[shanoger]

Hi all,
I have recently installed my machmotion controller to my old router table powered by Delta ASDA-A2 servo drives. Y and A moves the gantry forward and backwards and have 1:10 reduction gear boxes with 1Kw Servo motor, the X axis has a 1:7 reduction gear box with a 1.5 kw servo motor. All drives of those servos are set to pulse direction and have been set to 1000 Numerator and 10 denominator electronic gear ratio.

When i cut a circle the dimensions along X and Y are perfect but the shape is oval skewed 1.5mm more than the correct size ? i tried increasing the acceleration on the motors and tuning, that helped a little but did not solve the problem. What could it be? could the different gearbox ratios be the problem?



Thanks

[alan_3301]

This must be a very heavy duty machine, those are big servos. how about some pics?

Do you account for the different ratios in mach3?

What kind of gearboxes are these? How much backlash is in them?

[shanoger]

This must be a very heavy duty machine, those are big servos. how about some pics?

Do you account for the different ratios in mach3?

What kind of gearboxes are these? How much backlash is in them?

I am trying to attach an image but no luck I will send a link to drop box

I did not take account of these gearboxes how to do that?
How to take account of different ratios in mach3

[alan_3301]

I am not familiar with mach3 but if you search for setting steps per inch, you will find the info to set it up

as you have it setup now with 1000/10 should equal 1000 steps per revolution
So what is your pinion ratio and ballscrew ratio?

that will tell you what you need to enter as the steps per unit field.

[shanoger]

I am not familiar with mach3 but if you search for setting steps per inch, you will find the info to set it up

as you have it setup now with 1000/10 should equal 1000 steps per revolution
So what is your pinion ratio and ballscrew ratio?

that will tell you what you need to enter as the steps per unit field.

I will measure the pinion diameter but my sizes are fine the only problem is that the circle is skewed ? I was thinking could it be the servo response time?

[alan_3301]

I guess I am confused

When i cut a circle the dimensions along X and Y are perfect but the shape is oval skewed 1.5mm more than the correct size ?

For it to be an oval, the x and y dimensions would have to be different right?

Is this the problem pictured here?
Attachment 276164

All the other circles look good to me..
This is thin stock, are you using a upcut bit?
Perhaps the stock is lifting and causing the problem I pointed out in the pic.

Or are we not talking about the same thing.

[shanoger]

I guess I am confused


For it to be an oval, the x and y dimensions would have to be different right?

Is this the problem pictured here?
Attachment 276164


All the other circles look good to me..
This is thin stock, are you using a upcut bit?
Perhaps the stock is lifting and causing the problem I pointed out in the pic.

Or are we not talking about the same thing.

Thank you for your reply, there are two problem in the picture of the cut material. The first which is not easy to see is the oval shaped holes. The second is that long cut out which has a bad cut at the end which I fixed by reducing feed rate only.
For problem 2 what I noticed is there is some knocking while cutting. What I mean is when the cut reaches the end of the arc there is a knock and when the cut reaches the end of straight line there is a knock ( knock meaning sudden change in motion) this looks like the servo changes direction quickly causing this knock.
Problem one I read the G code and it seems to be all line vectors and not one circle. It's like the circle is broken down into small lines. Could that be the problem?

[victorofga]

mightbe your acceleration too high..
it takes a while to find the right one..

if it set right, no matter what federate you set, the acceleration will limit on direction changes, and short segments how much it accelerating up..

because if it too high, then you might don't notice on a large square or circle, but on small shapes yes..

you router will make a parabolic like curve on corners if acceleration too high..
also, due circles are made of 2 or 4 segments small circles will be visible oval..

the several segments wont be problem, because your control wont slow down due the included angle between two vector is close to 180..
it calculated in advance in the control..
but again the acceleration need to be set right.. it vary machine by machine

looking for your picture, im not sure but looks for the gantry height the length of the sides are too short.. so can happen despite the square rails it might flexing also..

[shanoger]

mightbe your acceleration too high..
it takes a while to find the right one..

if it set right, no matter what federate you set, the acceleration will limit on direction changes, and short segments how much it accelerating up..

because if it too high, then you might don't notice on a large square or circle, but on small shapes yes..

you router will make a parabolic like curve on corners if acceleration too high..
also, due circles are made of 2 or 4 segments small circles will be visible oval..

the several segments wont be problem, because your control wont slow down due the included angle between two vector is close to 180..
it calculated in advance in the control..
but again the acceleration need to be set right.. it vary machine by machine

looking for your picture, im not sure but looks for the gantry height the length of the sides are too short.. so can happen despite the square rails it might flexing also..

Thank you for your help I really appreciate it.