What CNC machine for our Hackspace

I'm starting a project to get a CNC mill /router at the London Hackspace (a UK maker community). I was hoping that you guys here could give me some advice about what directions we should be looking in.
I've surveyed members about what they want and how much they're willing to donate towards getting such a machine. The results were:
- the biggest group of people - $2500 budget - would be happy with a 12" x 12" that could do PCBs, wood, plastic and softer metals such as aluminum;
- a further smaller group - taking the budget up to $3000 - wanted the machine to be able to do up to 20"x20" or 24"x24", cutting the same materials
- another small group - taking the budget up to $4000 - wanted a 4'x8' wood router.
All of these people want to be able to carve complex shapes, but there was little appetite for undercuts, so we're talking 2.5d.
I should clarify that when we're talking about cutting softer metals, it's not simply a matter of cutting out shapes in 1/8" sheets -they want to sculpt complex shapes with maybe 3" of z travel.
Robustness is a priority as it will be used by people like me with little training who won't know how to mother it and will damage it often if there's a way we can. Speed is not important as this is a hobby environment not a production one. Machine will probably be running about 1-2 hours per day.
This budget needs to cover absolutely everything - spindle, software, dust extraction, cutting bed, etc.
Building from scratch or upgrading/converting is realistic option for us. We have in our hackspace metal working tools (mills, lathes, but not CNC) and a laser cutter (wood not metal). We can definitely get plastic parts 3d printed by members who have 3d printers, and may be able to get metal/wood parts CNC machined by members who have a CNC at home.
The way I see it, we have three choices:
1) abandon the people who want 4'x8' and their money, and spend $3000 on 1 good machine 20"x20"
2) get 2 machines for $2000 each: one 12" x 12" for precise work like PCBs that can also cut metals OK, and one 4' x 8' primarily for wood that has less precision/accuracy and can do metals only very slowly.
3) get 1 machine for $4000 that can do 4'x8' with enough rigidity to do metals but good enough on detail to do PCBs.
Which is the right strategy to pursue? Particularly given that we need a machine that is as user-proof as possible.
Once point to reiterate: it's fine if metal cutting is very slow. Speed is not an issue.
Any advice much appreciated.
Jonathan

Noise!!!
You will need an enclosure.

To get a 4'x8' that can do metal cutting for under $2000 you would have to build it plus scrounge almost every part instead of buying it new.

When you say speed is not important for the metal cutting aspects, I think a few calculations are in order. I assume that you would be looking to machine aluminum and soft brass that would machine at ~300 sfm with HSS, probably twice that with carbide. You will need a high speed spindle. Spindle speed for an 1/8" HSS end mill would need to be about 9200 rpm (twice that for carbide). If you use a 2 flute end mill with .0005 feed/tooth, that gives you about 9 ipm feed. You could probably feed at about half that rate, but any slower and you will likely rub and dull your tool. Cutting forces should be fairly low as long as the tool is sharp and take light cuts, very much cutting force and an end mill this size just breaks. The question is, for very complex 3d carving that you are talking about here, it would be prudent to have one of your members that has a 3D cam program input parameters like these for what you think will be common and worst case projects and see how long it will take to machine them. I think complex shapes that need a lot of metal removed could take longer than you think. I think one of the Chinese 20,000 rpm spindles with an ER collet chuck built in with a VFD for speed control would be able to do work like that on a router; if it were built fairly stiff (other members that have tried that could chime in on the effectiveness of it). Anyway, good luck.

I'm starting a project to get a CNC mill /router at the London Hackspace (a UK maker community). I was hoping that you guys here could give me some advice about what directions we should be looking in.

You probably won't like what we have to say.

I've surveyed members about what they want and how much they're willing to donate towards getting such a machine. The results were:
- the biggest group of people - $2500 budget - would be happy with a 12" x 12" that could do PCBs, wood, plastic and softer metals such as aluminum;

Unless you DIY this machine even $2500 is less than realistic. Unless of course people donate $2500 per person. If you do DIY the machine you have good potential to hit that $2500 mark. The problem is there are many"cheap" machines on the market but in many cases they are more kit than finished machine.
Depending upon the interests expressed this might be a high priority machine. A bench top CNC machine for PCB processing and sheet goods work can be extremely useful. Honestly though I consider such machines to be in a different class than larger router type machines.

- a further smaller group - taking the budget up to $3000 - wanted the machine to be able to do up to 20"x20" or 24"x24", cutting the same materials

Waste of time for such a club.

- another small group - taking the budget up to $4000 - wanted a 4'x8' wood router.

This should be a high priority as it can help shore up membership in the club. However a decent machine will cost big bucks. Frankly you want to spend the bigger bucks to get a machine that supports the higher Z clearance,and has the ability to handle the wide array of materials you mention.

All of these people want to be able to carve complex shapes, but there was little appetite for undercuts, so we're talking 2.5d.

Here is an example of a well done machine: Table Saw, Jointers, Planers-Woodworking Machines-Oliver Machinery. in the 13" class. It can be had for $2100+ dollars but I'd consider it to be a very limited machine due to the 150 watt rating in the spindle.
I'm not sure I buy your definition of 2.5D. In any event a machine like the one above is suitable for a limited set of your probably uses. You really have to ask yourself how serious people are about carving large pieces of aluminum because frankly it might make more sense to buy a CNC milling machine to supplement this sort of machine.

I should clarify that when we're talking about cutting softer metals, it's not simply a matter of cutting out shapes in 1/8" sheets -they want to sculpt complex shapes with maybe 3" of z travel.

There is this concept of using the right tool for the job. A little machine like the Oliver above simply isn't suitable for carving up large sections of Aluminum block.

Robustness is a priority as it will be used by people like me with little training who won't know how to mother it and will damage it often if there's a way we can. Speed is not important as this is a hobby environment not a production one. Machine will probably be running about 1-2 hours per day.

Speed is very important. Lets say you are using the machine to route PCB. A slow machine could literally take hours where a faster machine might spend a fraction of an hour on the same job. I'd have to say speed is real important especially if everybody shows up at the club house after work and all want to use the little machine.

This budget needs to cover absolutely everything - spindle, software, dust extraction, cutting bed, etc.

This is a problem. Seriously one needs to up the budget here. If a basic machine is $2200 then you will quickly blow the rest of the budget on the extras.

Building from scratch or upgrading/converting is realistic option for us. We have in our hackspace metal working tools (mills, lathes, but not CNC) and a laser cutter (wood not metal). We can definitely get plastic parts 3d printed by members who have 3d printers, and may be able to get metal/wood parts CNC machined by members who have a CNC at home.

This is certainly the way to go if the club has the right skills set. Doing so you could end up with a far more robust machine especially if the budget is high enough to allow you to afford real linear rails and othEr nice features.

The way I see it, we have three choices:
1) abandon the people who want 4'x8' and their money, and spend $3000 on 1 good machine 20"x20"

No go in my mind. A 20 x 20" machine lease everybody out in the cold. Better to concentrate on one need at a time. That would be either the small machine or the one able to handle sheet goods.

2) get 2 machines for $2000 each: one 12" x 12" for precise work like PCBs that can also cut metals OK, and one 4' x 8' primarily for wood that has less precision/accuracy and can do metals only very slowly.

I don't see any $2000, 4' x 8' machine being worth it at all. You can't even buy a decent spindle for that money.

3) get 1 machine for $4000 that can do 4'x8' with enough rigidity to do metals but good enough on detail to do PCBs.

If you are going to go large do so in a way that results in a robust machine that many club members can leverage. Such a machine should be thought of as a different beast than the PCB router. A good machine will have a tendency to enhance membership once word gets around.

Which is the right strategy to pursue? Particularly given that we need a machine that is as user-proof as possible.

I'd go for the PCB routing machine first. Then establish a fund, maybe even a fundraiser, for the 4 x 8 machine.

Once point to reiterate: it's fine if metal cutting is very slow. Speed is not an issue.

Not to argue with you but slow can be very bad. You need to be able to feed the mill at a rate suitable for your spindles minimal speed.

Any advice much appreciated.
Jonathan

If you have machinery, doing a 12" square PCB type machine should be easy. You should be able to build a very robust machine handling a wide array of machining needs ( with a possible spindle change). Scrounging can do wonders here.
You can do a 4 x 8 machine DIY also but it is a lot more work. Some of that work can be reduced by buying pre built parts. One place to look for parts is plastics business selling off old hardware. Many of the parts extractors on the market have nice slide assemblies that can be converted to use on a CNC machine.

I'd probably start off with a 6040, and allow the extra $275 or so for changing the TB6560 based drivers to a Gecko G540. That way for well under $2k you have a complete, robust machine made of solid aluminium, with a decent work envelope that will not only do fine for PCB work, as well as moderate aluminium machining, but will crunch timber and plastic projects with ease. The spindle that they are supplied with, either a 0.8Kw or a 1.5Kw, are way better than domestic routers, and will really help with keeping noise down, while giving great performance and reliability.
You could use this then to start machining parts to build a larger 4' x 8' machine based on MDF or whatever.
cheers, Ian

Thanks for all the replies guys.
Enclosure: yes, we'll definitely need one. Any ideas on a good source for plans/designs of one?
Noise: fortunately we have a workshop basement so noise is not too critical. Also, I hear these affordable Chines water-cooled spindles are much quieter? We'll enclose anyway.
Speed: you're right, I was underestimating the importance of this in an evening hobby context. People need to get things done.
Metal removal: few people will want to remove large volumes of metal. Just nice that the machine could if pushed. An 8 hour daytime job for someone who really wants to machine an injection mold cavity (possibly in multiple long sessions even) is not too bad. That it can whiz through cutting some mdf in 30 minutes during at evening time is more important.
Z capacity: I think I'm going to compromise on this. I'm sure 1-2 inches would be enough for 98% of uses.
Size: I'm abandoning all talk of 4'x8'. I want to focus on something in the 30cmx40cm or 60cmx40cm size range.
Naturally I'm very interested in the Chinese Yoocnc 3020 3040 6040 series - carving-cnc.com YooCNC machines. I hear the electronics are actually OK on the latest versions? There's a frame only option for $838 that's quite tempting.
A lot of people seem to think the mechanics of these are OK, and in fact difficult to beat on cost even DIY. Is there a DIY route that is either same quality but cheaper, or better rigidity at same price? What's the best DIY options to explore if I want to cut aluminium but want this size of machine?
Unfortunately we'd need quite detailed plans. I don't think we'd manage to get it together designing it ourselves. Nobody is really up for a 6 month labour of love.
Looking beyond YooCNC, I hear Jquick / Jcut are better but more expensive??
The Heisz S series is the most affordable non-Chinese option I've seen. Any thoughts?
However, all of these push the budget into dicey territory.
Thanks again for helpimg,
Jonathan

Thanks for all the replies guys.
Enclosure: yes, we'll definitely need one. Any ideas on a good source for plans/designs of one?

You will likely have to design your own and how that is designed depends upon which machine you go with. More importantly in a Hackerspace part of the reason for an enclosure would be to control access.

Noise: fortunately we have a workshop basement so noise is not too critical. Also, I hear these affordable Chines water-cooled spindles are much quieter? We'll enclose anyway.
Speed: you're right, I was underestimating the importance of this in an evening hobby context. People need to get things done.

If you are the only user and owner speed doesn't matter. When you have people waiting in line it does matter. It is really hard to predict demand for the machine ahead of time, you just don't know if those expressing interest really are interested.

Metal removal: few people will want to remove large volumes of metal. Just nice that the machine could if pushed. An 8 hour daytime job for someone who really wants to machine an injection mold cavity (possibly in multiple long sessions even) is not too bad. That it can whiz through cutting some mdf in 30 minutes during at evening time is more important.

I'm still of the opinion that somebody making such aluminum pieces needs a mill not a router. As such there should be a project afoot to install a CNC mill. You could buy a router type machine suitable for die work but it won't be cheap.

Z capacity: I think I'm going to compromise on this. I'm sure 1-2 inches would be enough for 98% of uses.

This is a tough one. The larger the machine though the more reason to increase Z capacity.

Size: I'm abandoning all talk of 4'x8'. I want to focus on something in the 30cmx40cm or 60cmx40cm size range.
Naturally I'm very interested in the Chinese Yoocnc 3020 3040 6040 series - carving-cnc.com YooCNC machines. I hear the electronics are actually OK on the latest versions? There's a frame only option for $838 that's quite tempting.

Some like those machines some don't. I see them as items that need so much TLC that you might as well build yourself or spend a little extra money upfront.

A lot of people seem to think the mechanics of these are OK, and in fact difficult to beat on cost even DIY. Is there a DIY route that is either same quality but cheaper, or better rigidity at same price? What's the best DIY options to explore if I want to cut aluminium but want this size of machine?

Well many have a slightly different view. The electronics and even the spindles leave a lot to be desired in some people's mind. I take it that is why the frames sell so well as they can be seen as a bargain.

Unfortunately we'd need quite detailed plans. I don't think we'd manage to get it together designing it ourselves. Nobody is really up for a 6 month labour of love.

You could easily build a router in the time it takes to ship a unit from China. Beyond that the designs are pretty much canned

Looking beyond YooCNC, I hear Jquick / Jcut are better but more expensive??
The Heisz S series is the most affordable non-Chinese option I've seen. Any thoughts?
However, all of these push the budget into dicey territory.

Yeah your budget sucks. Even low end you are in a tuff position buying new, especially if you want a complete solution. In fact I think you are doing this backwards.
What you should do is develop a set of firm requirements for one or more machines and come up with all the price tags to sum up the complete cost of the machine. In other words get the pricing on the frame, the electronics, the PC, the spindle, the enclosure and base tooling, with these prices you get your base budget positions. With that number you have a value that you can drive home to the group for fund raising. If that value is $4000 or $6000 you have a number that will illuminate the members of the Hackerspace and get them to either commit or drop the subject.

Thanks again for helpimg,
Jonathan

I need to add one more thing here, an opinion really, and that is that if this is a Hackerspace why the resistance to building something of your own. Especially in the context of a PCB sized mill which should be easy if you already have machine tools. In fact I find it hard to understand why if there are that many people interested in a small machine that a bunch of hackers haven't already started a project. A scrounged up PCB mill can be had relatively cheaply if you have enough members scrounging up parts. Beyond that there are many examples and plans on the net to get people started. Even if there where no plans to speak of this isn't a complicated machine to build one off.

I looked for a local hackerspace just now and there are none within 50 miles. This thread got me interested in helping a local one but is sad I don't have one available. I would be interested in supporting a local hackerspace with a donation of linear slides, ballscrews, motors, drives but I am not motivated enough to want to start one up from scratch.
Perhaps you could find someone like me in your area who has some extra equipment they might donate to the club. I am not sure how you would advertise for that other than word of mouth or just getting lucky on a forum.

Thanks for all the replies guys.
Enclosure: yes, we'll definitely need one. Any ideas on a good source for plans/designs of one?

This would be nothing more than a big box made of whatever material you can source, MDF, plywood, whatever. Or even a small section of a room closed off.

Noise: fortunately we have a workshop basement so noise is not too critical. Also, I hear these affordable Chines water-cooled spindles are much quieter? We'll enclose anyway.

The spindles these machines come with are just awesome to use, and beat any domestic wood router hands down, apart from the fact they will also outlast said routers greatly! They are powerful, quiet, and will happily run for hours or days at a time.

Speed: you're right, I was underestimating the importance of this in an evening hobby context. People need to get things done.

This will depend on the material, cutters used, and project details. If your cutting speaker boxes out of MDF for example, you can absolutely fly as geometric shapes are the simplest and fastest things to do, but if your doing 3D models on cupboard doors, expect a job to take hours possibly. Same for aluminium work, you'll do light cuts but at high feed rates, so it might take 30mins to cut out a motor mount.

Metal removal: few people will want to remove large volumes of metal. Just nice that the machine could if pushed. An 8 hour daytime job for someone who really wants to machine an injection mold cavity (possibly in multiple long sessions even) is not too bad. That it can whiz through cutting some mdf in 30 minutes during at evening time is more important.

As I said above, a 6040 will power through aluminium, but at light depth of cut, but fast feedrate. Otherwise you can end up breaking cutters. I find when doing this the limiting factor is how well can I clear the chips as they are ejected, otherwise the cutter binds up, and is re-cutting chips, which can eventually break the cutter. For this you really want either fluid lubrication spraying, or more practically, an air hose and nozzle hooked up to the blow the chips out while a dust extractor sucks them up, but this itself can present a safety hazard you need to be aware of.

Z capacity: I think I'm going to compromise on this. I'm sure 1-2 inches would be enough for 98% of uses.

Good idea, makes it much more realistic and affordable.

Size: I'm abandoning all talk of 4'x8'. I want to focus on something in the 30cmx40cm or 60cmx40cm size range.

Same as above.

Naturally I'm very interested in the Chinese Yoocnc 3020 3040 6040 series - carving-cnc.com YooCNC machines. I hear the electronics are actually OK on the latest versions? There's a frame only option for $838 that's quite tempting.

I've heard positive things about the Carving cnc machines, but you'd have to do the analysis on the Carving complete cost vs the Chinese 6040 inc G540 complete cost. I don't know how much better the construction of the Carving is compared to the usual 6040's, but I do note it's quite expensive, so it still may be cheaper to buy the cheap import, and fit a G540, than get one from Carving.
I'd actually PM a few people in the threads who have bought one, to get their opinion of the Carving machine. To my mind, even if the import with a G540 worked out a little more, I'd be much happier with a G540, than any TB6560 based board, no matter how good people say they are. A G540 is bullet proof, and I'm sure will outlast any other cheaper driver.

A lot of people seem to think the mechanics of these are OK, and in fact difficult to beat on cost even DIY. Is there a DIY route that is either same quality but cheaper, or better rigidity at same price? What's the best DIY options to explore if I want to cut aluminium but want this size of machine?

Unless you have a pipeline to good quality rails, bearing blocks, ballscrews and ballnuts, etc, etc, etc, I don't see how you could make a machine, as robust, for the same amount. Don't forget too, you've got $400 worth just in the spindle and VFD. Add a G540, and your already at $775 just for those two components! Plus, unless you have an experienced benefactor to give design help and build advice, this may be a project that takes a very, very long time. Do you have the lathe and mill to manufacture the parts for example?
Most builds people start, end up going nowhere, and just a glance around this site shows these people invariably end up buying a 6040 or similar in the end. Others end up after a year or so, with an MDF machine with a wood router and skate bearings, that's cost them upwards of $2k-$3k. Buy one, then you have it ready to go! Even use it to build a group effort machine.

Unfortunately we'd need quite detailed plans. I don't think we'd manage to get it together designing it ourselves. Nobody is really up for a 6 month labour of love.

As above!

Looking beyond YooCNC, I hear Jquick / Jcut are better but more expensive??
The Heisz S series is the most affordable non-Chinese option I've seen. Any thoughts?
However, all of these push the budget into dicey territory.

The next step which would be really awesome for the group would be a 6090, these are a massively beefy machine, and capable of production work. They are around the $3k-$4k mark, but well worth it my opinion, they are a fraction of the cost of any equivalent locally produced machine. I would suggest this would be your end goal, if not now, then as a second or third machine.
NEW 6090 CNC Router Engraver Machine 23 6"X35 5"X4"Worksize Freeship Worldwide | eBay
Thanks again for helpimg,

Jonathan

cheers, Ian

I looked for a local hackerspace just now and there are none within 50 miles. This thread got me interested in helping a local one but is sad I don't have one available. I would be interested in supporting a local hackerspace with a donation of linear slides, ballscrews, motors, drives but I am not motivated enough to want to start one up from scratch.

A common problem, I've found nothing in my area also. Atleast not oriented towards creating things with machine tools. One local supposed hacker space is more of a ham radio club house.
As far as being motivated that is an issue but also it is a huge financial burden to take on. Any facility robust enough to allow club installation of machine tools is by definition expensive to rent.

Perhaps you could find someone like me in your area who has some extra equipment they might donate to the club. I am not sure how you would advertise for that other than word of mouth or just getting lucky on a forum.

In this regards advertising does work. Also search Criags list, government auction sites and places like Dove bid. Much can be found dirt cheap at auctions.

Thanks for those thoughts. This has been very helpful.
Got an option on a Dahlgren engraver for $900:
SUREGRAVE 3 AXIS CNC ROUTER « Pennyfarthing Tools Ltd
I haven't had time to research it properly yet but it looks tempting. Even if we end up replacing the motors, electronics and router that might not be bad value for a body and linear mechanics. Some blurs mention this machine as capable of engraving stainless steel.
Any thoughts on this machine? How might it compare mechaically to a YooCNC or cheaper DIY for cutting aluminium?

Thanks for those thoughts. This has been very helpful.
Got an option on a Dahlgren engraver for $900:
SUREGRAVE 3 AXIS CNC ROUTER « Pennyfarthing Tools Ltd

Interesting machine. Missing the controller but that should be easy to deal with. It is advertised as an engraver with a small spindle drive so don't expect much in the way of milling capacity.

I haven't had time to research it properly yet but it looks tempting. Even if we end up replacing the motors, electronics and router that might not be bad value for a body and linear mechanics. Some blurs mention this machine as capable of engraving stainless steel.

Engraving doesn't take a lot of power. You could replace the router but you need to make sure the mechanics can handle the extra power.
As for the controller you will want to have a new computer anyways and support the machine with either Mach3 or LinuxCNC. Even new this isn't a huge additional expense the problem then is interfacing but I know nothing about that specific interface.

Any thoughts on this machine? How might it compare mechaically to a YooCNC or cheaper DIY for cutting aluminium?

I would have to say cutting aluminum would be out of the question but I guess that depends upon what you mean by cutting. The router on the machine ony accepts 6mm cutters, it may or may not have enough power to handle milling aluminum for any length of time. You can always take the approach of a small cutter running at high speed with light cuts. The trick would be finding the optimal cutter size, spindle speed and feed rate that work well. The machine still has to be able to handle the cutting mechanically it doesn't look bad but that traveling gantry design is a negative for machining metals.
In a nut shell it doesn't look to bad on the surface at all as a fixer upper. It is a nice frame with an included enclosure at a reasonable price. Reasonable if the ball screws and bearings are in good order.
One thing I would look at closely though is coolant handling. Machining aluminum really requires some sort of coolant/lube to keep the aluminum from sticking to a tool. This can be something sprayed on like WD 40 or flood coolant at the other extreme. Either way you need to contain the fuilds some how.

Thanks Wizard. Isn't that design a moving bed though not moving gantry? Could you double-check that photo? Not sure what the implications are for aluminium milling either way.
Jonathan

It looks like a fixed gantry moving bed to me. You can see the extended linear ways coming out the back of the bed.

Thanks Wizard. Isn't that design a moving bed though not moving gantry? Could you double-check that photo? Not sure what the implications are for aluminium milling either way.
Jonathan

Yep closer examination does seem to imply a fixed gantry.
As for implications, for a given amount of material, the fixed gantry machine should be a bit stiffer. This makes machining metals more feasible. The machine looks like a nice base to recondition into something very useful.
I still have this idea in my head though that it will be too small for many uses and too big to use conveniently for PCB routing and other small activities. You really need an idea as to where club members interests lie here. It could be the perfect machine to get started with. I'd be concerned about the engraving focus of the machine, you really need to think about how successful it will be milling aluminum.

Thanks again Wizard - much appreciated.

I still have this idea in my head though that it will be too small for many uses and too big to use conveniently for PCB routing and other small activities.

Can you help me understand why it would be inconvenient to use a this for PCB and small things? We have the space, the machine likely won't be that busy (judging by how busy the lasercutter is). I have no experience here so don't get some of the practicalities that may be obvious!

I'd be concerned about the engraving focus of the machine, you really need to think about how successful it will be milling aluminum.

I am very concerned about that. Do you have any thoughts on how the mechanics of it might compare for milling aluminium with a Chinese 6040? With either machine I'm assuming we'd likely end up kitting it out with G540, good steppers and a Chinese 1.5kw spindle.
These look like the 3 choices I can see so far for the frame/mechanics:
1) This Suregrave machine
2) A chinese 6040 body
3) A DIY fixed-gantry moving-bed (60cmx40cm working area) with some kind of heavy-duty gantry, maybe steel or cast-in-place epoxy granite.
Does anyone have any ideas about existing design plans for such a DIY machine? The idea would be to try to focus on rigidity, for milling aluminium.

Oh, and lastly, any ideas on how we can get a firm idea on the mechanics of the Suregrave, how it might handle aluminium.
So far I can only think of
a) try before we buy - not possible
b) searching factorydaily/Google - but this kind of machine is not common enough for much to turn up
c) start a new thread more exactly on this machine in a more appropriate sub-forum
Anyone got any other ideas?

Thanks again Wizard - much appreciated.
Can you help me understand why it would be inconvenient to use a this for PCB and small things?

I imagine in a club setting most PCB work would be small where a very accessible machine would make all the difference in the world. Mainly for registering the cutters properly especially after a board flip. Maybe I'm biased here as most examples of PCB machining seen on the net is done on small machines.

We have the space, the machine likely won't be that busy (judging by how busy the lasercutter is).

Which makes investing in the machine questionable.

I have no experience here so don't get some of the practicalities that may be obvious!

I look at it this way , if it won't be used much it might as well be easy to put out of the way. That is the appeal of a small PCB milling machine.

I am very concerned about that. Do you have any thoughts on how the mechanics of it might compare for milling aluminium with a Chinese 6040?

You will need to visually inspect this machine to get a feel for it. There just aren't enough references on the net to draw from. However as I said before if milling aluminum is so important I think you are making a mistake going with a light router type machine. Routers have their uses of course but from what you have said I can't imagine and light weight router doing the type of work you have implied. Sheet goods are likely not a problem, carving up blocks of aluminum might be. It really depends upon the structure of the machine.

With either machine I'm assuming we'd likely end up kitting it out with G540, good steppers and a Chinese 1.5kw spindle.

You might want to check out the axis motors, they could be servos.

These look like the 3 choices I can see so far for the frame/mechanics:
1) This Suregrave machine
2) A chinese 6040 body
3) A DIY fixed-gantry moving-bed (60cmx40cm working area) with some kind of heavy-duty gantry, maybe steel or cast-in-place epoxy granite.

Go the #3 route and you are sure to get a machine that will cut the mustard. Well that given that you have a team that can engineer the machine.

Does anyone have any ideas about existing design plans for such a DIY machine? The idea would be to try to focus on rigidity, for milling aluminium.

Seriously with so much focus on Aluminum you would likely be better off doing a CNC conversion of a bed mill. It would likely be cheaper with far less DIY in the build. A suitable machine would set you back someplace between $1500 and $2500 plus the controls.
Building a router isn't a bad idea, just that they are less versatile for milling aluminum or other materials. Again this depends somewhat on your groups interests. If you DIY the mill you can certainly design in the features and capacity you want but you have to take care. The X and Y aren't that bad but you need to be careful with the Z to be certain it can handle the torgues involved if you add lots of Z travel.

Inspect! Inspect! Inspect!
Really it is the only choice you have when it comes to non mainstream machines.
The only other thing I can suggest is to consider alternative machines or bump the budget to buy a more robust machine. Well that and watch for auctions and such.

Oh, and lastly, any ideas on how we can get a firm idea on the mechanics of the Suregrave, how it might handle aluminium.
So far I can only think of
a) try before we buy - not possible
b) searching factorydaily/Google - but this kind of machine is not common enough for much to turn up
c) start a new thread more exactly on this machine in a more appropriate sub-forum
Anyone got any other ideas?

We took the idea of a real mill seriously ... we're looking at a Bridgeport Series II CNC mill.
Are we mad? Can we afford repairs to the electronics on this?
I started a thread in the Bridegport section just for this:
http://www.factorydaily.com/forums/bridge...ml#post1327518 (Real cost of buying Bridgport Series II CNC)
thanks!

We took the idea of a real mill seriously ... we're looking at a Bridgeport Series II CNC mill.

Nice but older technology.

Are we mad? Can we afford repairs to the electronics on this?

This is up the club. If you pull it off such a mill would likely attract more members to the club long term. Doing a rebuild though involves all sorts of uncertainties which members of the club must buy into. More so proper parts for a Bridgeport rebuild aren't cheap.

I started a thread in the Bridegport section just for this:
http://www.factorydaily.com/forums/bridge...ml#post1327518 (Real cost of buying Bridgport Series II CNC)
thanks!

Your postings do seem to indicate a need for a mill. Buying a mill would make doing a CNC router a bit easier too.
In any event returning to your big question, are you mad? That is easy no, the desire have a CNC mill is not madness. However trying afford such a mill might be for your club.

We lost the auction, machine went for GBP £800 in the end.
We'll regroup and do some more proper research. Thanks for your help.

Bummer!
That is about $1200US or real money, not bad price actually. It does highlight to others that rebuild opportunities do exist for commercial grade mills.

We lost the auction, machine went for GBP £800 in the end.
We'll regroup and do some more proper research. Thanks for your help.

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