphuric acid than buy that. .:hysterical:

EddyCurrent
19-09-2013, 09:56 PM
Any use ?

Denford Micro Mill Cnc Machine 3 Axis | eBay (http://www.ebay.co.uk/itm/Denford-Micro-Mill-Cnc-Machine-3-Axis-/300970090194?pt=LH_DefaultDomain_3&hash=item4613371ed2)

GEOFFREY
19-09-2013, 10:08 PM
The Denford micromill is basically a small Sherline mill cnc'd by Denford. When I suggested a Denford I was thinking of a heavier mill, something more like a Novamill/ starmill etc. or perhaps even a Triac. As Jazz has already stated, the limiting factor is likely to be slow spindle speed for engraving with very small diameter tooling. G.

lanky_streak
19-09-2013, 11:24 PM
Thanks for the replies / suggestions. I've been having a look at the Denfords just to get an idea of what they're capable of - I was originally put off having seen them in many schools, but I've seen a few threads where the electronics have been upgraded, the enclosure ditched and Mach 3 installed & they appear to be quite sturdy / accurate machines for the money and relative ease to getting started. The Novamill on ebay looked interesting, but I wasn't (and am still not yet) decided on what it is I should really go for - plus the seller looked a bit dodgy (cheap motorbikes, Bentley wheel rims and a mill from a school!).

I hadn't realised the Denford was basically a Sherline mill; I know someone that recently bought a Taig mill converted to CNC with 4th axis, which was a comparible machine and seems to be serving well to do very similar type of work to me. The small diameter tooling doesn't worry me - most of the jobs I have in mind will be using sub 1mm end mills, and I'm aware I'm not going to end up with a machine that can do everything. A build from scratch does seem to be the way to get everything I'm after, but it's a bit daunting & small mills do appear to offer what I'm looking for.

Thanks again - the suggestions / comments are useful and very much appreciated.

Jonathan
19-09-2013, 11:45 PM
I would be worried by the smaller diameter tooling. For less than 1mm endmills you really want a high speed spindle. One of the chinese 24000rpm spindles would probably be ideal. Maybe eventhe more expensive version with lower runout to get the required accuracy.

lanky_streak
20-09-2013, 12:08 AM
I would be worried by the smaller diameter tooling. For less than 1mm endmills you really want a high speed spindle. One of the chinese 24000rpm spindles would probably be ideal. Maybe eventhe more expensive version with lower runout to get the required accuracy.

Ah - showing my ignorance again! If upgrading the electronics is worthwhile anyway, would adding a high speed spindle to the Denford be possible / sensible? I.e. would it be a good base to start, or for all of that hassle, is a new manual mill a better starting point? I've looked at some of the Proxxon's but read that these are far more capable for the money: Peatol Machine Tools - The Home of the Peatol Micro Lathe and Mill (http://www.peatolmac.talktalk.net/mill.html)

EddyCurrent
20-09-2013, 10:40 AM
Aren't these outside your required accuracy ? Proxxon (from Axminster site "Proxxon FF 500 CNC MICRO Mill. For repeat accuracies of up to 0.05mm") Peatol is better though at 0.0005 in (0.0127mm)

lanky_streak
23-09-2013, 08:00 PM
Aren't these outside your required accuracy ? Proxxon (from Axminster site "Proxxon FF 500 CNC MICRO Mill. For repeat accuracies of up to 0.05mm") Peatol is better though at 0.0005 in (0.0127mm)

I was actually looking at a manual mill for conversion to CNC, but have read mixed reviews on the Proxxon anyway - it seems to be fine, but is very much a budget mill and quite lightweight. I think the Peatol falls within a usuable level of accuracy, but I still need to find exactly what's involved to convert it (unless the UK distributer offers this, which I've not looked into yet).

JAZZCNC
23-09-2013, 09:02 PM
I'm currently designing and working out moulds etc to build small Fixed gantry Epoxy Granite based machine. It will have profiled linear rails and use Closed loop stepper system using preloaded double-nut ball-screws.
The Epoxy granite structure will minimise vibrations and resonance and coupled with linear rails will make for very high quality surface finish. The preloaded double nut will make for near zero backlash and coupled with Closed loop steppers will make it very accurate. Will most likely have 2.2Kw spindle on it which will just about match the machine accuracy.

Reason for telling this is because I'm sure it will cost less than any small converted CNC mill and will hold much better tolerances and be more suited to your type of work due to spindle. You'll need to spend at least 10k to get off the shelf machine that will hold tolerances anywhere near what machine built like this will hold.

Even a fixed gantry steel framed machine filled with sand or Resin/aggregate mix with same double nut and closed loop steppers and WC spindle will blow the small Chinese milling machines away and be cheaper to build.

MY ADVISE IS BUILD BUILD BUILD has you'll only be disappointed or limited with Cheap Chinese mill conversion.!!

FatFreddie
24-09-2013, 06:31 PM
I'm currently designing and working out moulds etc to build small Fixed gantry Epoxy Granite based machine. It will have profiled linear rails and use Closed loop stepper system using preloaded double-nut ball-screws.
The Epoxy granite structure will minimise vibrations and resonance and coupled with linear rails will make for very high quality surface finish. The preloaded double nut will make for near zero backlash and coupled with Closed loop steppers will make it very accurate. Will most likely have 2.2Kw spindle on it which will just about match the machine accuracy.

I'd be very interested to hear how you get on with this - I'm thinking of doing something similar.

JAZZCNC
24-09-2013, 06:43 PM
I'd be very interested to hear how you get on with this - I'm thinking of doing something similar.

I'll throw up a thread when starting and your close enough to see it in flesh when done, I'm actually closer to Barnsley than Wakefield 20-30mins to Meadow Hell.!!

mekanik
24-09-2013, 10:40 PM
Will look forward to that Dean, will you be casting in gauge plate lengths to secure the rails too, and will it be relieved to form pads @ the fixing locations like the French dude did on his build ?

JAZZCNC
24-09-2013, 11:10 PM
Will look forward to that Dean, will you be casting in gauge plate lengths to secure the rails too, and will it be relieved to form pads @ the fixing locations like the French dude did on his build ?

Yes it will have Ground plate cast into it for rails along with mounting areas for ballscrew mounts etc.
Not sure I've seen the French Dude's machine so not sure what pads you mean.? But yes it will have areas relieved for clearance etc and mounting plates, Tapered dowels & sockets for locating and fixing etc.

I'm thinking to make it sectional and bolt together for simplicity of casting and practicality's of moving. That much epoxy granite cast in one go will create hell of a lot of heat and be handful to handle in one go so for a first attempt I'm going to play it safe I think.

When I know more what's involved then I'll look to cast in one mould.??

mekanik
24-09-2013, 11:50 PM
I think it was Jonathan in one of the threads posted a link to a guy that had built a gantry mill and it all seemed solid to say the least(that's a compliment from an x shipyard fitter) then for some reason he went and painted it pink.can you use a slow set hardner to try and reduce the exotherm ? is there any way you could surround your mold in a water bath, when we installed D5 Launch tubes they were back filled with water and the water was circulated with a pump, all in an attempt to reduce shrinkage and seperation of the two component parts(our tubes were better than any of the yank's)
What sort of size were you thinking of.

JAZZCNC
25-09-2013, 01:01 AM
What sort of size were you thinking of.

Will only be small 600x300 cutting area for a first attempt. Will sell it on then when it's proven it's self and build a larger version.
Don't really see any problems with building in sections anyway if done correctly and actually will allow some adjustment if not quite 100%. Single cast piece would be quite difficult to tweak any slight errors out and will be bit unwieldy for moving etc. Personally Don't think the slight extra strength it will add will be worth the trouble in long run.? . . . Time will tell and that's what first one will determine.!

Yes I did think about some form of Cooling and maybe surround mould with skin and fill with bags of ICE.!! . . . . I'll try and keep it simple first thou because by time I'm ready it will be bloody freezing in workshop so don't get much simpler. . Lol

FatFreddie
25-09-2013, 11:59 AM
I'll throw up a thread when starting and your close enough to see it in flesh when done, I'm actually closer to Barnsley than Wakefield 20-30mins to Meadow Hell.!!

Thanks, I look forward to seeing it.