Problem- Can I spiral in?

[mphjunky]

A few months ago I got a TM-1 that is the first cnc machine I've ever turned on let alone wrote any program for. The advise about learning to hand code I took and after 2 months I have about 20 programs I'm happy with. These last few days has me stumped however. I know I can spiral out to bore something but I have a heat sink I need to make for a buddy and I need to bring in a 4X.310" slitter blade from the side to cut the fins in some 4" al' round bar. I can't figure out how to spiral in to a fixed point then move away. I can't invert the start and stop points in VQC either. I called a friend of a friend to see what he thought and he tells me I need something like Mastercam to do that. Now it seems if Mastercam can do it so can I by hand right? It's just code but I'm stumped. Maybe because of my lack of experience or is it because it's not possible? I can feed the blade in then 360 around it but the bar has a good taper in it and no matter what the feed in is it leaves entry mark. I take more then one pass and the first has varied from a scratch to maybe .050".
So is it possible to spiral in?
And for all the advise I have recieved in reading this forum I thank you all.

[mc-motorsports]

I would highly reccomend a CAD/CAM package. You will be able to do things you wouldn't dream about attempting to program by hand.

[mc-motorsports]

And no, you don't need mastercam to program a TM-1. Mastercam is great if you can justify the cost. There are people on the forum talking about free CAD/CAM packages, maybe not integrated, but functional stand alones. May take a little more time and less ability than some or most, but better than doing things by hand, trust me!

[wwendorf]

Check out Dolphin Cad/Cam for 2.5d type work or Alibre Design for full 3d Parametric modeling capabilities.

Wade

[Geof]

Originally Posted by mphjunky .... I have a heat sink I need to make for a buddy and I need to bring in a 4X.310" slitter blade from the side to cut the fins in some 4" al' round bar. I can't figure out how to spiral in to a fixed point then move away....... .... Now it seems if Mastercam can do it so can I by hand right? It's just code but I'm stumped.....

To answer your Mastercam question. No, your can program things in Mastercam which are literally impossible to program by hand. Cam programs can create complex curves and spirals by breaking the code up into millions of straight moves each only a thousandth of an inch long. This is impossible to do by hand, you wouldn't live long enough to do all the calculations.

Regarding what you want to do I am a bit puzzled. Is the round bar held vertically or horizontally, what dou you mean by spiral in? Is it possible to post a picture? jpg please I am software limited.

[mphjunky]

Thanks for the input and in time I will look into getting a software package. For now hand coding works as the parts I've done aren't too complex and I'll learn to program faster doing it this way. When I start to do really involved parts I will make the switch.
Geof, I will get a picture as soon as I can. To try to answer the confusion, the part is .900" tall 4 dia' and mounted horizontal in a rotary table. It has a bore about 1.750" and the chuck jaws mount and hold from this so there is room around the outside without problems. I am trying to cut 5 grooves with a slitter blade interpolating around the workpiece about 3/4" into it. Kind of like if it were to be done on a lathe with a .310" parting off blade.
I'm sure a picture will help so I'll post one soon. Thanks for the help.
Kevin.

[cadman@teluspla]

Does your mill have VQC?

[Geof]

Originally Posted by mphjunky ..... Geof, I will get a picture as soon as I can. To try to answer the confusion, the part is .900" tall 4 dia' and mounted horizontal in a rotary table..... Kevin.

You mean the 4" dia is horizontal?

If the 4" diameter is indeed horizontal what you are doing makes sense.

Spiralling in, that is gradually approaching your 3/4" slit at about 1/8" per circle is something that would need to be done using macros, or with a cam program.

Approaching it stepwise is feasible using hand coding, i.e. going in 1/8" around the circle then in again. Are you familiar with tool compensation? I will see if I can write a program later this evening or on the weekend that will do this with the mininum number of hand coded lines.

As a hint; you use tool compensation and write a subroutine containing a tangential approach, the circle, and a tangential departure using the final diameter for the bottom of the slit, in your case 2-1/2". Then you have several entries for the tool diameter starting about 1-1/4" larger than the actual diameter and reducing by 1/4" until you get to the actual diameter.

You set tool comp using the largest tool diameter then go to the subroutine and go around the circle. Before leaving the subroutine you cancel tool comp back to the original start point. Then you set tool comp using the next smaller diameter and go to the subroutine again, repeating this until you have used the correct tool diameter for your final pass. The thing to watch is that your move which cancels the tool comp does not bump into the part; sometimes when cancelling tool comp the actual path is difficulty to predict. I always check thing carefully using graphics.

You may be suspecting I have done something similar to this, your are correct.

[mphjunky]

Geof, the slitter is .0310" sorry about that. I'll work on those pictures tomorrow as soon as I get back home. That's where the mill and parts in question are. I do watch the tool path in the graphics screen before I run any program. That's a great feature. I have used the cutter comp' in a few programs to keep from writting the same operation and I understand how that works pretty good now. I'm still a little confused as to why I have to take it out only to put it back in so often. It seems I should be able to leave it in until I'm done but I have to take it out after every rotation around the part only to put it back in on it's G01 move in X toward the part.
Cadman, I do have VQC on the mill but it won't work from the outside in.
Thanks for the input and advice. Kevin.

[Geof]

Here is a program that uses a 3" OD slitting saw to cut five heatsink grooves stepped down at a spacing of 0.1" inch. Each groove is done in five cuts.

Select and copy this and it should run in your Graphics.

This was only run on my Simulator, not actually cutting metal.

%
O00099 (HEATSINK)
N1 G00 G20 G40 G49 G80 G90 G98
N2 G53 G49 G00 Z0.
N3 G10 L12 G90 P61 R4.5
N4 G10 L12 G90 P51 R4.25
N5 G10 L12 G90 P41 R4.
N6 G10 L12 G90 P31 R3.75
N7 G10 L12 G90 P21 R3.5
N8 G10 L12 G90 P11 R3.25
N9 G10 L12 G90 P1 R3.
N10 (---)
N11 T1 M06
N12 G43 H01
N13 M03 S1000
N14 G54 G00 X-4.5 Y-4.5 Z1.
N15 Z0. M08
N16 G91 G00 Z-0.1 M97 P100 L5
N17 G53 G00 Z0.
N18 M30
N19 (------)
N100 G90 G41 D61 G01 X-1.25 Y-3.55 F10. M97 P1000
N101 G90 G41 D51 G01 X-1.25 Y-3.55 F10. M97 P1000
N102 G90 G41 D41 G01 X-1.25 Y-3.55 F10. M97 P1000
N103 G90 G41 D31 G01 X-1.25 Y-3.55 F10. M97 P1000
N104 G90 G41 D21 G01 X-1.25 Y-3.55 F10. M97 P1000
N105 G90 G41 D11 G01 X-1.25 Y-3.55 F10. M97 P1000
N106 G90 G41 D01 G01 X-1.25 Y-3.55 F10. M97 P1000
N107 M99
N108 (-----)
N1000 G90 G01 Y0. F10.
N1001 G02 I1.25 J0.
N1002 G01 Y3.55
N1003 G40 G00 X-4.5 Y4.5
N1004 Y-4.5 F400.
N1005 G90 M99
N1006 (-----)
%

[mphjunky]

Thanks Geof. I really thought I would be home by now and able to try what you posted but it's going to be another day or two.
Thanks for taking the time to write it and I'll let you know as soon as I can. Kevin.

[M_D]

It’s true a CAD program often breaks arcs into short lines and thus creates thousands upon thousands of lines of code that would take forever to program by hand using a calculator, but often that can be replaced by a few lines of code using G02 and G03 and the machine will probably run smoother too. A CAD program is good at crunching numbers and generating toolpaths, but they basically are lacking when it comes to logically generating efficient toolpaths. For complicated 3D work like most molds and 3D surfacing the CAM program is definitely far superior, for simple toolpaths like this hand coding is not bad.

Knowing how to write code by hand is always good, those who use a CAD program without knowing how to tweak and edit with hand code leave a lot on the table, at least on production programs where efficiency and cycle time matter. So if you do get a CAM program, your time spent hand coding was not in vain.


The following program would ramp the tool in and out on an arc and spiral in using cutter compensation. It will only do one groove as is, so you could either copy the toolpath to multiple Z levels or configure it as a subprogram. Run it on your simulator and see what you think. I had no idea what the location of the grooves should be on the Z level, otherwise I would have written a complete program for you.

I was assuming your saw was 4" in diameter exactly, if it's not which it probably isn’t, you can adjust the “R2.” number to reflect the true radius. The toolpath has a .125” step over, whether that and the speeds and feeds are realistic for your particular tool, I don’t know.

Your tool would need to run true so it doesn’t leave an entry and/or exit mark, that is a relatively thin saw for the diameter.

I did this on a CAD/CAM program, but to be honest it would not take long to plot the geometry and toolpath out on graph paper or whatever, and program it by hand, it’s actually a simple toolpath.

%
O10000
(SPIRAL TOOLPATH)
(X0 Y0 CENTER OF PART)
(Z0 TOP OF PART)
(4" DIAMETER STOCK)
(SAW RAMPS IN AND OUT ON AN ARC)

T9 M06 (4" x .0313" SAW)
G80 G90 G40 G49
(SET TOOL COMPENSATION FOR 4" DIAM. SAW LINE BELOW)
G10 L12 G90 P9 R2. (Set tool diameter in offset register)
G54 M08
S1000 (?) M03
G43 H9 D9
G41
G00 X-4.5 Y-2.5 Z2.
Z0.1
G01 Z-0.2 (?) F12.5(?)
G03 X-2. Y0. R2.5
G02 X-2. Y0.001 R1.9375
X1.875 Y0.001 R1.9375
X1.875 Y0. R1.9375
X-1.875 Y0. R1.875
X-1.875 Y0.0011 R1.8125
X1.75 Y0.0011 R1.8125
X1.75 Y0. R1.8125
X-1.75 Y0. R1.75
X-1.75 Y0.0012 R1.6875
X1.625 Y0.0012 R1.6875
X1.625 Y0. R1.6875
X-1.625 Y0. R1.625
X-1.625 Y0.0012 R1.5625
X1.5 Y0.0012 R1.5625
X1.5 Y0. R1.5625
X-1.5 Y0. R1.5
X-1.5 Y0.0014 R1.4375
X1.375 Y0.0014 R1.4375
X1.375 Y0. R1.4375
X-1.375 Y0. R1.375
X-1.375 Y0.0015 R1.3125
X1.25 Y0.0015 R1.3125
X1.25 Y0. R1.3125
X-1.25 Y0. R1.25
X-1.231 Y0.2171 R1.25
X1.25 Y0. R1.25
X1.231 Y-0.2171 R1.25
G03 X1.193 Y-0.6512 R2.5
X3.2589 Y-3.1132 R2.5
G00 Z1. M09
G40
X5.7209 Y-3.5473
G00 Z2. M09
M30
%