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How to convert kilonewtons to tons (operating tons of a hydraulic press)

Discussion in 'Manufacturing and Related Processes' started by S1D3K1CK, Jul 8, 2020.

  1. S1D3K1CK

    S1D3K1CK Member

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    Hello, I am working on a PPAP and one of the hardware that is required states "installation force: 57.7KN Nom.". Now, when I convert the Kilonewtons, it gives me a result of 6.49 tons-force(short). The problem is, our "gauged machines" start operating (ram movement/hydraulic pressure) at 10 tons without touching any material. The item is a stainless steel self-clinching heavy head stud and will be press fit into 1/4" A36 steel. I am concerned about a few things: 1. the safety of the personnel installing the hardware due to just "blindly" installing the stud and 2. installing it incorrectly by not being able to gauge the installation force. The company I work for does not want to purchase any tool/machine or measuring equipment due to the uncertainty of the customers ordering of the completed part. They give a Torque-out of 36 N-M(26.55FT-LBS), which can be tested easily after installation.

    Is there an easy way to figure this out and I'm just gaining grey hair or do I have a problem at hand?
     
  2. Andy Nichols

    Andy Nichols Moderator Staff Member

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    One option might be to find a supplier who can do this operation. Or do a 25/50 piece study and check the torque to see what you get.
     
  3. S1D3K1CK

    S1D3K1CK Member

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    The organization I work for isn't willing to locate another supplier to assemble this, hence adding another cost and process that the part would have to be re-bid on. The reason why we are dealing with this in the first place (it wasn't verified in the quoting process) the original item callout was not able to be supplied anymore due to a manufacturing process according to the supplier. Because this part is a PPAP and the supplier of the new item is not a normal "approved" supplier for our customer, they require documentation of all drawing requirements of the item. I can do a 25/50 piece study no problem but I am not sure if that is acceptable for "measuring" the installation force. Feel like I am stuck between a rock and a hard place.

    What would you do in this situation?

    P.S. sorry if this seems like a rookie situation. I am the Quality Manager at my facility and when I got into quality in 2014 I knew nothing about quality (I actually started peeling the plastic off of scrap aluminum). The person that trained me was in his 70's and he retired within 13 months of my start date in quality. So my knowledge is almost all trial and error. I have over 200 PPAP approved and none rejected, giving that I've had roughly 8 interim approvals. But I have never dealt with this type of situation and have nobody to refer to besides this forum.
     
  4. Andy Nichols

    Andy Nichols Moderator Staff Member

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    Understand. I feel for you. I'm not sure that in this specific case the installation force is anything to worry about. What you can show, by studying the torque-out values over a number of parts is that the end result is robust. If by studying the result you see a lot of variation, then you can start breaking down the other parts of the process for variation - part size, hole size etc. As a mechanical engineer, I'm looking at this and, given your dilemma, I'm thinking that as long as you can prove a result is capable, then how you got there is less important (at the moment). Of course, you'd need to be scrupulous with component variation controls.
     
    Last edited: Jul 10, 2020
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  5. Miner

    Miner Moderator Staff Member

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    I agree. You are losing an important process control, and that will force you to rely more on product controls. The 6.49T installation force is probably a minimum requirement to seat the hardware. Is your press adjustable to less than 10T? I assume the 10T issue relates to the ability of the gage to measure force vs the adjustment of press tonnage. If the minimum press tonnage is 10T, you will have to verify that there is no deformation of the materials.
     
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  6. S1D3K1CK

    S1D3K1CK Member

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    Well, it seems like that is my only option at this time. I guess proving the consistency of the torque values are good enough (for fit, form, function). As for the Press Brakes, I am not sure if they are adjustable under 10T or if that is a false reading from initial movement of the Ram. Because these are CNC I believe it could be. I will record any and all information I can on this just so I can help our case on the PPAP and not get my first rejection haha.
     

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