Re: what is POSTPROCESSOR? a fundamental question

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jerry Kimberlin least 2
>years > So let me ask a specific question starting from the machine
>end.
> If you have a Sherline and a Taig mill and each are driven with
> size 23 stepper motors of the same brand and lot number, then how
> is a post processor for each different? Probably not different.
> So lets say that both machines have steppers driven via Gecko
> drives. Does that change anything? Probably not. So, say the
> Sherline has Gecko drives and the Taig has Xylotec drives. Does
> that change anything? What I am after is the point at which the
> machines become different and why?
>
>
> JerryK

OK Jerry I'll try to run a bit further with this.
The post processor is MAINLY controller related but also machine
related.
Lets take your senerio above. If you are using the same controller on
very similar machines then these could share the same post.
Keeping to machine topics here still if you now compare your Sherline
to a series 2 bridgeport the nain area of code will be the same but
it's all the start up procedures. On the Sherline you will have a
pause to start the spindleand set speed. On the bridgy it will
command the spindle to start and automatically set the speed.
On the sherline it will stop for a tool change. On the brdgy it will
go to a defined point , stop, and automaticaly swap tools then return
to the program again.
It's all in how the post is written for your machine.

Now for the controller part.
Not all controllers use the same G codes. As an example G70 / 71 are
the older codes for imperial / metric. The newer codes are G20 / 21.
It depends on what your machine understands. The post needs to be
able to put a file out that's perfect for your machine and requirs NO
editing.
Some controllers can do full 360 degree circles with one command,
some need to split them into 4 90 degree arcs. There are vast numbers
of differances.
Someone has used the example of sending the same part to two
machines. This is a good example but you need to be able to get the
code out that your machine and controller understands.

As an example below are three short programs of the same simple
square.
In all cases the code for the part is the same but as the last one,
the Heidenhain, uses atotally different methos of writing code this
isn't as obvious.
What differs mainly is how it tells to controller it's setup codes.

This is where a good program with a user configurable post comes into
it's own. All these three programs took less than 5 seconds to post.

[Fanuc code]
%
O100
N25G00G21G17G90G40G49G80
N35G49
N45T1M06
N55G00G43Z30.H1
N65S1000M03
N75G94
N85G40X-0.162Y4.838
N95Z3.
N105G01Z-2.F100
N115G41X45.819Y4.838D1F200
N125G02X50.819Y-0.162I0.J-5.
N135G01X50.819Y-38.029
N145G02X45.819Y-43.029I-5.J0.
N155G01X-0.162Y-43.029
N165G02X-5.162Y-38.029I0.J5.
N175G01X-5.162Y-0.162
N185G02X-0.162Y4.838I5.J0.
N195G00Z30.
N205M09
N215M30
%

[ Older Phillips post ]
% 100
N10G00G17
N15G80G40
N20G90G54M05
N25G00G53D00Z-22
N30G00G53Y0
N35T1M06
N40S1000M03
N45G00X-0.162Y4.838
N50Z3.
N55G01Z-2.F100
N60X45.819Y4.838D1F200
N65G02X50.819Y-0.162I0.J-5.
N70G01X50.819Y-38.029
N75G02X45.819Y-43.029I-5.J0.
N80G01X-0.162Y-43.029
N85G02X-5.162Y-38.029I0.J5.
N90G01X-5.162Y-0.162
N95G02X-0.162Y4.838I5.J0.
N100G00Z30.
N105G80
N110M30
%

[ Heidenhain post}
%
0 BEGIN PGM 100 MM
1 TOOL DEF 1 L100,000 R0,000
2 L Z0,000 F9999 M92
3 L X0,000 Y0,000
4 TOOL CALL 1 Z S1000
5 R F M03
6 L X-0,162 Y+4,838 R0 M
7 L Z+3,000 R0 M
8 R F M8
9 L Z-2,000 R F100 M
10 L X+45,819 Y+4,838 RL F200 M
11 CC X+45,819 Y-0,162
12 C X+50,819 Y-0,162 DR- RL M
13 L X+50,819 Y-38,029 RL M
14 CC X+45,819 Y-38,029
15 C X+45,819 Y-43,029 DR- RL M
16 L X-0,162 Y-43,029 RL M
17 CC X-0,162 Y-38,029
18 C X-5,162 Y-38,029 DR- RL M
19 L X-5,162 Y-0,162 RL M
20 CC X-0,162 Y-0,162
21 C X-0,162 Y+4,838 DR- RL M
22 L Z+30,000 R F9999 M
23 L Z0,000 R0 F9999 M92
24 L X0,000 Y0,000 R0 F9999 M
25 STOP M02
26 END PGM 100 MM