Macro Programming for Taper Bore machining

[yaji63]

I need to make macro program for machining a taper bore which also has a fillet at the top. Though this can be made with spiral option in many CAM softwares it does not yield desired results and i felt macro may be the solution as it has better control on such 2 1/2 D profiles. Can someone help ?

thanks
yaji

[Kiwi]

Is this for Mill or Lathe and what make is your controller?
Would generating the code with a PC then downloading to the controller acceptable?

[yaji63]

This is a CNC milling machine and the controller is Mitsubishi M70 A. This accepts Fanuc type macros when it comes to trignometry. It is very much acceptable to generate the code on PC and then transfer it to the machine controller but the issue here is that there are 2 different tapers in a single bore and added to that is a fillet of R16 at the top of the bore. I guess one has to make 3 different programs for these 3 different regions of the bore.

Another issue is that i have to use a bullnose type tool (16mm with 2mm corner radius). Is it possible to use such tools with a macro program as the contact point of the tool with the workpiece varies at each spiral point.

thanks
Yaji

[Kiwi]

Yaji
I can only help with a G-Code file as I don't know either Mitsu or Fanuc.
I'm sure what you want can be done with a Macro but with all requirements I believe it would be quite difficult.
I have VBasic programs which will generate code you need.
If you post the specs of the hole and the cutter, I'll generate code for you to try.

[yaji63]

How do you want me to post the specs of the hole ? It is a hole with two tapers and then a fillet on top like i mentioned to you. How will you generate a G code with a VB file for a profile like this ?

Cutter is a 16mm tool with corner radius of 2mm.

[Kiwi]

Figures as shown in picture.

[yaji63]

Here is the drawing as per your advice.

I have already generated a G code program using a CAM software but i was looking whether a continuous spiral program can be generated for this profile with helical interpolation codes so that the machine lag if any does not spoil the profile. I do not know whether Helical interpolation is possible in a taper bore.

Thanks
Yaji

[Kiwi]

Yaji
Don't know if Fanuc has tapered helix feature.
The path will not be helical interpolated.
The path will be a continuous spiral made up of straight paths as short as you wish and the step-over as close as acceptable.
Short increments makes a large file and small step over will take more time to machine.

[Kiwi]

Yaji
Three files attached. These can be joined together to make one file.
Check for step-over (cusp) and arc smoothness and advise if usable.

[yaji63]

Thanks for the codes ! What software did you use to generate these codes ? These look pretty smooth. I' am looking at a constant stepdown of 0.2mm, 0.15mm and 0.1mm. I will know which one to use only after i ascertain the cusp achieved on different surfaces. My only worry is on the radius surface which may have larger cusps with larger stepover / depth of cut.

[yaji63]

What is the chordal tolerance used in these programs when splitting into G01 codes ?

[yaji63]

Kiwi,

I just checked the programs and the depth of cut seems to be varying a lot in the lower taper program and in the end it has gone even upto a depth of cut of 0.7mm which is pretty large for the given tool. Is there a was of maintaining a constant depth of cut of 0.15mm ?

Yaji