Thanks, I'm a previous machine tool designer so well aware of basic structures etc. quality etc. I was really trying to get an idea as detailed in my question. The trouble with buying second hand is you buy the problems that the seller gave to the product as well as those given by the manufacturer.
Looking at those three manufacturers I can see that the Bulkman suffers from poor quality aluminium extrusions and far too much Chinese equipment. I'm not sure what the quality issue with the other two manufacturers are, but any advice appreciated.
I agree completely that using a router is not the way to go. With our users I don't think we need to go to the spindle solution as our up-time will be tiny, so I suspect a milling head will do better but I'm happy to be convinced by someone who has real experience of them both.
Thank you for the three company suggestions, I'll dig into them. Space and access are at a premium in our space and everything needs to come through a normal front door and be reassembled without lifting equipment which makes some of these impossible.
The issue I have with the shapeoko is that it uses wheels on an aluminium extrusion, dust gets in there the wheels wear and the aluminum is soft.
In comparison, profiled linear rail has wipers to keep dust out and many lubricated ball bearings in the carriages to keep everything smooth and in perfect alignment.
Also belts can stretch and move and I feel its a little underbuilt in general. It is not a bad machine but I feel for the money there is better value to be had.
The onefinty is possibly ok but I am unconvinced its structure is the best, it has used oversized round rail as both structure and bearing surface which would be almost impossible to shim back straight if it needed it, at least it looks like there is dust sealed bearings etc.
The other thing is that it has no structure in the base, its relying on your bit of mdf or plywood as a base instead of metal frame, the base is where it gets much of its rigidity, so you need to build a really good bench for it which is extra money and time.
The other thing is the control unit which looks like an all in one chinese (see ali express) unit which are not very well regarded. You may be better of with a PC and UCCNC or Mach3/4 which is how many systems are run.
For some context, my machine which I bought second hand is made from 90mm by 45mm aluminium extrusion and the gantry is 2 bits of this bolted together with 20mm tooling plate ends, I think I could stand on the gantry with no issue. I would not stand on a shapeoko.
The reason I recommend the water cooled spindle is because they are made to a higher tolerance than routers and are much smoother and quieter in operation, there are aircooled versions too. Make sure your milling motor will go fast enough as small bits want to go fast.
I was not specifically suggesting those companies but those types of machine, many will be the same under different names. The Denford machine is the exeption and probably costs at least £12k to buy a new one.
Avid cnc is a company that do a sort of modular system where you can upgrade and expand as you go. Stoney CNC have a range of decent machines so you can compare specs and why some are more expensive etc.
It can be a minefield but I am sure you can find something good.
Olie
