Sketchy setups, don't like'em but sometimes ya gotta
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  1. #1
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    Default Sketchy setups, don't like'em but sometimes ya gotta

    I thought I'd toss this up here just for the halibut. I try not to make flaky setups, but I have a few that I wouldn't "recommend".

    This is one of those. I had to make 20 of these today, so I snapped a couple pics.

    This part is 1/4" x 2" flat bar, 5.2" long, profiled all the way around, and corner rounded on the top side. Finishes at 1.625" x 5.000" with an elliptical profile.

    It has 2x 3/16"x1" spring pins on the backside, .200" deep in the holes. That's it. It's a cap for an extrusion, nothing fancy.

    I could use 3/8" material and profile it first, then flip, hold in interpolated jaws, put in the holes and deck to .250" thick. But that would take more time and material than just starting with 1/4" flat bar, so this is what I came up with.

    Pic 1 is the left vise, put in the holes for the pins.
    Pic 2 is the part flipped over on the workbench with the spring pins installed. The orientation of the slot is a callout.
    Pic 3 is the right vise. I made some aluminum jaws to grab it by the spring pins, profile and corner round holding on to nothing but the 2 pins.

    I have tossed a part or 2 over the years doing this- squeeze the vise too hard, you squish the spring pins and the part lifts up. But I have found that if I'm careful closing the vise, they don't move.
    Attached Thumbnails Attached Thumbnails 1.jpg   2.jpg   3.jpg  

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    How many do you do a year? I see a pined vacuum plate for op2 if you do many.

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    Quote Originally Posted by DavidScott View Post
    How many do you do a year? I see a pined vacuum plate for op2 if you do many.
    Very few. Typical run 20 pcs, 2-3 times a year.

    Not worth putting any money into.

    I posted as an example of a bad idea that works, lol.

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    As long as it works it's a good idea. If you helicopter a part that may change. Mind saying how you profile them out? This is where that down cut corn cob would work well.

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    I have fallen in love with the 'tabs' function in CAM. I think I would cut it out of 1/4 bar with tabs and drill the holes, using your setup just for the corner rounding. Could probably run faster since the milling is in a solid vise

    Yeah, but I do all sorts of crap you shouldn't do on short runs

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    Quote Originally Posted by DavidScott View Post
    As long as it works it's a good idea. If you helicopter a part that may change. Mind saying how you profile them out? This is where that down cut corn cob would work well.
    I just plow it out with a standard 1/4" 2 flute HSS end mill. First pass gentle on the feed since it's cutting full WOC, , then kick up the feed and run a spring pass. The only cut I have to baby is the first profile op to keep it from lifting off the pins.

    If I was running a lot of them I wouldn't use such a crappy setup, but there's just not enough of them to make it worth dorking around...

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    Quote Originally Posted by gustafson View Post
    I have fallen in love with the 'tabs' function in CAM. I think I would cut it out of 1/4 bar with tabs and drill the holes, using your setup just for the corner rounding. Could probably run faster since the milling is in a solid vise

    Yeah, but I do all sorts of crap you shouldn't do on short runs
    This is one of those jobs that won't go away, but it's not worth putting a lot of effort into either.

    When I first started making them I did a couple runs that were more parts. I was going to retool it, then it went away for a few years.

    It came back a few years ago- always in these runs of 20, so now I don't want to retool it- the second I do, it will go away again...

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    ....................do it how ever you like........your shop....your time................... but I'd be runnin 3/8 material..............cost ya maybe another 25¢ in material and no worries on the 2nd op...............

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    Quote Originally Posted by david n View Post
    ....................do it how ever you like........your shop....your time................... but I'd be runnin 3/8 material..............cost ya maybe another 25¢ in material and no worries on the 2nd op...............
    I hear ya, it would be more rigid to use 3/8" and profile first.

    But it's a low dollar part, I could run the profile faster, but I'd still have another tool for decking, and the trade-off time and $$ would be a break even.

    So I leave it alone. If the orders get more frequent or larger quantities, I'll retool then, just to make it less fussy to run.

    The reason I started with this idea was mostly because I had a shitload of 1/4-2" 6061 FB on hand. I wanted to see if I could use it up on these parts.

    It worked, and I've been slowly working through the pile of flat bar- down to 2 or 3 sticks left on the rack after today...

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    I like it. If it works and the job doesn't justify anything fancier then it is the way it gets done.

    The manager of the shop I learned CNC milling at in the early 80s rarely put fixture money in his quotes. Had to get really creative and figure out how to jerry-rig most set-ups. It was even tough to get them to buy soft jaws. Of course all the dicking around made the jobs go over budget and made the programmer or operator the target of an ass chewing.

    If the pins were inserted rotated 90 degrees from how you have them they would be less prone to getting squashed. Might not be consistent in the vise though.

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    Quote Originally Posted by Vancbiker View Post
    If the pins were inserted rotated 90 degrees from how you have them they would be less prone to getting squashed. Might not be consistent in the vise though.
    The slot orientation is called out on the dwg. It goes into that extrusion I run, and I guess they want maximum surface contact for the loctite.

    They are fatter in that direction, and since my X0Y0 is the center of the left hole, it would probably introduce some variability that I wouldn't like.

    Even with the spring pins, they seem to stay centerline symmetric within .002".

    There's probably been 3 or 4 times over the last ten years that I told myself I was going to retool that job when I got some spare time, but you know how that goes, lol.

    Out of sight, out of mind.

    Quote Originally Posted by Vancbiker View Post
    I like it. If it works and the job doesn't justify anything fancier then it is the way it gets done.
    That's kind of where I am on this part.

    It works, customer likes the part, on to the next thing...

    I usually don't brag about my crappy setups, lol. I must have been bored this morning...

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    I used to make a ton of automotive steering shaft spacers. They stacked in with the rag joint for doing a body lift in the rust belt where the steering shaft slip won't slide anymore.

    The laser cutter I was using couldn't make clean 3/8" holes in 1/2" plate so I went to milling them from flat bar. One 1/2" bolt in the center and it worked. I was always going to add a pin for the second op, but same scenario, low$$ part and "I'll do it next time". I eventually had one spin and take out an endmill. I wondered if I put a piece of paper or thin cardboard if that might help and it made a big difference. I turned the feed up.

    Since discovering that paper trick I have used it many times and never had a part spin half assing a setup.

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    I keep super gluing flat plate parts down instead of buying a vacuum chuck. It works but its slow and somewhat finicky. Only takes a 1/8" and a 1/32" end mill so not much tool pressure anyway. It's very small quantities so its kinda not worth doing anything else. I really should buy or build a vacuum chuck.

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    Quote Originally Posted by jancollc View Post
    This is one of those jobs that won't go away, but it's not worth putting a lot of effort into either.

    When I first started making them I did a couple runs that were more parts. I was going to retool it, then it went away for a few years.

    It came back a few years ago- always in these runs of 20, so now I don't want to retool it- the second I do, it will go away again...
    Oh absolutely

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    I like the spring pin idea. Another tool in the toolbox.
    Do you think spring pins work better than a dowel pin since you could orient the gap in the pin with the vise jaw so as you tighten some the pin bulges in the hole?

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    Quote Originally Posted by vmipacman View Post
    I like the spring pin idea. Another tool in the toolbox.
    Do you think spring pins work better than a dowel pin since you could orient the gap in the pin with the vise jaw so as you tighten some the pin bulges in the hole?
    I don't think I've ever tried to grab a part by a dowel pin, so I can't say.

    I don't think the spring pin bulges in the hole. I have .800" of it in the vise, and only .200" in the part. I think it squeezes the entire length.

    I don't just drill the hole. I use a 5/32 end mill, plunge and interpolate to .185" dia. I'm fussy about the hole size, and it takes some effort to get the pin in. That's actually the hardest thing about making these parts- installing the pins straight and slot-aligned.

    The complete cycle is about 4 minutes, prolly half of that is the first profile pass.

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    Are the pins part of the finished part or just for holding while machining? Just food for thought but Garr makes some 3/16" x 5/16" loc corn cob mills for aluminum that would be real good at profiling with minimal cutting pressure, and lift.

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    Quote Originally Posted by DavidScott View Post
    Are the pins part of the finished part or just for holding while machining?
    The pins are specified in the drawing, used to secure the cap to the end of the extrusion. Once they're in, they stay in. There is a channel on each side of the extrusion that the pins fit into, the cap gets loctited in place after powdercoat.

    caps.jpg

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    I make flaky setup all the time doing proto work. I'm always doing mental math... if I get away with this, I'll save a couple of hours building a real fixture. I never remember the ones that work, but I generally have a pretty good recollection of the ones that didn't... sometimes because they involved loud noises and a trip to the First Aid cabinet. I'm dumb that way.

    My favorite flaky setups are the ones that you do for a couple of proto parts. Then the stupid customer orders 6 of them and you skank by again. Then they order 12 of them, and you skank by again. Then 5 years later you are bemoaning all of the time you've wasted and parts you've scrapped because of this flaky fixture... all to save a couple of hours. On the flip side, if you made a perfect fixture for every onesy twosy part that walked in the door, you would be out of business with a pile of beautiful shiny fixtures

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    I'm wondering if an LH spiral RH cut downcut endmill like Onsrud makes for routers would be helpful on a job like that, to push the part down instead of lifting it. Anyone here use them?

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