intermittent unwanted move

[jpwoo]

Hi all,

I'm new at CNC machining and here at work we just picked up a fancy Haas Mill. So there are ton of simple things that we are getting wrong here I'm sure. I've just dipped a toe into G-code and the like.

We have started running into a strange problem. The main thing that we are doing on the mill right now is cutting holes in what is essentially a powder coated steel junction box. Things have been running pretty smooth, but recently I have hit a hiccup.

One of the holes we are milling is a circular cut with a single flat edge. The program takes several shallow cuts to complete the cutout, and then it seems to take a single final pass to expand the hole slightly. It seems like that final cut is going a bit too far perhaps? One time it has milled an excess divot outside of the regular cutoff, and two other times it has broken the endmill at that step. In between these instances the machine has run smoothly. We are looking for some advice as to where to start troubleshooting this.

We are using a Haas VF 2

the mill is HSS 1/8 x 3/8 x 3/8 x 3-1/16 doubled ended, from niagra cutter

The spindle speed is 3667
The feeds very from 15 inches to 19

You can see the little divot on the box with the pink tape. The hole directly below is what it should look like, but it was also the cut that broke the last bit.

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[Jim Dawson]

I have found that electrical boxes are really difficult to hang onto. I have one in my shop that has a cutout with the same type of problem, the box moved. Is it possible that the box is moving on the last cut?

[LeeWay]

I think I would drill a larger starter hole rather than use shallow cuts. then plunge as far as you can on the flutes for the cutting. Less chance of deflection that way.

[Machineit]

Hi all,

I'm new at CNC machining and here at work we just picked up a fancy Haas Mill. So there are ton of simple things that we are getting wrong here I'm sure. I've just dipped a toe into G-code and the like.

We have started running into a strange problem. The main thing that we are doing on the mill right now is cutting holes in what is essentially a powder coated steel junction box. Things have been running pretty smooth, but recently I have hit a hiccup.

One of the holes we are milling is a circular cut with a single flat edge. The program takes several shallow cuts to complete the cutout, and then it seems to take a single final pass to expand the hole slightly. It seems like that final cut is going a bit too far perhaps? One time it has milled an excess divot outside of the regular cutoff, and two other times it has broken the endmill at that step. In between these instances the machine has run smoothly. We are looking for some advice as to where to start troubleshooting this.

We are using a Haas VF 2

the mill is HSS 1/8 x 3/8 x 3/8 x 3-1/16 doubled ended, from niagra cutter

The spindle speed is 3667
The feeds very from 15 inches to 19

You can see the little divot on the box with the pink tape. The hole directly below is what it should look like, but it was also the cut that broke the last bit.

You can't expect us to help much without the code you are running.

Mike

[jpwoo]

Here is the relevant section of the code. The specific lines where it seems to go wrong would be
n1375, N1440, N1505, N1570 or N1640

(2D Contour1)
N1010 G0 Z0.6
N1015 G1 X2.4305 Y-6.7935 F500.
N1020 G0 Z0.2
N1025 G1 Z0.0544 F15.
N1030 Z0.035
N1035 G19 G3 Y-6.7435 Z-0.015 J0.05 K0.
N1040 G1 Y-6.731
N1045 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1050 G1 X2.2327 F19.
N1055 G3 X2.6033 I0.1853 J-0.2815
N1060 G1 X2.418
N1065 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1070 G1 Y-6.7435
N1075 G19 G2 Y-6.7935 Z0.035 J0. K0.05
N1080 G0 Z0.2
N1085 X2.4305
N1090 G1 Z0.0394 F15.
N1095 Z0.02
N1100 G3 Y-6.7435 Z-0.03 J0.05 K0.
N1105 G1 Y-6.731
N1110 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1115 G1 X2.2327 F19.
N1120 G3 X2.6033 I0.1853 J-0.2815
N1125 G1 X2.418
N1130 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1135 G1 Y-6.7435
N1140 G19 G2 Y-6.7935 Z0.02 J0. K0.05
N1145 G0 Z0.2
N1150 X2.4305
N1155 G1 Z0.0244 F15.
N1160 Z0.005
N1165 G3 Y-6.7435 Z-0.045 J0.05 K0.
N1170 G1 Y-6.731
N1175 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1180 G1 X2.2327 F19.
N1185 G3 X2.6033 I0.1853 J-0.2815
N1190 G1 X2.418
N1195 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1200 G1 Y-6.7435
N1205 G19 G2 Y-6.7935 Z0.005 J0. K0.05
N1210 G0 Z0.2
N1215 X2.4305
N1220 G1 Z0.0094 F15.
N1225 Z-0.01
N1230 G3 Y-6.7435 Z-0.06 J0.05 K0.
N1235 G1 Y-6.731
N1240 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1245 G1 X2.2327 F19.
N1250 G3 X2.6033 I0.1853 J-0.2815
N1255 G1 X2.418
N1260 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1265 G1 Y-6.7435
N1270 G19 G2 Y-6.7935 Z-0.01 J0. K0.05
N1275 G0 Z0.2
N1280 X2.4305
N1285 G1 Z-0.0056 F15.
N1290 Z-0.025
N1295 G3 Y-6.7435 Z-0.075 J0.05 K0.
N1300 G1 Y-6.731
N1305 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1310 G1 X2.2327 F19.
N1315 G3 X2.6033 I0.1853 J-0.2815
N1320 G1 X2.418
N1325 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1330 G1 Y-6.7435
N1335 G19 G2 Y-6.7935 Z-0.025 J0. K0.05
N1340 G0 Z0.2
N1345 X2.4305
N1350 G1 Z-0.0206 F15.
N1355 Z-0.04
N1360 G3 Y-6.7435 Z-0.09 J0.05 K0.
N1365 G1 Y-6.731
N1370 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1375 G1 X2.2327 F19.
N1380 G3 X2.6033 I0.1853 J-0.2815
N1385 G1 X2.418
N1390 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1395 G1 Y-6.7435
N1400 G19 G2 Y-6.7935 Z-0.04 J0. K0.05
N1405 G0 Z0.2
N1410 X2.4305
N1415 G1 Z-0.0356 F15.
N1420 Z-0.055
N1425 G3 Y-6.7435 Z-0.105 J0.05 K0.
N1430 G1 Y-6.731
N1435 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1440 G1 X2.2327 F19.
N1445 G3 X2.6033 I0.1853 J-0.2815
N1450 G1 X2.418
N1455 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1460 G1 Y-6.7435
N1465 G19 G2 Y-6.7935 Z-0.055 J0. K0.05
N1470 G0 Z0.2
N1475 X2.4305
N1480 G1 Z-0.0506 F15.
N1485 Z-0.07
N1490 G3 Y-6.7435 Z-0.12 J0.05 K0.
N1495 G1 Y-6.731
N1500 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1505 G1 X2.2327 F19.
N1510 G3 X2.6033 I0.1853 J-0.2815
N1515 G1 X2.418
N1520 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1525 G1 Y-6.7435
N1530 G19 G2 Y-6.7935 Z-0.07 J0. K0.05
N1535 G0 Z0.2
N1540 X2.4305
N1545 G1 Z-0.0656 F15.
N1550 Z-0.08
N1555 G3 Y-6.7435 Z-0.13 J0.05 K0.
N1560 G1 Y-6.731
N1565 G17 G3 X2.418 Y-6.7185 I-0.0125 J0.
N1570 G1 X2.2327 F19.
N1575 G3 X2.6033 I0.1853 J-0.2815
N1580 G1 X2.418
N1585 G3 X2.4055 Y-6.731 I0. J-0.0125 F15.
N1590 G1 Y-6.7435
N1595 G19 G2 Y-6.7935 Z-0.08 J0. K0.05
N1600 G0 Z0.2
N1605 G1 X2.4305 Y-6.7897 F500.
N1610 Z-0.0656 F15.
N1615 Z-0.08
N1620 G3 Y-6.7397 Z-0.13 J0.05 K0.
N1625 G17
N1630 G1 G41 X2.4368 Y-6.7272 D1
N1635 G3 X2.418 Y-6.7085 I-0.0187 J0.
N1640 G1 X2.2316 F19.
N1645 G3 X2.2282 Y-6.7095 I0. J-0.0063
N1650 X2.6078 I0.1898 J-0.2905
N1655 X2.6044 Y-6.7085 I-0.0034 J-0.0052
N1660 G1 X2.418
N1665 G3 X2.3993 Y-6.7272 I0. J-0.0188 F15.
N1675 G1 G40 X2.4055 Y-6.7397
N1680 G19 G2 Y-6.7897 Z-0.08 J0. K0.05
N1685 G0 Z0.6

[LeWhite]

G19? And G40 in da cut?

[Machineit]

What a mess of code for a simple hole. You say you are just dipping a toe into G code, but I think you are dipping your toe into a Cad-Cam system. I don't have time to go line by line and figure it out, but looks like you have a lead-in/out issue. If you call for a 1.0" lead in on a 1/2" hole the CAM system will write it and do damage like that. The CAD system doesn't know what you want done it just do as instructed.

This hole could be done with a total of maybe 5 lines of code.

Mike

[Fletch_CNC]

If the code has run parts successfully, then most likely the issue is with the part itself flexing/moving. I agree with some of the above replies-- the code seems excessive for that part, but if it works, it works. But electrical boxes can be a problem to machine-- they flex a lot, and can be a little tricky to hold securely. See if you can't devise a way to clamp the box closer to the sheet metal you are trying to cut, and you'll probably have better results.

[Tribalnewt2]

just wondering what program are you using for cad/cam if any???
there might be an option to simplify your code so it doesn't spit it out long hand.
i have cut alot of junction boxes in my day and i also agree that your box might be moving. just double check before taking out your next part. better to be safe then sorry.

[jpwoo]

Yah. that code is crazy. We hired someone to create the code for us, I'm sure he used some kind of CAD software, I'm not sure what he used. I most certainly did not write it.

It may be flexing (catination?) I have checked the piece in the vice on failure twice now, and the box was solid both times.

We have had a problem with tool wear. We are using a tiny endmill for the size of hole we are cutting (hopefully this will change soon). To the point where after cutting less than ten pieces we are out of tolerance.

So if as Mike said, the Lead in/Lead out cuts are even slightly off, would the tool wear compound that situation?

Hopefully soon we get our setup guy back in and revise the program with some more appropriate tools for the job, but in the meantime I'd like to understand this as best as possible.

Thank you all for the responses so far!

[LeeWay]

Are you clamping the part that is actually getting cut?
The door panel itself or the bx itself if the holes are there.
Door panels can move quite a bit if the box only is locked down.
Again, why use lead in's and lead outs?
Drill a hole and cut the profile from there high on the flutes of the end mill. This is how that type of cut will be the strongest. Against the edge of the metal rather than kinda pressing down from the top with lead in's etc.

[mactec54]

Here is the relevant section of the code. The specific lines where it seems to go wrong would be
n1375, N1440, N1505, N1570 or N1640(2D Contour1)

Yes your program, has been very badly done, if you want some programs done you can send a PM

G19 is the only code that, could cause you problems

To hold your boxes secure, you fit a block of wood or plastic inside the boxes ,a tight fit inside the box, then clamp it in your vice, or how ever you are clamping them

[mactec54]

Yah. that code is crazy. We hired someone to create the code for us, I'm sure he used some kind of CAD software, I'm not sure what he used. I most certainly did not write it.

So if as Mike said, the Lead in/Lead out cuts are even slightly off, would the tool wear compound that situation?

No it will have nothing to do with tool wear