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Messages - hyildiz

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1
Hi Steve,

That is the problem i am facing with i think too, increasing FRO %100 messes up the control, u explained it technically of course, i am gonna do it like that by manipulating the gcode from now on, thanks.

Hakan

2
Hi RecceDG,

This does not happen when u move the x alone, this happens when couple or more axis move simultaneously, i decreased the speed and acceleration and go on working like that after this happens last time but i am not sure thats the problem(it was already adjusted to half speed that 3phase 16nm motor can drive)

and when this happened the feedrate in gcode was 300mm/min i increased it to 750mm/min or so with the FRO, 750mm/min is not fast, actual speed that x can do with the 16nm stepper(keeping the 10-15um accuracy) is 3000mm/min in my case.

3
Hi,

The problem that i thought we fixed by decreasing the microstepping came back today while machining a wood mold, this time i was touching to the ballscrew because cv_feedrate was not on so that the machine was shaking while turning the corners and i was touching the ballscrew to see if it is because of the X axis motor, so i felt the stall by chance when it did it. But this time it was for a very short period of time like a second or so and machine miss aligned the gcode by 1cm(or so) on the x axis.

This happens when i play with the FRO, because today the tip of the endmill was not touching to the part so i didnt want to loose time and increased the feedrate by %150 and in one of the sharp corners machine did this error.

obviously decreasing the microstepping 10 times fixed the error to some extend but x, y and zth axis are all within the range of pulse frequency of pmdx bob, ess and motor drivers so i dont know what mach4 does when u increase the FRO but thats what is causing this error(as it seems microstepping was exaggerating it).

In actual feedrate(the feedrate embedded in the gcode) there is no error what so ever but when u increase the FRO this happens once in a while, hard to say when exactly.

Hakan

4
Hi Craig,

Yes i slow it down to 5m/min, its still very fast for the size.

Do u have any advice for the manual servo tuning? I know that linuxcnc has an internal oscilloscope so that u can check the actual movement and commanded movement and try to bring them closer in a graphic window by tuning the driver parameters but Mach4 has no such an option, so any advice?

Hakan

5
Hi Craig,

So we can say 2.2kw servo can drive the 600kg of mass with 1.79ms speed right?

ok now i have to find a way to tune this servo without harming the equipment which it will be connected.

Hakan

6
Hi Craig,

sorry for the late reply,

diameter:40mm pitch:5mm length:2000mm, the weight of the axis(both Y and Zth) is 600kg, servo is 11nm 2.2kw AC servo, i connect the motor to ballscrew with direct coupling.

I asked about the oscilloscope because i think to buy one from taobao next month if i can tune the servo with it, it would be very nice because this servo driver has no auto tuning. Its a servo motor at the end there is no meaning to leave it there idle.

Hakan

7
Hi Craig,

You are right, i know that its not just the g, one side pushing of a gantry heavier than lets say 250kg will likely create more wobble on thinner ballscrews since the x axis is the longest (ballscrew length is 2000mm) i got 40mm because of that, just to make sure. So its not just to create higher torque, wobble in the ballscrew will kill the c3 precision according to the manufacturer TBI, they advised it for the length of the axis and weight of the gantry. U can drive an axis which weighs 2 ton with that ;-)

They are good at what they are doing for example i thought to use the ballscrew on the zth axis one end open, thats the way some bigger manufacturers like makino use ballscrews on zth axis just to keep it short but engineers in TBI said u should never use a ballscrew like that because it will shorten its life. And if u want precision they said always fix the opposite end with c3 bearings. so i dont know how the manufacturers use it like that and keep up with the precision.

U auto tuned the delta servos with their pc software right? Is it easy to tune them? is it full automatic or u had to tune them manually?

Also, do u think an oscilloscope will be helpful for manually tuning the servos? i still wanna use 11nm 130mm flange servo, its worst performance is still better than open loop stepper i guess. Can i tune it by seeing the signals on oscilloscope? i never used an oscilloscope before but is it useful for this purpose?

Hakan

8
Hi Craig,

u can check taobao.com u can get good equipment from there with good prices sometimes.

I got the diameter big for stiffness, i am driving the axis from one side, u should drive that kind of axis from double side normally, if u do so u can use smaller diameter(32mm) ballscrews but if u do it on one side for the machining precision bigger diameter is the better.

Hakan
 

9
Hi Craig,

This is a prototype machine that we built, its a 4 ton machine in total with 1200mm x 800mm x 500mm machining area and the x axis is the heaviest axis because u know there is y and zth axis connected to the ballscrew(its a 2 column machine like dmg dmu 340) so u have to push them at reasonable speeds and with 10um precision, now i can drive the x axis with 6000mm/minute but even with 40mm diameter 5mm pitch ballscrew and precisely leveled roller guideways 16nm is not enough(to precisely cut a perfect circle for example)in higher accelerations/speeds so i am looking for a 20Nm yaskawa or panasonic servo for the x axis.

On the other hand i saw that 11nm servo motor moved the 4 ton body front and back couple centimeters when it made sudden movements on x axis because of the inertia but for precision positioning i think its better if the torque is higher then needed.

Delta is also nice but its my second choice because approx. same price you can buy a yaskawa/panasonic from China or even from ebay if u catch the right bid.

Hakan

10
I have an 11nm servo motor for the X axis but its gservo(made in china) brand and it does not have an auto tuning software so u have to tune it by your self manually, need to be connected to the load to adjust the gain parameters, actually i did that at first but while playing with some parameters motor did a very strange resonance it was so high that the plastic between 2 piece servo coupling literally melted. It was connected to the ballscrew at that time, it is a c3 zero backlash ballscrew which is little bit expensive so i was afraid that the balls in the nut damaged the ballscrew but again God helped and it didnt do any harm. After that incident i afraid to harm the ballscrew and removed the servo and put the stepper, thats why i am going on with the open loop stepper.

when i get a yaskawa, panasonic or delta in equivelant torque(16-20Nm) i will change it with servo, those brands have auto tuning softwares with oscilloscope screens etc. as u know.

For guys like you, who knows the details about the stuff it may be easy to tune a servo manually but guys like me who is relatively new in this stuff its a little bit risky.

Hakan

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