Encoders

Good evening...
not sure where to start here. but let me give some background.
I am building a complete DIY CNC mill, not a CNC router, so I am using DMM's largest AC servo as a spindle motor (1.8Kw) with the Dyne 4 driver. for my axis motors I am using Teknic servos using step and direction. forgive me for being on a budget (in certain areas) but I am using Chinese linear rails and ballscrews (C7 grade). after the build I am getting OK results but not where I would like to be. I am using a CNC4PC C11G breakout board to control everything. I used a linear encoder from my lathe to map my axis' and am using the screw comp on each axis. even with screw comp I am getting +/- 0.003" accuracy. IMHO thats not bad for complete scratch built. but that being the case I still want to look at using the same linear encoders on each axis and patching that into linux using a second parallel port.

I am not a the point yet that I can purchase a mesa card or something similar. right now I am looking to see if it is even feasible to do what I want with what I have.

So here is the question;
Can I use linear encoders (TTL) on each axis and feed that into Linux on a second paraport to give real time position info?

(as a side note, I am fairly new to alot of this so 3rd grader talk as much as possible would be appreciated)

For anyone who is interested here is a build album on google photos: photos.app.goo.gl/T8qGS1b2s8TRNwRR8

I second what tommylight said. That is a nice machine and I would also recommend some Mesa cards. I'm using the same servo motor and drive for my spindle. I drive the servo from a 7i83 connected to my 6i25+7i76 combo.. My mill uses steppers on the XYZ.

Damn,, that is a nice machine !
The usual A/B/Index linear encoders can be used through a parallel port, but it will limit the maximum velocity a lot. Parallel port can do anything from 10000 to 50000 counts per second, if you are very lucky in choosing the mainboard, most can do around 20000. Linuxcnc is also capable of using two feedback devices for each axis, in case the drives have encoder outputs.
Have a look at Mesa 7i76E and mos probably something like 7i85 (not sure what version), the investment is very well worth it. Or check if the drives can be controlled by +-10V analogue and get the 7i77 with one of the following: 5i25 (PCI) or 6i25 (PCI-E) or 7i92 (ETH). There are also some new all in one solutions from Mesa, but PCW is the expert, so you might want to wait for him to reply.
Again, that is a way to good of a machine to be held back by parallel port.

I understand and its my plan to upgrade to upgrade to mesa system, i am just wanting to know if its possible to do what I want with what I have. Trust me I would love to upgrade everything to that system because I hear its bees knees... im just not there yet. and from the little I have looked into it I am a little nervous about working with that system as there are alot of things I am unfamiliar with that their manual talks about so it seems there is a steep learning curve.

I second what tommylight said. That is a nice machine and I would also recommend some Mesa cards. I'm using the same servo motor and drive for my spindle. I drive the servo from a 7i83 connected to my 6i25+7i76 combo.. My mill uses steppers on the XYZ.

Tommy,
I would love to see it. one thing I dont understand about the mesa system is that you need more than just the PCI card (5i25/6i25) and the daughter board. I figured it would have had everything you needed on those two. but from what you are saying you need the 7i83 as well. this is what make me nervous as it doesnt seem very intuitive as to what you need to get in order for the system to work

As a quick sanity check, how big is one step with your chosen step-per-rev scale?

before or after the screw comp files is applied?

right now I have the ClearPath servos set at 800 pul/rev, balls screw is 5mm pitch, so that gives me 4064 pul/in but I didnt sanity check that, its just the math.

For a s simple step/dir system with linear encoders and mesa hardware, I would use
a 7I96 +7I85 or 7I85S