4th Axis and SMC5 CNC controller help

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Gary8151
Posts: 3
Joined: Fri Oct 29, 2021 2:04 pm

4th Axis and SMC5 CNC controller help

Post by Gary8151 »

Hello all
I'm very new to the DIY CNC community so i hope my questions are not too painful. I recently built a cnc mill with a fourth axis and the controller I used is a SMC5-5-N-N controller. I can run parts in 3 axis pretty well but when I try to use the 4th axis the rotation federate doesn't match the feed rate for x axis. The 4th axis runs much slower than the x axis feed rate. I read the user manual but it a little confusing. I want to say the rotation is set in degrees on the controller and i use a Mach 3 post processor. i did a test part and it makes the correct dimensions but very slow in the 4th axis.

Does anyone know if the SMC5 controller has a setting that i may need to change to get the feed rates to match? or a possible other solution? can someone tell me if there is more information on the SMC5 controller?

this is the beginning of the code

(T1 D=1.587 CR=0. - FLAT END MILL)
G90 G94 G91.1 G40 G49 G17
G21
G28 G91 Z0.
G90

(2D CONTOUR1)
M5
T1 M6
S11999 M3
G54
G0 A-36.059
M8
G0 X62.54 Y0.
G43 Z30.099 H1
A-36.059
Z19.939
G1 Z16.621 F233.
Z14.256
G93 X62.533 Z14.195 A-36.105 F8947.1414
X62.515 Z14.143 A-36.236 F7434.2807
X62.486 Z14.109 A-36.432 F6983.9295
X62.453 Z14.097 A-36.664 F7023.2536
X62.366 A-37.268 F2752.2086
X62.343 A-37.53 F7411.3588
A-37.812 F9280.8217
X62.367 A-38.072 F7368.3155
X62.411 A-38.27 F6991.5304
X62.515 A-38.637 F3619.4417
X62.603 A-39.076 F3561.8339
X62.674 A-39.576 F3602.3778
X62.727 A-40.122 F3746.7695
X62.759 A-40.7 F4016.7495
X62.77 A-41.294 F4459.6134
X62.774 A-65.618 F116.8891
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Bill Shields
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Joined: Fri Dec 21, 2007 4:57 am
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Re: 4th Axis and SMC5 CNC controller help

Post by Bill Shields »

do not know about that control, but can provide information regarding what you are seeing:

feed rates on rotary axes are often calculated on on DEGREES / MINUTE rather than LINEAR UNITS / MINUTE.

this is why the F values are higher on controls in units / minute mode.

however: then there is G93 which is INVERSE TIME -> which your control may or may not support....which is the code that you are seeing. If the control did not support it, then I would think that you would get an alarm.

The mach 3 appears to support G93....

if the rotary moves appear to be too slow...then it can be that your software is not calculating the inverse time moves correctly....

either that or your rotary axis cannot keep up with the F value commanded by the software -> and is hitting a degrees / minute limit.

First question: what is the degrees / minute limitation of your 4th axis?
Second question: what is the degrees / minute feed limit setting in your software?
3rd question: when running the code you showed in the example: does G93 appear as 'active' on the control screen? If so -> what actual feed rate appears for the moves that are linear only? what feed rate appears for the moves that include rotary motion?

section 5.5.2 of the manual 'setting the maximum motor speed' is a place to start
Too many things going on to bother listing them.
Gary8151
Posts: 3
Joined: Fri Oct 29, 2021 2:04 pm

Re: 4th Axis and SMC5 CNC controller help

Post by Gary8151 »

I found out that the controller I use does not support G93 G94. I found a website with something like tech support for the controller and the person just said "it does not support". the controller feed rate seems to the same as in the program and it doesn't show that G93 on the controller monitor.
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Bill Shields
Posts: 10460
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
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Re: 4th Axis and SMC5 CNC controller help

Post by Bill Shields »

Ok...so are rotary feed rates in linear units per minute or degrees per minute?

Post processor needs to be modified accordingly

As long as you know what you need...the goal is attainable.

It is easy enough to find out with a few experimental lines of code it you cannot find it in the manual
Too many things going on to bother listing them.
Gary8151
Posts: 3
Joined: Fri Oct 29, 2021 2:04 pm

Re: 4th Axis and SMC5 CNC controller help

Post by Gary8151 »

it's in degrees. I appreciate the help my friend. i will look into how to edit the post processor. can you point to any good reading material on the subject? i watched a video about it but i think i need to study a bit more it went way over my head.
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Bill Shields
Posts: 10460
Joined: Fri Dec 21, 2007 4:57 am
Location: 39.367, -75.765
Contact:

Re: 4th Axis and SMC5 CNC controller help

Post by Bill Shields »

Posts are entities unto themselves...and vary greatly based on the parent software....

Some posts are customer editable...others are not.

Before you start...did you obtain the maximum rotary feed limit of your rotary axis? No matter what...you are going to need that number.
Too many things going on to bother listing them.
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