Slaving axis (rotating nut, 2 steppers for Y-axis)

Hello,
sorry for the late reply, but was planning the frame and today i was buying the CRS tubings.

Todd, that was how i thought about it, but i mean how the closed loop of both motors works for one axis. I mean if the one motor looses steps. Are in Linuxcnc some settings for the usage of 2 closed loops on one axis, so that the whole axis stops even if only one motor looses steps?

@andypugh: Looks really interesting your build. Could you tell me why you use rotating nut on an Milling machine ? I mean, rotating nut are used for long axis to have not the problem with whipping ball screws, but what advantages it gives you on a milling machine ?

Guys, i have an question about brakeout boards:
Of course i have to think how i spend my money to build an good, but not too expensive cnc router (upgrades i can always do later), so e.g. i thought to not buy the expensive hiwin rails and buy and also some parts form Aliexpress etc... Now, because i decided to buy the Leadshine easy servo motors, i thought to not buy the Mesa cards (345€ inc. shipping) but to buy TWO cheaper brakeout boards. Now my question is, if that makes it much more difficult than using ONE brakeout board like e.g. the Mesa 7i76 ?
This is the brakeout board i am talking about: www.ebmia.pl/plyta-glowna-sterowania-sskmb2-p-42777.html
Unfortunately the description is only in Polish, but this brakeout boards are not some china stuff and are tested with good reviews. The problem is, that on one brakeout board is for 4 axis, what of course would be enough for 4 motors, but later i would like to use an 5. axis and also i think there are not enough connections for 4 x home switches + 4 x Limit switches. Two of this cards would cost me 45 € instead of 345€ for Mesa, but i dont want go the cheap way and be later not satisfied or that i will not manage to get it to work.

Is it something very difficult to setup ? The CNC router will be not for production use, at least not in the first year, so i think you can understand that i try to save some money and like i wrote already - upgrades i can always do in future. Also someone told me that the Mesa cards are really good, but he uses a cheap board (on LinuxCNC) and is satisfied, so he thinks it will not make such an big difference in hobby usage.

Before i forgot (wanted to write it already in my last post): You guys are really helpful. Thanks for that and i hope you are there when it start to become serious

*Tried to install 2.8 Pre Master Branch on my laptop (where i have rly bad jitter) just for tests, but its not so easy, or i have made something really wrong, because when i start LinuxCNC it shows 2.70 and then it crashes with some error.(dont have the error message now, but if someone is interested to see it, then i can post it later)
I think on tomorrow i will try it on the computer which i want to use for CNC, just need to put my VGA inside the computer.

Have a nice evening and thanks in advance!

BR,
Denis

I think the size of your machine justifies the use of Mesa Hardware. I have almost finished building a plasma table with the 7i76e and it really has been great to work with once you get past the OS prerequisites to run ethernet. Its taken me almost 12 months. Today I'm wiring up a 6 axis remote pendant that uses one of the two MPG encoder inputs. It needs 2 inputs for the scale select and 3 inputs for the axis select. Even at this late stage in the build, I still have enough inputs and can also add another encoder with axis and scale selects on the operator console if I want to. If you want to add a warning light or something like that you can as you are not constrained by the number of I/O ports.

The Mesa stepgens get double the speed I was hoping for based on playing with steppers before I started this build. I am also running separate home and limit switches on every axis (except the upper Z uses a shared home/limit switch due to space constraints.

Not to mention I have virtually unlimited expandability just by adding daughter cards..

Thanks for the explanation Andy!

@rodw: Then, maybe i should go for the Mesa cards...

Maybe i do understand something wrong, but it took you 12 month to get the 7i76e to run ? i hope i understand it wrong...

I want to use the standard 7i76 + 5i25 with Leadshine easy servo steppers and drivers and i am not sure how difficult it will be but i cant believe it will take that long..., also because there are some tutorials out for the Mesa setup.

Again, like you are saying, there are some very useful advantages of the Mesa cards, but unfortunately the price for both cards is pretty high here in EU.

Thanks Tommy.

But, should i go for the ethernet version or the standard 7i76 for an cnc router (which maybe will be also used as an plasma cutter in future) ?

thanks in advance!

@Andy: That are good news and thanks again for the explanation!

Yes, i have couple available PCI ports on my MB (M4A88TD-V EVO/USB3), so i think i will spend the 345€ for the both mesa cards (5i25 + 7i76). Maybe its better to not save money on that parts.