Messages

1

Tangent Corner / Re: "Click and Buy" Bunch of scabs

« on: August 17, 2010, 03:59:25 AM »

i thought this thread was for "click and buy a bunch of scabs"- like a convenient online store that sold piles of scabs. i am disappointed. also sorry to hear about your situation- i am actually upset with audible.com that the cancel subscription link gives you their phone number. making it difficult to stop a service is just a lesser degree of robbery.

2

General Mach Discussion / Re: lathe/threading question

« on: August 15, 2010, 08:19:43 PM »

is there any word on when slaving of the Z to the spindle might be implemented using encoders- or should that be a question in the smoothstepper section, as the Z pulses would actually be re-timed in the SS itself? also- yes, "Rich's Guide to Mach3 Threading" is good stuff!- assuming thats the document people are referring to..?

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General Mach Discussion / Re: lathe/threading question

« on: August 15, 2010, 06:52:45 PM »

thanks, a floating holder shouldn't be a problem- as long as it makes threads

4

General Mach Discussion / Re: lathe/threading question

« on: August 15, 2010, 05:31:45 PM »

Ohhhh... I think i see whats going on then- if mach waits for a pulse to start threading then it DOESNT MATTER how much lag there is, as long as its the SAME every time! you can still cut multiple spring passes and will come in at the same angle with any arbitrary lag - the difference between each pass will be the distance moved (on the 'C' axis) in the first lag time MINUS the lag the second time, not the total lag for both, or even one. and the lag will be consistent to a much smaller time-frame than the duration of the lag itself. im not sure why i had such little confidence in this before you said it was accurate. I was stuck thinking about some kind of real time synch rather than simply repeatable, though unknown, starting conditions and then jamming through it predictably. sounds good now. If i'm misunderstanding though stop me!

As for the VFD, thanks for explaining, i should know this!! while i was posting at 4AM i think i was just tired enough not to care that it might be silly- its good to learn what is silly about it!

Between the two issues ill just get a decent VFD and move right along. this wont be much harder than the mill project. thanks guys!

PS: any luck with tapping, where cutting force is less consistent through the depth?

5

General Mach Discussion / Re: I need urgent help..!please...

« on: August 15, 2010, 06:11:37 AM »

I think he wants to be able to do some work in there with his hands, and not have the cutter in the way. so he would like the machine to go to a safe position when a button is pressed, let him get in there and move clamps, remove chips, whatever hes doing, and then press the button again to get back to where he was in the program. The VB script would need to save the current position and line in the program, go to a safe z, then go to x0y0, and on the next press of the button go back to that position on the xy then z before finally resuming the program at the line it stopped on. i don't know how to do this, but thought we should think about what the problem really is first and hope that i have interpreted it correctly. isnt it easy to write this data to a text file and read it later in VB? you might not even have to save what line you are on if you can call the feed hold button from the VB script and just be exactly in the same spot when you resume- the program should just still be at that line. also, turning off the spindle would be required im sure.

6

General Mach Discussion / lathe/threading question

« on: August 15, 2010, 05:19:08 AM »

hey, im totally new here, though i retrofitted my Bridgeport series II a couple years back and am quite happy using it with mach3 so far.

I recently picked up a Mori SL1 and am hoping that just sticking with mach3 is an option. What im wondering is this: how can the synchronization of the spindle with the other axes possibly be accurate using a VFD where the steps are converted to a 0-10v analog, it just seems that theres no real position control using this method. id like to use a smoothsttepper (+ any simple step to analog converter board) and a sensorless vector drive or something along these lines, but cant find anyone producing threads with this method and reporting meeting ANSI specs with the results- they just look good on a webcam, which doesn't really tell me if they are good threads. if anyone is making good threads with mach and not installing a servo for the spindle let me know how... please? the machine has an encoder on the spindle already, and wouldn't it just be a matter of a single setting in mach to use this instead of the single pulse per rev method ive read about? would this help, or is the control loop so slow anyway that it wouldn't make any difference?

one final, possibly silly question- a VFD 'steps' through a finite number of digital states when producing a wave anyway, so why cant an actual step/dir signal be used to 'step' it through these states, bypassing the idea of frequency (in the ac sense) altogether. it is a digital device, so why the analog input- should there not be an inexpensive VFD or vector drive which take step/dir commands that make a 3 phase motor behave essentially like a stepper- or even take pulses from an encoder and perform as a servo? i just don't see the intrinsic difference between a real servo and what id imagine a vfd and 3 phase motor could approximate given tiny changes which would negligibly effect the cost of the hardware itself and pretty much just be a firmware change- apart from things like low near zero rpm torque etc- not talking about a real c axis, just good threading. thanks to anyone who even read this long post, and my apologies for my ignorance of the basics of spindle synchronization and threading using mach3!