Suggestions for starter machine to learn linuxcnc and for lightweight projects

New to cnc and new to the forum.  Hello!

I have many old pc's and experience in linux and freecad.   I would like a starter machine that can see me through establishing a FOSS toolchain to get a few projects done and still be servicable for light jobs when I inevitably graduate to more capeable machines.    The software skills I learn along the way are the real goal and it is of primary importance that the toolchain be usable for the more capeable machines iin the future.

What do I want to do with this machine?  Besides learn linuxcnc, I would like a starter machine that can:

1. Carve wood trays.   No aluminum.   Workspace minimum size :  20" x 11" x 3"
2. Carve foam.

I understand that, bed size aside, nearly any cheap machines will work for the above if I am ambivalent to the software that runs it.   Thing is, I am here to learn linuxcnc and I will not stoop to using any watered down or proprietary software.   If freecad and linuxcnc cannot be the backbone of my toolchain, then I want to know that at the start.

I am prepared to buy a ~$600 desktop cnc, add $400 in add-ons, strip the control system (preferable non-destructably), wire it up to fresh drivers and power supplies, hook it all up an old PC's paralle port and start the learning process.   Thing is, I can just see me not having enough parallel port input pins, or incompatible such and such, so I figured I should just ask those with experience if what I want is as elusive as it seems.     I want the power of linuxcnc in a weak, but servicable, machine that will handle my first few projects without costs ballooning past hobby cnc levels.  Is this possible? 

   


 

CNC is expensive, there is no getting around that. Costs balloon, ideas change. And as was said in Snatch by Boris 'The Blade' Yurinov "Heavy is good, heavy is reliable. If it doesn't work you can always hit them with it." Not sure who'd you'd need to hit, maybe yourself at times during the project.

FreeCAD does work but there is a steep learning curve with the Path workbench, but that's no different to any other CAM package.

A parallel port will easily drive 4 axis (assuming 4 for a gantry router), 5 inputs and 4 extra outputs. Add a second parallel port and you can get 12 inputs & 5 outputs.

Now what you need to do is find a PC with a built in Parallel Port, Lenovo ThinkCentres have them but require a proprietary cable eg M72e Tower (which are quite good with an i5). Buying PCie Parallel port cards is a bit of a pick & mix. A lot of new users have issues setting them up.
Now for a little extra a good starting point is a Mesa 7i92 or 7i92T (different FPGA but functionally the same).
Benefits are:
1 Latency constraints arent as stringent as for a Parallel Port based system. As no base thread is required.
2 Ethernet connection, so transferring to another PC is easy as plugging in an Ethernet Port.
3 To begin with can be used with 2 generic Parallel Port break out boards.
4 Later on you can if needed\wanted\can do it without your better half noticing expand your system with other Mesa cards, the 7i73 makes for the basis for an awesome pendant without relying on any USB based ones.
5 The size of the PC can be well physically smaller (if that's an issue)
6 Pete from Mesa give great support, that great of support that he is willing to assist in using Mesa firmware on non Mesa projects. I owe him many thanks.
7 Depending on how many PCie (or PCI) Parallel Port cards you have to try, the cost could be similar to a 7i92.

And yes I am using a Mesa 7i92, along with a number other Mesa products in my 3 Axis mill. You will hear a lot of people recommending Mesa products, this isn't a "fanboy" situation, its because they work reliably, are well supported and an established company. Tommylight builds Plasma cutters for others in the industry and swears buy Mesa products. Rodw is another who uses them in a commercial situation, and untold hobbyists use them successfully as well.
Now you might see some other projects floating around, I wont mention remora as that is not in this category as that project is geared towards reflashing commercial products to work with Linuxcnc. Having tried some of the other projects and developed my own Mesa based board here are my thoughts.
1 To begin they seem a cheaper option, until you start to think about the electrical interface to the cnc machine, eg level shifting from 3.3 to 5v and back. Can get a little more complicated if you want to go with 12 - 24v signalling.
2 Rarely does the designer develop the above.
3 You are at the mercy of the interest of the developer and how far they want to take it.
4 Some of the hardware it's based on can be difficult to get as time goes one, or the sellers change the hardware and you can left with a piece of hardware that isn't suitable.
5 Getting the development environment together can be tricky.
6 Extra hardware need purchasing to program the devices in most cases.
7 The Linuxcnc drivers are not part of the main tree and need to be built by the end user.
8 Some may need reflashing to change their config, up to a point Mesa products can be configured at run time within the constraints of the firmware.
9 If you ask nicely Pete from Mesa will rebuild to suit your card and situation and no special hardware is required to do the job of uploading new firmware.
10 As these project are being developed new issue expose themselves, so unless you are really interested in a project and want to "get your hands dirty" it can be frustrating. They are fun to be involved in and I tip my hat to the developers, but I'm a curious guy.

So there you have it.
Yes Parallel Port systems are possible, find the right PC that has suitable latency can be frustrating, even same model PCs can give different users different results. Finding the right cards can be a lucky dip, depending on what the vendor sends. The Big Brand cards can be almost the same price as Mesa 7i92.
Oh yeah once you've done your budget on building your machine then the biggest expense is just around the corner...tooling.

Now if you just want to carve wood trays a router and modular jigs would do the job, not every answer is cnc .

No matter which way you jump you'll get lots of help.