Valve sequencing

Hi!
I am relatively new to Labview (been doing some easy measurement (analog, digital,...) but have now stubled upon something new and don't know how to approach it. This is the problem:
I have 2 valves with 2 electromagnets. It the valve gets signal from left EM it goes into position 1, if it gets from right EM it goes to position 2. It there is no signal it stays in position 0. On the top with number 3 and 4 are inductive switches. So what I would like to do is next:
Stage 1: Valve1 and Valve2 both get in position 1 at the same time.
Stage 2: When top piston activates inductive switch (red number 4), Valve2 stays in position 0 for 2 seconds.
Stage 3: Both Valve1 and Valve2 go to position 2. (the top piston starts moving left)
Stage 4: When it activates inductive switch (red number 3), Valve 2 again stays in position 0 for 2 seconds.
Stage 5: The loop is repeated.
So the question is how to begin building code for sequencing. Should I build code in Flat Sequence Structure, Timed Sequence or something else?
Thanks for all the help you can give me.
Much appreciated!
Jure
Solved!
Go to Solution.

Thanks for giving me some direction... As I'm compleatly new in State Machines I have a couple of questions.
So far I have done is attached below. In the VI attached I have build a default case with a button to start sequence. If the button is pressed it goes to first case "1", where valves 200.0, 209.0 and 209.1 are opened (position 1).
Below I have simulated a signal, which represents inductive switch I4. When maximum peak is reached it goes to case "2", where valve 200.0 is opened in position 2, therefore it shouldn't receive signal for position 1, but for some reason I cannot shut down signal for position 1. I tried simply putting false statment but the valve keeps being open in both positions. How do I shut it down?
Thanks for all the help!
Jure Hrovatin
Attachments:
StateMachineLPKH.vi ‏88 KB

Similar Messages

How to keep that valve open for certain period of time and shut off automatically

Hi everyone,
The objective of the VI is to measure pH and then open acid or base valve based on pH valve. Below is my UNFINISHED VI
My question is: if, for example, the pH is 10, then, the program will open acidic valve for 5 seconds and then shut off automatically. After that, wait for 5 second. this process will go on and on as I use while loop, but I just dont know how to control the valve on for 5sec and off and then wait for 5sec.
Anyone can help me out? Thank you very much
In the picture, please enter those values before running
P.S The VI is based on previously posted vi by someone who made it 1 yrs ago.
Attachments:
project_trial_1_26.vi ‏27 KB
Capture.JPG ‏79 KB

1. The reason the valves close immediately is that the Elapsed Time VI does not cause any wait, it only measures the time. So the valves closed within a small fraction of a second of the time they opened.
2. I modified your VI to wait until the Elapsed Time has ended. See the "wait" state. I probably modified some of your other functionality in the process, but this shows one way you could do the timing.
3. You do not need any Value property nodes. They should never be used if the value can be wired directly.
4. You do not need any sequence structures. Dataflow will determine the order of things occurring.
5. If you use an enum for the state machine (and it is a good way to name and select states), you should make it a type def. Then when you need to change it as I did to add several states, you only need to change the Type Def in one place and the changes propagate through to every place you used the control or constants derived from it.
6. I added a Halt state which will close both valves before stopping the program. When you are controlling a real world process, it is important to consider the start up and shutdown requirements. For example the digital outputs of the USB-6008 default to inputs when the device is first powered up. And, the inputs are pulled high by a 4700 ohm resistor (at least I think I recall that value). Will this open your valves before the program starts running and sets the I/O lines to outputs and forces them low?
The USB-6008 has rather limited drive on the digital lines. You will probably need a buffer between it and the valve coils.
PID and PWM are more complicated than I want to get into here. First, are your valves proportional or on/off? Second, (assuming that they are on/off) how fast can you open and close them without destroying them in the first week? What is their expected lifetime in terms of the number of operations? How fast do you need to be able to change them to keep your pH where you want it? Are these values compatible?
Lynn
Attachments:
pH State.ctl ‏12 KB
project_trial_1_28.2.vi ‏66 KB

File adapter reentrant valve

Hi,
I am trying to implement a pipeline in the File Adapter. I am facing a problem if I try making the XSD using a DTD. In this case I am only able to get the first file present in the zip file.
The DTD is as follows:
<!ELEMENT EmployeeRecords (Employee+)>
<!ELEMENT Employee (Ecode,Name,Addr,DOB,BaseSalary,NoOfDaysWorked,InsurancePlan,NoOfDependents)>
<!ELEMENT Ecode (#PCDATA)>
<!ELEMENT Name (Fname,Mname,Lname)>
<!ELEMENT Fname (#PCDATA)>
<!ELEMENT Mname (#PCDATA)>
<!ELEMENT Lname (#PCDATA)>
<!ELEMENT Addr (HouseNo,StreetName,City,Pincode,State)>
<!ELEMENT HouseNo (#PCDATA)>
<!ELEMENT StreetName (#PCDATA)>
<!ELEMENT City (#PCDATA)>
<!ELEMENT Pincode (#PCDATA)>
<!ELEMENT State (#PCDATA)>
<!ELEMENT DOB (#PCDATA)>
<!ELEMENT BaseSalary (#PCDATA)>
<!ELEMENT NoOfDaysWorked (#PCDATA)>
<!ELEMENT InsurancePlan (#PCDATA)>
<!ELEMENT NoOfDependents (#PCDATA)>
The XSD that has been generated is as follows:
<?xml version="1.0" encoding="UTF-8" ?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="http://TargetNamespace.com/rcvZipFile" xmlns="http://TargetNamespace.com/rcvZipFile" nxsd:version="DTD" xmlns:nxsd="http://xmlns.oracle.com/pcbpel/nxsd">
   <xs:element name="Name">
      <xs:complexType>
         <xs:sequence>
            <xs:element ref="Fname"/>
            <xs:element ref="Mname"/>
            <xs:element ref="Lname"/>
         </xs:sequence>
      </xs:complexType>
   </xs:element>
   <xs:element name="Mname" type="xs:string"/>
   <xs:element name="Employee">
      <xs:complexType>
         <xs:sequence>
            <xs:element ref="Ecode"/>
            <xs:element ref="Name"/>
            <xs:element ref="Addr"/>
            <xs:element ref="DOB"/>
            <xs:element ref="BaseSalary"/>
            <xs:element ref="NoOfDaysWorked"/>
            <xs:element ref="InsurancePlan"/>
            <xs:element ref="NoOfDependents"/>
         </xs:sequence>
      </xs:complexType>
   </xs:element>
   <xs:element name="Pincode" type="xs:string"/>
   <xs:element name="BaseSalary" type="xs:string"/>
   <xs:element name="StreetName" type="xs:string"/>
   <xs:element name="HouseNo" type="xs:string"/>
   <xs:element name="Lname" type="xs:string"/>
   <xs:element name="NoOfDependents" type="xs:string"/>
   <xs:element name="DOB" type="xs:string"/>
   <xs:element name="InsurancePlan" type="xs:string"/>
   <xs:element name="State" type="xs:string"/>
   <xs:element name="Ecode" type="xs:string"/>
   <xs:element name="City" type="xs:string"/>
   <xs:element name="Fname" type="xs:string"/>
   <xs:element name="NoOfDaysWorked" type="xs:string"/>
   <xs:element name="Addr">
      <xs:complexType>
         <xs:sequence>
            <xs:element ref="HouseNo"/>
            <xs:element ref="StreetName"/>
            <xs:element ref="City"/>
            <xs:element ref="Pincode"/>
            <xs:element ref="State"/>
         </xs:sequence>
      </xs:complexType>
   </xs:element>
   <xs:element name="EmployeeRecords">
      <xs:complexType>
         <xs:sequence>
            <xs:element maxOccurs="unbounded" ref="Employee"/>
         </xs:sequence>
      </xs:complexType>
   </xs:element>
</xs:schema>


I am using the same XSD at both the input and output file adapter. I am facing two issues:
1. I had put 1 zip file with two internal files, each containing 2 records. I had configured the output File adapter to make one file per record. The output folder contains two records BUT only of the first file present in the zip file.
This problem does not come in case I make an XSD using the Delimited option(CSV). In both the cases, i.e., Case1 in which the XSD was made using a DTD and Case2 in which the XSD was made using a delimited option(CSV) the valve settings have been made as reentrant. Please find below the entries in the pipeline.xml
<?xml version="1.0" encoding="windows-1252" ?>
<pipeline xmlns="http://www.oracle.com/adapter/pipeline">
<valves>
        <valve reentrant="true">valves.ReentrantUnzipValve</valve>
</valves>
</pipeline>
2. a) When I make an XSL using the mediator and do a mapping of all the elements, the output that I get does not contain any data values. If i remove the name space of both the input and output message structures then I am able to get the output.
b) I had added a sensor on the incoming file adapter and was trying to check on the value of an incoming data element. But the sensor does not get any value. If I delete the name space in the variable that I am trying to check, then the sensor gets the value.
Thanks,
Aditya

Is there any special format for reading a file containing hexadecimal control characters?
The file to be processed has hexadecimal separators:
Field Delimiter        : '09' or '05'
End of record delimiter: '0A' or '25'
End of Table delimiter : '07' or '2F'
Initially i would like to read the file into XI as it is i.e without any split by using "xml.fieldFixedLengths= "
However, everytime I process the file(with hexadecimal contol characters), I have noticed that my file is getting split, even when I did not specify anything for field separator(i.e when i used fixed field length).
Thanks,
Dorai

Timed sequences. Is that hte right choice and how does it works!

Hi!
I'm a newbie in LV, and I'm trying to create a VI that is capable of controlling a small filtration unit I have build as a part of my engineering studies.
I have to control three magnetive valves which are connected to the digital output port Do0, Do1 and Do2 on my MyDAQ 6009 USB device.
I have to control the sequence by which the valves opens / closes as to avoid damage of som sensitive pressure transmitters. How do I manage to programme a time controlled sequence that opens and closes the valves in the right order and , in reverse order, repeats the sequene after a user defined choice of time?
I have looked at the "Timed sequence" but cant find a "down to earth" description on how to use it.
Maybe my problem is a bit to general. In that case I can surely help with a clarification if needed.
I hope someone can help me with my problem. By now I have spent 6 hours in watching different tutorials without any luck.
Thanks in advance
Henrik
Solved!
Go to Solution.

Hi Anders!
I have looked on the State Machine solution, but couldn't really figure out where to start. As I mentioned, I'm a newbie. All I have done so far is data logging and working with analog signals (temperature logging, controlling a pump and so on). I have build a filtration unit as a part of my studies to become a chemical engineer. In order to clean the ceramic membrane in use, there is a procedure where the fluidstream is pumped back in to membrane to loosen fouled particles etc (called backflush). This is done with high pressure air. I have mounted three magnetic valves to be able to control this process.
Valve one and two has to close approx 0.5 sec before valve three opens. Valve three is allowing the high pressure air to push fluid in reveres direction and valve one is protecting a pressure transmitter with a max. overload pressure [bar] below the required pressure. After a userdefined number of seconds, the process has to be repeated in reverse order. The three valves are connected to digital I/O channel 0,1 and 2 on the USB 6009. With the Measurement and Automation explorer testpanel I can open and close the valves manually, so the connection is established. I don't have access to a PLC, which probably would be the right choice for my problem.
If you could help I would appreciate it a lot. My thesis isn't about building a filtration unit. It is more the process using it, and that is not possible right now
If the above information is insufficient, I will provide any information needed.
Best regards
Henrik

Real-Time Sequencer Feedback and Questions

Post your questions and feedback to the Real-Time Sequencer Architecture and Real-Time Sequencer Architecture Example here.
Brian K.

I just purchased the USB 6341 DAQ card. I am using Dev1/.Port1 to control 4 driver transistors. The transistors fire 4 SSR. I am trying to create a sequence for the 4 transistors. Sometimes a test unit that is driven by a SSR will fail. So I have to change the sequence for the failed DUT.
Basically each SSR will be ON for 6 seconds. There will be a delay of about 5.75 seconds for the next valve to fire. The delay is used to balance the pressure testing. The second valve will need to start at 5.75 seconds later. Basically the two valves must cross at the 50 % turn OFF. How can I perform this task. There are at least 7 different test sequences??
Thanks,
Philip

Creating a control sequence of digital outputs with timing

I'm trying to create a controls system for a cleaning process. I am controlling a pump, heater, and several solenoid valves using relays that I am opening and closing with the +5V from my USB 6008 and each relay goes to one of the digital I/O lines, where I provide a sink to switch the relay.
I am using the front panel as the user interface for the machine, so the user can specify three different processes, so I'm using an event structure to call each process. An example of the steps in the process are as follows:
1. Open relay #1 (solenoid valve)
2. Open relay #4 (heater)
3. Wait 30 seconds (while relays #1 and #4 are still open)
4. Close relay #4
5. Close relay #1
6. Open relay #2 (solenoid valve)
7. Wait 5 seconds (while relay #2 is still open)
8. Close relay #2
I am trying to use a framed sequence structure within the event cases, with the DAQ Assistant saying which lines are sinks and which are also outputting +5V (no delta, keeps relays closed), but I don't think this is working and will bog down the system if it did. I think inverting the lines will make it so the lines nominally output the +5V so I just need to send it a sink when I want to close the relays, and make sure it keeps doing that while it waits so the process can be completed.
What is the best way to do this? I've used Labview before, but I'm hardly a pro, so any help would be greatly appreciated.

As nijams mentioned a state machine architecture is a good place to start. In case you are unfamiliar in how to implement this in LabVIEW there is a blank state machine template available in LabVIEW. When you create a new VI select From Template->Frameworks->state machine. In addition I've included a link to a simple example posted on our NI Community.
State Machine Example.zip: https://decibel.ni.com/content/docs/DOC-15515
Regards
Regards,
Isaac S.
Applications Engineer
National Instruments

Making sequence structures a state machine

Hey I would like some help I need to work on changing my code and get rid of the flat sequence structure and replace with a state machine I have attached my code at an earlier state but would like some input on changing it over to a state machine in the sequence at the bottom of the code this program is used to cycle a valve and the sequences need to be done in order .any input would be great.
Attachments:
valve Cycles with temp.vi ‏132 KB

Right click on the Flat Sequence and pick Replace with Stacked Sequence (never would have thought I'd say that.)
Right click on the Stacked Sequence and Replace with Case Structure.
Now a lot of wires will wind up broken. So you'll need to hunt them down and fix them. Those wires will probably need to go to shift registers so there values are maintained for the next loop iteration. Keep a copy of your original VI so you have something to refer back to.
Create a Typedef Enum and define what your states will be.
Start wiring the Enum into a shift register at the left of the loop, then into the selector of the Case Structure. Rename all the cases to what their respective state should be.
Wire enum constants in each case to direct what the next case should be. It will run out of the case structure to the right hand shift register.
Keep working and cleaning still everything is fixed.
Try running your VI to see if it behaves like it originally did.
Now you are safe to start making modifications to make it behave like you really want it to.

Need to Create a 4 step sequencer

I just purchased the USB 6341 DAQ card. I am using Dev1/.Port1 to control 4 driver transistors. The transistors fire 4 SSR. I am trying to create a sequence for the 4 transistors. Sometimes a test unit that is driven by a SSR will fail. So I have to change the sequence for the failed DUT. I will have one less DUT to test.
Basically each SSR will be ON for 6 seconds. There will be a delay of about 5.75 seconds for the next valve to fire. The delay is used to balance the pressure testing. The second valve will need to start at 5.75 seconds later. Basically the two valves must cross at the 50 % turn OFF. How can I perform this task. There are at least 7 different test sequences??
Thanks,
Philip

hello,
in a first time you can have a look on how to use state machine
which is base of sequencer
http://zone.ni.com/devzone/cda/tut/p/id/3024
regards
Tinnitus
CLAD / Labview 2011, Win Xp
Mission d'une semaine- à plusieurs mois laissez moi un MP...
RP et Midi-pyrénées .Km+++ si possibilité de télétravail
Kudos always accepted / Les petits clicks jaunes sont toujours appréciés
Don't forget to valid a good answer / pensez à valider une réponse correcte

Rig start up sequence

Hello,
I'm looking for a way to create a laboratory start-up sequence.I'm using Labview 6i, and using the fieldpoint FP-CTR-502 counter input module. For the purpose of start up we are going to use the 4 discreet output channels on the CTR-502.
I'd like to know how the to issue the bits I want in a sequence so as to enable various stop buttons, valves and motors on the rig.
The bit logic should look like this...:
Discreet Channel No:
3 2 1 0
Step 1: 1 1 1 1 Start/Reset (watchdog state?)
(Stop button shut, control valves shut, heaters shut, DC motor shut)
Step 2: 1 1 1 0 Enable stop mechanism (powerup)
Step 3: 1 1 0 0 " " "
At th
is point the program should stop and should only be able to continue once the enabled stop button has been manually reset (a FP-AI-110 signal will feedback the signal to the program that the emergency stop mechanism has been reset, thus enabling the sequence to continue).
Step 4: 1 1 0 1 Enable control valves.
Step 5: 1 1 0 0 " " "
Step 6: 1 0 0 0 Enable the three heaters
Channel 2 bit is the 'master' bit. The heaters controlled by channels 0 and 1 cannot be ON until a 0 is issued to channel 2.
Program should stop here for adjustment of set point. No feedback required just a click on a 'continue' button, once the required temperature is set.
Step 7: 1 0 1 1 Heaters not required are shut(channels 0 and 1)
Step 8: 0 0 0 0 DC motor enabled
And that's the whole program! I would have thought that a sequence loop would be appropriate.
Cheers,

One thing to consider is how you want to address the output channels on the FP-CTR-50X modules. You can individually address each channel by the channel name/number, or you could create a multi-channel item allowing you to address all 4 channels at the same time. If you address all 4 channels simultaneously, there is a little trick to make it work correctly. The 4 output channels are channels 12-15 on the module. Each channel would be represented by a single bit in a 16 digit number with channel 15 (Output Channel 3) being the most significant bit. Thus for step 1, you would write a value of 0xF000 or decimal 61440. Step 4 would be 0xD000 or decimal 53248.
Regards,
Aaron

Labview Crashes when adding case and sequence structures

I am running into a problem that I have never experienced before - when I am adding case and sequence structures to a version of code I am writing, Labview 6i crashes (i.e CPU allocation jumps to 95% on the task manager and hangs there) requiring an "end task". I am writing the code within XP Pro running on a 1.7 Ghz Pentium 4 machine with 512 MB.
The code is used to control valves and temperature controllers on a Noble gas analysis line and is fairly simple. There are multiple nested sequence (30 steps long) and case structures within a while loop. The code itself is around 1.9 MB, so given the speed and on-board memory of my machine I doubt that I am reaching and physical limit in terms of the memory or proce
ssing power required.
Has anyone ever seen something like this? Could the code have been corrupted by an email transfer? If so are there ways to recover? Any help would be greatly appreciated.

Yes. At least to 6.0.2. Also, you might be able to fix the problem by doing a mass recompile of the directory that the vi resides in, this fixed a similar problem I had about a year ago. Just start Labview, but don't open any of the VIs in that program, then select Tools->Advanced->Mass Compile. I am not sure why it worked for me, but it did, I think it cleans up the code a bit.
Jon D
Certified LabVIEW Developer.

Help with cycling sequence structure, I may need a state machine?

Hi All,
So I have this VI that needs to control two solenoid valves by opening and closing them through the digital outputs.
I want the program to have a function like this
Phase 1: Valve 1 open, Valve 2 closed (Amount of time for this defined by user)
Phase 2: Both valves closed (for .1 seconds)
Phase 3: Valve 1 closed, Valve 2 open (Again, this amount of time is defined by user)
and I want it to cycle through phase 1-3 100,000 times. However, every 10,000 cycles of phase 1-3 I want it to change the condition on Phase 2 so that both valves are closed for an hour instead of .1 seconds, then after this hour loop I want it to return back to the original cycling conditions (.1 sec instead of 1 hour) until it does another 10,000 cycles.
I was thinking that a sequence loop would be fine because I would wire it up with timing and a counter, and every time it goes to the last sequence it would increase the counter so that when its at the phase 2 timing I can use a case structure (if counter > 10,000 hold 1 hour, if counter <10,000 hold .1 sec) and then in the last sequence reset the counter to 1 if it is >10,000.
I thought a sequence structure would be good for this but I'm fairly new to labview and if theres a better way to do this I'm open to suggestions .
Attached is my code so far, except that I have not finished wiring the ports for valve B
Attachments:
Adhesive Pressure Cycling.vi ‏100 KB

First, you should avoid the use of a sequence structure. Don't even consider it to be an option. At least not at this stage of your learning. Learn how to use data flow. Also, avoid the use of local/global variables. They tend to lead to race conditions which in turn result in some difficult bugs to find and fix. Think of the wires as your variables.
As for the time delay in your state machine, your actual state should delay for a short time like 100 ms. Use the current time of day to determine when you have reached your desired timeout. If you use a single delay of an hour your program will be unresponsive for that hour. Users tend to get very annoyed if they try to stop the program and they have to wait a long time for it to actually stop.
Here is a basic example that shows the concept in a state machine.
When naming states for your state machine give them a meanigful name. Use a typedefed ENUM for your state variable. For simplicity sake the example attached does not use a typedef. But naming things like State 1, State 2 and so on makes the code difficult to read and understand. Your Open/Close valves states can be written in such a way that they are generic and take the valve data as input. At a minimum I would create a subVI to do this so you only have one piece of code to manage. You could have explcit states though such as Open Valve A and Open Valve B that call your generic Open Vavle subVI with the appropriate input data.
One last comment, the express VIs tend to be very inefficient. They are OK for learning how things are done but I would implement their functionality directly. For example, the express VIs tend to open, initialize, do something, close the instrument. You really don't have to do all of that every time. Open and Initialize once in the begining (hint, this could be a state), put the stuff that does the work in appropriate states/subVIs (other states) and then close at the end of your application (the exit state for example).
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot
Attachments:
Simple Delay in State Machine.vi ‏15 KB

Digital Output Sequence (variable timing) NI 9472

Hi,
Wondering if anyone has any suggestions for creating a VI to do the following:
I have 6 valves which I want to control with a NI 9472 module (8 digital outputs). The valves have a set sequence of 6 stages, each with different times (which I would like to be able to vary)
I have 3 of the above setup (ie 3 sets of 6 valves) that I would like to control in the same way but independent from each other.
I have attached a diagram of the valve setup and sequencing that i would like to achieve.
Thanks for your ideas.
Setup:
NI cDAQ-9174 Chassis
3 x NI 9472 24V sourcing module.
Solved!
Go to Solution.
Attachments:
Valve Positions.JPG ‏20 KB
Sequence Timing.JPG ‏36 KB
Valve Setup (3 x 6).pdf ‏24 KB

OK here is a quick idea about my suggestion. Let me know what you think. For now you need to set up the array for the time and valves before you start the program.
Tim
Johnson Controls
Holland Michigan
Attachments:
Timed Valves.vi ‏26 KB
Time Array.ctl ‏6 KB
Valve Array.ctl ‏5 KB

Valve control

Hello wise NI people. I am trying to use the text file attached below to control a series of valves. After several tries, I keep getting errors (200524,etc) and when it does run the sequence is way off. I have an idea were I am messing things up but I need some ideas on how to fix it. I will appreciate any suggestions or references.
Solved!
Go to Solution.
Attachments:
Flush and Sample.vi ‏58 KB
AF 17.txt ‏1 KB

Charles,
The way your text is formatted was causing an error. I took out the errors from your text and now reads in ok.
I can see that you are taking the first column to give you your time delay. You are then getting the rest of the array from the 5th column? is this what you are meaning to do? This means that in each iteration you are trying to send a 1D array consisting of 11 booleans. I have never used this hardware, could it be that it needs to see a 1D array of 16 bits and this is the error you are getting?
Rgs,
Lucither.
"Everything should be made as simple as possible but no simpler"
Attachments:
New.txt ‏1 KB

Controlling a timed relay process and not using a sequence to do it

I am using the fieldpoint system with the RYL-421 module and am trying to control a step by step timed process to open and close valves to automoate a chemical synthesis in our lab, (i.e. relay 1,2,3 (valves 1,2,3) on for 30 seconds followed by Relay 2, 3 off and relay 1, 4,5 on for 2 seconds, ect). I have written a several panel sequence that works, however I am interested building a new program without using a sequence so that I can scale the application to many more additional steps than the three I currently have. What method would be the best to go with?
Thank you for your help.
Danny

I would use a statemachine for this and with each different state set the state of the relays and the time. See the examples for a state machine type architecture.
if you have any more questions then do not hesitate to ask and I will try to help.
Joe.
"NOTHING IS EVER EASY"

Why self-defined access sequences of free goods can not work?

Hi gurus,
I have maintained access sequences of free goods self-defined.but when i creat the SO it does not work!
when i used the standard access sequences ,it is OK .
Can anybody tell me why?
thanks in advance

Dear Sandy,
Go to V/N1 transaction select your self defined access sequence then go in to the accesses and fields and check all fields are activated.
Make sure that these fields are flowing in your sales order.
I hope this will help you,
Regards,
Murali.

Valve sequencing

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