Don't hit me - I'm a newbie!

I'm an amateur electric guitar builder and want to get into CNC surface routing/engraving for designs on the front of guitars - solid wood, maple, mahogany, etc. of dimensions 450mm x 350mm x 10mm maximum - but these carved tops are often split down the middle and I can probably move and clamp the wood pieces along the long axis - so can get away with a 300mm x 200mm table operation area. I don't want to spend a lot of money on a machine only to find I don't often use it or don't like the results.
And I've always been an open-source advocate from way back - yes I'm quite old. I currently run Mageia 4 as my OS - so if I use LinuxCNC I will probably have to compile it myself, dual boot Ubuntu or use a dedicated PC.

So here is where you don't hit me - there are any number of 3 axis CNC 3020T Desktop Router/Engraving/Drilling/Milling machines on the UK Ebay site. They all look more or less the same and cost around £350 including Mach3 software. Are they any good - for my type of use?
I'm not a newbie workshop operator having both bench-top lathe and milling machines in my workshop - so I understand about what you can and can't do with mini machines.
Question 2. All these machines use a parallel port for communication - so despite the machine looking modern, they are using old communication technology - will this be a problem in using LinuxCNC?
Question 3. You can get Parallel Port-to-USB conversion cables - might this be the way to go to avoid needing a parallel port on the motherboard or a Parallel Port card?

ok just a brief outline to cover , as i'm away for a few hours, and will not be home for a while .
but thought i'd cover a few points

those cnc routers are really only for light work , and no good at all for serious wood that you need , they just are not sturdy enough
the boards you mention are a waste of time for what you need and expensive for what you get
USB is not supported in linuxcnc , because of the way it works , this is well documented around the forum and always pops up
USB to parallel port adapter are only for printers , and not for realtime communication , won't and will never work .
also Laptops far poorly with linuxcnc . so use a full desktop and a pci parallel port card

their is a full live cd available see the news pages down the left side for details

however for an alternative look at Mesanet.com at the 5i25/7i76 combination , far superior to a parallel port
their is also a ethernet adapter for small machines using a parallel port thats easily built , so thats an option

i have plans for a diy router that will just about fit the bill for you details by email if you wish
you need to build strong or mechanical issues will ruin everything you try to do
it needs to be aluminium or steel , these wood built ones are again useless for the forces you will be dealing with
though they are fine for thin plastics and balsa , that they were origionaly designed for

and happy to help you sort it all out and get through the maze , without falling into the many traps .

by all means email me direct .

Thankyou cncbasher for your information. I thought as much regarding the parallel port issue - but am interested from a technical point of view why CNC is still using an old technology - can you enlighten me? Surely modern fast serial communication can cope with real-time communication. I do a lot of guitar recording to my PC via a USB Audio I/O unit and I have no problems with real-time latency even with this wide frequency bandwidth operation. I'm not saying its wrong - but am very interested in why parallel comms is used.
The machines on ebay (I've attached a photo of a typical one) are made of aluminium and videos of their use show them making decent 3D images in aluminium. If you want to cast your experienced eye over these machines - one is at:
www.ebay.co.uk/itm/CNC-3020T-Router-Engr...?hash=item35edbd444e

LinuxCNC's architecture locates all the complicated real time functions in the host PC
this requires bidirectional real time communication with the I/O device(s) and standard
LinuxCNC does not work with buffered devices for motion control.

Parallel ports are still commonly used with LinuxCNC because they are inexpensive and _can_
do real time I/O

Real time I/O is much more difficult with USB (at least a working reliable real time open source
USB driver has not been demonstrated)
This means that currently all USB CNC interfaces are buffered and do not work with LinuxCNC.

LinuxCNCs real time architecture has some advantages compared to the buffered architecture
used in other CNC control systems (like Mach4 for example)

Advantages of LinuxCNC's architecture:

Almost all control resides in host, so any improvements in the control software become
available to all systems regardless of I/O hardware.

The software/hardware environment for control development is excellent:
hardware has nearly unlimited memory, speed and fast floating point, on the software side
almost any language is available, plus LinuxCNC is open source so all
of the control is available for examination and improvement.

Having most of the control run in real time means a simpler
control model compared to buffered systems.


Note that your USB audio devices are _buffered_ devices, and not capable of real time I/O.
They may have delays in the couple of ms region but this is too slow for LinuxCNC

Thanks PCW - exactly the answer I was looking for - all makes sense now.