Created Date: August 06,2002

Created by: nitewatchman

I need to develop a closed loop control for an existing milling machine with hydraulic axis motors. This application will require that a constant programmable taper be cut by dropping the head syncronized with the table feed over 40 feet of table travel.

I want to use the existing 405 with linear scales, high speed counters and analog output cards. The analog cards will be used to drive the a servo hydraulic valve to be added to the head axis circuit.

Anyone done anything like this?

Can the output card drive the servo valve directly or will a drive interface card be needed?

Any suggestions on building the Gain logic?

Gary Click

nitewatchman

Created Date: August 06,2002

Created by: cj

This may be achievable with an automationdirect PLC but my guess is that it won't be. AutomationDirect PLCs, as a rule, do not do closed loop control. Depending upon the servo valve, you may be able to control it with analog and you probably won't have any problems getting a pulse from a linear scale into a High Speed Counter card. The problem will be the reaction between the two. You will have a scan based latency that, I would imagine, created a "terrace " effect upon your part. The underlying factor will, of course, be the speed of the process. The faster the part feeds, the worse the slope will be. Maybe others have a different opinion.

Created Date: August 07,2002

Created by: Ray Kissane

Gary;

I have used the output to drive a Proportional hydralic valve but it had an on board electronic package so the current draw was acceptable. Other wise you will have add an interface card. You also have to look at the valve and make sure if it is voltage or current driven. Most of the servo's I deal with are current but the proportional hydralic valves can be either voltage or current.( I prefer voltage driven)Proportional valves do not have as tight of manufacture tolerances and can take abuses better(ie.. oil cleanness, contamination)than servos and their reliability and cost are better than servos.

We use linear pots on a PLC input and make a routine in the PLC for closed loop. You have to determine the speed of the process because the AC output cards can not easily drive all of the outputs every scan of the PLC. You need to figure out the number of scans that it will take you drive all of the valves and verify that will be acceptable to the proces speed.

Hope this helps.

Ray Kissane