Centroid CNC4

forhire wrote:

andypugh wrote:

Do you know what your current peak step rate is? You can work it out from the current rapid rate, gear ratios and leadscrew pitch.
You can then see how close you will end up to the limit with a 50uS base-thread rate.
Example calculation: 30ipm rapid rate, 4tpi screws, 1:1 gears and x4 microstepping:
30ipm = 0.5 in/sec. = 2 rev/sec = 2 x 200 x 4 steps/sec = 1600 Hz = 625uS/step. In this case a 50uS base thread is fine.

The manual states it does 120ipm rapid. It moves pretty quick but I've never measured it to see if it's truely reaching that speed. Ball screws are 5tpi with 1:1 gears and x8 microstepping. I follow the math all the way until the conversion of Hz to uS/step. At 1:1 it's 16000Hz and 1:2 it would be 32000Hz.

You want "a few" base threads per step ideally, otherwise you end up trying to make huge instantaneous speed jumps from 3 to 2 periods per step, then from 2 to 1.

I assume this is a ramp up to speed or soft start/stop type thing? Does the software handle this or the driver? I'm thinking the G203V is the driver I'll use.

Should I expect the machine to do ok? Or should I look for something with less jitter?
I would suck it and see. I can't remember if you were planning to use an external step generator (Pico or Mesa). It will be perfectly OK if you are.

I can't really imagine sending all the steps out an lpt port using software stepping. I'm planning on using a step generator like the Pico Universal Stepper Controller. With that I offload the work and pick up all my required I/O at the same time. Am I on the right track?

BigJohnT wrote:

On an axis page I put
200 steps per revolution
10 microstepping
1:2 pulley
4 leadscrew pitch
1.25 in/s maximum velocity

This is nearly perfect except my screw is 5 tpi and my target is 120 ipm rapid. Of course I'm currently running 1:1... so when I go to 1:2 my rapid will be half on my current control. Still should work... I'm not too worried about rapid speed... it's not like I cut at 120 ipm. Ideally, I'm cutting not bouncing around using rapid. [/quote]

forhire wrote:

andypugh wrote:

Do you know what your current peak step rate is? You can work it out from the current rapid rate, gear ratios and leadscrew pitch.
You can then see how close you will end up to the limit with a 50uS base-thread rate.
Example calculation: 30ipm rapid rate, 4tpi screws, 1:1 gears and x4 microstepping:
30ipm = 0.5 in/sec. = 2 rev/sec = 2 x 200 x 4 steps/sec = 1600 Hz = 625uS/step. In this case a 50uS base thread is fine.

The manual states it does 120ipm rapid. It moves pretty quick but I've never measured it to see if it's truely reaching that speed. Ball screws are 5tpi with 1:1 gears and x8 microstepping. I follow the math all the way until the conversion of Hz to uS/step. At 1:1 it's 16000Hz and 1:2 it would be 32000Hz.

You want "a few" base threads per step ideally, otherwise you end up trying to make huge instantaneous speed jumps from 3 to 2 periods per step, then from 2 to 1.

I assume this is a ramp up to speed or soft start/stop type thing? Does the software handle this or the driver? I'm thinking the G203V is the driver I'll use.

Should I expect the machine to do ok? Or should I look for something with less jitter?
I would suck it and see. I can't remember if you were planning to use an external step generator (Pico or Mesa). It will be perfectly OK if you are.

I can't really imagine sending all the steps out an lpt port using software stepping. I'm planning on using a step generator like the Pico Universal Stepper Controller. With that I offload the work and pick up all my required I/O at the same time. Am I on the right track?

BigJohnT wrote:

On an axis page I put
200 steps per revolution
10 microstepping
1:2 pulley
4 leadscrew pitch
1.25 in/s maximum velocity

This is nearly perfect except my screw is 5 tpi and my target is 120 ipm rapid. Of course I'm currently running 1:1... so when I go to 1:2 my rapid will be half on my current control. Still should work... I'm not too worried about rapid speed... it's not like I cut at 120 ipm. Ideally, I'm cutting not bouncing around using rapid. [/quote]

forhire wrote:

andypugh wrote:

tpwjayson wrote:

I was planning on using a USB to serial adapter to connect. Anyone had any luck using one of these?

USB breaks realtime.

However, it _might_ not matter if what you are doing is sending a stream of motion commands, and the motion planning and control is done by the existing controller.

What do you intend sending on the serial line, in what format, to what part of the system?

tpwjayson, you understand that the cnc4 has a control system built in that you can access via serial terminal? You can use a usb to serial adapter and any serial terminal you wish. Default settings are 9600/8N1. You can drip feed commands line by line using option 4 on the control menu. I use gtkterm and did a 1.2 meg file yesterday using this method. If you choose to use gtkterm you'll need version 0.99.6 as 0.99.5-1 that comes bundled with ubuntu is broken.

Does emc2 have a serial dnc mode?

So I have everything all hooked up now. Not really sure if I am doing everything correctly. Using option 4 do I have to type each line as I go? I cant figure out how to send a complete file to the controller.