[pinguS]

Hi all

Just wondering if there is such a thing, which lets you state the taper amount on the machine control.

I currently have a 18t control, and as my machine is moving towards the spindle, the axis tapers down slightly, so when cutting the diameter reduces towards the spindle.

Can this be adjusted in any sort of parameter, normally ok if taper is about 0.02mm as I can just make adjustment in the program, but now after a slight smash, the taper over 100mm in Z towards the spindle has about 0.25mm down in X, and when doing complex parts, its too much to adjust the whole program.

Basically looking to see if a parameter is available to allow compensation, or am I better off calling an engineer take apart and fix the machine?

cheers for any help....

pinguS

[underthetire]

Call someone to do a headstock alignment. Do it right. Electronic compensation for mechanical problems never works out well.

[angelw]

Hi all

Just wondering if there is such a thing, which lets you state the taper amount on the machine control.

I currently have a 18t control, and as my machine is moving towards the spindle, the axis tapers down slightly, so when cutting the diameter reduces towards the spindle.

Can this be adjusted in any sort of parameter, normally ok if taper is about 0.02mm as I can just make adjustment in the program, but now after a slight smash, the taper over 100mm in Z towards the spindle has about 0.25mm down in X, and when doing complex parts, its too much to adjust the whole program.

Basically looking to see if a parameter is available to allow compensation, or am I better off calling an engineer take apart and fix the machine?

cheers for any help....

pinguS

You fix this issue by adjusting the alignment of the spindle, parallel to the Z axis travel.

You will find that the headstock of the machine is arranged on a generally central pivot pin and on most machine tools there are jacking bolts associated with the headstock that facilitates slight rotation of the headstock about the aforementioned pin. Accordingly, the headstock can be aligned by manipulating its position with these jacking bolts.

You will most likely have to remove some of the covers to get to these jacking bolts, and to the bolts that secure the headstock to the frame of the machine.

The procedure to align the spindle is as follows:

1. Place a piece of material in the chuck of the machine that will allow a cut of 300mm in length. I like to use a soft material such as brass or aluminum, the latter being my preference. The diameter should be such that you get no deflection or chatter during the cutting procedure. I use minimum diameter of 70mm in aluminum, and have approximately 305mm protruding from the chuck jaws.

2. Use a turning tool with a very small tool nose radius and positive geometry. You are seeking an arrangement that will give absolutely minimum deflection of the test part away from the tool. I use a screw cutting tool with the smallest radius possible.

3. Undercut the center section of the test piece by approximately 2mm on diameter, leaving a section close to the chuck and at the other end of the bar of approximately 10mm long. The test bar is to be cut unsupported by a tail stock or any other device.

4. Write a program that will take a light cut on the larger diameters at each end of the test bar.
i.The program should start at a diameter larger than the diameter to be cut.
ii. Feed down to the first diameter to be cut.
iii Cut past the end of the first cut diameter.
iv. Rapid to just short of the cut diameter near the chuck.
v. Cut the second diameter.
vi. Feed off and Rapid back to the start position.
vii To take successive test cuts, just apply a new depth of cut with the tool offset and run the program again.
viii Once the test diameters are being cut on their full circumferences, only take test cuts of about 0.10mm on diameter.

5. Measure the two diameters and compare. Based on this comparison, you will know in what direction the headstock needs to be moved.

6. Arrange a dial indicator so that the stylus contact the test bar at the end diameter furthest from the chuck.

7. Lets say that the test bar shows a taper of 0.25mm over the 300mm length. Its not a case of moving the headstock half this taper and calling it done, because the headstock is pivoting on a point quite a distance from where you're measuring. It merely gives you an indication that the headstock is moving, and after you have taken a few test cuts, measurements and moves, you will quickly determine what movement on the dial indicator, gives what amount of correction to the taper.

8. Undo the headstock hold down bolts, but keep them nipped. Watching the dial indicator, use the jacking bolts to move the headstock into closer alignment.

9. Firm the headstock hold down bolts and repeat the cut, measure, and align procedure until the test bar cut diameters are indicating a parallel cut.

10. European standards were in the tolerance range of 0.0 to 0.01 taper per 300mm, smaller at the end furthest from the chuck, if not 0.0. I always aim for 0.0 taper.

11. When satisfied, tighten the headstock hold down bolts, and take a final cut and measure before replacing the covers.

Given that the machine has had a prang sufficient to move the headstock, you will probably find that the tool turret will also be out of alignment, both in the turret body and the disk that hold the tools. This should be checked and rectified if you want to get the best out of your machine.

If you don't know how to check, and, or align the turret, post back for an explanation.

Regards,

Bill