Hi All:
I am building a new mill from scratch, and will be converting a PM25MV when I can get one in.
I will be using high precision ball screws (hard to source reasonably off ebay), and I already have an adequate supply of SHS25 rails and blocks.
I will be using Parker servos series BE with J type encoders (2000 ppr). I will be running them using Parker Gemini GV U6E and GV U12E controllers.
Ultimately I might end up with as many as 8 axis on the scratch build, and maybe even eventually 8 axis on the PM25MV.
First off I must decide between the Klop/Kmotion setup or I am also considering a Galil DMC-4080 using CamSoft. Any other high performance suggestions? The second option is much more expensive. Naturally I expect this forum area to be partial to the Kflop, but any of you have much experience with Galil to compare?
Some general Gemini specs:
servo updates: 50 micro seconds
Velocity and torque modes: 12 bit +/- 10 V
Enable, Reset: 5-24VDC Selectable, 1/3 1/3 1/3 voltage switching threshold
Neg/Pos Limits 5-24VDC Selectable, 1/3 1/3 1/3 voltage switching threshold
User Fault 5-24VDC Selectable, 1/3 1/3 1/3 voltage switching threshold
Encoder 8 MHz Post Quadrature
Regarding wiring for the Gemini controllers for step & direction inputs, here is more info:
Gemini Step & Direction Inputs
The step & direction circuits on the Gemini are designed as RS422 differential. Because the inputs are not optically coupled, they cannot accept 24V, except with the GC-SDA adapter kit (described below). As with any single-ended signal, it is much more susceptible to noise when it is NOT differential. Parker recommends using a differential driver circuit.
To use with a 5V single-ended indexer/controller, do not connect anything to the Step- input. Connect the 0V or GND side of the indexer to Digital Ground. Connect the Step signal of your indexer to the Step+ of the Gemini. Use the same procedure for the Direction signals.
If you measure across the Step+ and Step- with nothing connected, you will measure a 2.5V difference. This is because the plus input has a 681 ohm pull-up resistor to +5V, and the minus input has both a pull-up and pull-down resistor. This allows it to accept either differential or single-ended signals. When wiring it with a single-ended input, a 5V signal on Step+ will be 2.5V above Step-, thereby registering as "High;" likewise, a 0V signal on Step+ will then be 2.5V below Step-, and will be seen as "Low."
It is possible to drive the Gemini with 24V Step-and-Direction inputs, using the GC-SDA I/O adaptor. This is a small, external PCB with user-selectable resistors that attaches to the Gemini's 50-pin I/O connector. It adapts the Gemini to +24vdc, +12vdc or any other voltage level. This is listed on the website as an accessory option for the Gemini. http://www.parkermotion.com/manuals/...-SDA_Guide.pdf
I was trying to decide between step-direction/cw-ccw modes or using torque mode? I think step-direct would be easier to establish, but I am thinking torque mode might perform better?
Here's this on Gemini update rates in a Torque Loop:
The Geminis (-U3E, -U6E, -U12E, -H20E) have a 62.5 micro-second update rate for the Torque Loop.
All the GV(6) drives have a 250 micro-second update rate for the Velocity and Position Loops.
The GV, GV6, GT, and GT6 all have I/O update rates of 1 ms.
Eventually the spindle and lathe axis might be run by velocity and absolute position servo motors.
So what dynomotion would will I need?
I am thinking that If I use step-direction then I might get by with just a kflop, but might still need another board for all the bells and whistles. But if I want to use the torque mode then I will need maybe a Kanalog or maybe a Konnect? Do you have any wiring suggestions?
Please comments/suggestions?