cnc cutting smoothly issue

[Chsmith2525]

For my work we have two shops with two different cnc machines to cut ice. Both machines were running fine for a year with the new settings I've made. Now one of the cnc machines is having problems pocketing with the 1/8", the other is running perfectly fine still. 1/32", 1/16", 1/4", and 1/2" all run fine, but for some reason the 1/8" bit started getting misaligned when pocketing.

The cnc that is hooked up to Mach 3 on an ancient computer running windows 7 still (I know It's not an ideal system). All I could think is, the computer could be dying and not able to process all the passes and stepovers from the 1/8"?

A file is attached, probably not the best example but it's what I got from my shop guy, the whites of the eye's and the glare from the glasses got off on the y axis.

[rig gap]

First question I would have...are the whites of the eyes and the goggle glare the only thing the 1/8" bit cuts...if so, I would guess your "Y" zero point has changed for some reason...maybe due to skipped steps somewhere along the way...if the 1/8" bit cuts more than those two things, and nothing else is wrong, then there is a discrepancy in the program.
Look at the toolpath simulation to see if the whites and glares are in the wrong places.
I would start by checking the zero point on all the axes first.

[GEdward]

I really don't think your computer is the problem. Mach3 is not that demanding of a program and a computer capable of running Windows 7 is more than adequate. I have a Windows 7 computer running my CNC router with Mach3 and I do a fair amount of 3D work with it without issues. The simple pocketing toolpaths your 1/8 bit is cutting are not all that demanding.
As rig gap points out, check the toolpath simulation in whatever version of Vectric that you are using. It should confirm that the toolpath is correctly calculated.
Does your machine have an ATC by chance? Perhaps there is an offset programmed into Mach for that particular tool. Since the shift is only in the Y direction it would seem like that could be possible.
Lost steps is a possibility but not likely. Does the problem repeat exactly from one piece to another? Does your setup run from an SD card or other memory device? Have you checked all your wiring and connections? Perhaps there is some corrosion in a wire/cable connection.
There is a lot to unpack here and I am just basically thinking out loud for what it's worth.

Ed

[Chsmith2525]

Rig Gap, I don't see how it could be a programing issue if I can run the program on a computer at one shop and it's fine. Then run the program on a computer at our other shop and it has problems. it's the same program. Simulation is fine and it was all the 1/8" bit.

GEdward, We don't have an ATC and we have the computer hardwired into the cnc by ethernet cables. No memory devices, the computer has to be on and mach 3 open the whole time, we have to keep our cnc in the freezer and the wires run to the computer outside the freezer. I assume a memory card reader wouldn't like 10 degrees. All the wiring and motors are fine. I was only thinking about the computer cause we've had to replace ram and a few other parts cause the computer is giving out.

Thank you both for your help! I've been doing this pretty regularly for 2 years now and check my toolpaths pretty frequently and the other shop running the same programs fine makes me question hardware or a setting in mach 3. It sometimes has problems returning to our origins too if that helps any.

i attached another photo of something that happened again. some things got off as you can tell. (there is a lot to unpack in this and i can explain all our toolpaths, but it's a lot.

[MiloScott]

It sometimes has problems returning to our origins too if that helps any.

I would suggest checking the bearings. Acts like it may be losing steps. Might unhook the motors and see if there is any binding in the drivetrain. Lubricate the rails...

[GEdward]

Plus one Milo Scott.
Having trouble not returning to the origins is a huge clue. I'm convinced that when that issue is resolved the rest will follow. I looked at the assembly instructions and specs for the Avid machines. The bench models use ball screws throughout and the larger machines use rack and pinion drive systems on X and Y axis'. But both use dual drives on Y axis which is the one acting up it appears? A couple of things come into play with that. It may be that the Y axis stepper motors are not synchronized; either one or the other having lost steps or the result of something in the drive train having come loose or is slipping. This can cause binding on the ways which, if you remove the motors, will not show up when you physically push Y back and forth by hand. Just something to consider as you hunt down the cause.

[ElevationCreations]

Have you checked for backlash on the machine?

If you don't keep the rack and pinion lubricated properly you could have higher than normal wear. Operating in a freezer you may want to consider a lower viscosity lubricant than what is typically used in a room temperature environment.

[TReischl]

Have you checked for backlash on the machine?

If you don't keep the rack and pinion lubricated properly you could have higher than normal wear. Operating in a freezer you may want to consider a lower viscosity lubricant than what is typically used in a room temperature environment.

I do not agree at all with that. I run a rack and pinion machine. It has been in operation about 14 YEARS, never had one bit of lube put on it, and there is no wear. None, nada, zip, zero. It is a CNC Routerparts machine (now Avid). I did not lube it because sawdust is abrasive, especially plywood sawdust. Lube on the gears would collect that abrasive dust, turn it into a nice grinding slurry. One other thing about it, the rack is steel, and the pinions are aluminum. The pinions are not worn at all, obviously neither is the rack.

A rack and pinion is a rolling load device, not a sliding device, so that may be the reason I am not seeing any wear.

[ElevationCreations]

Have you checked for backlash on the machine?

If you don't keep the rack and pinion lubricated properly you could have higher than normal wear. Operating in a freezer you may want to consider a lower viscosity lubricant than what is typically used in a room temperature environment.

I do not agree at all with that. I run a rack and pinion machine. It has been in operation about 14 YEARS, never had one bit of lube put on it, and there is no wear. None, nada, zip, zero. It is a CNC Routerparts machine (now Avid). I did not lube it because sawdust is abrasive, especially plywood sawdust. Lube on the gears would collect that abrasive dust, turn it into a nice grinding slurry. One other thing about it, the rack is steel, and the pinions are aluminum. The pinions are not worn at all, obviously neither is the rack.

A rack and pinion is a rolling load device, not a sliding device, so that may be the reason I am not seeing any wear.

If you have 14 years of service out of your machine with no degradation in backlash without lubrication, that's outstanding. Everyone's mileage will vary depending on the environment and usage.

The reason the pinions are aluminum and rack steel is so the pinions wear, not the rack. You can observe the wear over time by measuring the backlash on each axis.

I've had to replace the pinions on my machine about every two years, it's an Avid Pro, more recent vintage than your machine. Pinions are considered a wear ( consumable) item. Some users replace the pinions every 6 months.

Avid recently changed the pinion assembly to only change out the pinion gear, not the belt/pinion assembly. You can check their website for details. I think it is a great improvement to minimize waste and reduce cost of consumables.

I haven't had any noticeable issue with sawdust building up on my machine on the lubricated racks and pinions even though it is a given that the fines in the air will settle in the lubricant, The machine has great dust collection. I don't imagine the dust which gets into the lubricant is any harder than the aluminum or steel to cause any damage to the machine.

BTW, Avid recommends lubricating the R&P, along with the linear bearings as part of the regular maintenance routine.

[TReischl]

Have you checked for backlash on the machine?

If you don't keep the rack and pinion lubricated properly you could have higher than normal wear. Operating in a freezer you may want to consider a lower viscosity lubricant than what is typically used in a room temperature environment.

I do not agree at all with that. I run a rack and pinion machine. It has been in operation about 14 YEARS, never had one bit of lube put on it, and there is no wear. None, nada, zip, zero. It is a CNC Routerparts machine (now Avid). I did not lube it because sawdust is abrasive, especially plywood sawdust. Lube on the gears would collect that abrasive dust, turn it into a nice grinding slurry. One other thing about it, the rack is steel, and the pinions are aluminum. The pinions are not worn at all, obviously neither is the rack.

A rack and pinion is a rolling load device, not a sliding device, so that may be the reason I am not seeing any wear.

If you have 14 years of service out of your machine with no degradation in backlash without lubrication, that's outstanding. Everyone's mileage will vary depending on the environment and usage.

Something I learned long ago is that woodworking, machine building and generally all disciplines have legacy practices that actually have no basis in fact. They are just handed down from the "old guys" to the "new guys". So stating that Avid recommends, blah, blah, blah does not mean much. Anyone can build a machine. I do have a degree in mechanical engineering, so I sort of know what I am writing about once in awhile. As I said before, a rack and pinion is a rolling load, not a sliding one. Do I think that there might be some wear on the pinions? Of course, but nowhere near enough to start slobbering grease and oil all over the place.

All that said, I did have to replace the pinion on one side of the machine years ago. The machine jammed up on something (dumb move on my part) and the stepper had enough power to jump that pinion on the rack and just chew the living daylights out of it. So it is a good idea to have some spares around.

If? There is no "if", it has been running for 14 years now.

The reason the pinions are aluminum and rack steel is so the pinions wear, not the rack. You can observe the wear over time by measuring the backlash on each axis.

I've had to replace the pinions on my machine about every two years, it's an Avid Pro, more recent vintage than your machine. Pinions are considered a wear ( consumable) item. Some users replace the pinions every 6 months.

Avid recently changed the pinion assembly to only change out the pinion gear, not the belt/pinion assembly. You can check their website for details. I think it is a great improvement to minimize waste and reduce cost of consumables.

I haven't had any noticeable issue with sawdust building up on my machine on the lubricated racks and pinions even though it is a given that the fines in the air will settle in the lubricant, The machine has great dust collection. I don't imagine the dust which gets into the lubricant is any harder than the aluminum or steel to cause any damage to the machine.

BTW, Avid recommends lubricating the R&P, along with the linear bearings as part of the regular maintenance routine.

There is no backlash in the rack and pinion system on the machine. None. Notice the picture below, that heavy duty spring loads the pinion into the rack. Even if the pinion wears, it will still be sprung into the rack eliminating backlash. That is why the Avid design is so good.

Something I learned long ago is that woodworking, machine building and generally all disciplines have legacy practices that actually have no basis in fact. They are just handed down from the "old guys" to the "new guys". So stating that Avid recommends, blah, blah, blah does not mean much. Anyone can build a machine. I do have a degree in mechanical engineering, so I sort of know what I am writing about once in awhile. As I said before, a rack and pinion is a rolling load, not a sliding one. Do I think that there might be some wear on the pinions? Of course, but nowhere near enough to start slobbering grease and oil all over the place.

All that said, I did have to replace the pinion on one side of the machine years ago. The machine jammed up on something (dumb move on my part) and the stepper had enough power to jump that pinion on the rack and just chew the living daylights out of it. So it is a good idea to have some spares around.

[Leo]

Both machines were running fine for a year with the new settings I've made. Now one of the cnc machines is having problems pocketing with the 1/8", the other is running perfectly fine still. 1/32", 1/16", 1/4", and 1/2" all run fine, but for some reason the 1/8" bit started getting misaligned when pocketing.

The problem is ONLY on ONE machine and ONLY with ONE cutter?

I would try a 1/8 inch collet ----- NOT a 3-4mm collet
Use a really good quality 1/8 inch collet -- do not use cheap 3-4 mm chinese collet
I will once again state ------ 1/8 inch ---- NOT 3-4 mm or any other metric collet

Also - clean the inside of the spindle where the collet taper fits into. Clean the collet nut as well. Maybe even replace the collet nut.

[Chsmith2525]

Thank you all!

I will preface this with that I do not work directly with CNC and just program the machine for my client. The person who works with out problem machine just notified me our boss has spliced the wires from the motors to computer about 6 times each, not soldered or anything. When they open a new motor, they rip off the connectors and splice the motors together. They don't even add lubricant because the machine is in a freezer, as we are cutting ice.

So when I was told the hardware was ok, it really wasn't... I'm sorry for any false alarms or wasting anyone's time here!

again thank you all!

[GEdward]

Thanks for getting back to the forum and letting us know what the REAL issue is. So often the OP never gets back to let everyone know if or how the issue got resolved; leaving everyone in the dark. Unfortunately, you can't fix dumb, which is the real problem in your case, but never apologize for asking for help. That is what reasonable people do and I, for one, don't mind sharing what little I know if I can help someone out.