Hi Guys,

I have recently got back to working with CNC after a couple of years doing other things.  I have used Mach for several years and I am in the process of getting a new Syil X5 mill and want to ad a ATC.  I have been studying the methods to ad additional ports and I am confused as to the pros and cons of Modbus vs pokey.  I have searched for some post regarding this but I haven't found anything that directly compares them.  Is there a clear advantage of one or the other?  Any info would be appreciated.

Thanks,
Larry

I would first start by looking at the actual number and types of I/O required for your entire machine + tool changer. Then you can look at which solution may work out best for your needs. Would a second LPT card be enough? Maybe a SmoothStepper would give you all the I/O you need for both the machine and tool changer? Etc, etc..

From the point of view of ease of configuration for a 'newbie' I would say that modbus would be the most complex but has the greatest number of external devices that can be connected through it. If your currently running a single LPT card then adding a second one would probably be the simplest. The SmoothStepper and Pokey would be somewhere in the middle.

I would use a PLC over any other means of extra I/O any day, it is however more expensive.
The main benefits I see with a PLC may be biased towards larger machines however.
The great thing is you can use 24v for all your I/O and thus not have the same worries regards noise. You can also make the PLC do the toolchange by writing the ladder and just have Mach tell it to start and the PLC will tell Mach when its finished. Same for external buttons, they can all be 24v, also the analogue inputs on my PLC are rock steady where the PoKeys will vary slightly, not a huge issue but does make it easier to reset to 100% for FRO and SRO.

Hood

Guys thanks for the feedback on this.  It did seem like they are basically doing the same thing, provide more I/O ports and like most things in life the answer is "it depends".  This information was very helpful.

Thanks,

Hook, (btw, I fixed the jitter in the PK analog)....

But, for reliablility and flexibility you can't beat a PLC.

scott

Good to hear Scott. Not using the PoKeys now as it was in a handheld pendant and I have come to the conclusion that handheld pendants are not for me

Hood

Good to hear Scott. Not using the PoKeys now as it was in a handheld pendant and I have come to the conclusion that handheld pendants are not for me

Hood

Hood,

"I have come to the conclusion that handheld pendants are not for me" - I assume that's because picking up the pendant required putting down the scotch?  "-)

Regards,
Ray L.