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Komatsu boom crack repair

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  • Komatsu boom crack repair

    Started this on Thursday afternoon & finished up on Friday. Cracked twice & welded by the companies mechanic (he's good but always rushed). This time he wanted me to do it. Right where the side plate meets the casting. Gouged it out completely so I had a 3/8" open gap to the inside. Snaked a piece of 1/4" bar inside with a rod tacked to it to hold onto. Pulled it tight up against the inside & tacked it good. Preheated, then welded it up.

    Not really much to see. Basically like a weld test.

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    Last edited by MMW; 05-04-2013, 05:32 AM.

  • #2
    I never realized there was a casting on the end. Thought it was all built from formed steel. The casting then is steel?

    Is this a usual location for failure ie is this an engineering design issue or working outside of engineering specs?

    I assumed you used wire as in other projects? How did you figure the preheat..was it just to warm it up or were you trying for a certain range? Did you attempt to maintain a certain temp interpass?

    Thanx again for taking the time to post pics, real interesting!

    Comment


    • #3
      Yes it is cast steel. Not sure if it's common but the rep said he has seen this before on this model (PC400). The machine also has 11,000 hours on it.

      The first passes I used 7018. One from the backer strip to the side plate & one from the backer to the casting. I did this because stick usually burns out any contaminants better than wire & I wanted to make sure I had a good root in there. I then finished with innershield wire doing stringers. I had about a 3/8" gap at the root & maybe a little more than 1" gap at the outside.

      I didn't have my temp gun with me but tried to get it to about 300* at the start. There is so much steel there that I didn't worry to much about interpass temps. I just didn't rush it & cleaned each pass real good.

      Comment


      • #4
        Komatsu boom crack repair

        MMW...I'm still learning....what do you mean by stringing?...like the pics an explanation on how you did the repair

        Comment


        • #5
          i have fixed about 5 of these so far on pc400's.. and also where the main boom cylinder goes into the bushing. The last one i fixed was from a bad weld, it was full of porosity on the whole bottom half of the weld. Not real good QC to let something like that come off of the line

          Comment


          • #6
            Originally posted by weldonwelding View Post
            i have fixed about 5 of these so far on pc400's.. and also where the main boom cylinder goes into the bushing. The last one i fixed was from a bad weld, it was full of porosity on the whole bottom half of the weld. Not real good QC to let something like that come off of the line
            Prob robotic welded and the 18 yo QC guy didn't care or didn't know. I saw it alot...Bob

            Comment


            • #7
              Originally posted by weldonwelding View Post
              i have fixed about 5 of these so far on pc400's.. and also where the main boom cylinder goes into the bushing. The last one i fixed was from a bad weld, it was full of porosity on the whole bottom half of the weld. Not real good QC to let something like that come off of the line
              Of course you have.You,ve seen it all.

              Comment


              • #8
                Originally posted by admweld View Post
                Of course you have.You,ve seen it all.
                lol ......

                Thanks, Billy, you just made my day.

                Comment


                • #9
                  Originally posted by JSFAB View Post
                  lol ......

                  Thanks, Billy, you just made my day.
                  Not just once either Joe.Five times.

                  Comment


                  • #10
                    Originally posted by MMW View Post
                    Yes it is cast steel. Not sure if it's common but the rep said he has seen this before on this model (PC400). The machine also has 11,000 hours on it.

                    The first passes I used 7018. One from the backer strip to the side plate & one from the backer to the casting. I did this because stick usually burns out any contaminants better than wire & I wanted to make sure I had a good root in there. I then finished with innershield wire doing stringers. I had about a 3/8" gap at the root & maybe a little more than 1" gap at the outside.

                    I didn't have my temp gun with me but tried to get it to about 300* at the start. There is so much steel there that I didn't worry to much about interpass temps. I just didn't rush it & cleaned each pass real good.
                    I was thinking about the backer and theres no danger of it becoming a problem later on? My familiarity w/ backers is they must come off. I think they can become stress risers. Also did you try to match the backer to the original material or just use mild steel/whatever you had on the truck?

                    To me it seems very difficult to repair heavy equipment. There are so many variables you may or may not know or be allowed to know. Ag equipment seems a lot more doable. Guess its all about what you know....

                    I find these threads very interesting! Thanks a million for explaining what you did and why.
                    Last edited by HayFarmer; 05-05-2013, 06:17 PM.

                    Comment


                    • #11
                      Originally posted by admweld:307270
                      Originally posted by weldonwelding View Post
                      i have fixed about 5 of these so far on pc400's.. and also where the main boom cylinder goes into the bushing. The last one i fixed was from a bad weld, it was full of porosity on the whole bottom half of the weld. Not real good QC to let something like that come off of the line
                      Of course you have.You,ve seen it all.
                      If ya look in my pics... pretty sure theres pics of a very simular repair on a pc 400.. ****. Since there is a komatsu dealer very close to me i do lots of work on them. They keep me pretty busy
                      Last edited by weldonwelding; 05-05-2013, 06:49 PM.

                      Comment


                      • #12
                        Originally posted by aametalmaster:307268
                        Originally posted by weldonwelding View Post
                        i have fixed about 5 of these so far on pc400's.. and also where the main boom cylinder goes into the bushing. The last one i fixed was from a bad weld, it was full of porosity on the whole bottom half of the weld. Not real good QC to let something like that come off of the line
                        Prob robotic welded and the 18 yo QC guy didn't care or didn't know. I saw it alot...Bob
                        Yep.. definetly robotic.

                        Comment


                        • #13
                          Originally posted by weldonwelding View Post
                          If ya look in my pics... pretty sure theres pics of a very simular repair on a pc 400.. ****. Since there is a komatsu dealer very close to me i do lots of work on them. They keep me pretty busy
                          There,s a dealer about 2 miles from shop.And ive worked on few also for them.

                          Comment


                          • #14
                            Originally posted by kerr74 View Post
                            MMW...I'm still learning....what do you mean by stringing?...like the pics an explanation on how you did the repair
                            Kerr74, Stringers are basically normal size welds overlapping each other to create a large weld. Here is a link explaining it.

                            http://www.weldmyworld.com/quick_wel...ger-beads.html

                            Comment


                            • #15
                              Hayfarmer, The reason I used the backer was the day before I got there the rep had stopped by for something else & happened to discuss this with the mechanic. He described the way they fix it in their shop which uses the backer so that's what I did. I most likely wouldn't have backed it if it wasn't mentioned. The side plate was about 5/8" thick & the "ear" on the casting was about 1"? thick. The outsides were flush but the insides weren't. The 1/4" backer I used layed on the inside of the side plate & butted up against the casting "ear". The backer was hot rolled steel. I don't know for sure but I think the side plates are hot rolled steel also.

                              As far as stress risers, I'm no engineer so I couldn't begin to figure out if this will be one or not.

                              As far as ag vs. excavating equipment, I don't find them much different. At least with the newer ag stuff anyway.
                              Last edited by MMW; 05-06-2013, 05:21 AM.

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