Messages

581

Show"N"Tell ( Your Machines) / Re: What The World's Been Waiting For - Yet Another Power Drawbar Design

« on: May 30, 2011, 09:56:07 PM »

Hi Ray,

I enjoyed reading about your ATC. I'm curious on how it's preforming?  I'm looking into building one for my cnc Bridgeport.

It isn't....  Never could get it to develop enough force to adequately retain the Tormach holders - over 2000# of drawbar tension is required for maximum retention.  The only practical way to achieve that is with an air over hydraulic system, or a large diameter, multi-stack air cylinder.  The other approach i'd love to try is using a stepper motor, driving a high reduction planetary gearbox to directly spin the drawbar.  This would allow the driawbar to be fully tightened to any desired torque, loosened a controlled about to enable using Tormach tool holders, or the tool released completely.  It's mechanically very simple as well.  You'd want to be able to generate 20-25 foot-lbs for tightening, and about twice that for loosening.

Regards,
Ray L.

582

General Mach Discussion / Re: Remote readout

« on: May 22, 2011, 08:10:22 PM »

Mach2 has VB functions for outputting to a serial port.  If you can find a USB display that looks to the system like a serial port, this would be an easy way to interface it, using a few lines of VB in a custom macropump.

Regards,
Ray L.

583

General Mach Discussion / Re: Gecko G320 and crazy faulting issues...

« on: May 20, 2011, 10:25:21 PM »

Still cannot find the issue here.... I have been playing with it for over a week now.  About to push it  out into the street in front of a dumptruck but that would not be fair to the dumptruck....   I got the X axis to run smooth again but the machine will still not run a program without faulting SOME axis.... Peace

Pete

Pete,

Given that all the problems started with the new computer, it's reasonable to conclude the computer is the source of the problems.  Does this machine have on-board video?  That is a common cause of problems with Mach3, as they can "hog" the memory bus.  Have you done the Windows optimization recommended for Mach3 use?  What processes are running?  Have you disabled ACPI?

Regards,
Ray L.

584

General Mach Discussion / Re: Can't get this hybrid stepper to run properly

« on: May 18, 2011, 10:39:19 PM »

Or, better still, get a servo motor.  A stepper turning at high RPM will have very little torque....  And with steppers, the larger the motor, the worse it will be at high speed.

Regards,
Ray L.

585

General Mach Discussion / Re: Wiring limit, home, an E-stop switches

« on: May 10, 2011, 10:07:05 AM »

Ray, doesnt your resistor do the same as a debounce setting? I was under the impression that once all the wiring was cleaned up and properly drained possibly no resistor or debounce would be needed. I am not sure why I thought/think the resistor has a time value also.

No, the resistor and de-bounce serve completely different purposes.  The resistor lowers the impedance of the circuit, requiring much stronger interference to be able to influence the signal level.  The stiffer the pull-up, the higher the current required to pull the line down, and the faster it will pull itself back up.  That higher current also helps keep the contacts in the switch clean.  De-bounce is a crude means of removing noise, and slows down the signal, adding time-delay from when the switch changes state to when the software "see"s the change.  A de-bounce of 2000 adds a LOT of delay.  Adding a capacitor on the input has more or less the same effect as de-bounce.  With noise, it's always better to prevent it from getting into the system in the first place, rather than try to remove it after it's already there.  I've never had to use de-bounce at all.

Regards,
Ray L.

586

General Mach Discussion / Re: Wiring limit, home, an E-stop switches

« on: May 09, 2011, 10:53:43 AM »

Input signals, like home/limit switches, probe inputs, etc. should work very reliably without having to put huge de-bounce values in IF you properly shield the wires (use shielded cable, with the shield connected to ground at the BOB end ONLY!), AND put a stiff pull-up resistor at the BOB end (220 ohms or so to +5V).  Being near the motor drivers should make no difference if things are properly shielded and grounded.  Mine are all inches from a 3HP VFD, and four servo drivers, and I run my encoder cables alongside the motor cable for their full 12-foot length.  Never a problem.  It's all in the grounding and shielding.

Regards,
Ray L.

587

General Mach Discussion / Re: Homing position is not absolute

« on: May 04, 2011, 11:20:50 PM »

AAARRRRGGGG, Yoous guys were correct (;-) It sets the home position AFTER it comes to a complete stop.

(;-) TP

Which, BTW, will be exactly as accurate as setting the zero when the switch actually opens.  The number of steps the machine takes after the switch opens will be exactly the same, as long as the home velocity and acceleration do not change.

Regards,
Ray L.

588

General Mach Discussion / Re: CNC4PC??

« on: May 03, 2011, 10:18:15 PM »

CNC4PC/Arturo is a 100% legitimate Mach re-seller.  You can buy from him with complete confidence.

Regards,
Ray L.

589

General Mach Discussion / Re: Axis' accumulating error - need to emulate Mach3 output for testing

« on: May 02, 2011, 11:50:37 PM »

I would be very suspicious of the BOB. The design of the opto circuits on that board leave a lot to be desired, especially for servo systems that require much higher step rates than steppers.  I had several C11s, and they all topped out at a very low step frequency, and  badly distorted the signal.  I was able to re-bias the optos and get them to run over 125kHz, but out of the box they completely stopped passing the step pulses at something well under 30kHz, due to improper opto biasing, and a strange pulse-shaping circuit they use.  If you slow down your max speeds, and the problem goes away, that would be a good indication this could be the problem.  If you can prove the BOB is at fault, I suspect you could get Arturo at CNC4PC to swap it out.  He exchanged mine several times over a number of years, and finally swapped the C11 for a, IIRC, C25, which behaves much better.

Regards,
Ray L.

590

General Mach Discussion / Re: Homing position is not absolute

« on: May 01, 2011, 02:27:37 PM »

Your understanding of how homing works is incorrect.  When homing, Mach takes a step, then checks the home switches, BEFORE taking the next step.  If it sees the switch has changed state, then THAT position becomes the "home" position.  The fact that the axis continues to move beyond that point does not affect the home position in any way.  Homing at high speed, however, WILL generally make homing less accurate.  It should be done at a low speed.

Regards,
Ray L.