Comparing two CNC usb PIC based DIY solutions

[PaulMakesThings]

I'd add in PDQ incase that's not enough 3 letter acronyms for you, but actually I have plenty of time on this. As the title says I'm looking existing project descriptions for PIC based CNC controllers with usb interfaces, they even both use the 18F4550. They each have their own propreitary software as well.

Theres CNC USB
http://www.planet-cnc.com/
The diagram is there for free, it has software that runs the G-code and it outputs the signal for a driver board. I'm not sure if the software is able to run a machine with the free version, the site only says that it will let you preview machine paths. Its not explicit as to weather it can drive a machine or not with the free version. I don't really want to build the board just to find out. If anyone has used this please give me your input.

and theres this USB to Parallel adapter
http://www.mycncuk.com/forums/showth...-DIY-Interface
But if you scroll down you'll see that they actually have their own software as well, so it isnt just an adapter, its more of a CNC controller with a parallel plug for an output to the driver. This software does appear to be free.

So Id apriciate any input on which of these projects I should follow, as well as any advice to the project of building and running ones own PIC based USB cnc machine.

I'm also considering just getting a paralelle port card for my computer and making one of the hundreds of projects that uses a PIC to controll a CNC machine off of that. But that wouldent make the machine as portable as I would like (its a tiney CNC mill)

[eSilviu]

http://www.mycncuk.com/forums/showth...-DIY-Interface it's a dead project (dead for about 2 years by now). It only knows G00 and G01, and has a few other small bugs (I have use-it in the past).

http://www.planet-cnc.com/ it's an active project, relatively new (about 1 year), and works very good (I'm using it now)

I recommend the second one.

or maybe...www.usbcnc.com, but this one is not so cheap (180EUR without VAT)

[PaulMakesThings]

Thanks, thats the kind of input I'm looking for. It's too bad none of these groups give their projects distinctive names, they're all called "cnc usb" or "usb cnc". But anyway. Do you know if the one at planet CNC can run a machine with the freeware version? I would certainly licence it before doing anything commercial, but for now I'm still seeing if I can make the machine run at all.

[eSilviu]

Originally Posted by PaulMakesThings Thanks, thats the kind of input I'm looking for. It's too bad none of these groups give their projects distinctive names, they're all called "cnc usb" or "usb cnc". But anyway. Do you know if the one at planet CNC can run a machine with the freeware version? I would certainly licence it before doing anything commercial, but for now I'm still seeing if I can make the machine run at all.

It will do only 25 g-code lines if it's not registered.
Enough for testing any commands you want.

[PaulMakesThings]

That would be enough to test with. on the other hand I would be stuck with that software if I built that controll board, or atleast I would have to program my own for their controll board if I wanted to go another way. Maybe the best way would just be to use a USB to Parallele adapter so I can use a wide range of existing software. I just dont want to go the route of installing a parallel card because then I could never use the machine with a laptop or a computer at school that didn't have a parallel port. I've noticed lots of discussion on USB to Parallel adapters, I could probably find on that works. I still plan to do a DIY PIC based project either way though.

[eSilviu]

Originally Posted by PaulMakesThings That would be enough to test with. on the other hand I would be stuck with that software if I built that controll board, or atleast I would have to program my own for their controll board if I wanted to go another way. Maybe the best way would just be to use a USB to Parallele adapter so I can use a wide range of existing software. I just dont want to go the route of installing a parallel card because then I could never use the machine with a laptop or a computer at school that didn't have a parallel port. I've noticed lots of discussion on USB to Parallel adapters, I could probably find on that works. I still plan to do a DIY PIC based project either way though.

I have used (some long time ago) a new PC + KCAM4, on the parallel port.
It was sluggish, it loosed steps, and used CPU at almost 100%.
Whem I've switch to (USB cncdudez), on the same hardware CNC + the same computer, I allmost doubled the speed, CNC runned smooth, and I never loosed steps.
Since I was using the same PC to desing the components, I couldn't use turbocnc (on the real DOS), or linux EMC with realtime.
You will be dissapointed when (with a 2GHz CPU) you will hear interrups (produced by antivirus, or any other software or driver that run on the computer) in steppers movements...

I's simple to put a PIC18F4550 + a few resistors, and test the software. A prototyping board will do the job as good as any other.

[PaulMakesThings]

Isn't the CNCDudez software free anyway? It may be a dead project, but if it works it shouldent really matter.

Did you mean that it gets interrupted with the USB also, or only without it? Actually I'm forgetting that this still has the problem of proprietary software. It would be preferable to be able to use all the existing stuff thats out there, Mach 3 and the like. But aparently those all don't work with USB directly, or atleast I would need to write my own drivers, which I don't know how to do. I'm good with C++, but I haven't written USB drivers or drivers for CNC software.

Do you think a USB-Parallel adapter could be a good soloution? For all I know I could be wrong about most CNC software not being USB ready, or a number of other things.

[eSilviu]

Originally Posted by PaulMakesThings 1.Isn't the CNCDudez software free anyway? It may be a dead project, but if it works it shouldent really matter. 2.Did you mean that it gets interrupted with the USB also, or only without it? Actually I'm forgetting that this still has the problem of proprietary software. 3.It would be preferable to be able to use all the existing stuff thats out there, Mach 3 and the like. But aparently those all don't work with USB directly, or atleast I would need to write my own drivers, which I don't know how to do. I'm good with C++, but I haven't written USB drivers or drivers for CNC software. 4.Do you think a USB-Parallel adapter could be a good soloution? For all I know I could be wrong about most CNC software not being USB ready, or a number of other things.

1. see here the list of bugs: http://www.cnczone.com/forums/showpo...0&postcount=86
2. with USB you will det no interrups in NCNC processing.
3. If you can write a driver... but there has been others that tried, and... nothing.
I saw many users prefere Mach. I can't give my opinion, since I've never use-it properly.
4. NONE of the USB-parallel port adaptor will ever work! Conversion is made in software, with a driver that is not real-time.

[PaulMakesThings]

Thanks for all the info. It doesn't sound like I want to go with the CNCdudez one. There are always compromizes to be made. Since this is a minature machine and I'm a student I want it to be portable so I can show it to people and use it in different places, and that logically leads to USB. I just don't like the idea of using something that can only work with one software package that I can't modify. If a cool new feature comes out in some other package I cant switch, and I can't add new features myself. I could concievably make my own software, but that would be a whole big thing that I don't want to even think about right now.

The reason I want to use a PIC is so I can build and modify the controller and driver myself. Any microcontroller could do that, but PICs are the ones I have the knowledge tools and equipment to use.

Just to give you an idea of my goals for this project, it isn't just to make a CNC machine, if that were my goal I could buy a controll system. I wan't to understand and work with the technology. Getting up and running with purchased software would be a good start, but at the same time I feel a bit wary of spending $100 for software that I'm going to use temporarily. But hey, why not build a controller board and use the limited free version for now while I figure that all out. The driver boards I make should work with other solutions either way.

[Hamish911]

I've compiled a small table of usb controllers on my website.
You may find it usefull.

[Larken]

What features and performance ?
Do you want a board that just runs one line at a time, or smoother continuous feed ?

None of these boards can run anywhere near as smooth or fast as Mach3.

The USBCNC (eding_cnc) one costs more because it is a lot more advanced and supports a big list of Gcodes including G41,G42 cutter offsets.
http://www.edingcnc.com/index.php?taalid=2
So if you spend a bit more you get a lot more.

[eSilviu]

Originally Posted by Larken What features and performance ? Do you want a board that just runs one line at a time, or smoother continuous feed ? None of these boards can run anywhere near as smooth or fast as Mach3. The USBCNC (eding_cnc) one costs more because it is a lot more advanced and supports a big list of Gcodes including G41,G42 cutter offsets. http://www.edingcnc.com/index.php?taalid=2 So if you spend a bit more you get a lot more.

Both "USBCNC" anc "CNC USB Controller" does support "lookahead" feature. So it will run as smooth as possible.

Mach3 will run smooth only with SmoothStepper, because it's not based on hardware interrupts from parallel port.