Problem w/ CC Pro skipping Code

[nathan32935 (Nathan Duval)]

Good afternoon,

Okay, what would cause CC Pro/CM to skip code? I’m a little irritated and I don’t know why this is happening.

I’m getting the cart before the horse…

Let me start from the beginning. I haven’t used my machine in probably 1½ to 2 months, simply because life has gotten in the way lately. I needed to cut and create something…anything. before beginning the cut, all the rails were wiped down with Vactra Oil #2.

I chose a simple tray with a little cat design in the bottom of it. I chose a scrap piece of ¾" pine board sufficiently big enough for the project. (I will attach some photos now and the g-code, NC file later once I get on my computer).

Anyway, I chose a #201 bit for rough stock removal, and I took the tool speeds/feeds for hardwood. (Yes, I know it would cut slower, longer, and not as aggressively, but that was my choice. Time was not an issue, a successful completion was!

The project started, it made 6 clearing passes, perfect. This is where things started to go sideways. The seventh pass started, and I have no idea, but instead of cutting the 1/16th of an inch (actually I think it is more like 2mm), it started cutting ¼" deep! Shame on me, I should of paused it right at that point as I knew it wasn’t supposed to be cutting that deep in one pass… the next pass, it plunged through the bottom, through the wasteboard, and probably 1/16" into the aluminum T-slot! Within a few seconds I was able to hit the emergency off button. But man!!

I’m just confused and frustrated as to why this happens. It is the story of my life right now.

I only understand the bare basics of reading G-code, so I’m not sure at what line things went awry. When looking at the simulation in CC and then when looking at the elevations and isometric views in CM, everything looked okay.

I just don’t know.

Thanks for listening to me vent…

Pic #1. The code is to cut the inside oval, then a back and forth clearing cut… working great!

Pic #2 & 3. After 6 correct cycles, then for whatever reason the computer cuts to the depth of about ¼". I was watching, the bit sounded like it was bogging, so I slowed the bit down within CM.

Pic #4 & 5. This is the action it took before I could get to the emergency switch

Pic 6…I see first hand it cuts aluminum well! smh

Pic 7.

[mhotchin (Michael Hotchin)]

This is 99.99% likely a mechanical problem, not a problem with the GCode. Likely suspects are either the bit slipping in the collet (so the bit end up longer), OR a problem with the Z Axis that causes it to lose steps.

Something to try is to set up the job in EXACTLY the same way, but then remove the stock from the machine before running the job - this is an ‘Air Job’.

You’d need to watch it to see if the bit is getting too close to the bed. If so, stop the job. If the job completes. then jog the Z axis to Z Zero, and compare against the original position. If it’s different, then there’s a problem with the Z Drive.

If that job completes accurately, you could re-run the job for real in a piece of scrap. Mark the shank of the bit with pen where it enters the collet. See if the bit moves during the job.

[Tod1d (Tod (with 1 'd'))]

The two most common causes of lost steps is electrical interference, and the cutter exceeding the force of the drive motors.

When you imbed the cutter so it’s cutting with it’s entire width, it could create enough force to pull the Z axis downward or pull the cutter downward in the collet. An upcut endmill acts like a really high rake screw, and generates a pretty good down force.

I would recommend, rather than cutting the oval first, cut the whole shape as a pocket. Or offset the shape a little bit (0.010") and pocket using a depth of cut ~1/2 of the cutter diameter. Then do a full depth contour to finish cut the remaining 0.010".

(Just saw Michael’s suggestion. Also a good one!!)

[nathan32935 (Nathan Duval)]

That makes sense. I didn’t mark the bit beforehand to see if it had slipped in the collet. I don’t think it did…but possibly.

If the program had cut correctly, it shouldn’t have gotten close to the bottom of the wood or the wasteboard. The piece of wood was ¾" thick and the overall depth would have only been ½" total.

[nathan32935 (Nathan Duval)]

Yeah, I always wonder how to get around cutting the full width of a bit. I try to use ramping in and also reduce the depth of cut.

Maybe I should have used a ¼" ball mill instead of an end mill to eliminate some of the forces

[HaroldO (Harold Osmer)]

Bit slipped in the collet. Multiple passes, especially with a 1/4-in end mill on pine, will run fine for many minutes then suddenly grab and pull across the stock. This happens when the mill pulls itself down, resulting in too much tension being added to the machine, leading it to faulter.

It’s not as big an issue when swapping bits through a process as the collet gets retightened each time. Best prevention is to hork it down tight then [PAUSE] to retighten every so often.

Not that it’s ever happened to me…