Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: comet on October 28, 2007, 02:26:51 AM

Title: high count servo encoders
Post by: comet on October 28, 2007, 02:26:51 AM

Guys,
  for my next project I want to retrofit a bridgeport mill,max feedrates on rapid will be about 3-4mpm
I am using 500 watt servo's with 2048 count encoders ( 8193 pulses to deal with)
I would like to use gecko 340's with 10 x dividers. My problem is going to be lost steps on direction
changes.I figure if I use exact stop rather than CV that will go some way to helping.
  I appreciate that I could use a higher kernal speed,but for the sake of reliability with the computer I'm
using I dont want to go above 45khz.
  What I really need to do is make mach3 pause for 1/4  second between direction changes especially rapids
Is this possible? I have bought Mach so can I get into the code somehow and do this?
I really dont want to have to put a G4 between every move,as a toolmaker I do alot of programing
and that would be very tiring!
  cheers
      Tony

Title: Re: high count servo encoders
Post by: Hood on October 28, 2007, 04:29:45 AM

Dont think that is possible without putting the G4 in, maybe if you are smart with VB you could write a macro pump to do that but as I am neither smart or good at VB I dont know.
 I have 2000cpr encoders on the lathe I am doing at the moment but I am using Giddings and Lewis Centurian drives and they have electronic gearing which seems to work reasonably well but the higher the ratio you use the rougher the very slow speeds become so I have stuck at 1:2 at the moment.
 This gives me rapids of 3300mm/min which is OK but I am hoping the new USB smoothstepper board will solve my problems by allowing me to go 1:1 on the gearing and get 5OOOmm/min or more rapids, might be worth your while hanging off a bit to see how this board works out.

Hood

Title: Re: high count servo encoders
Post by: comet on October 28, 2007, 06:07:07 AM

Hood,
  USB smoothstepper board? whats that all about then?
   cheers
    Tony

Title: Re: high count servo encoders
Post by: Graham Waterworth on October 28, 2007, 07:21:14 AM

Hood,

you have got to look at this one, I saw the prototype in Galesburg, its very smart, FPGA based, so its programmable. Not by the user, but if you ask, well, maybe!

Graham.

http://www.machsupport.com/forum/index.php/board,65.0.html

Title: Re: high count servo encoders
Post by: Hood on October 28, 2007, 08:35:03 AM

Dont understand Graham, thats what I was talking about in the above post,are you meaning to link to another?

Hood