Manually Milling an Ellipse.....Say What ??

[Music] [Music] hey guys Joe pie here at Advance Innovations welcome back to the shop today's video is very technical and a little long- winded initially so if you just want to see chips fly well then fast forward through all the digital stuff in the beginning and just go back to where the Machining is but if you really want to learn something new a new technique well not really a new technique but an existing technique uh then suffer through the beginning because it's very it's detailed it's Technical and it's valuable it'll help you out anyway today's video is inspired by a video that I recently watched by another maker named Alec steel that's Alec with a c steel with an e on the end he's a blacksmith he's young he's got a lot of energy and he's building a miniature steam hammer and in his kit he got some elliptical material now an ellipse is not something that is easily achieved on a machine that only moves left and right in and out up and down it is a little bit more technical than that there's a lot of math involved there's a lot of setup involved uh the part can easily be done if you have an XY Vice on your rotary table that makes life a whole lot easier but if you don't well then you're just going to have to do it the oldfashioned way and that's what I'm going to show you today so the first first half of this video is going to be how to center up the material the logic behind the positioning of the part uh followed immediately by the math involved showing you how to determine how far to rotate for all the different radius tangent points and such yada yada boring AF but a necessary evil if you want to throw chips and have a part that looks pretty good anyway let's move on to the digital animation and take a look at how that's done hope you enjoy this one okay guys before we get started I want to cover a couple of very basic rotary table setup facts this part is going to be moving around a bunch on once it gets to the rotary table and I want you to have some type of comprehension of exactly what's going on the big round part in front of you that is the rotary table model that I've created and the little green part in the center is the ellipse that will be done on that table the red represents the endmill and the spindle of the machine so let's just get that out of there for a second you can see that the ellipse that we're going to create has four protrusions on it those protrusions represent the axes of each feature on the rotary table model itself there are two curves drawn on this line right here where the mouse or the cursor is jumping around and the small one in the center they represent their radiuses radi that will be machined onto the part when the part hits the table let's see if I can grab a hold of that piece and show you how this part is going to bounce around on that table the first radius that I'm going to cut on this piece is the one uh facing away from me as the part is positioned on the y- axis and you can see if you take the little protrusions that I've drawn on there representing the axes of the feature let's go for wireframe that the part lines up very nicely with the radius drawn on the table okay so anytime you're going to put a round feature on a part the center line of that round feature absolutely must be over the center of rotation of the rotary table that does not guarantee that dimensionally the radius is going to be the correct size that just guarantees that it's going to be on the right spot spot the dimensional conformance of the feature will be determined by the placement of the endmill if the endmill is a little too far out naturally the radius is going to be bigger if it's too far in now it's going to be smaller so the size of the radius is dependent on the relationship between the center of the rotary table and the center of the endmill the placement or the accuracy of the feature like I said depends on the part to the rotary table relationship and for the end features it will be buly let see what that looks like from above there we go okay make sure that the axes of the feature are in line with the rotation point on the Rotary table now when I bounce this part around on the table once I start Machining it and it will move it will move uh forward and backwards initially and then it will go back to Center and it will move left and right to do the ends when you do this the rotation of the rotary table is going to be very sensitive the setting of The endmill to the rotary table is going to be very sensitive and right here on the ends of the part where the tangent line is where the tangent point is uh that's a very sensitive area and chances are you're going to end up with a small dig or bump or dimple or something in that area and of the four opportunities that I had to get it right on this part one of them did present a small dig which was easily removed with a file next question I'm sure is going to be how do you figure out the rotation you can see that I did a cad representation of the angle of the tangents up here let's get that in the center so using cat it's a piece of cake in order to figure that out but if you got to figure it out with a piece of paper I'm going to show you how to do that just before we start cutting right so let's get out to the bench I'll draw you a quicky little sketch on how to figure out how far to spin the rotary table in a setup like this and I'll make some chips let's do it all right let's take a look on how to figure out the rotation of the rotary table to find the tangent points for the end Cuts okay end Cuts going to start off with the representation of the major diameter okay this is a 2-in circle or a radius of 1 inch as called out on the print going to establish the center point of this particular drawing right here and I'm going to strike a one-inch cord or a one inch yeah it's a one inch cord straight to the edge of the part we'll call this a we'll call this B AB 1 inch because it's a 1 inch radius simple here comes the center line of the part we know that the part is 500 thick so we're going to call this C that makes BC 750 BC 750 why because AB is half the part the part is 2 150 per side so now we know this is 750 triangles are starting to jump right off the page for you the distance from the center line of the part to the center of the end tangent radius is 424 let's call that D well we're not going to call it anything right now I'm just going to call it 424 okay so now you have two legs of a given triangle 750 and 424 realistically that is all you need to calculate the sweep angle for the rotary table movement let's take a look at the geometric rules that will fall into place here I'm going to connect B let's call that D what the heck right I'm going to connect B through D and Watch What Happens where the centers of these two arcs connect and project this point right here is the tangent point of that end radius so as the top radius comes around it's going to stop right here transition to the small radius and come back around now by also by geometric construction let's project these lines out a little bit B further so you can see this whenever you have lines that cross over like that they form two sets of identical angles this angle on the outside is equal to this angle on the inside and you can see if that was a scissor and you started moving it they would pivot around this point and these angles would always be the same because if you laid this flat it would be a straight line right so open it up like a butter butterfly these angles are the same these bigger angles on the outside are also the same so once you figure out what this angle is right here you know how far that rotary table has to move based on this rule right here and that particular angle depending on what you work with you can also figure out what this leg is here if you want to figure that out that's 1 in minus the radius of the smaller Circle that turns out to be 8 62 so in the long run you have a triangle that you have all three sides of and you can pick your poison which trig formula you want to use to figure that out this being the angle that you want to find out that's your rotary table sweep right there now be careful when you bring the cutter around chances are it's going to dig hit depending on the flex of the cutter the accuracy the setup uh 99 different variables are going to cause that to leave a mark and if it happens no big deal that's why they invented files right you can file out the bump file out the blemish do what you need to do to make it pretty but that's a very very sensitive setup to get tangent arcs like that especially three tangent arcs chances are one of them is going to leave a mark out of the four that I did on the part that I'm going to show you one of them did leave a Mark I did file it out so no shame there it's not as tough as it looks remember that take a snapshot of that and put that in your tool boox first step in this process is to make sure the table is true to the spindle now since the center hole isn't doing the work and the motion of the rotary table is you've seen me preach this a 100 times disconnect the worm on the table spin the table track the spindle when those two lines line up all is well zero out the digital readout right now going to return my table to the x0 position and this rail on my rotary table is true to the world true to the xaxis position that's very important place to start okay let's get on with the rest of the components now this is a setup that you're going to be seeing in your sleep for a very long time if you attempt to do this you're going to be scratching your head and probably walking away from the machine about nine times and believe me it's justifiable I have gently Sharpie markered the profile of the part on this block just to illustrate exactly what I'm trying to convey here the Left Right shift for the end radii will be established by a stack of gauge blocks between the side of the Vie and a stop on the table I can move the Vise a Precision amount this way and I can move it back to Center and I can move it a Precision amount that way and back to Center I've got the same ability to move the part on the Y AIS in and out with the use of 3/4 in parallels in the back right there so if the part is going to move incrementally exactly the same amount in both directions starting on Center you would be required to have a spacer of the shift value against the fence at that time when I want it to move I'll just remove this and this slides in and when I want to bring it back out Beyond Center to the second position I will add a second parallel stick it back in there contact the way you go same thing with the side remove the shim over it comes when you go back the same size shim will get you back on Center double the thickness of the shim we'll take you to the second position so there's a lot going on on this part this is something you may have to watch one or two times but I'm going to see if I can track the stylus on the line that I printed on this part with a single parallel in the back and a single stack of blocks against the side stop that Stylus is now on zero going to set the 1in radius by moving the table the rotary table the Bridgeport table everything is going to move one inch in that direction now when I actually make the cut depending on the size of the cutter that I use I will have to accommodate that 1in shift to allow for the diameter of the tool that I'm going to use so if I was using a/ in tool I would have to move an inch and a quarter to allow for the radius okay now in order to put that cutter where I want it I have to double up on that back shin and move this surface under the cutter and now by sweeping the table with the position of the part as is you can see that the radius stays on that line the backside radius will be done exactly the same way table moved in that direction shims taken out table back to zero table at one inch not a problem now believe me the first time you try this you're going to step back from the machine you're going to scratch your head until you have a bald spot and then you're going to decide to do something else because this is not easy but comprehending the movement of a part part versus the position of the rotary table to the spindle once you get it it's like an aha moment Palm to forehead I finally see it so let's clamp this thing down and see if I can make that cut and then we'll worry about blending in the tangent end radi I radiuses wherever you are in the world whatever it is you however you say that that's what we'll do next let me swap out the drill Chucks swap in a cutter and we'll make those cuts and see what it looks like I'm using a 250 diameter cutter so my digital right now is set at 1in 125 I want to make a rough and finish pass so I added 30 to that the digital is now positioned at 1 in 155 I I'm 30,000 away from final I may nibble at this Peck at it who knows what I'm going to do but I'm going to get the the material out of there so we can see if the radius is going to fall where I hope it is looks good let's do it by climbing on all those plunge cuts the cutter will Flex away from the part and not leave deep vertical lines in the part if I were to Conventional that that thing would look like a a curved staircase right now with all the lines that would be in it 30,000 away from final so let's take a couple of finished passes clean that surface up and we'll spin it around after we clean up the messes on the rotary table good gracious all right let's do it first side radius complete real time approximately 6 minutes from the start of this particular video seg blow it all off I'll show you the second side setup and we'll cut the other side exactly the same way first feature is complete let's move on to the second feature first thing I'm going to do is release the clamps on the Vie do not move the part in the Vie itself you can move the whole Vie just don't move the part going to return the table to the zero position right now the rotary table is true to the center of of the cutter okay let's move that cutter closer so you get a better feel for what's going on now when I return the cutter the vice back to the original 3/4 inch offset can see that the cutter is now over the center of the part what I need to do is I need to get the center of rotation of the new feature over the center of the rotary table okay the feature itself has to be centered over the rotary table and then everything else should fall in based on where the rotary table is pushed to but the center axis of that feature the new feature must be over the center of the rotary table makes perfect sense right like the centered axis of a of a wheel the only way to do that right now is to add another shim behind it so now I have two 3/4 inch shims back here at this point the center of this Arc is directly under the or excuse me the center of this Arc is directly over the center of the rotary table so it's basically dealer's choice however big you want to make this feature the center of that feature will always be over the center of the rotary table I know this is confusing guys I have really do apologize if I figure out a better way to convey what I'm trying to show you then I will definitely speak it out I guess a good way to look at it is if we're setting a boring head the boring head is only going to cut the hole that it's dialed to bore right it's going to cut a specific size where it cuts that hole that is up to the position of the table position of the part that's exactly what's going on here and the rotary table is the booring head so this setup right now is set up to create a very specific radius Center Line the size of that Center Line depends on where I put the table itself so the rotary table table everything's got to move to give me that number right there that allows me to do the rough and finish passes and have everything in the right spot so now I'm going to move off my 1 inch plus the radius of the cutter which is 125 plus 30,000 for a rough cut which is 1in 155 and I'm going to to lock down the Y AIS of the table right now I think you can see that when that cutter comes down it is going to cut right on the outside that black line going to make a little football here that's what I'm looking for I can round the ends off at a later date and I will do that within this video by manipulating the little side block the same as I've been manipulating the parallels in the rear make sure everything is nice and snug kill the camera here for a second to secure some clamps and be right back let's take a very superficial cut just to check the tracking of the cutter and with any kind of luck that is now about 530 across let's see what [Music] again close enough I'm going to nibble away at it and we're going to take a look at the finished shape and offset for the end ruses you seeing how the sides are formed I don't see any point in actually showing that I'll show the Finish result here in a second all right little change of plans here I had not planned on showing the removal of the the material on the back side but it's a great opportunity to show how much these Cutters can Flex I'm going to plunge nibble away at this the same way I did the far side but this is going to be done with the cutter in a clockwise rotation but in a conventional approach so if this were an exposed surface that I was creating this would be a conventional cut the cutter is going to want to dive in and when I get to this side I'm going to pull the rotary table I'm going to retract the rotary table in a rotary motion back to the starting point and the finished surface will probably look a lot like that surface back there it's going to have all these little dig marks in it if everything goes as expected all right let's do it now as expected the rippled surface right there as you can see is cutter Flex the outside climb cut when the cutter returned back to the starting point was set at the exact same y position the exact same X position the table did not move the rotary was the only thing that shifted each one of these digs is how much the cutter kicks in as it's traveling down so you can see the advantage of a conventional cut versus a climb cut approach on something like this when you nibble away even if you're not nibbling away you need to be aware that these Cutters do Flex carbide is really hard but you'd be surprised how much it can actually Bend I'm 30,000 away from my final Dimension I'm going to shift the table in 30,000 on the Y take a couple of climb cut finish cuts and we're going to move on to the end radius is let's do it all right the larger two radiuses of this particular ellipse are complete sorry about the Sharpie marker being off center like that I did that by eye let me draw this camera out a second way there we go let's clean this mess off the table and the next ship that we're going to do is the entire Vie back and forth on the Y AIS excuse me on the x axis Orient this true to the machine the part sits like this so the x-axis is left and right I'm going to change the spacer right here we're going to do the two end radiuses stay tuned okay with both of the outer features successfully created let's put the entire setup back on zero since one radius is 750 off center this way and the other was 750 off that way putting it back on Center is a matter of returning to a single 750 3/4 in parallel on the back we're going to move the table back to the zero position as well right now the center of the part is over the center of the rotary table center of the rotary table is aligned with the spindle of the machine now to do the ends of an ellipse we're going to have to take this block out right here and now will shift the part to the right so this is considered a neutral position since we're going to go approximately 48,000 in both directions the center section the center position would be 408 away from where it's going to ultimately end up man I'm even confusing myself on this one here we go take the blocks out shift the setup to the [Music] right now for anybody that may have rolled the video back to see exactly what that Dimension is the part is shifted 424 off center by removing the block that was down here against the stop by putting the part 424 off center the center of the feature that's going to be the round on the end of the ellipse is now over the center of the rotary table okay the spindle is still lined up with what is the center of the end feature the end feature is lined up with the center of the rotary table establishing the size of the radius that you want to put on there is a matter of moving the xaxis and determining based on the radius of the tool where to put the cutter so the first thing you can do is move 125 off zero out your incremental on your digital if you so desire and then just dial in the radius I'm going to go 60° either way on this and we're going to round that end off do the exact same thing to the other side then we're all going to scratch our heads and Rewind and watch this 14 more times to figure out exactly what the heck just happened here we go a rough passage should be about 20,000 away from Finish but let's take a look right dial it in finish up back to the zero position I'm going to double up on the bumper shim that's down here so in order to get back to Center I would have to go 424 in that Gap right there and then add another 424 to get to the center of the feature on the end of the part blow the stuff off put that shim in there and continue now like you've heard me say a 100 times in the past the easiest way to create features on a part is to leave the part in the fixture and do as many operations as you can without moving the part it would be very easy to generate a boss on the top of this and hit three points along this part but that would really not be the demonstration that I want to give you I'm going to take this over to the saw and I'm going to cut it off and deeper it and then I'm going to show you how to work with an elliptical shape like this how to rotationally line it up and get your Center fairly easily little bit of prep but once you're there it's going to fall right into place all right let's do it okay Fresh Off The Band Saw let's take a look at what we got I am very pleased with this part as I stated somewhere in the body of this video one of these radiuses there it is you can just barely see the line right there did leave a track mark where the tangent was and that's either a position of the cutter or a rotational issue or God knows what many different ways uh that could have happened there's a lot of different ways to do this naturally CNC is like about seven lines of code in your done if you have an XY rotary table then you're way ahead of the game and as far as holding this for secondary naturally 10 different machines are going to do it 10 different ways depending on how many likes thumbs up comments I get about this particular video I may follow up with the video on how I would approach that and there really is no wrong way to do it so long as the feature comes out where it should be in the end let's take a look at it dimensionally see what we got looking for 500 on the width anything within five is going to be acceptable 497 and a half it's about two and a half thou under nominal nominal would have been 500 so I'm about 2,000 under that that's very acceptable for a part like this 1in 125 long this one you got to find the high spot because it is looking like an egg so rock it around until you're happy with the way it's seated and rotate it 1255 half a thousandth over max length also very acceptable that was a fun part I hope you enjoyed the video hope you didn't get too bored with all the technical stuff in the beginning but that's all I got for today I thank you very much for spending some of your time with me today wherever you are in the world I hope you're well and happy and safe and warm it's getting a little cold these days me Joe pie Advanced Innovations atin Texas I'm out

Channel: Joe Pie

Views: 45,329

Keywords: Joe Pie, JoePieczynski, Advanced Innovations, advanced innovations llc, how to, machine shop, shop tricks, shop hacks, shop techniques, shop tutorials, Scale models, mini lathe, steam engines, beginner machinist, hobby machinist, advanced machiniist, professional machinist, turning, milling CNC, manual machining, machining, milling an ellipse

Id: JSEPDHyr1LY

Length: 35min 20sec (2120 seconds)

Published: Sat Jan 13 2024