ACME Screw Machine Controls Upgrade
Padnos College of Engineering and Computing
Grand Valley State University
August 4, 2006
Table of Contents
Table of Contents _______________________________________________ 2
List of Inputs and Outputs ________________________________________ 3
Preparations for Job Setup _______________________________________ 4
Logic _________________________________________________________ 5
Program States _________________________________________________ 6
State Descriptions ______________________________________________ 7
Appendix-A ___________________________________________________ 10
The following tables display the current input and output connections in the control
Table 1: Inputs to the PLC
1 Start Push Button
2 Stop Push Button
3 Jog East
4 Jog West
5 Run West
6 Run East
7 Index Proximity Sensor
8 Out of Stock Sensor
9 Pickoff Close
10 High Pressure Pump Input
11 MCR Input
12 Pickoff Open
13 Stockup Push Button (ONEPB)
Table 2: Outputs from the PLC
1 Not Used – DC Output Only
3 High Pressure Pump
4 Main Motor
5 Coolant Pump
6 Yellow Light
7 Green Light
8 Air Blast
9 Feed Engage
10 Feed Disengage
11 Part Counter
12 Close Pickoff
Notes Regarding Input and Output Connections:
The wiring for the output on the GE Fanuc Micro 90 PLC that was installed in the
Control panel is different than one might think at first glance. A schematic showing the
correct wiring is shown in Figure 1. This particular figure came from page 91 on the
Figure 1: Input Relay and Output Modules.
PREPARATONS FOR JOB SETUP
Depending on the pickoff setup for the job, the cams for the pickoff sensors may need to
be adjusted. In this case, complete the following steps:
1.) Jog the machine until the pickoff is in the desired closing position.
2.) Rotate the cam corresponding to the sensor with Input 9 until the sensor first trips.
Lock the cam in place.
3.) Jog the machine until the pickoff is in the desired opening position.
4.) Rotate the cam corresponding to the sensor with Input 12 until the sensor first
trips. Lock the cam in place.
Note: The cam corresponding to input 9 (for closing pickoff) corresponds to the sensor
on the left as you are facing the cams from the same side of the machine that the control
panel is on. The cam corresponding to input 12 (for opening the pickoff) corresponds to
the sensor on the right as you are facing the cams from the same side.
Several lines of logic were written in order to help the programmer to discern the proper
amount of parts that the machine needs to run after the “out of stock” sensor is tripped.
As of 8/4/6, the corresponding rungs were rungs 65 – 68.
*ADD INT registers are present in case any “fudging” needs to be done in selecting the
number of parts for the cutoff cycle. If you want to increase or decrease the bar length,
you can do so by modifying the IN2 values. The following table is for a quick reference
of the register variables used and whether or not they need to be modified for each
Table 3: Reference of Register Values Used for Determining Bar End Length
Title Register Description Setup?
Gauge This measurement is the distance from the face of sensor is
Length R00052 the collet to the out of stock sensor relocated)
Part Length R00053 Part Length Yes
Temp R00054 Temporary register No
This is the length of bar that remains after two part
lengths have been subtracted. The two part
Bar Length R00055 lengths assures that the bar end won't be too short. No
Cutoff Length R0059 This is the width of the cutoff blade being used Yes
Faceoff This is the mount of material removed by the
Length R00056 faceoff Yes
This is the number of parts that will be made after
the out of stock sensor is tripped before any
OSPARTS R00057 additional correction parts are added. No
This is the GRAND TOTAL number of parts that
will be made after the out of stock sensor is tripped
TOTPART R00058 after any additional correction parts are added. No
When a new job is setup on machine 17, the following steps must be taken in order to
assure that the PLC knows how many parts to produce after the “out of stock” sensor is
tripped. This will assure the proper length of scrap bar ends, and prevent the batch from
becoming contaminated with short parts.
1.) Change the “Part Length” value shown as register 53 to the corresponding
measurent of the part to be produced.
2.) Change the “Cutoff Length” value if the width of the cutoff is different than the
3.) Change the “Faceoff Length” value to compensate for the length of material
removed by the faceoff.
The code for this setup is shown in Appendix-A. Cimplicity software was used to
construct the ladder logic. The electronic file name is M0017REV3 and is stored as a
The following state diagram lays out the different states and functions of the machine.
The logic for this machine was written based on these states and their orientation.
Figure 2: State Diagram
Machine remains idle with all outputs disengaged except for a conveyor, which
may remain on for several minutes after the machine has been running. This
allows the conveyor time to remove excess shavings from the bottom of the
All states of the machine must default back to this mode.
The Idle Mode can be reached from any state by pressing STOP. This will
disengage the feed and stop the machine at its current position. This is used as a
safety precaution ONLY. Stopping the machine while the tools are in the process
of cutting will damage the tools.
This mode allows the user to rotate the spindles, engage the feed of the machine,
and/or disengage the machine manually by having both RUN inputs enabled, and
by holding down a start button.
When the user releases a start button the machine will return to Idle Mode.
The feed can be engaged and disengaged manually by pushing/pulling a lever
located on either side of the machine.
The coolant pump is on as long as START is held down.
The purpose of this state is to allow the screw machine’s components to begin
moving and to get the coolant spraying on the internal working components and
the tools before they are engaged.
This mode is initiated by pressing START with both RUN switches selected.
Idle Mode can be reached at any time in this mode by selecting either JOG
switches while the machine is running, or by pressing STOP.
The motor, coolant pump, and conveyor will all be turned on in this mode, and
will remain on throughout it. The machine will remain in an idle state with the
previously mentioned components on.
From the Machine On mode, this mode can be reached by pressing a START
button a second time.
After the START button is pressed a second time, the feed cylinder will engage
and the machine will start to move. The tools will move forward toward the
workpieces. The pickoff will move towards the finished part, clamp onto it while
the part is being cut off, and retract and release the part. The process is repeated
as the machine indexes.
The feed is held in place by a cylinder while in this mode to prevent the feed from
If the machine takes longer to complete a cycle than usual, the machine will fault
out, the feed will disengage, and the Idle Mode will be selected.
Finish Part and Index Mode
In order to stop a cycle without damaging the tools, the Finish Part and Index
mode is used. In the Machine Running mode, if a RUN button is switched to a
JOG button the Machine Running Mode will end and the Finish Part and Index
mode will be selected.
At any time during a cycle this mode can be initiated.
This mode can be reached from the Machine On Mode by pressing the One Cycle
Start button twice. This is used during the stockup mode. After an operator loads
a new bar, this button will run one cycle and stop.
When the index proximity sensor is detected, Idle Mode will be selected and the
feed will disengage.
Finish Stockup Mode
This mode is set when the machine is running in Machine Running Mode and the
out of stock sensor is tripped while the index proximity sensor is tripped.
When the out of stock sensor is tripped, there is a substantial amount of stock left
in the pusher in the spindle. A counter is used in the logic to count the number of
cycles (and thus the number of parts made) until this stock is used up. When that
number is reached, the machine shuts off, the index is disengaged, Idle Mode is
At any time during this mode, Idle Mode can be reached by pressing STOP or if
the machine becomes jammed.
If either of the JOG switches are selected, the Finish Part and Index Mode will be
set and Idle Mode will be set after one cycle.
Jog Manual Mode
This mode is used primarily for setup purposes. The operator must have both
switches in Jog Manual Mode. This will turn on the motor and coolant pump,
leaving the feed alone so that the operator can use a lever to manually engage and
APPENDIX – A