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Author Topic: Mach 3 & Denford Orac spindle speed headache!!  (Read 5915 times)

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Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #10 on: January 01, 2015, 09:13:39 AM »
ok, I'll have to study the inverter manual again...

and reading between the lines about css and feed rate per rev are best avoided in mach3 - I'm not too worried as I can manually program them to keep chip load and spindle speed approx constant (just need to keep a calculator to hand) :)

BTW happy new year to all, and thank you again for all the help :)

Offline Hood

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Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #11 on: January 01, 2015, 09:28:47 AM »
Not sure if it will be of any use but attached is a spreadsheet I made up for myself.
Hood
Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #12 on: January 02, 2015, 09:12:51 AM »
question about constant surface speed... I've just read elsewhere that G96 relates to a constant RPM....

eg
X10
G96 S1000

would give a spindle speed of 1000rpm at the current X tool position 10mm diameter .. then as the tool comes in closer the RPM increases to max... if the tool moves further away from X10 (ie X15) the spindle will slow down below 1000rpm

have I interpreted this correctly or is the S followed by a surface metres / min

Btw, HOOD, thanks for the calculator xls sheet - it will come in handy :)

Offline Hood

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Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #13 on: January 02, 2015, 09:21:43 AM »
G96S1000 would give you 31,837 RPM at X 10mm dia.

BTW not sure if the spreadsheet opens part way down with you. I just opened it to calc the rpm and it was sitting with the No of Teeth box uppermost, if you scroll up yuou will see the VC, Dia etc fields.


G96 is Constant Surface Speed
G97 is Constant Spindle Speed

Hood
Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #14 on: January 02, 2015, 09:29:23 AM »
shame about the CSS idea... the website I read it from was mis-informing me then :(

Offline Hood

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Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #15 on: January 02, 2015, 09:33:19 AM »
Not sure what you are meaning but CSS will vary the spindle speed depending on the Dia. What was wrong in your post above was that G96 was Constant RPM, that is G97.

So to summarise if you call a G96S200 the RPM will go to whatever is required to give a surface speed of 200 at the diameter you currently are at. If you move to a smaller dia the spindle will increase in RPM and move to a bigger dia and it will decrease.
Hood
Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #16 on: January 02, 2015, 10:08:14 AM »
Head to:

http://www.hsmworks.com/docs/cncbook/en/#Ch08_CuttingSpeedsAndFeeds

and look at table 8.9

This is where i got the suggestion that G96 gives constant surface speed

Sorry if I'm sounding idiotic, but I've read and re-read about CSS, and it makes sense on paper, but in reality it doesn't quite behave ...

Hood, you mention that CSS is in units per minute, so if I have set the code to run in mm then should I multiply out the Surface Metres / Min given in cutting tables to become Surface mm / min for the G-Code?

Offline Hood

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Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #17 on: January 02, 2015, 10:17:30 AM »
The Units in CSS are either Meters or Feet depending on whether your code is metric or Imperial.

So if metric the S word after a G96 will be meters, so G96S200 will be a surface speed of 200m/min.
In your previous post you said that the site you had looked at was saying G96 was constant RPM, it is not. G97 is constant RPM, G96 is constant surface speed.

If you call G97S200 it will rotate the spindle at 200rpm and it will not vary if you vary the X axis and it will not matter what the current X axis value is when you call the G97S200.

If you call G96S200 it will start the spindle rotating, what the RPM will be will be dependent on the current X axis position. As the X axis moves the RPM will follow to keep the surface speed constant, so decrease the dia and the spindle speed will increase, Increase the Dia and it will slow..

Hood
Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #18 on: January 02, 2015, 10:26:35 AM »
That link is not correct as far as Mach is concerned.
It says G96 actually sets the RPM. ... if I see it right.

 Russ
Re: Mach 3 & Denford Orac spindle speed headache!!
« Reply #19 on: January 02, 2015, 10:35:19 AM »
Overloaded - I am agreeing with you ... but I've ended up getting myself confused .... :(

G96 = CSS
G97 = Constant RPM

sorted:  :)

Hood - one last question for your spreadsheet calculator: is the feed per tooth the cutting depth on that pass?
If not, where would I find the data to enter into that cell?