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Messages - comet

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201
Have you matched your peak motor revs,with a reasonable max feed,i.e. are the motors geared correctly?
if they are just mounted directly onto the lead screws you could be over geared.

202
General Mach Discussion / Re: electro-pneumatic slide lock
« on: July 05, 2009, 12:44:48 PM »
vmax,
 when the pulses start the brake releases when the pulses stop the brake locks after a 1/2 second delay.Its that simple.
The pulses themselves trigger the 555 timer which inturn triggers the brake.
the cylinder is a single sided with a light spring holding it continuosly against the lock pad,it unlocks in a fraction of a second as there
is only a few microns of movement to release.
I would concede however that a stepper setup might lose steps that it will never make up but thats always the problem with steppers!.
The Idea is to use it on a Z quill lock. The delay on lock will keep the lock off during rapid direction changes when peck drilling.

I have built the 555 circuit and it all works fine.

 Fixing the backlash is a very expensive option on this machine.Or any knee type machine that has the quill rack and pinion motorised,
because the only option you have is to bolt a ballscrew on the side ala anilam. And even then when using a big milling cutter
it can draw the cutter in.
 I used to have a Beaver knee CNC which used a auto quill lock and it was a far better machine than the bridgeport type.

     Tony

203
General Mach Discussion / Re: electro-pneumatic slide lock
« on: July 03, 2009, 07:08:44 PM »
Cheers Ray,
Sounds good, any suggestions of a circuit I could try? I have built 555 based PWM circuits so I am reasonably familiar with them.
the thing that I was wondering was would the tap on the pulse stream short it or interfere at all?
I dont mind experimenting if pointed in the right direction!!
 tony

204
General Mach Discussion / Re: electro-pneumatic slide lock
« on: July 03, 2009, 12:29:10 PM »
Ray,
 My machine has normal lead screws,so there is always a touch of back lash.
I am not fussed about the step loss you mentioned as I use servo's and they make up the "lost"
steps of there own accord.
   Tony

205
General Mach Discussion / electro-pneumatic slide lock
« on: July 03, 2009, 11:29:21 AM »
Hi,
   I would like to make some pneumatic slide locks for my  mill.
What I'm thinking is a tap off the step line to a transistor then to a small 5V pcb type relay finally to a 24V solenoid and an air cylinder.
 I would like it to open or release instantly upon sensing the first step ( within reasonable workable boundaries) then lock again when the pulse stream stops I would like a delay on re-lock of about 0.5 second.
  How can I achieve this? can I use a cap/resistor delay or a 555 timer? or is it a job for a PIC ?
Any help or circuit suggestions would be welcome.
    Tony

206
The other problem with lazers and in fact high power LED's is they sometimes dont trigger the blink response.
this can lead to perminant damage to the retina from what appears to be,really a low power light source.

207
General Mach Discussion / gecko servo drive
« on: April 26, 2009, 08:56:40 AM »
Hi,
 can anybody tell me wether a gecko 340 servo drive will be wrecked if
is back driven by a servo generating current?
  What I mean is that I would like to retain the handles (retractable) to
use my mill manually,I am just concerned that turning the motors might
burn the drives out?
  cheers
   tony

208
General Mach Discussion / Re: Servo with Gecko320 blowing fuses
« on: March 27, 2009, 10:48:54 AM »
Donny,
 I believe that putting the fuse between the motor and the drive is just about the worst thing you can do.
It can blow the rdrive if there's a sudden loss of impedance on the out put.
  Why are you fusing the servo's? there is an adjustable current cut out built in.that is by far the best way of
dealing with it.
   Tony

209
Joel,
 yes practically the same,I don't know why it was a bit unstable.
I ended up biting the bullet and using 902's.
 I have always built my systems to have a machine resolution of about 1/10th
of the expected work accuracy.
  Are you sure your power supply can provide enough umph? is it the correct voltage for the motors?
if so your best bet would probably be to mount some 200 count US digital encoders on your motors.

210
Hi,
 I have never had any problems on a metal cutting machine (lower feeds,less chance of tripping up)
using up to 5 times pulse multiplier on a g340 (902 fitted).I would not use 10 times on anything other than a point to point machine.
When you have the modifier in 1x mode it is in effect a g320.
  The Idea of the encoder divider circuit sounds fine I did try and make one once but it didnt really work.
The only thing I would say is that it will make the motors noisey on stand still as they will have further to "hunt"
Plus the system will only be accurate to 4 encoder counts,those four counts could under the right circumstances add up or decrease and lead to position inaccuracies.In my case the 3d mold making can take up to 8 hours to machine.
   To sum up if your not using very high CV feed speeds,and you cant change your encoder, then the puse multiplyer is great.
I always buy g340's over g320's just to have this benifit,once you are aware of the limitations the "problem" can be worked around.
Tony

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