adccommunitymod (AutomationDirect) asked a question.
Created Date: December 10,2008
Created By: daveinarmstrong
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I have written a program to control 3 separate router heads, a ¼” slot, a 3/8” slot and a “T” slot. These router heads slot the edge of boards as they are fed past. Each router head has its own board start sensor limit switch. When the sensor detects the start of the board, the PLC calculates when to move the router head out to start the slot and when to move the router head in to end the slot based on the user entered data from the EZtouch screen. The machine is a converted wood edge shaping machine and the boards are held down by pressure rollers on top and fed by a conveyor on the bottom, very accurate. The conveyor has an encoder to read its position. The problem is that when smaller boards (4” wide and up to 7 at a time) are fed into the machine, the slot starting points start earlier by up to ¼” (The slot is supposed to start 1” from the board edge. It is starting ¾” from the board edge instead) and varies from board to board but never starts later. This only happens when the machine is processing multiple boards at once. If only one board is fed the slot starting point remains accurate. Nothing mechanical is showing up as a problem. Using a PLC D4-450 HIGH SPEED COUNTER D4-HSC from Automation Direct. Ladder Logic attached, count factor 1 " = 42.6 encoder pulses. Dave
Created Date: December 10,2008
Created by: bcarlton
I know this is obvious but check if the reference limit switch is being made in a different manner with the different boards. Could it be a switch bouunce effect?
Created Date: December 11,2008
Created by: daveinarmstrong
The boards are perfectly squared up against a fence and are cut square so each board start edge is nice and straight and uniform.
The board start switch has been replaced and also the boards go through fairly slowly, 15 feet per minute. Which should minimize any switch bounce.
Problem is only exists with multiple boards. If one board is processed at a time there is no problem.
Created Date: December 11,2008
Created by: milldrone
daveinarmstrong,
First my limitations I have never worked with a 450 before. Plus many more (too numerous to mention):eek:
I have briefly looked over your program after correcting the import errors (18 characters in a nickname).
Question #1: If the slot "happens " too early is it the correct length?
Question #2: Does this happen to all of the slotting heads or just one?
Question #3: In rungs #15 thru #20 I see some speed variables that get loaded into V4000, but there is no listing in the Xref for this variable to be used that I can find. I'm presuming there is some actuator travel time and this is an attempt to solve this, correct?
Question #4 You have stated that the feed is very positive. Is there a possibility that as the hold down rolls somewhere in the machine (not necessarily near the slot head that is giving you problems) is "slowing the board or conveyor for an instant just before the slot happens? What I'm suspecting is you have made allowances for the "actuation time " when running single boards. And that when you run multiple boards the feed speed is being altered in some way even if it's just for an instant.
Created Date: December 10,2008
Created by: daveinarmstrong
I have written a program to control 3 separate router heads, a ¼” slot, a 3/8” slot and a “T” slot. These router heads slot the edge of boards as they are fed past. Each router head has its own board start sensor limit switch. When the sensor detects the start of the board, the PLC calculates when to move the router head out to start the slot and when to move the router head in to end the slot based on the user entered data from the EZtouch screen.
The machine is a converted wood edge shaping machine and the boards are held down by pressure rollers on top and fed by a conveyor on the bottom, very accurate. The conveyor has an encoder to read its position.
The problem is that when smaller boards (4” wide and up to 7 at a time) are fed into the machine, the slot starting points start earlier by up to ¼” (The slot is supposed to start 1” from the board edge. It is starting ¾” from the board edge instead) and varies from board to board but never starts later.
This only happens when the machine is processing multiple boards at once. If only one board is fed the slot starting point remains accurate.
Nothing mechanical is showing up as a problem.
Using a PLC D4-450 HIGH SPEED COUNTER D4-HSC from Automation Direct.
Ladder Logic attached, count factor 1 " = 42.6 encoder pulses.
Dave