New PM-728V-T Mill

[jimrk]

This might do the trick. I can send Fusion-360 model or could send the part, I have no need for it.

 

[rwm]

Jimrk- that is a very generous offer! Let me see how far I get with the stepper setup. I'm kind of anxious to do that as a learning and experimenting process.
Robert

 

[jimrk]

Jimrk- that is a very generous offer! Let me see how far I get with the stepper setup. I'm kind of anxious to do that as a learning and experimenting process.
Robert

Very good.

 

[jimrk]

Finally made some chips.
Working on a Power Draw Bar. Fabco-air cylinder from Ebay (MP4X1X4X1FT). Made some standoffs for the lift plate that use the existing cylinder rods.

Printed a Mock up of the tophat that will thread onto the spindle.

 

[rwm]

Slick. Is that going to be used for R8 collets?
Robert

 

[jimrk]

Slick. Is that going to be used for R8 collets?
Robert

Tormach tool system is the plan. A special R8 3/4"

 

[AlanB]

...
Can somebody shoot down my idea of using a 555 timer with a potentiometer and a couple of switches?
Robert

With a pot on a 555 you get a range of pulse rates. It goes from fast to slow, but not zero (stop). A couple of switches will give you direction and move/stop. I'd prefer a knob interface to that myself, but whatever you want. You could always choose a picaxe chip and program it in basic, or one of the circuit python boards if you'd rather use Python.

These days with Arduino or any of these little programmable modules you can always find someone else has already done almost exactly what you want to do, so you start with their project and modify it as needed. So it doesn't require starting from scratch. It just depends on what you want the user interface to be. The crank that's there is a nice user interface. Perhaps if it is too high make a chain drive on a couple of sprockets and bring it lower.

 

[jimrk]

Plugging away a bit at a time. PDB is coming along. Made lots of chips doing the lift plate and sides. Need to move the motor back a bit. Have a longer belt that should do the trick. I think the encoder will work well right in front. Have a drawbar nut complete so next will be the tophat. Need to make a BIG sign.. ZERO THE Z YOU IDIOT!

 

[kiloseven]

I guess the quill tolerances aren't any concern to anyone who are converting their 728V-T's to CNC as it won't be used. I would assume that''s why my question is of little importance. I only ask this because I have read several other threads about the various models of PM bench mills and the one complaint they all have is the slop between the quill and spindle and the backlash in the gearing for the quill. I guess I am the lone wolf on this forum, most of the threads in this section are about converting these mills to CNC. I am interested in these mills as an alternative to a manual Bridgeport type mill. Hopefully someone will chime in. Thanks

Hi, The 728VT is no exception to quill slop. Even drilling vertical , with no side milling , you have to watch it. After all its only 400 lbs or less. For CNC on the 728VT I have definitely locked the spindle all the way up. I tried to bore , using a adjustable boring bar with limited results. If you use the upper travel of the spindle , with the offset boring operation, I get ok results. Using the mill by hand results in mostly accurate cuts in all directions. All quill table top mills, like you indicated, have the quill weakness. Don't get me wrong , I have owned the mill since they came out at PM. A decent Manual mill . A decent CNC as well , Centroid Acorn, Clearpath nema 34's , And I used the PM727 Double ball screw kit from Chai. I only had to trim the screws slightly.
Cheers

 

[currinh]

I think all these options for providing a single stepper like motor with step and direction pulses are valid. But don't you also need a stepper driver and power supply? Those would add considerably more cost than an Arduino, but require no programming.

Just read through the thread and no-one mentioned these "add ons".

Thanks.

Hugh

Tio- Thanks for that link! That explains a lot.
However if I understand it correctly, using an Arduino to control this is way over kill! Why can't I just use a variable pulse generator to supply the PUL input and use mechanical switches to activate the direction and enable? That would be a very minimal effort. Perhaps I am missing something here?
Robert