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NEWBIE: Far along..but need some help...please..please..
« on: September 14, 2008, 08:46:56 AM »
OK, I have a custom 4-Axes CNC for guitar building.  It is made from extruded aluminum and uses a Bosch Colt.   I will be cutting exotic hardwoods.

1.)  I have tested the G-Code and started to make my first cuts.   Mach3 defaults to 1.5 in the feed rate.  What does the 1.5 represent?  I hear people talk about 60 to 120 "ipm" for feed rates.  Does that mean I change the 1.5 to read 60?   Does that 1.5 Mach3 default represent the "inches per minute"? 

What are conservative/safe feed rates for cutting hardwoods with a 4-flute 1/4" end mill at about 25,000 rpm????   

2.) Also, I think I understand the setting for zero, but when I want the tool to "return" it doesnt.   What can I be doing wrong?  How can I set it so it is saved forever?

Offline Hood

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Re: NEWBIE: Far along..but need some help...please..please..
« Reply #1 on: September 14, 2008, 09:06:03 AM »
ok your code should have a feedrate set in it, for example
 G0 will move at full rapid speed of the axis which you have set in motor tuning
 G1, G2,G3 will move at the feedrate that is commanded, if you have not commandded a feedrate it will move at the default or the last commanded feedrate.
 To command a feedrate you put f*** in to your code. Example if you want to cut in a staright line you would have
That would move the x axis to 20 inch position at a feedrate of 100IPM.
However if your machine is set up in metric units the same code would mean move to 20mm position at 100mm/min.

Sorry cant help with cutting feeds as I dont cut wood, would imagine 2 or 300IPm though but wait for someone who knows to tell you right.

The tool may return to zero but you may be watching the machine coordinates, the Go to Zeros button returns your axis to your offset zero.

Offline ger21

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Re: NEWBIE: Far along..but need some help...please..please..
« Reply #2 on: September 14, 2008, 09:32:33 AM »
I answered you at CNCZone yesterday, but I'll add a little more here.

A 4 flute endmill is not your best choice for cutting wood, as it doesn't have enough room for the chips to be cleared out. Get a good quality 2 flute spiral router bit made for cutting wood, not metal.

Feedrates can vary greatly depending on the exact tool your using, the density of what your cutting, sharpness of the tool, and how much power your spindle (Colt) has. It's more than likely that a 1/4" spiral bit is capable of cutting deeper and much faster than your Colt is capable of. Like I said yesterday, start at 1/4" depth and 60 ipm. Increase speed until you see a decrease in cut quality, or until the Colt can't handle it anymore.

Not sure where you're getting the 1.5 from, as I've always seen Mach default to 6 ipm, never 1.5. Are you sure your CAM software is not putting the 1.5 in the code?

What CAM software are you using?

Are you saying you want the tool to return to 0,0 after the part is cut? If so, that'll need to be in your g-code.

Can you post some sample code for us to look at?

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Offline Sam

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Re: NEWBIE: Far along..but need some help...please..please..
« Reply #3 on: September 14, 2008, 06:50:00 PM »
I agree with Gerry. With my 1.75 HP router, I can go about 50 ipm, .5" depth, with a 2 flute .5" diameter router bit through oak without tear-out or overtaxing the motor. I would assume that performance would increase with a good quality spiral cutter. I have tried using 2 flute and 4 flute end mills. Only tried it once, and that's all it took for that learning experience. As Gerry suggested, .25 depth at 60 ipm with a .25 cutter sounds like a great starting point. Good luck.
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