linear motion feedrate problems

[tigran]

Hi everyone...
I've just noticed, that my coordinate table moves with different feedrates at arcs and lines... From lazy cam I'm postin Gcode, where the feedrate set to 60 mm/min. On the arclines the feedrate is quite normal(60+-1mm/sec Idon't like this too), but when it's passing the linear states of Gcode the feedrate falls to 49-50 mm/min. But I need straight 60 on all the contour not+-, please help...
And one more thing...
When I write this simple Gcode : F60 G0 X25 the axis is moving with feedrate 88-90mm/sec????
In Motor Tuning options the velocity is 100

[ger21]

Originally Posted by tigran When I write this simple Gcode : F60 G0 X25 the axis is moving with feedrate 88-90mm/sec???? In Motor Tuning options the velocity is 100

F60 G0 will NOT move at 60, it'll move at rapid rate. Why it's not going 100, I don't know, but to go 60, try:

F60 G1 X25

[tigran]

Thank you for reply Ger21! I'll try it...
But the most interesting and strange is the behaviour of coordinate table at straight lines... Could it be connected with CV mode, or with Axis Slaving?

[tigran]

Please could you tell me, what feedrate is showing the feedrate DRO in Program run menu?
Is it X, Y,Z??? Or it is dhowing the speed of movement of tool on the contour? I cant understand, what is feedrate for example 55mm/min if both of axes are moving?

[ger21]

The Feedrate DRO is the commanded feedrate. The Units/Min DRO is the actual velocity of the tool, no matter which direction it's moving.

[tigran]

Originally Posted by ger21 The Feedrate DRO is the commanded feedrate. The Units/Min DRO is the actual velocity of the tool, no matter which direction it's moving.

Thank you for explaining!
I'm finally lost!!! Maybe my Mach3 is crazy!!! Because it shows commanded feedrate say 60, but its actual velocity shows 52-53 at straight line, 62-63 at arcs...
Today I tried to command feedrate 70, the movement velocity was 58-59 at straight line, and 65 at arcs... But i still need 60!!!

[tigran]

I've installed Mach 3 on two different computers. The 1st is 3.4GHz CPU 2Gb of ram, and it shows the feedate in CV mode 58-59 instead of 60! On the second comp CPU 3.0GHz 512Mb RAM in case of the same settings it shows 53-54 intsead of 60?
Is it possible, that the feedrate DRO is showing wrong feedrate or cant fit in time?
And other question... Where else I can adjust feedrates in MACH 3???

[ger21]

Do you mean the Feedrate DRO or the Velocity DRO? (inches/min)

The only other place to change feedrate is in the G code with an F word (F60)

[tigran]

[QUOTE=ger21;636150]Do you mean the Feedrate DRO or the Velocity DRO? (inches/min)

Sorry my mistake Velocity DRO units/min.
However two computers are showing different numbers... But settings are the same, and this is getting very big problem, because I need exactly that speed which is given by F command...

[ger21]

How long are the moves? Straight or arcs?

I read recently on the Yahoo group that feedrate can vary slightly from PC to PC, based on the actual PC clock frequency I think. Try compensating by calling for a slightly faster feedrate and see if you can get it to run at the correct rate by telling Mach to go a little faster.

[tigran]

I've removed the Mach3 R3.042.020 and installed an older version on my worcing computer... And it works Perfectly!!! This newer version I'm using for experiments on the other PC an its worcing prefectly too!!!
The difference between clock's arent so much... One shows pulse frequency 24000 and other shows 21000-23000 both of them should work properly... My steps per is 800!!! However, I'm glad that this problem is solved...

[LeeWay]

The versions of mach in the past year have all had issues with me. Just today I was having issues with my mill computer, tried the latest lock down, and then only partial Gcodes was showing up in the tool paths. Switched back to R2.63 and have no issues with Mach.
This computer is running Vista. Apparently for no reason after running 1.5 years, it decided to start adding steps downward on my Z during a cycle. That ain't good. I witch to my IBM laptop that runs my router. It has XP. No more issues.
Not sure what suddenly occured to the new machine, but don't have time to troubleshoot. I'll pick up another IBM laptop off Ebay for $150 and be back in business.