Tool Changes

[Mini Beast]

I'm almost to the point of making my first part. I've been doing a lot of thinking about strategies for workholding, programming, etc. I just wanted to get an idea about other peep's strategies for tool changes. As in, do you use the smallest endmill you will need to get all the detail? Or, do you rough with larger tools and then move to smaller ones?

I guess it's nice to have the whole operation done without any toolchanges needed, but if you did that all the time, it seems like the smaller bits would really get worn out.

[japroach]

You will quickly become frustrated if you use only a small endmill.

I've found its best to use the biggest one possible, to remove as much material as possible. Even if your part is quite small, using a 3/8" endmill makes a huge difference in cutting time.


To switch tools, I use the piece of paper method (drop the Z down until it just binds, then I think its 2 thousandths or so). Simple, cheap, and fairly accurate.

[Mini Beast]

Very good, that makes sense. Thanks for the reply.

[ALpmc]

I agree. You have to have tool changes on every project or you will have long run times, increasing the possibility of problems developing. Tool changes are really easy and there are many techniques for accomplishing them without headaches.

My controller allows me to turn off power to the steppers so I can lower Z by hand until it contacts the top of stock and set Z. Do not touch X and Y while power is off. Power back on and Jog Z to safe height and start the program. Note: Programs stop for tool changes. The controller should (mine does) remember its location where it stopped for the tool change. So.......I can jog to anywhere on the part to set Z. After I jog Z high enough to change the tool, I jog to the desired position to set Z. Using a a built in function in the controllers program and not the actual power switch, (called De-select or D on the keyboard) I turn power off to the steppers and lower Z by hand to set, zero Z. Don't touch X and Y. Power back on (S for select on the keyboard), jog Z to a safe height and continue milling operations/program......it should return to last coordinate before tool change stoppage and resume the milling operation with the new tool. Run a test to see if yours will do the same.

If the project requires tool changes, I can program different starting points for Z to start from, such as pockets within pockets, or just use the original TOS for each tool change.

For example.......let's say a pocket within a pocket. The first pocket is large and I use .25 endmill. The second pocket(s) is smaller and I want to use a .0625 endmill. I have two choices in how I program.

The final depth of the second pocket will always be referenced from the TOS.
1. I can program my tool change's Z height to be set where the first tool started from.......TOS.

2. Or I can program the second pocket to begin from the bottom of the first pocket. My tool change's Z height would have to be set at the bottom of the first pocket. (As a rule I only do this if I'm continuing with the same tool and the program won't stop between operations, otherwise I use the first method.)

By using this method, I can always set a new tools Z height even if I have to jog to un-milled stock next to a hold down outside the milling area. As long as I never touch X and Y! (They are set to the parts original origin)

Hope this makes sense!!!! Sorry......I'm not familiar with other cad/cams or controllers and their programming.......I just assume they are similar.
Good luck.