Advice on Small CNC Mill - From Scratch or Pre-Built?

[DrCNC]

Hi all,

This is my first post and I'm a newbie when it comes to CNC milling . I'm an electronic engineer and would like to build/buy a small CNC mill to be used for

- Panel designing (arbitrary holes/openings on sheet metal & label engravings).
- Milling of small parts for use in my own projects.
- Cutting tool travel: x = 150-300mm, y = 80-100mm, z = 50-80 mm. Longer/shorter travels may also be OK.

The material would be almost exclusively aluminium sheets/blocks, and a bit of copper & plastics. I'm very experienced in electronics, so I can easily handle the stepper motor control and s/w interfacing part. What I cannot do/choose easily is the mechanical part. Should I buy a ready-made mill and convert to CNC myself (by attaching 3 steppers to the x, y, z knobs), or should I buy separate parts like CNC rails/bearings/slides & drill and combine them together to build my own CNC mill from scratch? Another option is to buy an already-converted mill like the ones from Proxxon, Sherline and Taig.

My priorities are (highest first)

1. Machine precision, robustness & repeatability.
2. Compatibility of controller with easily available & good quality s/w (Mach3 or others).
3. Relatively low cost (say, up to $2,000 - I'm only a hobbyist, not making money out of this).

The easiest solution would be to get a ready-made CNC mill retrofit, like one from the following.

- Proxxon MF70 (http://www.usovo.de/).
- Sherline (http://www.sherline.com/).
- Taig (http://www.taigtools.com/).

A friend of mine has just bought the Proxxon MF70 (which comes with the SMC-800 controller), but he's now discovering that there's a serious lack of good and cheap s/w for this controller. He's already spent a lot of money on s/w (WinPC-NC & Filou-NC) and still hasn't been able to really use the machine!

What do you guys think/recommend I should do? Which ready-made mill would you suggest I get? Or maybe build it from scratch? I found this link in the UK that sells parts for linear movement.

http://www.marchantdice.com/

Any pointers or information is greatly appreciated.
Apologies for the long post & thanks to all for the great forum & info.

Costas

[digits]

Hi, a couple of months ago, I bought myself a Sieg X1 and CNC'ed it. It was quite a lot of effort researching and sourcing the motors, the motor mounts, the drivers, the PSU and the CAM and machine controller software, and it ended up costing me a lot more than I expected - making some of those prebuilt CNC machines look like good value.

I am already considering a larger machine as I want to be able to make bigger parts and to make small ones is much less time. This time round, I am considering building from scratch, probably using parts from marchant dice, but even my initial cost estimates are rather scary. I have already bought the parts for one axis, and while they are of lovely quality, they did cost more than my manual X1!

I am also more electrically than mechanically skilled, and so am finding the prospect of building from scratch a bit daunting, but atleast I have a CNC mill and a lot of software to help me cut parts for the new machine - do you have access to the tools you'd need to make your own mill?

I'd also recommend that you budget at least 300-500 Euros for tooling - vices, collets, mills, measuring devices etc eat up cash like you wouldn't believe!

Also if you're going to be doing a lot of aluminium, you should probably consider a coolant system - this means an enclosure, which is a whole other adventure!

Best of luck, whichever way you go!

[DrCNC]

Many thanks digits for the very informative reply. A CNC mill is almost essential for those of us who need to make high quality custom metal parts/panels for projects, etc., but can be very expensive to build from scratch as you say. In terms of availability of tools to make my own mill, a friend of mine has just bought a ready-made Proxxon MF70 mill (CNC'ed by a German company called USOVO) and some s/w, but he's still struggling to make the machine work (and he's more experienced than me in metalworking). Also, the MF70 may be too small for such a project... Anyway, based on your post, my best option would probably be to purchase a ready-made (CNC'ed) mill like the Sherline/Taig/Sieg/Proxxon.

You mention about the need for coolant. The problem is that I will be using the mill inside my house (I don't have a workshop, only a small electronics lab inside the house). I watched a movie clip once showing a CNC with coolant and the thing was very messy! Do you think it'll be absolutely necessary to use coolant for aluminium parts?

Another thing I want to ask you guys is about spindle speed. The Proxxon MF70 that my friend has bought has a spindle speed of 5000-20000 rpm. The Sherline and Taig, however, have spindle speeds of 70-2800 and 1100-10000 rpm, respectively. For the type of stuff I want to do (mainly aluminium panels/blocks and a bit of copper & plastics) what would be the most appropriate speed range? I don't just want to do engraving, I also want to be able to use a solid aluminium block and "dig" into it to make special parts, etc. Which of the main brands (Proxxon/Sherline/Taig/Sieg) would you recommend? My budget is around 2000-2500 Euros.

Finally, about software. The name I keep coming across when searching for CNC s/w is Mach3, so I'd have to build or buy a stepper motor controller that is compatible with it. What do you guys think? Are there any other good s/w I should be considering except Mach3? My friend with the Proxxon MF70 has bought something called WinPC-NC (for driving the SMC-800 controller that came with it) and another s/w for the CAM part called Filou-NC. What about these? Are they any good?

Again, apologies for the many questions.
Thx guys, I really appreciate your help!

Costas

[digits]

You don't have to buy a pre CNC'ed mill, you could buy a mill and convert it - if you can find someone who is doing packages with motors mounts drivers and PSU's, it could be a one-stop-shop, and with hindsight, I don't think it would save you all that much to shop around for each component.

I would be a little wary of a mill that forces you to use a dedicated H/W controller - I wouldn't like to be tied in to using their software. I went with Mach 3 and I don't regret it at all - it is very easy to use and performs well, but I could just as easily switch to a Linux solution as the hardware isn't tied to any particular software.

As for stepper drivers, I made the mistake of buying a shoddy ebay 4-axis driver board for £90ish - it caught fire when one of the motors stalled, but before that it was losing steps due to thermal shutdown - and at half its rated current with additional fans and heatsinks Anyway, I got myself some excellent 4.2A drivers from Motion Control Products for about £35 an axis - I should have got them in the first place when I bought my motors from them! Anyway, they are a breeze to wire up - they have optoisolated inputs, so all you'll need to do is wire them to a parallel port connector and add a PSU.

You don't have to use coolant - but you will forever be brushing off chips and spraying on WD40 as it runs to keep the cuts clean. I lasted about 5-6 weeks before I gave in and built a (hideous) coolant table - my mill is so slow that I don't want to have to stand and watch it for 2 hours with eye and ear protection on! The cuts are much cleaner and quieter too - and as I'm in a 1st floor apartment, that matters to me and my neighbours!

My mill tops out at about 2000 rpm - which isn't really enough for aluminium with small cutters, and it's too weedy for big cutters. I am aiming for about 4k rpm on my next machine, but IMHO, even that's too slow for engraving.

Hope that helps and sorry about all the waffle!

[DareBee]

I can give no advice on these machines, but a 6mm carbide cutter should be running 10,000 RPM + in aluminum for best efficiency.

[DrCNC]

Thanks again digits, that really helped a lot, I appreciate it.

OK, so I'll have to get a manual mill and CNC it. This would mean properly attaching the 3 steppers to the three axes. For the controller I'd also want something open (non-proprietary) and compatible with Mach3. I've heard there's also a Linux CNC s/w called EMC that was ported from a US military project. This may also be a good choice. In any case I want to steer clear of proprietary controllers & s/w. My friend has paid more than 300 Euros for what I would call average-quality s/w, only to find out that he now has to pay another 150 Euros to upgrade to a different version!

The difficult part right now for me is to find some shop/company in Greece that can do the modifications on the manual mill. Will try Google but I have the feeling it won't be easy. Fortunately I live in Athens, hopefully I'll be able to find someone who can help. I might even try to use my friend's mill to build some parts myself. If that fails, I'll get a pre-CNC'ed mill.

Will post here once I have something going.
Many thanks to all for the many posts in these forums.

Costas

[digits]

Originally Posted by DrCNC Thanks again digits, that really helped a lot, I appreciate it. OK, so I'll have to get a manual mill and CNC it. This would mean properly attaching the 3 steppers to the three axes. For the controller I'd also want something open (non-proprietary) and compatible with Mach3. I've heard there's also a Linux CNC s/w called EMC that was ported from a US military project. This may also be a good choice. In any case I want to steer clear of proprietary controllers & s/w. My friend has paid more than 300 Euros for what I would call average-quality s/w, only to find out that he now has to pay another 150 Euros to upgrade to a different version! The difficult part right now for me is to find some shop/company in Greece that can do the modifications on the manual mill. Will try Google but I have the feeling it won't be easy. Fortunately I live in Athens, hopefully I'll be able to find someone who can help. I might even try to use my friend's mill to build some parts myself. If that fails, I'll get a pre-CNC'ed mill. Will post here once I have something going. Many thanks to all for the many posts in these forums. Costas

For what it's worth, my CNC conversion was from www.cncfusion.com - it was a simple bolt on job - no tools other than an allen key required! I'm pretty sure that if you have a look on the net, you'll find something similar somewhere.

Best of luck

[MIKE JEFFERS]

for cam software have a look at the excellent cambam
the guy that codes it is on here sometimes
it works and is free (at the moment anyway)
get a cheap autocad lt package and for most 2/2.5d stuff they're all
you need www.brusselsprout.org/CAMBAM
oh and deskengrave http://www.deskam.com/deskengrave.html
mike