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Benders and Bending Which bender is best? How do you use a bender? How do you calculate bends? Everything Bender related...


Benders and Bending Which bender is best? How do you use a bender? How do you calculate bends? Everything Bender related...

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  #61  
Old 04-10-2006, 08:55 PM
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Quote:
Originally Posted by jackalope
Not sure if this would help or not, but a "button" die might help a little. Put it on and reverse it. Do it CAREFULLY though. just a "thought".
I have never heard of that, but I will check into it. Thanks for the tip! I think I will simply extend the relief cut that I started and get it down to the minor diameter of the threads. That shoudl give me enough clearance and shouldn't affect the strength too badly

UPDATE

Due to some problems in the shop last week, I wasn't able to cut the hex into the drive pin or get started on heat treating, so I spent the day working on some other items. I forgot my camara that day, but I took a few pictures today of what I did.

I decided to get back on the swingout suppot welding. Unfortunately I think this will be remembered as my worst design in terms of manufacturing. Now I will keep my fingers crossed and see if I can do a half decent job of welding it.

I went to a welding handbook that suggested adding a 60 degree (included angle) groove for butt welding this size material. At the bottom of the groove, it called for a slight gap between parts, but I have decided not to include that. I went after things with a large bench grinder and here are the grooves I came up with.





Below: I plan to weld as much of the part as possible with it attached to the bender arm. Hopefully this will minimize distortion. I think to begin with, I will use clamps and a piece of plate to keep the base part and the top part parallel while I tighten the rollercoaster bolt holding the support to the swingout shaft. Once the bolt is tightened, I will remove the plate and add the other pieces, which will be carefully tack welded into place.



Below: Because the welding is certain to cause warpage, I am adding this washer between the swingout shaft and the z-support while welding. Afterwards, this will be removed and I can machine the surface that mates with the bender arm flat.



I did a bunch of practice welding using some 1/8" 6013 rod at 150 amps on some scrap. It looks like it will penetrate fine, although it will require multiple passes and of course I am getting some distortion. The welding book recommended a larger diameter rod, so I will check with the welding supply and see what they have or recommend for this before making more practice welds and finally welding the actual part.

We'll see how badly it distorts. If I have to toss it in the trash and start over... well... lets just hope that doesn't happen.
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  #62  
Old 04-10-2006, 09:50 PM
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Holy smokes, that's some goovin'! Doing stuff like that is why I'm wanting to build a bad ass belt grinder, beats the heck out of a bench for moving metal.

I'm sure you know this, but you better fixture the crap out of that or it's going to pull like crazy, particularly the top piece. Good heavy tacks, maybe including a good solid stitch before hitting the groove on the rest will probably be ok, but that top, I dunno. Also looks like a good candidate for spray transfer if you've got the equipment. And ether way, I would plan on machining afterwards. Like I said, I’m sure you’ve been over this every different way, but that’s what comes to my mind when I look at it... Looking forward to seeing the results.
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  #63  
Old 04-10-2006, 11:14 PM
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Great job on the grinding. The gap is to help with getting 100% penetration on the root pass. Your first pass should go all the way through both pieces and should protrude out the bottom approx 1/16", the gap you use can be adjusted for personal preference but a good rule of thumb is 1/2 the diameter of the rod. I agree with BadDog about the tacks, also on your filler passes be sure to swith directions this should help with distortion. Can't wait to see it all welded up.
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  #64  
Old 04-11-2006, 11:23 AM
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I would certainly weld that rib to the bottom and upright first. Might be good to make another rib out of 1/4 or something to weld between the top and upright temp. while welding then cut it out. Would significantly keep warpage down.

I would recommend a 7018 1/8 inch rod for that, or bigger. The 7018 will leave you a cleaner bead and is rated to 70000 PSI, much above that of the “farmer” grade 6013. I run 7018 1/8 on everything I do, little tricky to get it to start to burn, but leaves great easily laid welds once it’s burning. Movement is the key to starting 7018. I run normaly 130-135 amps DC, would probably be able to run hotter on that weld though.

Good luck!
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  #65  
Old 04-11-2006, 08:10 PM
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UPDATE

Well folks, it's welded!

Thanks to everyone for their input on welding. Between your tips, the welding professor, a couple welding handbooks, and the local welding shop, I felt I had pretty much thought this through from every way I could before I got started. Those that suggested 7018 rod, I appreciate your help! The welding shop agreed that was the way to go for this job and I am happy that's what I did. I got a box of 5/16 7018 rods, practiced with 5 or 6 of them, then went to work.

First, I mounted the bottom piece and the very top piece using the clamped method I discussed yesterday. I tried clamping the rib into place, but I couldn't find a good way to do it, so I ended up just leaving it sit while I tacked it into place. I was able to do some clamping with the verticle piece, but the part was certainly not fixtured as much as I had hoped for. Surprisingly, it turned out fine anyway.

Below: First I put tack welds on either side of the bottom of the triangular rib, fixturing it to the base piece. Then, after some clamping, I tack welded it to the vertical piece. Next, I found it was necessary to remove the front two cap screws and I welded the fillet at the base of the verticle piece.



I didn't take a picture of it, but after I had made the above tacks/welds, I made single pass fillet welds all the way around the rib, starting with the bottom of each side first, then doing the vertical. Before welding the vertical part, I rotated the whole arm and all so that I could weld it in a flat position. These welds didn't turn out very good, but I was improving as I went since this was my first time attempting this.

Below: Next I made the root pass on the bevel that holes the verticle piece to the base piece. I did the root pass with everything still bolted together, but found out the swingout shaft was just plain in the way of welding, so I took it apart for further passes.



Below: I can't remember how many passes it took to fill, but I did them as suggested by my welding handbook. It said to run them parallel with the groove, alternating the direction of welding. There was a little diagram showing how to place each weld, but it was pretty obvious that you filled in the Vs left by previous passes. Of course I spent quite a bit of time between passes with a wire brush cleaning off remnants of slag, but most of it came off in big chucks using a slag hammer. This is what it looked like fully welded.



Below: Next, I reattached the top plate using the rollercoaster bolt and swingout shaft. I put a washer in between the shaft and plate as I decribed yesterday. After it was tightened down, I made this root pass.



Below: Here it is on one of the subsequent fill passes. I can't remember exactly how many it took to completely fill, but I think it was somewhere near six or seven



Below: Satisfied with the filling on the grooves, I removed the part and made a single fillet pass on the underside.



A few more passes around the rib... drum roll.... and... tada!





My first welds around the rib I was holding the rod at an angle that was away from the bead (maybe 30 degrees from vertical). At some point I had to hold the rod vertical and discovered it welded a heck of a lot better. In addition to that, I found that keeping the arc shorter (almost dragging the rod) made a much better weld too. So all the subsequent welds (the groove and one fillet weld) were made with the rod vertical and the arc shorter. As you can see from the pictures, it made a BIG difference.

As for amperage, I was using a 5/32 rod and I had it at 150 amps. I tried both higher and lower when I was practice welding, but I found the 150 to work the best for me.


Okay, so it looks like crap, but I don't doubt the strength of these welds. It's obvious my stickwelding skills still need some honing, but cosmetics aside, I am thrilled and relieved with how well this came out.
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Last edited by TheBandit; 04-12-2006 at 12:13 AM.
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  #66  
Old 04-11-2006, 08:11 PM
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So what about distortion? That has been my biggest fear from the beginning. Well, it turns out there wasn't very much! Perhaps it was the beveling, the order of the welding, or a combination of forethought and those things, but the end product could just about be used as is. With the naked eye, you'd be hard pressed to identify any distortion and all the bolts still fit fine.



I should point out that I did weld the rib on a little crooked, but just ignore that and pretend you never saw it. That had nothing to do with welding distortion, I just didn't catch it when I was tack welding.



So now I have a whole bunch of grinding and flapper disking to do to clean things up, but I am SO RELIEVED to have the welding on this part done. I don't think I'll be redoing anything about it.

*EDIT* Here it is after going after it with the grinder and a flapper disk. There are a few things to note here. First, I hadn't really thought about it but all the threads that the cap screws were in got a little screwy after welding. I think they were acting as the electrical ground path, so I had to chase them with a tap to get them smooth again. You can see how the shaft and z-support are separated a little from due to the washer I installed while welding. Once I machine the bottom flat that will come back down as planned. Also, the cap screws at the front are inhibited by weld, so I will have to use a counterbore to give them a surface to tighten against.







The welds on the rib don't look all that great, but the groove welds turned out perfect. :)
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Last edited by TheBandit; 04-11-2006 at 11:44 PM.
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  #67  
Old 04-11-2006, 10:55 PM
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Oh my GAWD a crooked part! Now you have to start the whole project over. Just kidding great work as always. Do you have access to NDI equipment? If so it would be interesting to see just how deep you root pass penetrated. The reason I mention it is in the picture of the single pass from the bottom side you can see a clear gap between the top and bottom weld on the edge. It would be interesting to see if as the weld progressed how deep it actually penetrated. After all the flap wheeling and grinding it is no longer visible in the pictures. Just curious is all not picking, keep up the good work. When do you think you will be bending your first piece?

Last edited by robs88yj; 04-12-2006 at 02:07 AM.
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  #68  
Old 04-12-2006, 01:54 AM
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Congrats, looks like things went well.
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  #69  
Old 04-12-2006, 02:01 AM
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Thanks.

It's definitely not as pretty as I would like, but it should do it's job.
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  #70  
Old 04-12-2006, 04:20 AM
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Looks good. I would have suggested more gap, a TIG or MIG open root pass and stick the rest of the way out. Probably some runoff tabs on each side to help with arc blow too.That way you wouldnt have any starts or stops ON the peice. Working in the industry where most everything has to be 100% X ray quality welds, its just the way Im used to doing things. Glad it worked out and didnt warp on ya.
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  #71  
Old 04-13-2006, 08:35 PM
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B-Rad, thanks for the suggestions. Adding tabs to the end would have been a damn good idea! I wish I had thought of that. Why MIG over stick for the root pass? Just curious. I considered doing the whole thing with a MIG, but I wanted to try stick out.

Too bad there's not an x-ray machine on campus or I would x-ray these and post pictures. Don't worry: after it breaks, we'll get a good look at how crappy my welds are!

UPDATE

I don't think I mentioned it above at all, but the first part I welded (before doing the z support) was the swingout itself. Unfortunately when I got it home, I discovered that the DOM tubing I used had warped a little, preventing the shaft from fitting properly. I thought about putting it in the machine and running a boring bar down the center, but it was so close to being right that I figured I would screw it up! So instead I put the part in my vise at home and went at the inside with some 80 grit sanding drums I had leftover from an old cylinder head port & polish I did years ago. By the time I was finished, the inside was smooth and fit great. The thing goes in and rotates like butta now!

So here's what I brought with me to the shop today:



Below: First thing's first; I machined the bottom of the z-support flat to get the correct height.



Below: Here it is all fitted back together. I wanted to run a counterboring bit to clean up the weld around the front cap screws, but I couldn't find one long enough, so I will probably use a small grinding stone at home.



Below: Next up I cut the main die drivepin using a bandsaw.



Below: I fixtured it in this rotary indexer (is that the right name?). This takes a little bit of time to setup properly. You can start by installing a shaft in the collet of the mill. Then, with the indexer sitting loose on the table, tighten the chuck against the shaft. This will center the indexer with the mill. Next, clamp the indexer to the table. Check center using a coax or other dial indicator. In my case it was already well within tolerance.



Below: First I faced the end. Next, I put the indexer to zero degrees and set the depth of the tool. Then I made passes in the x-direction, feeding the y direction closer to the center on each pass. Once the correct amount of material was removed, I rotated the indexer 60 degrees and repeated.



Below: After the first four passes, I was able to check the dimesions of the hex. First I used calipers and then, of course, an open ended wrench.



Below: Once all six sides were cut, I checked it again with the closed end of the wrench.



Below: With the hex complete, I went back on the lathe and used a parting tool to cut a wider/deeper relief near the shoulder of the threads. I wish I could have ground a radius into the parting tool ahead of time to get a proper radius at the shoulder.



Below: I didn't have the main die arm with me at the shop, but I checked the fit later and it now threads all the way in without a hitch!



Next I will polish it on my bench grinder at home and next week I am going to heat treat it.
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  #72  
Old 04-14-2006, 01:43 PM
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MIG would be on an OPEN root(gap between the two peices). Its just a way to get a full penetration weld. Stick doesnt like gaps(makes them bigger if you dont know what you are doing). Like I said, its just something Im used to with all the stuff I do having to be "code" welds
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  #73  
Old 04-18-2006, 11:33 PM
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B-Rad, I understand the need for code quality welds. My part will eventually fatigue and crack due to my poor welding. But I think given my lack of experience, I did the best I could do.

UPDATE

With the machine work done on the main die drive pin, it was time to do some heat treating. You may appreciate how critical this part is if you have ever accidentally bent a drive pin by not putting the pin all the way through on a Pro Tools or JD2 bender. Unlike with those benders, my drive pin is not in double shear, but rather cantilevered out from the bender's arms. This kind of loading is much, much worse, so maximizing strength is very important. To combat the bending stresses, my drive pin is larger in diameter and made of 4140 cromoly. Getting the most out of this material takes heat treating, so that's what I did today.

Below: Here I am suited up in some awfully crappy PPE. The apron was missing it's waste strap, the leathers over my arms were ripped, and I only had one high temperature glove. Dear Cal Poly, please buy some better PPE!



Below: The process starts by heating the part to 1550F. The part was left in the oven for about 45 minutes to ensure uniform temperature. At this high temperature, steel goes into a phase called austenite. This refers to the structure that the material forms, or, how the molecules reorganize themselves. Even though the material remains solid, the structure is affected.



Below: Upon removal from the oven, the part was red hot. Immediately it was quenched in oil. During the quenching process, the part is cooled so quickly that the molecules do not have a chance to rearrange themselves into the same structure they normally would be in at room temperature. They end up locking into a phase called martensite. In this phase, the molecules are rearranged such that the material has a much improved strength. It also increases the hardness of the material.



Below: After quenching, I used this piece of equipment to measure the surface hardness of the part in several locations. It was lower than I was expecting, with a hardness between HRC46 and HRC47. I was expecting a hardness between HRC50 and HRC55.





Due to the rapid nature of quenching, the material may form ununiform grain boundaries and internal stresses. This makes the material very brittle. To counteract this, the part must be tempered. To do this, I reheated the part to a much lower temperature (800F). This allowed the material to improve its grain structure without changing phases. Then it was allowed to air cool. This process is called tempering. When tempering, the hardness and strength are slightly reduced, but the material becomes much less brittle.

Below: Here is the part air cooling after being tempered.



Below: Next, the hardness was checked again using the machine shown above. I checked it in several places and it measured between HRC42 and HRC44.



I am a little concerned that my tempering temperature may have been too low, since I was expecting the hardness to reduce to near HRC37. At this point I'm not sure if I should try tempering it again at a higher temperature or just use it as is. I am a little disturbed that (1) the hardness was not as high as expected after quenching and (2) the hardness was not as low as expected after tempering.

At this point I have to decide whether I should temper the part at a higher temperature. I would be happy to take advantage of the higher strength that the increased hardness has to offer, but I'm not sure if the material will be too brittle to combat fatigue. Any thoughts?
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  #74  
Old 04-19-2006, 01:12 AM
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Even engineers don't get it right the first time, No pun intended. Besides this is the first in many more projects that im sure your going to tackle. consider it a learning experience, im sure your heat treating processes was correct. But when was the last time the oven you did the work in get calibrated? the temps may have been a litttle off, Im sure your part be ok. Will steel age harden at all? When I have Aluminium heat treated alot of the time it will harden on it's own over a short period of time.
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  #75  
Old 04-19-2006, 11:08 AM
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I think your varied results could be caused by many things. I would not suggest only retempering the part. I would suggest if you do anything that you reperform the entire heat treat if you decide it's neccisary. However, I can't help you determine what a difference of 5.5 RC will do to part strength and fatigue life, sorry.
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  #76  
Old 04-21-2006, 12:08 PM
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Thanks for the responses.

I did some more research and digging. I still can't explain the lower hardness after quenching, but the final hardness is consistant with my 800F tempering temperature. It may be that I did not get the part into the oil bath quickly enough and the outside of the part was able to air cool a bit. I think I am going to use it as is and hope for the best. Fortunately this isn't a difficult part to make, so if it fails it may only take a day in the shop to remake.

UPDATE

Yesterday was another day in the shop.

I started by machining this slot in the main shaft.



Next, I drilled and tapped a couple holes in the lower main die arm.



Regular set screws will replace these cap screws to locate the shaft vertically and also ensure that it rotates with the main die.



Next I spent quite a bit of time on the main die. I wanted to fixture it to a rotary table and use an end mill to cut out the center, but the shop didn't have the appropriate tooling to fixture it to the rotary table. So instead I had to use a boring bar again. This made enlarging the hole a VERY slow process, but after some work it turned out fine.



Here it is with the new center sleeve loosely installed.



Today I will enlarge the hole that accepts the drive pin. After that I have to fully weld the rear cylinder mounts to the frame (right now they are just tacked in) and weld the center sleeve into the main die.

Then...

well then I am gonna bend some tubing!
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  #77  
Old 04-21-2006, 10:07 PM
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Quote:
Originally Posted by TheBandit
Then...

well then I am gonna bend some tubing!
Nice to see you this close! It's been fun reading along as you go!

Can't wait for the video of your frist full bend!
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  #78  
Old 04-22-2006, 12:55 AM
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WAHOO!!!!





OOOOOH YYYEEEAAAAHAHHHHH!!!!!!


More pictures and video coming later... I'm off to celebrate!!!
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Last edited by TheBandit; 04-22-2006 at 01:06 AM.
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  #79  
Old 04-22-2006, 12:58 AM
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Congrats! Looks like it went well!
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  #80  
Old 04-22-2006, 08:33 PM
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Now does the whole world not seem a bit brighter and the weight off your shoulders. I love the feeling you have when you see the results of the major project are complete.
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