Putting Together the Pieces: Engineer in Training Open Web Level Two Blog: Part II
by Jason Fitch, Engineer in Training at RedBuilt When I arrived at the Hillsboro Plant, I was introduced to Ed Medley, who would teach me and help me with the construction of my truss. I don’t know if Ed had pulled the short straw and had to babysit the visitor, or if he had won the coin toss to get a front row seat to watch this designer try to build a truss. Either way, with a smile on his face, he patiently instructed and watched me as I went through the production process. I figured my presence at the plant would be like having visitors on the jobsite back when I was framing: It would disrupt the routine as well as give everyone the extra task of watching out for the visitor who doesn’t know the routine or what to watch out for. I did my best to minimize my impact on the plant by being mindful of and minimizing my disruption the best I could. [caption id="attachment_395" align="alignleft" width="300"] Nick David (left) watches as Ed Medley (back) shows Jason how to set the punch press for different web gauges.[/caption] We started by punching webs. I was joined by Karl Herinckx from the Hillsboro Engineering office and Nick David from the Stayton plant. Both observed and helped with the construction of my truss. Ed showed us how the punch worked, as well as how to set the length of the web and the machine settings for different web gauges. This is where I learned the importance of web pairing, which is the term we use for when consecutive webs are the same length and gauge. The truss I designed was tapered and intentionally designed so that the number of paired webs was low. This meant that after almost every web I punched, I had to readjust the length and/or the settings on the machine for different gauges, I had to label each web and then I set them on the cart. It is clear that pairing the webs is the best practice because it eliminates the need to change the machine, which leads to a faster production process. [caption id="attachment_396" align="alignright" width="225"] Jason adjusting the main panel on the driller to 0.0001.[/caption] With the webs punched, we moved on to drilling the chords. Due to time constraints, the chords were already finger jointed together and waiting for me. First, Ed walked me through how to spot the top chord. Since we were using high grade lumber, there weren’t a lot of knots in it. This made the spotting process go much easier. Next, we walked over to the driller, and he showed me how to adjust the stops for the panel lengths. The main panel had a digital read out, so narrowing down the exact dimension to the 0.0001” was possible. After making all the adjustments, Ed looked it over and made adjustments to a couple of the “specials” (used where pin-to-pin lengths differ from main panel pin-to-pin lengths), so I concluded my eyeballing to the 0.0001” must not be up to par. Ed then showed me how to set up the driller with the drill and route codes. He explained how the driller worked and that I was responsible for making sure that I was using the correct panel stops to space the routs and that pin holes line up correctly. He also let me know that I needed to hold the chord so when the router comes up it does not kick out the chord and that the router may make more than one pass. No problem, I thought. The hard part is done, all I need to do is move the chord forward to the proper spots and hold the chord down as the router is going…easy enough. The first panel went fine but when the router came up for the second panel, the board kicked up. When the stage stopped I told Ed, “The board kicked up and I’m pretty sure the rout is messed up.” He rolled the chord forward to a safe place for him to feel the rout and said, “Let’s take a look.” As he felt the rout he said, “Wow, I don’t think I’ve ever seen a missed rout this bad.” Well there goes my plant associate of the year award. We cut the chord off where the last rout was and pushed it back up to see if there was enough chord to try again. As we flipped the cut piece over to see how bad it was, the chord revealed that I had let it shift enough so it was not just an extra wide rout, but that it moved far enough to have two routs. We went back to the chord and re-measured and re-spotted it . We were amazed to find that there was just enough unaffected chord and we could still use it! Ed made sure to remind me that I need to hold the chord in place this time because if I messed up again, we would need to make a new chord. We re-started the drill cycle, and this time I went through it without another mistake. Then we used the top chord we just made to spot the bottom chord and we drilled the proper camber plate for the bottom chord. With the chords and webs made, it was time to assemble the truss. Read about the next part of this series, Assembling the Truss.
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