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This Is So Mechanical...


RestorationAD

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A good point Doug is making about the climb cut and flex.

question for you RAD. does EMC2 have a plasma function? If so, it will use an algorithm that will smooth out the passes. By not stopping at exact points. This is very handy when trying to maximize speed on curves and cuts out jerking of the machine. Now the problem when using this mode is that exact stop features are turned off and if you are trying to get exact 90 corners it will round them some. But most PU pockets have a radiused corner so this would help smooth that out.

If you look at your vectors in node edit mode you will see all of the points/nodes. The machine interprets these at point to point starts and stops at each one. The closer they are more jerking. Plasma mode will smooth that out. This is a function I use in Mach3 all of the time when doing 3d work and curved 2d work.

So EMC2 has what it calls "continuous mode" and this tries to use a look ahead to read the upcoming move and smooth out the transitions. It is probably the same thing as plasma mode (where stopping is a bad thing). I use the machine in this mode all the time. I bet that is why some of the pickup tabs are a little rounder than square.

I am still using AutoCAD (Drawing) and CamBam (toolpathing) so I am not using vector drawings. The advantage in using Autocad is that I am drawing using lines and arcs (they have math) and CamBam does a pretty good job with Arcs and Poly lines.

It happened on three different pockets all during the finish passes so I think you guys are right about flex and the climb cut.

I will run some tests one night this week if I get some time and see how outline/pocket clean works.

I am also going to look at my pickup drawing and see about breaking it up into separate shapes that are easier to mill. I really want to be able to let this thing run while I work on other stuff...

On a positive note with the new bit and advice from Mikro I got a really nice Body outline.

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I am also going to look at my pickup drawing and see about breaking it up into separate shapes that are easier to mill. I really want to be able to let this thing run while I work on other stuff...

I always separate the individual shapes instead of having a single "model". In the case of a humbucker rout, I do the main body as one 2D area clearance, then I do the two deeper areas as another. In ArtCAM you can group them together in one toolpath (along with other parts). The downside is it takes a little longer to setup, and there is some overlap in machining. But, I find it gives you better control over the features.

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I am also going to look at my pickup drawing and see about breaking it up into separate shapes that are easier to mill. I really want to be able to let this thing run while I work on other stuff...

I always separate the individual shapes instead of having a single "model". In the case of a humbucker rout, I do the main body as one 2D area clearance, then I do the two deeper areas as another. In ArtCAM you can group them together in one toolpath (along with other parts). The downside is it takes a little longer to setup, and there is some overlap in machining. But, I find it gives you better control over the features.

This is what I am in the process of doing for my HB routes. So you route the main body first then the tabs?

CamBam can group different toolpaths under a "Part" that allows you to generate gcode with multiple separate toolpaths as one piece of code.

I will definitely move to this for the next run.

So any advice on the climb cuts? Maybe I just bail on them for now and see how it looks with a last 0.015 pass regular direction?

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(In my best Obi-Wan voice) star-wars-smiley-5492.gifTrust your feelings Brett... Be one with your machine

But seriously... Often times for me it comes down to my "gut feeling". Back when I was running a Prto-Trak milling machine, I never could get used to increasing my feed when the part began to chatter. It just didnt make sense...but it worked. Climb cutting gets a much better finish. With woods there are so many variables: tool dia, speed & feed rates, wood species, grain orientation, setp down, step over, etc.. When you factor in Zed flex, then all other variables are out the window. All it takes is for the bit to grab one time to cause you to have to change your shorts, and spook you into permanent conventional milling. The biggest problem I find when climb cutting on a machine that has Z flex is that even if you are only taking a .015" cut, it is a full height cut.

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(In my best Obi-Wan voice) star-wars-smiley-5467.gifTrust your feelings Brett... Be one with your machine

But seriously... Often times for me it comes down to my "gut feeling". Back when I was running a Prto-Trak milling machine, I never could get used to increasing my feed when the part began to chatter. It just didnt make sense...but it worked. Climb cutting gets a much better finish. With woods there are so many variables: tool dia, speed & feed rates, wood species, grain orientation, setp down, step over, etc.. When you factor in Zed flex, then all other variables are out the window. All it takes is for the bit to grab one time to cause you to have to change your shorts, and spook you into permanent conventional milling. The biggest problem I find when climb cutting on a machine that has Z flex is that even if you are only taking a .015" cut, it is a full height cut.

This is where we are now. The full height cut in "grabby" wood is just bad mojo. I don't really want to define a different CAM style for each type of wood I cut because I use so many different species.

I think the safest approach is going to be the best. I don't really care about how long it takes within reason if I can be doing other things while it is working.

Yesterday I was slotting fretboards while the machine was cutting... it was amazing when I looked up at the end of the day I had 3 days worth of building done. (And a days worth of cleanup after the machine chattered)

This is all really good information and I hope it helps others as well.

Thanks to you and Mikro I might get through this!

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So EMC2 has what it calls "continuous mode" and this tries to use a look ahead to read the upcoming move and smooth out the transitions. It is probably the same thing as plasma mode (where stopping is a bad thing). I use the machine in this mode all the time. I bet that is why some of the pickup tabs are a little rounder than square.

On a positive note with the new bit and advice from Mikro I got a really nice Body outline.

Continuous mode is not Plasma mode. Mach3 has continuous as well as exact stop. I use exact stop and continuous mode at the same time and it (exact stop) only affects the corners as I have it set for >=89 degrees to go into exact stop mode in corners. Plasma mode uses an algorithm that defines the entire path as one from start to finish on each pass. The reason for this is that a plasma cutter cannot stop at a point, otherwise it will burn through at that location. Whereas,it will virtuly eliminate a point chatter in the machine and it will speed certain types of milling ops faster. :D Most people think I'm nuts when I tell them to try plasma mode when doing 3D/2.5D carves, as well as 2D curves, but it is amazing the difference. :D

Keep records of your trials and errors, these will get you closer each time to the sweet spot.

MK

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So EMC2 has what it calls "continuous mode" and this tries to use a look ahead to read the upcoming move and smooth out the transitions. It is probably the same thing as plasma mode (where stopping is a bad thing). I use the machine in this mode all the time. I bet that is why some of the pickup tabs are a little rounder than square.

On a positive note with the new bit and advice from Mikro I got a really nice Body outline.

Continuous mode is not Plasma mode. Mach3 has continuous as well as exact stop. I use exact stop and continuous mode at the same time and it (exact stop) only affects the corners as I have it set for >=89 degrees to go into exact stop mode in corners. Plasma mode uses an algorithm that defines the entire path as one from start to finish on each pass. The reason for this is that a plasma cutter cannot stop at a point, otherwise it will burn through at that location. Whereas,it will virtuly eliminate a point chatter in the machine and it will speed certain types of milling ops faster. :D Most people think I'm nuts when I tell them to try plasma mode when doing 3D/2.5D carves, as well as 2D curves, but it is amazing the difference. :D

Keep records of your trials and errors, these will get you closer each time to the sweet spot.

MK

I am not finding a plasma mode in LinuxCNC documentation so I doubt they have it.

Good Point need more notes rather than trying to remember.

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Mach3 has continuous as well as exact stop. I use exact stop and continuous mode at the same time and it (exact stop) only affects the corners as I have it set for >=89 degrees to go into exact stop mode in corners.

MK

I was unaware of that...I'll have to take a look at that, and give it a try....Looks like you are Yoda star-wars-smiley-5504.gif

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Mach3 has continuous as well as exact stop. I use exact stop and continuous mode at the same time and it (exact stop) only affects the corners as I have it set for >=89 degrees to go into exact stop mode in corners.

MK

I was unaware of that...I'll have to take a look at that, and give it a try....Looks like you are Yoda star-wars-smiley-5504.gif

This is in the General Config menu. Continuous is Constant Velocity

Machconfig.jpg

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So changing my humbucker drawings so that the Tabs are separate pieces to cut has pretty much fixed chip out and shape issues I was having. The test cuts from the weekend look stellar.

Removing the final climb cut from my pockets has resolved the issues of biting and tear-out. I then moved my pockets to have a 0.015 final pass but it is a conventional cut instead of a climb cut and it happens on a per level basis. I would say that the pockets I cut in Ash this weekend were the best I have ever cut.

I will update with pictures soon...

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  • 1 month later...

Working on angled neck pockets and pickup routes this weekend on the cnc... any advice?

My plan is to angle the blank a few degrees and cut a normal neck pocket (adjusting the depth of cut of course)

Using A3, do a 2 rail sweep with the difference in depth using 2 profiles at the predetermined depths at each end between the rails for the neck pocket . This is another way to get it done and keeps the blank flat. Also go with the grain on the pocket cuts. If you go cross grain then Keep the stepover at 25% to 15% depending on the endmill used.

MK

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Since you guys do these on CNC, why aren't you making keyed mortice/tenons that lock into place? Even Gibson have progressed out of the 18th century on that one! ;-)

Just because CNC appears to those that do not know the workings of one can do everything. It is sometimes not as easy as it appears. Many of the tasks that are seen in factories are not able to be done with hobby machines. Most hobby machines have 3 axis, XYZ this is not 3D, believe it or not. They are capable of doing what is called 2.5D It is movement in 3 planes in relation to a flat plane. Now adding a 4th axis A, this allows some 3D work, although only rotational in the 4th axis, still not true 3D. The cost associated with adding the 4th axis is akin to adding 50% to the 3 axis machine in a hobby machine and is doable. Now adding the 5th and 6th axis (B and C rotational axis)is out of reach unless one wants to spend 250K plus.

Also the CAM software available is cost prohibitive to do True 3D work as well as the controller software and electronics. Now to do what you ask at least a 4th axis is required to allow for at least 2 axis to work in a perpendicular plane to the original plane of XYZ but the 4th axis would need not to be rotational but angular. Again very little options in software for this kind of work. So it is easier to set the plane sometimes manually

to get there but the size limits of each dictate what will fit.

So I hope I have answered your question to some extent. :D

MK

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You know when you read something and your eyes just see a brick wall.? :D

I understand all that, however I thought that making a simple flat-bottomed shape (mortice) on a body angled at whatever neck angle is required would be no problem. Of course, a more complex system allows you to achieve more. We're not made of tool changers!

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You know when you read something and your eyes just see a brick wall.? :D

I understand all that, however I thought that making a simple flat-bottomed shape (mortice) on a body angled at whatever neck angle is required would be no problem. Of course, a more complex system allows you to achieve more. We're not made of tool changers!

Yes a flat bottom dado would be easy to do just a few more steps added, making one that was say dovetailed interlocked or something similar is different. :D
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Outside of the context of CNC. I happen to like my neck joint. It is a simple mortise and tenon. It has straight sides I can sand with a sanding block. So when it is a few thousandths off it is easy to fit by hand. No trying to relocate/index the neck blank correctly on the CNC. It is also easy to make templates for so I can cut the pockets by hand if needed.

Dovetail tenons are fine looking but to properly cut one that actually improves the neck joint on a guitar would require a very expensive machine with a very expensive 4th axis option (explained above).... then we could argue if it is actually a better joint.

I know I am using mine as an expensive table router... it is still faster/more accurate than doing it by hand.

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Honestly, if you're gluing a joint I don't see any benefit to building a 'locking' joint. Just more shear faces and places where differential wood movement could theoretically pull things out of whack. Complexity for its own sake is not something to strive for.

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