Armory Sponsor
Posted: 9/2/2011 6:17:17 AM EDT
|
Just for my personal knowledge, because It's not obvious to me, how are spiral grooves (spiral fluting) cut?
Best thing I can come up with is a sort of jig with gears that spin the piece at a constant rate as it pulls it across a cutting piece. |
|
CNC with 4 axis if machining is being done on the light side (most production shops have 5 axis CNC machines, with a Z head axis as well))
X axis is the milling bed moving left to right Y axis is the milling bed moving front to back. Z axis is the milling mead moving up and down A axis is a rotary table set up horizontal to hold the work piece, and allows rotation of the barrel on the bead as the machine is working. So in standard straight fluting, the head drops down on the Z axis when using a end mill, or a combo on Z down and Y back into the work piece if using a side wheel type cutter, and the X access makes the passes back and forth for the flute. Once that flute is completed, then the A axis/ rotary table is indexes/ rotates the barrel for the next flute passes. In spiral fluting, the same for the X and Z (or Z and Y for a side wheel cutter) passes, but instead of the A Axis/rotary table staying fixed for straight passes down the barrel, the rotary table rotates as the machine is cutting to create spiral fluting down the barrel (read makes the passes to create the one spiral flute, head pulls up, the A axis rotates to the next flute path, then starts the next flute passes. As for doing spiral flutes on manual machine with just rotary table A axis holding the work piece for the fourth axis control, It's possible if you gear the rotary table in to the X axis so you get the right rotation per Z distances movement. As for round end mill over side wheel cutter, depending on the twist and depth of the spiral cuts, although a side wheel cutter will last longer (stay sharper longer), you may not be able to achieve the desired cut with a wheel side cutter, and a ball end mill will have to be used. |
| On a manual machine, you would need a template and following device to act as a 4th axis. With this setup, you would simply traverse the work and allow the follower to control the additional rotation. This really is, nowadays, best done with CNC. Most specialized tooling and copiers were a necessity during their time, but they were instantly very obsolete as soon as computer control came into the picture. If you plan on creating such a setup, do it for the satisfaction of the project. Don't expect it to be an inexpensive alternative to modern iron. If you want to get into the fluting business, definitely consider saving your investment for a CNC mill with a 4th axis. |
|
Cutting a helix on a manual horizontal milling machine requires a dividing head with change gears between the worm shaft on the indexing head and the milling machine lead screw. The universal milling machine table is swung to the correct helix angle and in the direction for the helix desired. The cutting tool is a form milling cutter of the correct radius.
The tooling and set up time must be offset by the number of items to be produced. (Read Money!) Including the math, setup time and machining time, a manual operation is cost prohibitive for one item, unless you are government or education based and supported. Forty years ago cutting a helix on a universal horizontal milling machine was the way of things, especially for helical gears. Today every thing is CNC but still cost prohibitive for one item. If you are still commited and have the time and deep pockets, (1) seek out a college machine shop course and get the training and access to the machinery, (2) Buy a used text book at Amazon.com and teach your self, (3) buy a ready made barrel for a couple hundred bucks. Enjoy the journey. |
Armory Sponsor