Messages

1051

General Mach Discussion / Re: oscillating tangential knife

« on: October 28, 2009, 12:17:09 PM »

Bill,

The simple version I mentioned doesn't really have any electronics. The mechanics takes care of the electronics. See the picture: when you close the circuit with S1, the electromagnet pulls the steel strip which immediately opens the electric circuit (S2) and disables the electromagnet, allowing the steel strip to spring back and close the circuit again, and so on...

It hard to predict the frequency with this design though, depends on the coil inductance and the core iron bar, as well as the steel strip. But it's easy enough to make and experiment.

Then, as I said, you can use a simple electronic circuit (based on a 555 IC or the like) to control the ON and OFF time intervals and frequency of the electromagnet power.

Daniel

1052

General Mach Discussion / Re: oscillating tangential knife

« on: October 28, 2009, 08:16:33 AM »

Bill,

The other idea i mentioned it not suitable for this application, since its movement amplitude is very small - in the range of microns, and it usually used for ultrasonic frequencies.

There is another, very simple way to achieve what you want though. You can build a simple device based on a solenoid principle. Use an electromagnet powered by an alternating current to alternately pull and push a small permanent magnet located in a tube of some kind. You could even use two electromagnets with 180 degrees offset phase on both ends of the tube to enhance the power.

Another variation of this would be using a simple electronic circuit (that can be achieved even with merely the mechanical parts of the design, without a single electronic component) to alternately power on and off an electromagnet that would pull a piece of steel loaded with a spring - as soon as the magnetic field disappears the spring will pull the steel piece back. I would go with this design. It is very easy to design to achieve the required amplitude.

Daniel

1053

General Mach Discussion / Re: oscillating tangential knife

« on: October 27, 2009, 03:39:08 AM »

Well, can't really see it oscillating

By the sound it makes I'd say it oscillates at a frequency around what you suggested. I think it should be very easy to make. Just use a cam wheel and calculate the required offset to give the desired travel. A small DC motor with speed control drive the cam wheel. Since you don't know the exact  frequency, you can use the speed control to change frequencies and adjust it till you get good results.

Daniel

1054

General Mach Discussion / Re: oscillating tangential knife

« on: October 26, 2009, 03:37:25 PM »

Bill,

What is the oscillation frequency required? There are two ways you can do it depending on the frequency required. Either mechanically, by rotating an offset weight - good for low frequencies and very easy to make, or electrically, by putting a ferromagnetic iron core inside a coil through which an alternating current of a desired frequency is flowing. The AC current causes minor dimensional changes in the iron core as it reverses polarity which makes the oscillation. It is good for high frequencies, but requires a cooling system, as it rapidly gets hot as it oscillates.

Daniel

1055

General Mach Discussion / Re: Draft Mach3 v3.x Programmers Reference Manual

« on: October 26, 2009, 04:38:38 AM »

Hood,

Just downloaded it, can't see what problem you're seeing... opens fine here...

Daniel

1056

General Mach Discussion / Re: Problems threading on the lathe

« on: October 26, 2009, 04:35:07 AM »

Sorry Rich, didn't mean to make it complicated

Daniel

1057

General Mach Discussion / Re: Problems threading on the lathe

« on: October 25, 2009, 03:19:57 PM »

Daniel,
Can you try out the the threading without compensation and not use the SS?
What is good is that your speed is rock solid. Your an apple and i am an orange ie; my speed will vary a small amount ( like 1000 other users out there ). 
RICH

Rich,
It is really a hassle for me to to make my lathe run from PP. The spindle servo needs 8096 steps per revolution, so even for a 500RPM speed it would require a 75kHz kernel speed. Can't run my computer at this speed. The only choice is to reconfigure the servo drive to use electronic gearing. But then my steppers take 4000 steps per mm, again requiring a kernel of at least 45kHz to be able to get some normal feedrates.

But if it can help you, I could try it after I finish the work I'm doing now on the lathe. Another thing is I don't have any precise means of measuring my threads, so don't know how much of a help would it be.

Daniel

1058

General Mach Discussion / Re: Problems threading on the lathe

« on: October 24, 2009, 01:54:59 PM »

Thanks Art. I don't use averaging ever since I've put an AC servo on my spindle and use its encoder index for speed reading - displays the speed rock solid.

Daniel

1059

General Mach Discussion / Re: Problems threading on the lathe

« on: October 24, 2009, 01:06:53 PM »

Art,

Does it all have any effect on the Smooth Stepper? My threads with the Smooth Stepper seem all to be perfect, but then I have never run such long threads and never subjected them to the kind of tests Rich does.

Thanks,
Daniel

1060

Show"N"Tell ( Your Machines) / Re: gears, ballscrews, and setscrews

« on: October 23, 2009, 10:51:23 AM »

On my machines the timing pulleys are screwed onto the ballscrew end, and are locked with a counter nut (or counter bolt in my case), and Loctite is applied to the whole assembly.

Daniel