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IndustryArena Forum > Mechanical Engineering > Mechanical Calculations/Engineering Design > Need help brainstorming a solution for this mill turn spindle
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  1. #145

    Re: Need help brainstorming a solution for this mill turn spindle

    Quote Originally Posted by QuinnSjoblom View Post
    I added to my last post. I think I'll adjust the design of those to be drawn into a tapered shape so they aren't relying on just bolt pressure to prevent shear slipping as I agree they could get loose over time. A slight amount of flexing is ok as it will make the servo happier when locking, but I surely don't want the joint loosening up

    I edited my post above also. Drive pins maybe? A couple of 1/2 or 5/8 dowel pins into plastic bushings might do the trick.
    Jim Dawson
    Sandy, Oregon, USA

  2. #146
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    Quote Originally Posted by handlewanker View Post
    Seeing as how you are not able to pass material through the 4th axis per se, I would think that you could do away completely with the 4th axis part and attach a chuck directly to the servo motor spindle......just thinking...….I doubt that would be a solution but ….giggle, imagine if it was.....such a compact unit.....maybe a very big servo....hmmmmmm, perhaps a pancake type servo with a big diam hollow shaft.
    Ian.
    I had considered that at one point too, but a couple things. Even blocking off the back end with the servo, I can still fit almost 1 foot stock within the spindle. Also my spindle will handle MUCH higher radial loads than a servo. It has huge bearings compared to what's in the servo.

  3. #147
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    Quote Originally Posted by Jim Dawson View Post
    I edited my post above also. Drive pins maybe? A couple of 1/2 or 5/8 dowel pins into plastic bushings might do the trick.
    I considered pins making the link as well, but with the direction of the forces, it's basically trying to parralelogram the square plates which surely isn't happening so I believe they will give a more rigid link than large pins would. I just need to make sure the joint can't slip. I'm modeling up an option to handle that

  4. #148
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    Re: Need help brainstorming a solution for this mill turn spindle

    heres what im thinking to change the joint of the linking plates. this would prevent any slipping. just need to make it a nice tight fit. similar to this but not exactly. probably want more meat in the "ears" of the pocket or they will just flex
    Attached Thumbnails Attached Thumbnails plate joint.jpg  

  5. #149

    Re: Need help brainstorming a solution for this mill turn spindle

    That should work if you have enough engagement.
    Jim Dawson
    Sandy, Oregon, USA

  6. #150
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    Quote Originally Posted by Jim Dawson View Post
    That should work if you have enough engagement.
    I'll also thicken up that rear plate like the front one is. I thinned it down trying to save overall length, but now that i figured out a way to shorten the ballscrew coupler an inch or so, i have room. It will be as thick as the front plate and give more engagement in the joint. Ill be able to get this joint a perfect press fit by starting with the side plates and then test fitting them into the pocket while removing a couple tenths at a time until the fit is perfect.

  7. #151
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    Re: Need help brainstorming a solution for this mill turn spindle

    Another thing I'm gonna do to get everything concentric and running true, the nub on the back that the ballscrew coupler references on will be left slightly oversized, I'll assemble it onto the spindle and then turn down that nub to size using a long endmill by slowly feeding it in and turning the spindle by hand. This will make the reference nub perfectly concentric to the spindle

  8. #152
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    Re: Need help brainstorming a solution for this mill turn spindle




    Sorry, pic got flipped. Decided to play around a bit before i rebuild the mill turn for direct coupling. Dont have lathe tooling yet but i did have a cheap single insert indexable endmill. whipped out a mount for it and tried a cut. completely the wrong tool for the job, not a rigid mount, too much tool stick out, etc. still cut halfway decent lol. cant wait to do some real turning once i have some proper tools and mounts. i thinks its gonna work great judging by the results already with a terrible setup.
    Another thing I just realized, my mist cooling set up is gonna need some serious expansion for turning/milling in same program without stopping. Nozzle for each turning tool as well as one for main spindle. Letting them all run isn't gonna work unless I get a bigger compressor and waste a lot of coolant. Really wish I could setup for recycling flood and just let all the nozzles go, but just not an option for me. I think I'm gonna need a solenoid for each mist cooling nozzle and get tricky with my tool change macro. Assign solenoids to groups of tools that will be mounted in specific position.
    Attached Thumbnails Attached Thumbnails 20190420_144055.jpg  

  9. #153
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    Finished the coupler. Still need to machine supporting structure. In the pic the servo and spindle are still mounted in the belt setup frame so ignore the orientation, servo will be behind spindle. The draw tube action is very nice. After loosening the tube with a torque bar in one of the bores of the wheel, I can then give the wheel a good spin by hand and it ejects the collet completely. The back of the wheel is a half mm away from the back plate of the coupler, so after loosening a half turn or so it starts pushing the collet out. Really fast convenient setup, although there's currently no way to add automated draw tube actuation. If you look closely at the joint, the coupling plates have a positive shape that fits tightly into the front and rear plate so there's no way for slop to develop. I slowly walked it in so its a press fit that gets pulled together by bolts. Right now the brake rotor isn't installed, but there's a bolt pattern on the front of the coupler for it. The spider coupler mounted on the servo to the right has been shortened and has counterbored holes for bolts to pass through from the inside. One i turn the nub on the back of the coupler for concentricity, the short end of the coupler will fit onto it and drill/tap chasing through the holes. I'm still a bit concerned about being able to lock the spindle without it faulting. The spider coupler may not have enough give to make the servo happy. Low integral gain is one way to allow it to be locked without faulting, but I would prefer being able to have it tuned more rigid and have just enough give in the coupler to allow it to be locked. We'll see how that works out. Side plates can still be modified to allow a bit of flex if needed. Right now it's pretty rock solid.

  10. #154

    Re: Need help brainstorming a solution for this mill turn spindle

    Nice work! :cheers:

    If you disable the drive when applying the brake then faulting would not be an issue. You could do it with a relay that simultaneously applies the brake and grounds the enable pin on the drive.
    Jim Dawson
    Sandy, Oregon, USA

  11. #155
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    Quote Originally Posted by Jim Dawson View Post
    Nice work! :cheers:

    If you disable the drive when applying the brake then faulting would not be an issue. You could do it with a relay that simultaneously applies the brake and grounds the enable pin on the drive.
    Hmm. Interesting idea. Timing would probably work out perfect just putting it in the same macro. Disable of the servo happens simultaneous to brake solenoid activating. Delay of the solenoid would give enough time for servo to disable first. Probably need a delay in servo enable going the other direction. But i wonder if all this can happen without ever losing position. With symmetric parts loaded which is usually the case, it probably doesnt move, something bigger that isn't symmetric might pull it off position during the split second that servo isn't powered and brake isn't locked. Could probably fine tune the timing and the intake/exhaust size of the brake so that the brake has partial hold while servo is still on. Enough to prevent movement but not enough to fault. I'll consider that idea for sure

  12. #156
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    Re: Need help brainstorming a solution for this mill turn spindle

    So heres what im thinking for the mill turn gang tool setup. Originally i was thinking i would slap a qctp on either side of the spindle and call it done which would allow for really quick tool changes, but it takes up a lot of room and limits me to 2 tools at a time. I decided i would rather be able to hold 4 or 5 tools with less convenient tool changes, but rarely need to change tools. Also much cheaper, 400 bucks for 2 decent wedge qctp's. This is based around chunks of 7075 that i already have. I think it could be even more rigid if i redesigned it with the main plate being much thicker and integrated as the spindle mount, but ill have to buy material for that so i think i might try it like this with no cost and see how i like the layout, then maybe redesign later with possible changes and thicker main plate integrated as spindle mount.

    This holds 2 1/2inch tools on the right, in most cases a parting tool and either a ccmt or dcmt. These tools are held with 3 m8 set screws. The tool closest to spindle is first installed with set screws within the material between the 2 tools, then outer tool installed with 3 more set screws in outer material. Outer tool needs to be removed to access inner tool. On the left side there is 2 er20 chucks for holding drills and boring bars. these are pretty cheap, 10 bucks a piece on amazon. They fit into a 25mm bore with 4 m8 set screws each, 2 pairs at 90 degrees. Those 2 bores will be interpolated to final size using a long 1/2" reduced shank endmill that i have mounted in the mill turn spindle to give perfect axial alignment. Much easier than milling them ahead of time and trying to get axial angular alignment adjusted afterwards. ill hog out most of the bore when making the part and just leave 20 thou or so for final interplolation with mill turn spindle, or better yet get a boring head.

    With these 4 tools, a dcmt, parting tool, drill, and boring bar, plus whatever tool in main spindle, i should be able to complete most parts that i have start to finish with only milling spindle tool changes. Clearance between tools allows work on up to about 1 1/4 diameter parts which is plenty for most of what i do. larger parts are just index milling and theres no clearance problems with that since the vertical spindle nose comes down further than any gang tooling. I would like to add a 3rd 1/2 inch tool on the right, most likely threading, but i think ill probably start to run out of rigidity with the current design reaching out that far, so possibly add the third when i redesign later with thicker more rigid setup. right now all the main parts are 1.75 inch thick so i think itll have decent rigidity as is. The main plate clamps onto the spindle as well as being bolted to the Z plate from behind. I'll need to really nail the bore size for the spindle so when i clamp the main plate onto the spindle, the 2 flat surfaces on the right stay coplanar for bolting on the right side attachment and the rear surface stays flat for being bolted into through the back of the z plate.

    I dont really know a lot about boring bars, but ive read about other guys holding them in er chucks no problem. The type that have flats on them might need to have a slotted sleeve for proper holding in the er collet. The other difficulty is getting the boring bar lined up at the right angle in the collet since the collet can sometimes twist a bit when tightening the nut. If anyone has a better idea for holding various boring bars in a compact space, Im all ears. I could use one er chuck for drills and something else for boring bars if theres a more simple solution.




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