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| CNC router shudder and jerky / jitter doing 3D toolpaths http://luthiersforum.com/forum/viewtopic.php?f=10106&t=47208 |
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| Author: | AlexanderJamesGuitar [ Thu Feb 04, 2016 5:42 pm ] |
| Post subject: | CNC router shudder and jerky / jitter doing 3D toolpaths |
Hey everyone. I have some toolpaths where I cut out a guitar neck. While doing any straight cuts, my CNC router runs great. When I get into doing the heel or volute carve on the guitar neck, the CNC is going through A LOT of little code to make the moves and it can start to shudder / jitter pretty bad. It shakes the whole CNC. I am running those paths at 50 IPM but Mach 3 only says it makes it to 10-15 IPM for all those lines. I don't know anything about CV mode but could it be that? Or would it be my post processor for Mastercam X4? Any help would be greatly appreciated. Thanks. |
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| Author: | Durero [ Thu Feb 04, 2016 5:45 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
I'm still learning about CV issues but if my understanding is correct you should make sure that Mach3 is not in Exact Stop mode. Sent from my iPhone using Tapatalk |
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| Author: | AlexanderJamesGuitar [ Thu Feb 04, 2016 6:15 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
Durero wrote: I'm still learning about CV issues but if my understanding is correct you should make sure that Mach3 is not in Exact Stop mode. I will check and see if it is. Thanks. |
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| Author: | Allen McFarlen [ Fri Feb 05, 2016 3:23 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
I had some jittery moves on some curves a couple of weeks ago. Using Fusion360 and the Mach3 post processor. It turned out that the code being generated had lots of little moves in some of the tighter curves. So what fixed it was to turn on smoothing for the tool path and altering the resolution. It also reduced the files size from 87kb down to 15kb. A really significant number of lines to do the same thing, but better. Idon't know if those options are available in your software, but certainly worth a look. |
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| Author: | Andy Birko [ Sat Feb 06, 2016 3:20 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
The problem is your CV settings. Oh, and by the way, Mach 3 has a terrible CV trajectory planner. I'm no longer using Mach 3 so I don't remember the exact settings but you need to play with your lookahead and tolerance settings but keep in mind, as far as I know, there's no way to know exactly what your maximum error will be and through experience, I know that Mach 3 is quite inconsistent when it comes to CV tolerance. Keep in mind though that as you tune your machine to be faster, the parts will get less precise. |
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| Author: | AlexanderJamesGuitar [ Fri Feb 12, 2016 6:53 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
Hey guys. It turned out that my cam post processor was writing the gcode to turn off CV mode. That was making my toolpaths run in exact stop mode and create a very jerky motion. |
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| Author: | Don Williams [ Sat Feb 13, 2016 10:52 am ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
Andy, what are you using instead of Mach3 now? |
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| Author: | Andy Birko [ Sun Feb 14, 2016 4:56 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
I'm using UCCNC/UC100 combo. The ups are that the trajectory planner is far superior to Mach 3. I'm able to double my accels because it doesn't violate accel settings like Mach 3 does. Machine runs far smoother and much more predictably than Mach3. The CV planner is also adjustable for tolerance. The down side is that it's still not fully featured. It doesn't support G18 or 19 and even worse that it will just do a G17 move when it comes across a G2 or G3 move. There's a few other goofy things about it but at the moment, I prefer it over Mach 3 because the TP is so much better. I have a part I'll be making with a 4th axis and I'll have to revert to Mach 3 for that because UCCNC doesn't support a 4th axis as a rotary axis so it's very difficult to get it to move fast enough. I have another machine that I'm setting up with Kflop right now and intend on using KmotionCNC. This has been taking me forever to get going unfortunately. If Kmotion does what everyone says it does, I'll probably switch my first machine over to it as well. |
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| Author: | Mike Kroening [ Sun Oct 23, 2016 7:17 pm ] |
| Post subject: | Re: CNC router shudder and jerky / jitter doing 3D toolpaths |
Andy Birko wrote: The problem is your CV settings. Oh, and by the way, Mach 3 has a terrible CV trajectory planner. I'm no longer using Mach 3 so I don't remember the exact settings but you need to play with your lookahead and tolerance settings but keep in mind, as far as I know, there's no way to know exactly what your maximum error will be and through experience, I know that Mach 3 is quite inconsistent when it comes to CV tolerance. Keep in mind though that as you tune your machine to be faster, the parts will get less precise. I agree with Andy on this. What I have done in mach3 when faced with this type of code is to set it for plasma mode. That being said any SQUARE corners will have some rounding as Plasma mode keeps the cutter moving so as not to have plasma heat stop at any point as Mach thinks it is a plasma cutter, when in reality it is a mill/router . This also works well with 2.5D or 3d work that is jerking. IN those though you would want to up your Z feed rate since all axis are being used in that instance so you get a consistent flow for the machine. Just my observation using MACH3 for 10years. MK |
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