Messages

711

General Mach Discussion / Re: Anyone Here Have Experience Milling 6061-T651 Wrought Plate?

« on: January 25, 2010, 10:11:51 PM »

 It now machines just fine, at 30 IPM with a 1/2" HSS 2-flute, and 75 IPM with a 1/2" carbide 3-flute, even with no coolant.

Regards,
Ray L.

Can you tell us the RPM's you are running?
Maybe what kind of cut depths you are running?

It will probably help some of us a lot if we run into a similar
situation.


Thank You,
Scott

For a 1/2" HSS 2-flute, 3100 RPM, 0.150" DOC, 30 IPM works well.  For a 1/2" Carbide 3-flute, 6100 RPM, 0.150" DOC, 75 IPM works well.
For a 1/2" HSS 2-flute, 3100 RPM, 0.500" DOC, 12 IPM.

I'm still playing with settings to find the optimum for deeper cuts.  I tried the HSS at 0.225" DOC, 18 IPM, but that didn't work terribly well - chipload was too high.

Regards,
Ray L.

712

General Mach Discussion / Re: Anyone Here Have Experience Milling 6061-T651 Wrought Plate?

« on: January 24, 2010, 10:27:16 PM »

Hmmm. They look almost the same except for the rolling vs extruding. Amazing that rolling the aluminum can can make that much difference in the machining characteristics of the finished product.

Sage

Well, when machined *properly* there doesn't seem to be a huge difference.  I can now use the same (revised) parameters for both with good results.  What I was using before worked well for T6511, but not for T651.  It appears to me the T651 just gets gummy at a significantly lower temperature.  The difference is just a much heavier chipload.

Regards,
Ray L.

713

General Mach Discussion / Re: Trouble with the iMach Pro pendant

« on: January 24, 2010, 09:29:31 PM »

If you're expecting the iMach to drive 12V inputs, you're going to have to add current limiting resistors and protection diodes to all the signals, so you don't blow up the iMachs TTL driver.

Regards,
Ray L.

714

General Mach Discussion / Re: Anyone Here Have Experience Milling 6061-T651 Wrought Plate?

« on: January 24, 2010, 09:27:59 PM »

Sorry to jump in here so late. It's been very interesting though.
When you refer to 6061 T651(1) "Wrought Plate" I assume you are talking about something other than your common 6061 everyday aluminum plate? Maybe someone can explain. I would have assumed 6061 T6511 would all be the same given the numbers pretty much dictate it's characteristics - no (?)

Thanks
Sage

T651 and T6511 are not the same thing.  T561 is rolled, stretched, then surfaced, rather than being simply extruded.  I can't explain why the real-world machining characteristics of this stuff is so different from the extruded 6061 I've used tons of in the past, but it sure is.  However, increasing the chipload/feedrate by about 2X has resolved my problem.  It now machines just fine, at 30 IPM with a 1/2" HSS 2-flute, and 75 IPM with a 1/2" carbide 3-flute, even with no coolant.

Regards,
Ray L.

715

General Mach Discussion / Re: Trouble with the iMach Pro pendant

« on: January 24, 2010, 04:14:25 PM »

4.7V is more than plenty for a high leve - as good as you'll get, in fact.  Are you getting a good *low* level?

Regards,
Ray L.

716

General Mach Discussion / Re: Trouble on the Z axis again

« on: January 23, 2010, 12:19:53 PM »

"I have got to start thinking here." - But that takes all the fun out of it!  :-)

Regards,
Ray L.

717

General Mach Discussion / Re: Trouble on the Z axis again

« on: January 23, 2010, 12:06:22 PM »

With steppers, you need to provide lots of margin when setting velocity and accleration.  I'd test them to the limits, then back off at least 30%, if not 50% on accel and velocity.

Regards,
Ray L.

718

General Mach Discussion / Re: Would like opinions on servo motor voltage and PS secondary in series

« on: January 23, 2010, 11:20:54 AM »

Simpson,

An analog voltmeter will, if anything, give you a more accurate reading of voltage on a PWM controller, as the analog meter movement will "filter" the response.

I would not expect to see any difference in "smoothness", unless the PWM frequency is very low.  Did you say you had a Minarik controller?  If so, I would expect it's probably using 120Hz, derived from rectifying the line frequency, as the PWM frequency.  A higher quality controller would likely use a higher frequency.  But there are also other factors, like I-R compensation, and the voltage and current feedback loops that can also affect smoothness.  I don't recall if any of these are adjustable on the Minarik or not.  A good PWM controller, well-matched to the motor, should be perfectly smooth, until you get down into very low RPMs, where the motor may start "cogging" due to commutation.  This is where BLDCs, excel.

Regards,
Ray L.

719

General Mach Discussion / Re: Would like opinions on servo motor voltage and PS secondary in series

« on: January 23, 2010, 09:59:29 AM »

Simpson,

The motor will basicallly respond to RMS voltage.  If you looked at the voltage waveform, and measured the area under the waveform, the RMS voltage would be the constant DC voltage having the same area.  How accurately your DVM will read the PWM waveform depends a lot on the PWM frequency, and exactly how the DVM is designed. It should at least be reasonably close in most cases.  How much voltage loss there is depends heavily on the design of the controller, so there's no way to answer that question without knowing the circuitry of the specific controller in use.

Regards,
Ray L.

720

General Mach Discussion / Re: CNC'ing both quill and knee

« on: January 23, 2010, 09:53:19 AM »

The belt on my knee drive is an XL, and it works fine, shows no sign of wear, even after using the knee as the Z axis for the last year.

Regards,
Ray L.