Cutting a Channel Same Width as Cutter Diameter

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Cutting a Channel Same Width as Cutter Diameter

Postby Doug » Thu May 18, 2017 6:40 pm

Hi guys.

A simple enough question which has possibly been addressed before. I was wondering whether it is possible to get MeshCAM to cut a channel (in my case a truss rod channel in a guitar neck) which has the same width as the cutter diameter, in my case 5 mm?

The channel is angled in the stock and has a rounded bottom so my intention/hope was to just use the same 5 mm 2 flute flat and ball nose slot drills I am using to mill the upper face of the guitar neck to rough and finish the truss rod channel.

I couldn't get this to work, even with the machining margin set to zero. However, when I used a smaller cutter set (4 mm flat and ball nose slot drills), perhaps unsurprisingly, MeshCAM calculated a plausible toolpath to cut the channel no problem with waterline finishing doing most of the work.

Any thoughts? I don't really want to change tools four times if I can avoid it :-(

I'm sorry but I the board will not allow me to attach either the STL file with the channel I want to cut but in the blank stock rather than the neck itself or the resulting toolpath G Code for the successful 4 mm cutter strategy.

Doug
STEPCRAFT 2/840 CNC machine with 4th axis, TurboCAD V19.2 Pro Platinum, MeshCAM, GWizard feeds & speeds calculator, UCCNC. Hobby use: guitar building (luthiery).
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Re: Cutting a Channel Same Width as Cutter Diameter

Postby ArchieF » Thu May 18, 2017 9:47 pm

Hi Doug,

perhaps this thread can help you :

viewtopic.php?f=3&t=15724&p=25574&hilit=same+width&sid=0efe231e5acb3ab2a878673476cc354b#p25574

Unfortunately Randy won't help us anymore as you can read in his post

viewtopic.php?f=3&t=15804

Richard
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Re: Cutting a Channel Same Width as Cutter Diameter

Postby Doug » Fri May 19, 2017 12:51 pm

O.k. Richard, thanks. I thought that I saw threads on this topic.

I bit the bullet and ordered extra flute length 4 mm flat and ball nose cutters. I re-calculated the toolpath with 4 mm cutters and sure enough, MeshCAM generated a plausible looking toolpath with waterline finishing doing most of the work.

Doug
STEPCRAFT 2/840 CNC machine with 4th axis, TurboCAD V19.2 Pro Platinum, MeshCAM, GWizard feeds & speeds calculator, UCCNC. Hobby use: guitar building (luthiery).
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Re: Cutting a Channel Same Width as Cutter Diameter

Postby cnczane » Tue Jul 18, 2017 5:14 pm

Hi, Doug,

I have stooped a few times to misleading MeshCAM about what I wanted to do--when I couldn't figure out what was happening--to get it to do what I wanted.

In your case, "you could" define a 6-10mm slot, to be cut with a 5mm cutter, and then edit the G-code to eliminate the half-path you didn't want...
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Re: Cutting a Channel Same Width as Cutter Diameter

Postby larynx » Wed Jul 19, 2017 3:43 am

Everything stated is true to the best of my knowledge.

BUT - and that could be a big but, you could simply manually run your machine to cut the channel. You could also write save/run the gcode by hand. There are other programs [I have heard freeware] that allow you to specify slot cuts. Some CAM software has built in routines for slots. Not sure what you use, but I know linuxcnc has some addin routines to cut slots although I have never used them. I find such simple slots easier to do in manual code or manually VIA MIDI Commands.

Slot Milling Program Example [only a few for an idea]

- http://www.helmancnc.com/slot-milling-a ... m-example/

- http://blog.cnccookbook.com/2013/02/11/ ... ust-learn/

Writing a slot cut is not complicated.

I suggest you play without a bit in your powerhead, and watch as you type basic MIDI commands - very simple and a good way to know how your machine behaves. You can set feed rates [speed of cut] too - look a a MIDI command site.

test everything by setting the Z-zero high so you can see the movement without cutting. then do the same with a scrap piece of wood and a scrap bit just to get the feel of it.

such as {VERY SIMPLE without bells, whistles or speeds.....defaults to your machine max speeds - you can adjust depth of cut to compensate and run full out if you want}

G0 X_ Y_ Z_ (your start position - mine always at bottom of stock / flat top of table)
G0 X18 Z0.025 (slot taper down from Z-start to X18 on my machine at a final depth of Z0.025 )
G0 X0 Z0.010 (return to beginning cutting 0.015 deeper on the return in this case the taper will increase on the way back so more cutting of depth)
rinse repeat until depth is correct
and so on
G0 Z4 (end of cutting raise bit out of cut so it doesn't sit still and burn)

or plunge [as MeshCAM does] from

G0 X_Y_Z_
G0 Z0.025
G0 X18
G0 Z0.010 (plunge another 0.015 down)
G0 X0 (return to start, cutting away 0.015 on the way back - all the way)
rinse repeat until depth is correct
and so on
G0 Z4 (end of cutting raise bit out of cut so it doesn't sit still and burn)

Whatever you start code and end code is required unless you do it in a MIDI command line then its "free"

you can get your commands out of you post processor file or look at any out code from a previous gcode file of MeshCAM

Anyone sees an errant mistake - sometimes happens - feel free to correct me.

Hope this helps your specific needs.
I am not aligned with nor do I have any relationship with MeshCAM or its staff other than being a user [that sounds a little like I have a dependency problem]
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Re: Cutting a Channel Same Width as Cutter Diameter

Postby cnczane » Wed Jul 19, 2017 4:06 am

@larynx

To make an excellent post perfect, because I happen to have visited both MIDI and MDI worlds, MIDI is the musical-instrument network, musical-instrument digital interface and MDI is for manual data input.

There. (I feel like Adrian Monk, satisfied that I helped while everyone else thinks I'm just crazy.)
If you have not received a reply from me in over a year, I am not ignoing you: more likely I am fallen asleep under a tree. Again. Please poke me if you think it worth your trouble.
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Re: Cutting a Channel Same Width as Cutter Diameter

Postby larynx » Mon Jul 24, 2017 3:22 am

:shock: :o :oops: ;) :roll: :) :D :lol: :lol: :lol:
I am not aligned with nor do I have any relationship with MeshCAM or its staff other than being a user [that sounds a little like I have a dependency problem]
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