DDSCV1.1 3 and 4 axis offline motion controller

[Boyan Silyavski]

I discovered that i have a problem with small carvings and very fine details. I tried 2 times to carve a stamp from aluminum ~30mm diameter, X and Y started slowly to loose position. Lowered the acceleration from 3000 to 1000, did a dry run also.

Same problem persists. .


Now the question is: the controller??? or the servos need further tuning??? or i have to slow further things down, which i dont believe is the case. I remember i bumped up servos quite much to be responsive via software and even 3000 accelerations and more than 10000 mm/m speeds on objects like 200x200cm there was no problem at all. Checked initially the machine, does not seem to have sth loose.


Any ideas??? Could that be the small lines? Exported v carving file as arcs also, same again. Thinking about it it looses both X and Y and moves slowly in diagonal on every step down of the Z is visible. At the end of tool path controller shows same machine coordinates as on start 0.

Should i try to find the look ahead in the controller and make it bigger, i was thinking of disabling drawing the tool paths?


i don know what exactly to do now except bump more the servo response and see what happens

[JAZZCNC]

Now the question is: the controller??? or the servos need further tuning???

If there is option to change Step edge ie: Active hi/lo then try this. You could be on the wrong side of the edge in which case you'll lose 1 pulse for every direction change.?

[Merlin201314]

In the controller, in the last part of the machine parameter you can fond the "interpolation period", set it up at 0,005 and try it, change even the "screen refresh" at not less than 4000, otherwise the screen will slow the cpu, as it not equipped with a graphic card.(you don't need to watch the screen, watch the machine).

Find even the "operating acceleration" parameter and set it up at 500mm is the diagonal interpolated acceleration try it and find a reasonable one for your machine.
Is just a bit of thing to try, maybe it won't help you, but it worth try.....

If you have servos, they are coming with resolver on the back, so your motors know exactly where and when they are at all time.
So, even with strong acceleration they shouldn't loose position... Here the problem: is your Router ridgid enough? Because with long traveling and strong accelerations the structure has the time to stabilize in between the movment, with very short traveling the machine is going into a factor called "structural resonance" and "inverted motion", what that mean? It mean that the axis is called to travel in a direction, but due to acceleration and mass involved the underneath structure is going in the opposite direction, and in a very small piece this factor is noticeable, even more when you are carving aluminium rather than wood, thats why the milling machines are heavy, especially CNC centers. Another thing to check is the connections between the motors and the ballscrews.... check all the mechanic parts first, as per very small pieces and high acceleration you are going to join another world with a high inversion rate, is called "jerk"
A router is a router, and as much as you like it, is shaking and flexible under high torque.....
I would suggest you to lower the acceleration to 300/500mm Min and look if the problem is persistent before retuning all the motors and blame them or the controller.

Regards

[Boyan Silyavski]

If there is option to change Step edge ie: Active hi/lo then try this. You could be on the wrong side of the edge in which case you'll lose 1 pulse for every direction change.?

I always forget about that one, but as far as i remember was correctly set to work with normal BOB. I will now check again. In controller could not find a way to change that. I know where to change that in the servos. Will have to read the manual again though.

PS. alright, there is that in the controller, i found it. will try it later

In the controller, in the last part of the machine parameter you can fond the "interpolation period", set it up at 0,005 and try it, change even the "screen refresh" at not less than 4000, otherwise the screen will slow the cpu, as it not equipped with a graphic card.(you don't need to watch the screen, watch the machine).

Find even the "operating acceleration" parameter and set it up at 500mm is the diagonal interpolated acceleration try it and find a reasonable one for your machine.
Is just a bit of thing to try, maybe it won't help you, but it worth try.....

If you have servos, they are coming with resolver on the back, so your motors know exactly where and when they are at all time.
So, even with strong acceleration they shouldn't loose position... Here the problem: is your Router ridgid enough? Because with long traveling and strong accelerations the structure has the time to stabilize in between the movment, with very short traveling the machine is going into a factor called "structural resonance" and "inverted motion", what that mean? It mean that the axis is called to travel in a direction, but due to acceleration and mass involved the underneath structure is going in the opposite direction, and in a very small piece this factor is noticeable, even more when you are carving aluminium rather than wood, thats why the milling machines are heavy, especially CNC centers. Another thing to check is the connections between the motors and the ballscrews.... check all the mechanic parts first, as per very small pieces and high acceleration you are going to join another world with a high inversion rate, is called "jerk"
A router is a router, and as much as you like it, is shaking and flexible under high torque.....
I would suggest you to lower the acceleration to 300/500mm Min and look if the problem is persistent before retuning all the motors and blame them or the controller.

Regards

Machine is quite rigid, servos are more or less quite accurately calculated, so actually they are not over sized for the machine but exactly sized. I had some under and overshooting before, but i raised quite much the snappiness of it all.

I started now changing things here. I did that just before reading what you said, but more or less i deducted the same. I lowered panel response time to 1000, raised read lines / not shown here in manual/ to max 3600. Which i assume is the read ahead? and lowered interpolation time to 0.002 , which should give much tighter corners or will lower mechanical resolution? its not clear what they want to say. Just testing it now. If not ok 0.002 i will raise it to 0.01 to see what happens

[Boyan Silyavski]

Ok. The changes did not work so i reset all back to normal. after all if the controller is capable of 400kz per axis i dont see what the problem could be from secondary details like display and so on.


First i took a look at my drive and motor timing specs and compared with the timing of the controller. Results that this controller is really high spec and the servos must not have any problem with the default setting:




So far so good. I include the above line of thoughts just for the sake if somebody needs to understand whats happening with his setup.

Again back to what Dean said, about the pulse. looking at the table below it seemed i should not have had a problem as both in the controller and drives was set to high / step pulse/ . Changed the controller pulse to low and now its working fine. Thanks Dean!





Though i still not get why on controller Z is set differently than X and Y as default? No i have to think of a way to check the correctness of Z . Problem seems to be as till now i had done files where Z has no more than 5 steps, so may be thats why i had not seen the problem. I dont know if it counts that the CAM makes the Z oscillate on the toolpath, i think that counts a a change, so it seems better not touch anything for now.

[JAZZCNC]

Again back to what Dean said, about the pulse. looking at the table below it seemed i should not have had a problem as both in the controller and drives was set to high / step pulse/ . Changed the controller pulse to low and now its working fine. Thanks Dean!

Your Welcome and it catches lots of people out. Seen people replace drives and motors because of it.
The problem I've encountered often is that while the Manual says one thing the switches on the drives are set opposite and this is probably the case here.?

Though i still not get why on controller Z is set differently than X and Y as default? No i have to think of a way to check the correctness of Z . Problem seems to be as till now i had done files where Z has no more than 5 steps, so may be thats why i had not seen the problem. I dont know if it counts that the CAM makes the Z oscillate on the toolpath, i think that counts a a change, so it seems better not touch anything for now.

Not quite understanding what your saying here Boyan.? If your menaing to check pulse edge (polarity) then it's easy.
Make up G-code file of short back n forth moves ending with move back to Zero. Mark the start position and when done should be back at same place.

[Neale]

Boyan - I can't quite read the small writing on the "command pulse" timing diagram but I think that it might say that you need a minimum of 3msec between direction change and step pulse. However, in the controller settings, this seems to be set to a lower value (300nsec, 0.3msec). As I say, I might have misread the diagram but it might be worth a quick check to make sure that the timings are OK. Apologies if I am wrong and you have already checked this.

[Boyan Silyavski]

Neale, i think you are right to note that.

I think they are talking microsecond in manual, not miliseconds, its marked "m" like handwriting. As it makes more sense to me looking at the numbers.



If i am right about that, then:


it says T3 , T7 <0.1ms which in controller is set by default Itime between DIR & pulse 300 ns where 300 ns=0.3ms, so this one seems ok

T4, T5, T6>3ms which in controller is width of pulsesignal(include time of #416)2000 ns where 2000ns=2ms , seems i have to raise that a bit , though somewhere the manual of the controller says: if you dont know better leave default




Dean, did you check the Rattm controller if software and firmware is the same? If you have time and spare motors / i am sure you have/ could you try what does that mean for the A axis , choose A or B. maybe even if it says degrees it is mm, who knows.

[JAZZCNC]

Dean, did you check the Rattm controller if software and firmware is the same? If you have time and spare motors / i am sure you have/ could you try what does that mean for the A axis , choose A or B. maybe even if it says degrees it is mm, who knows.

Not exactly sure where to find firmware version. I can see on main screen it says whats below which presume is software version. Can't see any ref to Firmware only this.
Normal Mod
Ver:2016-06-29-81NOR

Not had much time to play with this but I will try to throw some motors on it and try.

[bmuessig]

Hello!

I just stumbled over this thread and decided to register an account here.

To introduce myself, I am Benedikt from MadModder / bmuessig.eu.

iocapa and I are working hard on a complete open-source GPL rewrite of the entire software which will take time.
Right now, we are still very flexible. If you have any special feature requests, now is the best time to ask!
In principle many things could still be added and more types of machines could be supported.

Feel free to ask.

Best regards,
Benedikt