Manufacturing lot numbers
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  1. #1
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    Default Manufacturing lot numbers

    One of my customers wants me to assign lot numbers to the parts I ship to them (medical).
    As you know there are a lot of variables in manufacturing. My question is what criteria would you use to differentiate between lots. Is this something I should decide or my customer?
    The obvious differences:
    New setup
    Change in material lot

    Any suggestions appreciated.

    Ken

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    The customer usually want some assurances that the parts have traceability to the material batch or heat number. If 'twere me, I'd use a combination of your invoice number and a number you've assigned to the material as you receive it. Hold on to ALL documentation pertaining to their order; material cert, inspection reports, heat treat certs, passivation... whatever.

    By the way, if you get into implants, the controls have to be bulletproof. I find it best in that case to only use one material lot for one delivery. That way they have less of a chance of getting mixed up with materials from another lot.

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    Alright!! a quality question!!

    Lot numbers like posted above must always be dependant by rawmaterial heat numbers. Do not confuse this by using your supplier purchase order numbers unless you have a system in place that prevents two material heats of material from coming in under the same purchase order number.


    If this is a small volume low quantity of lots, use a 3 digit lot number system. Could be numbers from the heat number, but I like to start lot numbers at 101 and then have a sheet of paper that documents the lot number, the raw material heat number, and the manufacturing date that way if bad things happen, you have all your necessary traceability on raw material information in one spot. Remember the more numbers you put in a lot number that are not needed, the more it costs you in the time it takes for someone to write or type these numbers. Pennies add up to dollars.

    Think these types of work instrutions out up front when you are starting them up. It is easier to do things right from the beginning.

    Make sure you have a work instruction written on how you perform lot control. It is a requirement for various quality standards and it is honestly good practice to have it even if you are not going for certification so that you can refer your employees to these instructions in your absence.

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    Default Julian Dates as Lot Numbers

    One technique I've seen was in a shop where they assigned the Julian Date to everything poured in a particular day.

    Office Max/Office Depot sell calendars that have the number of the day of the year indicated in the lower corner of either each page or each box (on a monthly calender,) i.e., 1 to 366 (when its a leap year.)

    Any day number with less than three digits should be prefixed with Zero(s), i.e., the full Julian Date has been standardized to a four-digit datum.

    You just prefix that day number with the last digit of the calendar year to create a Julian Date.

    For example, today's Julian Date is 9065 as 6 March 2009 is the sixty-fifth day of the year, hence anything poured/made on this date could have 9065 assigned as the lot number.

    For multi-lots produced on the same day you could use 9065-A as the first batch, 9065-B the second, etc. Or, 9065-01 through 9065-99 for when you have a bunch of different lots/batches created on the same day.

    What makes this technique nice is if someone later calls and asks when lot number nnnn was poured/made, you can flip to any calendar in the office with the indicators and tell them the date without having to hunt down and fiddle in a paper record.

    Also, if later you find out that lot number 9065 had 28% rejection by your customer, you can examine any related production records for that date and/or the employee assigned that day to try to narrow down and correct the cause of the problems.

    What ever technique you use, Julian Date or some other, be consistant and keep good records.

    You may also be aware that the US Federal government also uses Julian Dates, but their fiscal year starts on 1 October, not 1 January.

    Please, do let us know which lot number technique you finally select.

    Stan Db

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    Quote Originally Posted by greyghost View Post
    One of my customers wants me to assign lot numbers to the parts I ship to them (medical).

    Any suggestions appreciated.

    Ken
    This is an FDA requirement and is nowhere near as stringent as FAA or something like that. As far as my understanding goes it just needs to be possible to identify when the parts were manufactured so the paperwork relating to that batch can be pulled. You don't need to worry about melt numbers for materials and that level of oversight but recording any QC issues such as unusual reject rate is probably a good idea. Your customer needs to be able to track when and where these parts came from and where they go to when they are sold for product recalls if needed. We simply engrave a serial number in our parts that is six digits; Y0MNNN where N is just the part count; so far our batch sizes have stayed below 999 parts so this works.

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    What we do on the tracable stuff is a material cert attatched to the PO, then the guy in the office looks at the calender and says "It's week 8 of 2009 so thats a lot number of 0809" and writes that on the PO and the job card which accompanies the job around the factory.
    It then gets to the VMC section and the bozo setting up the job instructs the machine to engrave '0909' because its the following week by then

    Boris

    <<pretending not to be a bozo

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    All jobs I run are assigned a job# (or work order#). This # is added to the invoice. All parts are package with labels showing p/n, date, job#, customer name, and my company name. I keep a job folder on each p/n and in that folder is the job# traveler with all the pertaining info and paper work on that job.

    GM

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    All of our parts are not only marked with julian date, but also military time. This lets us trace it back to exactly when the problem occurred, should there be one. That also lets you inspect the SPC data, other inspection checks, set-up report sheets, downtime system, etc to see what all went on during that time frame. Very handy.

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    As a job shop we only bring in material per job. So we use the date finished parts shipped as the lot number. It's easy to back track with dates. 030609A is the first shipment of the day. B,C,D....... to follow. That is if there is any work to do...

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    Quote Originally Posted by Boris View Post
    "It's week 8 of 2009 so thats a lot number of 0809"
    +1 for this concept.

    We also use this for generating work orders. So, If i kick a work order first thing in the morning, It will have a "batch" number of 0809-1(1 being the first work order for that week.) By the time I get to the end of the week, the batch numbers would be something like 0809-35

    If i have to "split" a W/O for any reason, then I will give it a letter designation. For example 0809-1A

    This works very well. Additionally, we put the material P.O, materials certs# and any outprocess certs#'s on the work order itself. At the end of the trail, we can go back to any W/O and pull the dates,PO#,cert#, OP certs#, Qnty ran, who ran it, when they ran it, what machine it was ran on right off of the W/O. Works great.

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    Quote Originally Posted by Spelunker View Post
    So, If i kick a work order first thing in the morning, It will have a "batch" number of 0809-1(1 being the first work order for that week.) By the time I get to the end of the week, the batch numbers would be something like 0809-35
    I do ours starting with the year - 0908-1 for example - So that they show up in a spreadsheet or etc. in chronological order

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    Well thanks for all the replies to my query.
    We use a work order numbering system similar to Mud's with the year/month-serial# as in 0903-0017. We will add a dash number to that for each lot shipped. This will refer us back to the work order which will have all the pertinent info on it.
    Thanks again
    Ken

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    Kodak used to have their own ratinalized calander with an extra month in it so every month had 4 weeks, makes sense, I don't remember what the extra month is called. [Sol in the middle of the year] I suggest that you keep a little book in your desk that who ever is in charge of serial numbers, enters by hand each day, the record, in addition to the regular record keeping. two reasons, this is a bullet proof back up, and it is a cross check. I ran a place a while back that had to keep track of serial numbers in each shipment to each distribution center, in case of recalls. After I left, I noticed when visiting a while later that they were still using the same numbers, ie some moo was just reentering the same numbers over and over, who knows what was on the product.

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    Default Duplicate Serial numbers

    Back in the 1980s I had the privilege of working with a Marine Gunny that told this tale...

    He had an old Italian shotgun and (after checking into a new duty station,) the NIS and FBI showed up at his door to arrest his butt for a bank robbery. Funny thing was, on the date this robbery took place he was overseas.

    Seems that the base required all service members living in government quarters to report all firearms belonging to the residents and stored in the govt. qtrs. Then the base conducted a check on the firearms.

    Anyway, his shotgun was on the FBI's Hot List. And, as the serial number matched (whatever source they had), he, obviously, was the robber.

    Of course my Gunny claimed his innocence left-and-right.

    Funny thing - when the Gun Control Act of 1968 went into effect, it required all firearms being imported into the US to have a serial number.

    And that is what the manufacturer did - they followed the law and applied a serial number to the hundreds of guns they sent to the US.

    Seems the GCA-68 was just a little vague. It didn't say anything about marking each shotgun with a different serial number. And all those guns had the same serial number applied.

    Moral of the story?
    Keep good records and do, please, use more than one serial number.

    Stay well & Happy!

    Stan Db

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    Quote Originally Posted by AccessDbGuy View Post
    Back in the 1980s I had the privilege of working with a Marine Gunny that told this tale...

    Seems the GCA-68 was just a little vague. It didn't say anything about marking each shotgun with a different serial number. And all those guns had the same serial number applied

    Stan Db
    Man that is funny!

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    Default Lot numbers and traceability

    Lot numbers are all about traceability and confidence.

    Let's say that a part from lot number 111 is rejected as out of tolerance. From this we can expect that more parts from lot 111 are also out of tolerance and the entire lot will probably be examined by the customer more closely.

    If we start lot 112 the next day without checking the setup, then all we know is that every part after lot 111 may be faulty. Every part supplied since lot 111 will probably have to be checked.

    If we tie the lot number to a setup/cal procedure and material change or possibly an operator/machinist change then we get real confidence and value from the lot number.

    Now we can isolate and quarantine just some of the parts, not every part when a defect is found.

    We expect lot numbers to tell us when things are good, but a good lot number will tell us how long things are bad, which is much more valuable.
    Last edited by technocrat; 03-12-2009 at 07:54 PM. Reason: addition

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    Quote Originally Posted by greyghost View Post
    One of my customers wants me to assign lot numbers to the parts I ship to them (medical).
    As you know there are a lot of variables in manufacturing. My question is what criteria would you use to differentiate between lots. Is this something I should decide or my customer?
    The obvious differences:
    New setup
    Change in material lot

    Any suggestions appreciated.

    Ken
    I read all the very good posts that have been made, but, the thing that I'm still not clear on why they want it and what they want?

    They must have a reason. If it is just simple numbers so they can trace when within their own facility, get a sequential numbering machine.

    If there is another reason, design your solution to fit the problem that they are addressing.

    At the extreme end of the spectrum you will have to document all incoming materials, machines, setups, operators etc etc.

    Don't do any more work than you have to, but DO the things that they are really seeking

    Just a thought.

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    Quote Originally Posted by Boris View Post
    What we do on the tracable stuff is a material cert attatched to the PO, then the guy in the office looks at the calender and says "It's week 8 of 2009 so thats a lot number of 0809" and writes that on the PO and the job card which accompanies the job around the factory.
    It then gets to the VMC section and the bozo setting up the job instructs the machine to engrave '0909' because its the following week by then

    Boris
    :
    Boris,how do you number them if you have more than one traceable lot that week?

    Mark.


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