Can't get rid of 'rapid move into stock' stock collisions on this operation ...

[chrisQX8DX]

hey everyone. i'm having issues generating a 'safe' toolpath to cut 0.6mm fretslots for a guitar fingerboard with a 0.5mm bit. i'm cutting this in super hard ebony so need to go realy slowly and avoid breaking the tiny mill bit which is really expensive. i've done this many times before and usually it goes ok and haven't broken a bit in a while but still would love to be as safe as possible.

So if you look at the fretslots toolpath there is two things i don't understand:

1. i don't understand why the toolpaths look so differently for the different slots, especially there is one in the middle which has a lot of retracts. The slots are pretty much exactly the same, same depth, same width just slightly different lengths.

2. Then i just can't get rid of the rapid stock collisions, i tried changing almost all parameters but there seems to be no way to avoid those collisions. Tried different ramps, tried using only high feed rate instead of rapids, and played around with all settings but still i'm getting these errors. Maybe another strategy would be safer for cutting these slots but 3d contour seems to be the only one that will give me the arched/curved bottom of the slots.

if anyone has any ideas on this that would be great.

cheers

[seth.madore · Accepted solution]

May I suggest an alternative (and in my opinion; better) path forward? I would use a 2D Contour to machine a small pocket:

 This will provide a "drop hole" for the next toolpath I would suggest; Trace:

Alternatively, you can avoid the 2D Contour "drop hole" and just turn on "Keep Tool Down" for Trace, which would net you this result (note the green linking moves as it progresses deeper along the Z axis):

 

 

[programming2C78B]

I used trace for mine. All radiused slots (this really is over hyped, a flat bottom is just fine) and adjustable for blind ends or not.

I could sell you my file if interested. Fully cam'd and entirely parametric for any string # and scale length, including fanned frets and even some inlays. 

I've cut over 100 fretboards, about 30 of them ebony on my machine. Lets just say I have the feeds and speeds pretty dialed in....

[chrisQX8DX]

hey @seth.madore thank you so much for taking the time to help with this. using trace looks indeed like a much cleaner solution. however i tried to set this up but i think there is a bug in the simulation module or sth. It seems i cannot get the trace path to cut from the top down. when i look at this in simulation it will always go all the way down into the stock and than ramp up which not only doesn't make any sense but will break the tool for sure. no matter if i select the top curve and do a negative offset or select the bottom of the slot with no offset, in simulation the tool always cuts all the wa down firt and then ramps up. 'keep tool down' doesn't seem to change this. obviously with this tiny tool i want to only take a depth of cut of max 0.1mm so i set multiple depths to 0.1 with 20 passes (for a 2mm deep slot)

now the reason i think this is a simulation bug is that yesterday i used trace on another project and the trace pass ramped down. i opened this file again to see wether i had used differrent settings but when i look at the simulation for the operation that ramped down correctly during actual cutting yesterday, the simulation now also shows the tool going all the way down and ramping up.

also as you can see in the video when i turn on stock simulation and press play you see that the entire slot appears cut suddenly and then only the toolpath starts and again goes all the way down and ramps up. What am i missing here ?

selecting the bottom curve of the slot and use no axial offset but multiple depths with 0.1mm adn 20 passes should cut from the top of the fretboard progressively down into the slot, right ???

[seth.madore]

While your video is processing, is there a chance that you've got simulation running in reverse? There is a slider, you want it to be "right of center"

[chrisQX8DX]

oh wow, yes indeed, i just saw that, didn't even know that was possible 🤣 must have done that while trying to slow down the simulation.

so i think i got what i want now and yes the keep down option is exactly what i need. not sure why i didn't use trace straight away for that, in my mind i think it was more sth to use for contouring single faces but in this case it's actually the cleanest pocketing operation. thanks so much @seth.madore  !!!

[chrisQX8DX]

thanks but i got my own parametric fretboard/neck generator in grasshopper.