Torqueing assemblies

[diptankd]

Hello everyone,
I want to start by saying this site is remarkable thank you all so much for helping me with my questions. I have a question on torqueing assemblies that I can't seem to find the best way to inspect and record the operation. I am required to use sampling plan mil-std-1916 to inspect a assembly line for torqueing the assemblies 1/12. The customer in an auidit said that 1/12 does not mean I could check 2/24 or so on it has to be 1/12. What I have been doing is shuting down the line every 12th part and haveing an inspector check the part for the torqueing and then the line may resume. This takes a lot of down time. The torque wrench the operators uses is calibrated so I thought I could check the first and last part off the line and as long as they were good and the torque wrench was ok in calibration the parts ran that day would have to be good but, that was not good enough for the customer. I am looking for any other ways I could set this up so the line flows better and the inspector could be freed up to do other inspections. The customer will not let operators do the check and sign they did it with records to justify the operator did it it must be an inspector. Any Ideas?
Thank you,
diptankd

 

[Coury Ferguson]

Hello everyone,
I want to start by saying this site is remarkable thank you all so much for helping me with my questions. I have a question on torqueing assemblies that I can't seem to find the best way to inspect and record the operation. I am required to use sampling plan mil-std-1916 to inspect a assembly line for torqueing the assemblies 1/12. The customer in an auidit said that 1/12 does not mean I could check 2/24 or so on it has to be 1/12. What I have been doing is shuting down the line every 12th part and haveing an inspector check the part for the torqueing and then the line may resume. This takes a lot of down time. The torque wrench the operators uses is calibrated so I thought I could check the first and last part off the line and as long as they were good and the torque wrench was ok in calibration the parts ran that day would have to be good but, that was not good enough for the customer. I am looking for any other ways I could set this up so the line flows better and the inspector could be freed up to do other inspections. The customer will not let operators do the check and sign they did it with records to justify the operator did it it must be an inspector. Any Ideas?
Thank you,
diptankd

Could you provide line speed information of the Torquing process? What I mean is, how many parts in 30/60 minutes are torqued.

I guess my other question would be: Why is the production line shut down during the inspection of the torquing? Couldn't you just remove the assembly at an interval of 1 out of every 12 torqued, as long as you know the amount of parts/assemblies that were done in 1 manufacturing day or every hour. If there is a failure, separate and segregate the group of parts and verify at a 100%

Added: What is your rejection rate of the torqued assemblies?

 

[Coury Ferguson]

I have moved this post to this forum, since it is asking about Inspection and Test, sampling and related.

 

[Benjamin28]

Coury's suggestion is quite valid, and I would echo his question as to why the line needs to be shut down for what sounds like a fairly simple inspection.

As to making changes to the inspection itself, it sounds as if your customer has left little room for interpretation, you have a sampling specification of 1/12 and a customer requirement that qualified inspectors perform the inspection....so the only option I can see is working with the customer to find something that is more efficient on your end and still satisfies their quality requirements. The best possibility that comes to my mind is spc of the torque inspections. Good solid statistical data is difficult to argue with and accomplishes the same goal while reducing commitment of inspection time after capability is established.

Personally I would find it annoying that production personnel aren't allowed to perform the torque inspections...seems like a silly requirement to me.

 

[diptankd]

The line does about 40 parts in 30 minutes, The reason the line is stoped is there is one fixture for this operation and one inspector, also the inspector checks other requirements on the same line at a different station. I am limited on room. The line stops so the inspector does not get so backed up he rushes to catch up and makes simple mistakes. My budget only allows me to have one inspector on this line. The reason I don't take 1/12 out and then inspect at the end of the day is that the parts are packed up and palletized as the line goes, so if there is a problem it could be found then and packing materials are not lost.
Hope this helps
diptankd

 

[vandenbar]

Dip,

My two cents is determine how much the downtime costs you and if you can, justify some new equipment that can record all of your torque results. DC electric torque tools usually won't break the bank and they can be programmed to stop if they over or under torque. They can also be tied into PLC's that can stop a production line if a part is not assembled to spec. A tool like this could eliminate your inspection entirely (if your customer agrees). You could even go as far as have all of the torque values linked to the specific assembly through a database. My experience is with Atlas Copco tools but there are others out there.

If you can't justify new torque equipment, could you modify the line so you can take the part to be inspected off line and keep production going?

 

[Coury Ferguson]

Dip,

My two cents is determine how much the downtime costs you and if you can, justify some new equipment that can record all of your torque results. DC electric torque tools usually won't break the bank and they can be programmed to stop if they over or under torque. They can also be tied into PLC's that can stop a production line if a part is not assembled to spec. A tool like this could eliminate your inspection entirely (if your customer agrees). You could even go as far as have all of the torque values linked to the specific assembly through a database. My experience is with Atlas Copco tools but there are others out there.

If you can't justify new torque equipment, could you modify the line so you can take the part to be inspected off line and keep production going?

Valid point (emphasis added in bold).

The line does about 40 parts in 30 minutes, The reason the line is stoped is there is one fixture for this operation and one inspector, also the inspector checks other requirements on the same line at a different station. I am limited on room. The line stops so the inspector does not get so backed up he rushes to catch up and makes simple mistakes. My budget only allows me to have one inspector on this line. The reason I don't take 1/12 out and then inspect at the end of the day is that the parts are packed up and palletized as the line goes, so if there is a problem it could be found then and packing materials are not lost.
Hope this helps
diptankd

My question still remains: What is your rejection rate of torqued assemblies?

As for Downtime verses costs of different equipment: This would have to be calculated (Downtime in $$$$), cost of packing material (in $$$$), and profit margin (in $$$$). These are just a few of what would need to be addressed.

As for the customer requirements: As far as I see it, they require that you sample 1 out 12 assemblies, not beginning and end of shift. Now if you are able to support, with statistics or some other form of documentation to your customer, they may change their requirements, which is their choice.

 

[diptankd]

I also forgot to say, I,m sorry I have alot going on today and my mind is full, but the parts get loctite on the threads and they have to be checked with in the drying time witch is 5 minites. Once it is dried you can't check the torque the parts are loctied down.
thanks,
diptankd

 

[Al Rosen]

I also forgot to say, I,m sorry I have alot going on today and my mind is full, but the parts get loctite on the threads and they have to be checked with in the drying time witch is 5 minites. Once it is dried you can't check the torque the parts are loctied down.
thanks,
diptankd

Then who cares? With Loctite they're not loosening.

 

[Coury Ferguson]

I also forgot to say, I,m sorry I have alot going on today and my mind is full, but the parts get loctite on the threads and they have to be checked with in the drying time witch is 5 minites. Once it is dried you can't check the torque the parts are loctied down.
thanks,
diptankd

Well, that is important information.

But if I understand Loctite (I have used various grades) it can be broken based on the specific type, and may or may not damage the parts.

Than let the production line perform the torquing inspection, but still have you inspectors validate the results. But that still should not stop the production line.

Please tell me what your rejection rate is on the torqued assemblies?