[Joe Miranda]

In conversational mode I can program my lathe with constant surface speed and and RPM limit so that I can run, say, at 300SF with a max RPM of 1200. Is there a way to do that in regular G-code so that I can do simple stuff manually - like when I face off one end of a part to give myself a reference.
Thanks
Joe

[HuFlungDung]

G50 S1200

[Joe Miranda]

Thanks Hu! It worked.

[HTG]

Hi Everyone,


Can someone please help us regarding CSS formula for our CNC Controller.


Basically we are trying to implement CSS on our CNC Controller and we have the job radius information through tool position and can control the spindle RPM through VFD drive.The formulas given on the internet are bit confusing and will appreciate if someone can guide us on how we can use the job radius information to calculate the spindle RPM.




Thanks,
Jat

[ZZZZ]

Pi x Diameter(in feet) x RPM = Surface Feet per Minute

When the Constant Surface Speed option is active, the control calculates the circumference of the part, multiplies that length x the RPM to get the current surface speed, compares the result to the programmed surface speed, then raises or lowers the Spindle Analog signal to adjust the RPM accordingly. If you have a Max RPM parameter, the control will clamp the analog signal so it doesn't exceed that RPM.

Larger diameter equals lower spindle speed, smaller diameter equals higher spindle speed. Remember that the part has a zero circumference at the center point so the spindle speed would have to go to infinity to maintain the surface speed, so plan your Max RPM to stay safe.

[HTG]

Thanks ZZZZ

Sorry and it might sound like a stupid question but is this calculated in Feet only or in case of mm we just convert the mm units to feet and then work out the same as

Pi x Diameter(in mm) x RPM = Surface mm per Minute?? is this the right way

[ZZZZ]

You are correct, it would probably be more accurate to say the surface speed is calculated by multiplying Pi by the diameter in some units, as long as the units are consistent through out the program. You will probably use a multiplier to convert all the distance values in a program into ones the controller will use.

[HTG]

It took me a while to try as I was trying to fix a bug in the controller code. After putting the numbers the spindle RPM was very very low and I guess I must be doing something wrong there.

One of the boys at work did a break down and said that we have to do it in the following way, which gave some good looking numbers but wasnt sure if we were doing it right, will appricate if you can have a look at the following:

Surface speed = Pi x D(inch) x S in/Min
Surface speed = Pi x D(mm) x S mm/Min
Pi = 3.14
D = Dia (mm/inch)
S = Spindle speed (rpm) ----------------1
Now convert Surface speed in feet Per minute SFM
Surface speed in /min divide by 12 For SFM
Surface speed mm /min divide by 25.4 For SFM

Now calculate rpm
RPM = 3.82 x SFM Divide by D
This RPM Value is approx same as S in no 1
& rpm vary with dia D


Thank you

[TRISHUL]

i am new to cnc zone . i want one help on constant surface speed

if i cut the half sphere how CSS will work????
:idea:

[ZZZZ]

CSS will match the spindle rpm to the diameter of the workpiece as the part jets cut. The RPM increases as the diameter is reduced. The spindle will speed up to the machine's maximum RPM at zero diameter unless you have a MAX RPM programmed.