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1

Show"N"Tell ( Your Machines) / emco pc5 lathe

« on: July 02, 2009, 04:18:02 AM »

I picked up this emco pc5 lathe a few years back, its my first refit of a lathe, i've been on manual machines for over a decade, not long enough apparently as im still slaving.  I wanted the lathe to learn a bit about code,  it is greener on the other side isn't it?  


   heres a picture of it inside before i finished wiring, and the outside, I also knocked up a quick cabinet so i could control both machines from the same interface, its no good having scores of pc's and screens laying around so i split the duty of the control for with a data switch, it would be nice to have machining centre that does both instead!
 
the lathe now has 2.2nm 4.3Amp motors, origonals were 0.5nm. i knocked up some hand dials for the double ended motors, engraved / divided them out and added handles, why didnt no-one tell me the ballscrews are R/H on the emco, pah!, i went to all that trouble and made the dials to make it a bit more useable .. turned the dials as you would....the slides went the wrong way!!    you just dont think of these things.

 it now rapids at 1.25m/min, origonals were 550mm/min. I put in some limit switches on all the axis, made the stops adjustable incase i use different tooling.   and a decent angular race on the spindle nose with a preloading mech instead of the standard deep groove bearing. I made a ground collet chuck, and made a set of matched ground tool holders.  i put in a 550w 3ph motor and modified mount plate, the next size up frame to the origonal and nearly double the standard motor torque, also a belt and timing pulley drive further increasing the torque by a 1.1:1 ratio,  it uses a vfd so i got some more torque available on overload!. its got enough beans i think  .    It runs upto 2750rpm standard, i could overspeed it to over 3k but theres not much point really unless i'm drilling tiny holes.

it has all the extra electronic bits that usually go in the cabinet, what more can i say, i just wanted to share it, its just a wee benchtop.

 i'd like to thank arturo from cnc4pc.com for helping me since i started building, and all who support mach, ive probably read your posts at some point or other when up the creek. robin of holland aswell who helped me thru with the elctronic side.  i'm quite happy with my little lathe, it aint a gildemeister! but it's got a place in my workshop, cheers.

2

General Mach Discussion / leadscrew pitch error

« on: July 01, 2009, 05:03:00 PM »

hi all, I recently finished rebuilding an emco5 pc lathe.
I am now working through the configuration of the software and testing the axis and motors / tuning etc.  The traverse I have is 50mm (2") on the X and 300 on the Z (12", for all those yankees  

I have a pitch error on my lead screw (the Z axis). I gauged it over 200mm (8") .  I gauged by moving the leadscrew in one direction only and using a 'setting standard' between the carriage and limit switch on the Z, i.e; a  200mm mic setting piece.

I know the mic setting piece is good as i cross referenced it with a couple of different mics, hot day aswell! 27 degrees C' in my workshop, (i started to sweat   )     but that didnt affect the setting piece or mics, theoretically they may have all three items  expanded by the same amount, but I doubt it they all read 200 within 0.01.     The limit switch is also very repeatable to within 0.01mm  ( i tested it over and over with homing (50% rapids), manual jogging 0.01 steps)  i'll also check the error early in the morning when its cool, just to be a fanatic  

I have 0.17mm pitch error over 200mm,  I used to get that same pitch error from 600mm travel off an old 'well used' bridgeport mill, go bridgeport!.

I am using a 2.5mm pitched 8mm dia ballscrew (o.e.m, tiny aint it) , geared with a 2.5:1 timing pulley ratio, and 800 step/rev config in quarter step mode.     it gives me a resolution of 1.2micron/step and a max rapid of 1.25m/min before the motors bum out.

i'm never going to get micron accuracy over 200mm, but 0.05/0.1mm would be more better at least!.

I got two choices i think, first is to put in a new quality ballscew and nut, and new bearings either end of the screw and hope it works as the box says,  or maybe configure mach to account for the pitch error,  i have been reading a few posts about screw mapping but have not yet figured out how to carry out this physically

all I have to go on is a setting standard and blame the lead screw    easy to blame something,

if i could just account for that error i could live with it ,  anyone got any help?, thanks!, adam.

3

General Mach Discussion / motor tuning for vfd spindle

« on: September 10, 2008, 05:28:58 PM »

hi all,
 i am attemping to tune my spindle motor, i have a vfd and 3ph motor for the spindle on my lathe, the vfd is bieng fed an analogue 0/10 signal with a step to volts card, which is bieng fed by mach3 steps.

i am experiencing some stuttering with the motor , like an engine mis-firing,  its more prominent at some rpm than others. it could be a motor mount plate issue not fixed proper etc,  or centrifugal balance issue etc.  I want to talk about the software side / mach3 first as i'm new to configuring it and there is alot of stuff to take in. 
the instruction for the step to volts card / C6 is to set 1000 steps per revolution in the config/motor tuning / 'steps per rev' box . so i did.

I tested the voltage at the vfd input at my max rpm and it was 9.96V. producing 2500rpm, great.
it accelerates well, generally seems o.k but for the small knock.  its nothing major, but somehting aint right.

as far as steps produced at max rpm:
1000 steps per rev = 2,500,000 steps per minute! @ 2500rpm  , correct?
so 2,500,000 / 60 = Hz = 42Khz correct?

now if my kernel speed in mach is set to 25Khz, is this going to affect the smooth running of mach or this spindle motor if its pumping out an actual 42Khz to control the spindle. did i get that right?

something else to mention here is i have a 100cpr index pulse  / timing plate on the spindle, this works o.k  as far i can tell relaying a speed to mach it only fluctuates from 2495-2500 when calling out for 2500rpm.
any ideas?

4

General Mach Discussion / pulse? or step and direction control for spindle speed?

« on: March 10, 2008, 07:07:36 PM »

i'm having trouble deciding what type of control to use for my spindle.   The spindle takes an analogue +/- 0-10VDC input.  Mach can output either a pulse width modulated signal (pwm) or step and direction control.  I cannot fathom which is better to use? or are they comparatively equals?   my spindle will run up to 3000 rpm, and has feedback from a tachy generator, I have a 1.4ghz pc running it.     There are a number of convertor cards/boards out there, some convert PWM to analogue volts, some convert step and direction to analogue volts,  any advice / opinions greatly appreciated   

5

Show"N"Tell ( Your Machines) / limit switches on emco compact 5 pc.

« on: December 21, 2007, 02:00:16 PM »

hello all, i've had some time to carry on fitting the emco compact 5 pc lathe with mach3. ive fitted mechanical limit switches to the axis. On the X axis i have used 2 switches, one for home and X- limit combined, and one for the X+ limit.  And then one for Z - limit & home combined.  So 3 switches in all.  I will use two inputs into mach 3 as i want the two axes to reference at the same time with no problems, both are braided screened cable etc.  pics later,.  i'm ready to hook upto mach3, well..  nearly!, i dont know how to connect them inside of the back of the emco compact 5 so as not to blow anything up!, ive basically worked my way through the mach3 turn manual on the limit switch section, and intend to connect the two X axis switches in series, and the Z axes just normally etc.   I need some answers perhaps there is someone who can help me through.   Where do i get the +5v from?    once I have +5v supply, i run that through the simple circuit as detailed in the manual / resistor etc, but then  how do i connect into the emco's breakout board.. ? thanks in advance.. 

6

Show"N"Tell ( Your Machines) / emco 5pc spindle motor help

« on: September 20, 2007, 03:07:15 PM »

hi all,
 i'm needing some help on modifying my lathe spindle motor, i'm not sure if im in the right place to ask please let me know and move as necessary (new user)

 the machine is an emco compact 5pc lathe, and at the moment uses a .75kw 240v motor, i'm not conversant with electronics so please be gentle!. Ive just converted this machine to run mach3 using eugenes conversion (thankyou eugene) and your software here thankyou all, i'm very pleased so far and impressed with the functionality of mach.  but..  while imagining screw cutting op's / parting and general turning the speed of the carriage for threading at 2400 rpm would probably go through the shop wall.    i'm a time served toolmaker/machinist like most on here i would imagine... having to change belts half way through a job is defeating the object of putting feet up!.

 i need some advice here,  i need a quality spindle drive motor and drive equipment to interface with mach3  so i can utilise mach3 and the machine as a machinist intends        i would like to detail the steps here once complete

where to start?