Repeated broken cutting bits.

[AngusB]

I am trying to get a project going, but when trying to cut out two pieces it keeps breaking bits. The first time I was using a 1/8" cutting bit, but figured the bit just could not handle the poplar, so I switched to 3/16" cutting, but it keeps breaking bits anyway. I keep simplifying the project to figure out whats causing it. I have attached the project file with everything removed except the cuts that cause the breaks. I have tried cutting the project just like this last night and broke another bit. Sometimes it breaks during one of the cutouts, but this last time it did the two full cut throughs, but then broke the bit during the .25" cut around the top edge of the one piece (arrow in pic).

I am now out of bits, and really do not want to even order more, unless someone can give me some idea why this is happening.

Thanks for any input.

[henry1]

I am trying to get a project going, but when trying to cut out two pieces it keeps breaking bits. The first time I was using a 1/8" cutting bit, but figured the bit just could not handle the poplar, so I switched to 3/16" cutting, but it keeps breaking bits anyway. I keep simplifying the project to figure out whats causing it. I have attached the project file with everything removed except the cuts that cause the breaks. I have tried cutting the project just like this last night and broke another bit. Sometimes it breaks during one of the cutouts, but this last time it did the two full cut throughs, but then broke the bit during the .25" cut around the top edge of the one piece (arrow in pic).

I am now out of bits, and really do not want to even order more, unless someone can give me some idea why this is happening.

Thanks for any input.

you have to have it cut 1/4 deep at a time like 3 pass to cut it out

[DianMayfield]

The simple answer is that the bit probably stopped stopped spinning while the truck was still moving.

Something is causing the motor to stop. These intermittent problems are the worse!
The bushes could be worn - cutting puts a lot more strain on the motor (in all of the broken bits I had - none happened while "carving")
The x-termination board could be bad - check for "burned" marks
We once had a bad wire connection inside the motor, so vibration caused random disconnects - you could see arc marks - didn't find that one until the "autopsy"

Where the arrow is, it looks like the the piece stepped over - is that just a trick of the light?

You should have quite a few responses on this one - everyone helped me through my broken bit (motor) patches!

[DickB]

It looks like you have used both the cutout tool AND assigned the 3/16" straight bit to the circle at full depth. This is going to cut through the tabs and allow your piece to move - is this not correct? I don't see any tabs in your photo. You should be using the cutout tool only to cut these pieces out. I would also suggest using larger tabs, as the 1/8" ones that you selected might not be sufficiently strong.

[DianMayfield]

Dick, I did not catch that he had two paths, one as the cutout! The cutout was at full depth, in a single pass.. really hard on a bit.

Thinking about it though, the image with the arrow, still shows the 1/4in pass as having broken the bit. Might still be a problem there!

I clearly need to think 3 times before I post :)

You are saying that the disk was completely cut out, then the Cut Path tool was used on something that was essentially floating in the space.

[Digitalwoodshop]

If I understand the orientation of the cut out, it looks like the machine broke the bit in the X Direction.

SO...

Do you have tape on the bottom of your sled to help tracking?

What is the condition of the Y Gear Box? How many hours since you changed the bearings? Is the shaft worn from bad bearings?

X Drive, do you have any missing teeth or bad bearings on the big plastic gears?

Were you near the machine when it broke the bits? Did the cut motor stop or slow down like posted above?

AL

[DianMayfield]

The 3 circles do not all cut out. The ones that are cutouts are at a full depth. Try making these max pass of 1/4". You may end up with some stair stepping you need to sand down. The 3rd circle at 1/4 in depth (first one in picture)should not have broken the bit (the arrow one in your picture), as cutouts happen last in the order of operations.

I have never been successful at cutting .75 in boards in a single pass. Some on here have been. I am concerned that something else is going on, as the 1/4 in depth shouldn't have resulted in a broken bit.

[DickB]

The 3/16" bit should have no problem cutting a 3/4" board in one pass full depth. Carvewrite recommends this. I do it often in oak, maple, and other hardwood. If you limit depth to 1/4" per pass you're essentially using only the tip of the bit and it will wear out faster.

Sent from my LGLS676 using Tapatalk

[Mugsowner]

I see that you joined the forum in 2008. Do you have an older machine? If this was my machine, I would pull the brushes out and see what they tell me. Bad brush leads to speed change, speed change leads to broken bits. Checking brushes is an easy task, does not cost any thing to look. Bad brushes also lead to burnt motors.

[AngusB]

Thanks for all the input.


DianMayfield
It didn't step over (if I understand what you mean) the point at the arrow is where the bit broke so it was no longer cutting. Why the edge above it looks odd is cause there was a chamfer being put on that edge first by cutting a circle with the 90deg V bit before the .25" cut was done. I removed the 90deg cut from the MFC before posting as it did not seem to be the cause of any issues.
Also Cutouts may happen last in order, but the full depth cut (probably the one I mistakenly left in as DickB mentioned) definitely happened Before the .25" cut.


Mugsowner
I have a 2011 era machine. I had a compucarve in 2008 that was a complete lemon. Just one issue with the thing after another with no help from Carvewright so I gave up on it. Few years later Carvewright machines were getting better reviews so I figuired I'd try again and picked up a new one. Due to 'life' I haven't been able to use it that much and then only really for carving V-bit text signs in pine.


Digitalwoodshop
I do not have tape on the bottom of the sled. But the bottom is one piece of plywood the full size of the sled, everything is attached to the top of it, so there are no gaps or edges to tape on the bottom. Unless I am missing some reason to tape it anyway?
Everything seems fine. I disassembled the unit today, and everything seems to move fine, nothing sticks or skips, bearings all seem solid and smooth, no missing teeth on any gears. I have never changed any of the bearings. Have only got about 46hrs on the machine, and most of that as I mentioned was carving V-bit text signs in pine.
I was in the room while it was running, but was not watching it. I did not hear any motor stop or slow down. In fact I heard no changes in speed beyond the norm. Even when the bit broke I did not notice anything more significant than the norm load sounds when cutting compared to free spinning while repositioning. I only saw the bit had broken when the machine finished running.


DickB
You are absolutely correct regarding the 'cutout tool AND assigned the 3/16" straight bit'. Not sure when I did that. The piece being loose and moving due to no tabs and causing the broken bit makes perfect sense. The only reason I never picked up on that is that each time the bit has broken, when I removed the the sled from the machine, the piece was dead center where it should have been, free but but still centered, not pushed to one side of the cutout space as I would expect if that was the case. Certainly could have moved and bounced back, just seems odd.


I'm willing to go with the loose cutout breaking the bit due to assigning the bit. When I get new bits I'll run it with the updated mfc and see how it goes.


Thank again for all the input.

[Mugsowner]

When I do cut outs without tabs I use two sided tape to hold project to sled, to keep loose parts where they belong.

[DickB]

I do not have tape on the bottom of the sled. But the bottom is one piece of plywood the full size of the sled, everything is attached to the top of it, so there are no gaps or edges to tape on the bottom. A sled like that should help with vibration and keep the cutting bit away from the brass roller. I would suggest that you keep using it whenever making cutouts.

[bergerud]

Climb milling is something else to try and avoid. In your picture with the arrow, it looks like the bit was climb milling when it broke.

[DickB]

Climb milling is something else to try and avoid. In your picture with the arrow, it looks like the bit was climb milling when it broke.Don't think you can control that on a circle.

[bergerud]

Don't think you can control that on a circle.
True, you would have to make the circle out of intentionally directed arcs.

[Digitalwoodshop]

If your using tape to hold the part.... I would do your artwork then assign the 1/4 inch ball nose bit but actually use the 1/8th inch cutting bit. I do it all the time to cut plastic tags with tape. It locks the feed rate into a slow steady rate that works for me... A LHR tip years ago. I use a 1/16th Circuit board cutting bit.