G code

[John Chapman 5Participant @johnchapman5]

[John Chapman 5Participant @johnchapman5]

Need help on programing an arc with G codes. I need to make six pieces of trim in wood for a vintage car. The length is 135mm, height is 32mm the radius of the arc is 44mm. Have spent time Googling but not much information on arcs. Not sure on using G18 or G19 codes, I have a small cnc mill using Mach3, attached picture of part to make, any help would be much appreciated.

[John HaineParticipant @johnhaine32865]

G18 and G19 seem to be plane selection, you surely need G02/G03 for cutting arcs?

I think JS is probably your man for this one.

[VCParticipant @vc44480]

Have had trouble with G2/G3 on a odd shape and just ended up plotting in the x-y.

Saved a lot of hair pulling and lying awake half the night

[geoff adamsParticipant @geoffadams14047]

HI john

if you are going to machine the rad first and machine every thing else after

it can be done with g19 y,z axis and a bull nose cutter write a subprogram to machine the arc back and forth

using m98 m99 to open and close the subprogram

moving in the x.010" loop it 550 approx. times with an incremental move of .01" using g91 then back to g90

if you have a cad cam system it will churn out thousands line of code

if you have a drawing and size of blank I could write some code for you

hope this helps and not confused you more

Geoff

[John Stevenson 1Participant @johnstevenson1]

John,

Can't help at the moment as I'm away from my computer but Geoff has hit the nail on the head in that you need to use the XZ plane with G19

[Involute CurveParticipant @involutecurve]

Are you wanting to re-create the surface or just the arc at the top as depicted? or am I missing something!

Shaun

Edited By Involute Curve on 04/05/2017 18:19:14

[An OtherParticipant @another21905]

Seems a bit overkill to me – they could be handmade (like the originals) in less time than it takes to set up CNC. Make a couple of jigs to check the curves.

[geoff adamsParticipant @geoffadams14047]

there is always more than one way to do a job

Johns question was how to machine it on a cnc mill and what g code to use

maybe he just wants to know how it can be done

I have 3 cnc machines two mills one lathe all for hobby use the challenge is how best to machine the part

and program it

got dropped into nc machines from a great height in the 70s as an apprentice no one new how to set program them

got sent on a coarse moved on to cnc no computers then only a calculator and log tables

left engineering to move to dorset worked in building for 35 years now retired back into model making

trying to get my head around cad cam using emachine shop and cambam

these programs don't seem to use all the functions available g41 g42 cutter comp g68rg69 rotate

m98 m99 sub routine if programing by hand very useful functions

I programed a 5 spoke flywheel in 50 lines of code the computer made 5000 lines

rant for the day Geoff

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