Messages

1131

General Mach Discussion / Re: Restarting after cutter breakage

« on: July 22, 2009, 10:08:11 AM »

Hi Nick,

First thing I'd do in this case is check the the part (X0,Y0,Z0)  point is maintained. Next, the best way to go to eliminate cutting the whole part again is using Run From Here. Beware: check what is the "safe Z" defined, when it will ask you to do the preparation move. Check where it is going to take the cutter on the preparation move and make sure nothing stands on its way. And don't forget to start the spindle

Daniel

1132

General Mach Discussion / Re: Pulse on scope but not being seen by machturn

« on: July 18, 2009, 01:38:30 PM »

You are not quite correct. Mach3 needs the index pulse to be at least 200 microseconds to reliably read it. That means that your speed can be as high as about 150,000RPM as far as Mach3 is concerned (considering that it takes 200 microseconds for the pulse high state and the same amount of time for the pulse low state).

The simplest way to go, and one that I used before I had a servo on my spindle and SS to read the encoder index, is to build a simple circuit based on the 555 IC. You can calculate the resistors you need to get a pulse width just above 200 microseconds. It had worked perfectly for me.

Daniel

1133

General Mach Discussion / Re: Pulse on scope but not being seen by machturn

« on: July 18, 2009, 12:54:03 PM »

Hood raised a good point. If you're using an encoder then the pulse is too sort for the parallel port to be seen.

If it's not the case then I would check the PMDX input.

Daniel

1134

General Mach Discussion / Re: Pulse on scope but not being seen by machturn

« on: July 18, 2009, 12:58:15 AM »

Are you using a breakout board?

Daniel

1135

General Mach Discussion / Re: Thread milling using Mach3 centering single point threading tool question

« on: July 18, 2009, 12:56:28 AM »

Hi,

What I do to setup a threading tool is I hold a piece of aluminum in the vise, find its edge using an edge finder (and set the DRO to 0) and then just touch off with the threading tool. The DRO reading is then the tool radius. For me it's easier and faster than boring a hole.

Daniel

1136

General Mach Discussion / Re: Mach 3 & Lathe Spindle Encoder Recommendations

« on: July 09, 2009, 09:48:21 AM »

Simpson,

This is true for any DC brushed motor. You may want to review this link:

http://lancet.mit.edu/motors/motors3.html#tscurve

Actually, it is even true for AC servos, but the torque of an AC servo doesn't fall that rapidly with increasing the speed as in DC motor, and the motor can still deliver torque at its max speed. Thus, practically an AC servo may be considered as delivering a constant torque through its practical operation speed range.

Haven't heard about the superior holding power. I think the same power rated DC and AC servo would have the same holding capability.

Yes, AC servos are quite expensive. I'm looking for one as well to replace the DC motor on my mill's spindle and can't find anything reasonably priced for my pocket...


Daniel

1137

General Mach Discussion / Re: Mach 3 & Lathe Spindle Encoder Recommendations

« on: July 09, 2009, 07:13:11 AM »

Simpson,

Yes, AC servos are available in a wide variety of sizes. Got one on my Emco Compact lathe spindle. Yet another big advantage of an AC servo is its small frame size for the same power rating as DC motors. Mine is 1/3 the size and weight of the original 0.44KW DC motor and is 1.3kW!

Hood,

DC motors are the contrary to VFD - they have max torque at zero speed and it drops liniary as you increase the speed. At max speed the torque is zero.

Daniel

 

1138

Tangent Corner / Re: CNC fire hazzard.

« on: July 06, 2009, 09:59:51 AM »

Hi Tweakie,

It's said looking at these pictures... Your machine has been seriously damaged and the spindle is scrapped

Was it a Mach fault?

Hope you get it fixed soon...

Daniel

1139

VB and the development of wizards / Re: Beginner looking for a place to start

« on: June 28, 2009, 01:16:43 PM »

Hi Jack,

You can have a look at the Mach wiki on the Mach support page. And, there is also a customization pdf manual that you can download from the downloads page, which contains a lot of useful information to start with.

Hope it helps.

Daniel

1140

Show"N"Tell ( What you have made with your CNC machine.) / Re: Video of my milling process - need advice on improving efficiency

« on: June 11, 2009, 11:31:30 AM »

Hi Aaron,

Thanks for the video. Nice to see the whole process of making a part.

I have a couple of thoughts:

Somehow, no one has mentioned this - your spindle speed is 6700RPM and you're using a feedrate of merely 10in/min. With a spindle speed like this and a 1/4" 3-flute end mill, your feed should be around 25in/min. Perhaps even closer to 30in/min. If your machine can't produce that feedrate, then no point running the spindle at that speed - you're heating the tool in vain. If 10in/min is as high as your machine would go, I would lower the spindle speed to around 2500-3000 RPM.

Also, like it has been stated, the more rigid the machine is the less cutting marks are seen on the part. The sharper the tool the less the marks. Flood coolant makes a better surface finish, even spraying some coolant on the final pass will do.

Like one of the guys said, cutting one part at time from a stock just enough to hold in the vice will reduce wasted stock. I agree with the idea of using soft jaws for the second operation.

Daniel