In the past, ANILAM and ACU-RITE developed DROs specifically for EDMs. Since those are no longer offered, ACU-RITE made sure that the functionality of its new DROs are capable of achieving all of the old functionality and can be used for EDMs.

The past EDM DROs had I/O functionality, so the minimum requirement for replacement of such a DRO is now with an ACU-RITE 200S DRO with 3 axes and a CSS I/O module. A VUE DRO cannot be used for this application.

Installing an ACU-RITE 200S or 300S DRO will require the assistance from two manuals: CSS IO Users Manual and CSS IO Mounting Instructions, (both can be found on the ACU-RITE website). Within the Mounting Instructions, the installer will find the wiring diagram as shown in figure 1. The installer will only use the X 103 side for wiring up the EDM to the CSS I/O module. The DRO should be setup in Mill mode to take advantage of the 8 switching outputs instead of 5 when in Lathe mode. (See figure 1.)

The ranges on the CSS I/O module represent the switching outputs which are programmed on the 200S or 300S. The ACU-RITE and ANILAM DROs used a maximum of three relays. The old EDM DROs displayed three values on the screen: desired Z-depth, remaining distance to the target depth, and the actual position relative to the zero position. With the 200S and 300S, the user gets to decide which axis on the display that he/she wants to display each piece of information.  The desired Z depth will be set on the 200S or 300S using a datum. The user would enter information for the desired Z-depth on one of the axes that doesn’t have an encoder plugged into it, and the axis that does have an encoder plugged into it will be the axis that tracks the actual position. The remaining axis will need to be setup in the display configuration settings of the 200S or 300S to subtract the actual position of the Z-axis from the desired Z-axis depth. (See figures 2, 3 and 4.)

Once the display has been setup, the next thing to consider is the switching outputs. The programming of the switching outputs will depend on the configuration of the old DRO versus the 200S or 300S. The switching outputs option is only shown when the DRO recognizes the CSS I/O module is plugged into the 200S or 300S. The user has the option of five separate conditions to choose from to accommodate a variety of conditions. The five conditions are: point greater than, point less than, range less than or equal to, range greater than or equal to, and directional (see figure 5). Each condition is entered in the menu shown in figure 6.


In figure 7, the DRO has three switching outputs setup. The first one tells the machine to retract the electrode once the position has exceeded the zero depth. The second switching output is setup to shut off the electrode if the position of Z axis is – 0.8” above the zero position; this is set to ensure the safety of the operator. The third switching output tells the machine to dwell at the desired depth for 10 seconds.

If the operator wants to turn a relay on or off between two specified points, he/she will have to use two switching outputs to perform this function. Also, if the operator wants to add a dwell at a particular point, he/she may use the pulse feature of the switching output and then enter a time in seconds for the dwell to take place. (See figure 8.)

The spark detector can be implemented by using the 3.5 mm audio jack or the D-sub 15 pin connector on the back of the 200S or 300S with the touch probe emblem and using the remote switch functionality which is found under the “remote switch” settings in the job setup menu. (See figure 9.)

When one of the conditions is met, a light will come on CSS I/O module. The second switching output has been triggered because the second condition has been met which is port 3 on X 103. (See figures 10 and 11.)

The example given in this article is just one way to setup the DRO to replace the EDM DROs.