Messages

5941

General Mach Discussion / Re: Continually incorrect thread pitch

« on: August 12, 2009, 10:55:36 AM »

The wizard only checks to see that the acceleration and max velocity are within your configuration settings for your motors. And warns you if not. it doesn't change the feed rate. Look at the code ( better yet change it over so that it's generating a G32 and you will see what i am talking about.

So you slowed the speed down, the contoller then was able to compensate the feed rate based on a slower spindle speed. SO the feed per revolution was correct for the feed rate.

You need to fix what / where you are getting the index pulse from so the rpm is correct to Mach.

It is not Gcode problem, it is not a Mach / threading problem, it is bad rpm input to the program.

RICH
 

5942

General Mach Discussion / Re: Continually incorrect thread pitch

« on: August 12, 2009, 10:37:29 AM »

Ok, backlash should not be a culprit.

Can you confirm that the steps / unit are correct.?

Do the lathe test i mentioned.

I do recall threading where my actual spindle rpm was higher than what i told the wizard  ( say 101 / 102 instead of
100 ) and the pitch was still ok. Also i will note that , the program will modify the the feed rate if the rpm is lower
but not higher on the next pass based on what it interpreted in the prior pass.

I assume you have one of those lathes that have the rpm readout and you know it's off by  20%.
I assume that the a slotted index is being used for the basis of determing the DRO readout.
Now if you are using something downstream from the Chinese readout / electronics that is incorrect to begin with
then that's a different story as the spindle to feed per revolution just is not right from the start.

Just somne thoughts,
RICH

5943

General Mach Discussion / Re: Continually incorrect thread pitch

« on: August 12, 2009, 09:33:16 AM »

Using steppers or servos? I don't have experience on servo's, Hood or someone else will know if there are any
quirks.

5944

General Mach Discussion / Re: Continually incorrect thread pitch

« on: August 12, 2009, 09:07:32 AM »

kdoney,
Some commments on threading in general:
1. LATHE - Threading requires a lathe with properly adjusted backlash compensation or better yet almost no          

backlash.The motor should not slow down during the threading pass, even though the porgram will account for it      

within reason. The lathe should be tested for accuracy before trying to do any threading.

     I would suggest that you turn down a piece to diameter, color it with say a blue permanent marker,  and then do
     a number  of fine passes ( say 10 or 20 at 0.0001" )  and inspect to see that each pass follows the same scribed
     line. The thread will only be as good as the lathe axis system is.

2. Code - I don't recall any problem with using G32 or G76( single start thread - for multi start you better have a good

system !) If you want, you can change the wizard so that it outputs G32 ( no canned cycle and all passes are coded

 individualy ). The only comment is that you should have a Z movement equal to, say 3 to 5 times the
pitch, so the axis has time to ramp to and maintian speed before the threading actually starts. So there is
a relationship here  in that your motors must be able to accelerate, but, the wizard informs you if things are not right
 for the selected spindle speed.

3. INDEX- You should have rpm display for your range of spindle speed. You may need to adjust slot width
               to get it. It can vary some 1 to 2 maybe at a particular spindle speed, the more stable the rpm reading the

better and it should be fairly close over your range.

If you don't have an rpm, I am not sure what the program is using to trigger the the start of the thread cycle,
in  fact it may never start it.

In config>ports& pins>spinde setup -  check / use -  spinde feedback in sync mode and  spindle speed averaging.
In config>ports & pins> input signal - make sure you use index for a single slot ....or  timing for a multi slot disc

4. Monitoring - You can use the turn diagnostics to monitor the threading cycle.

SO............................................
Make sure your index is working properly and then do the lathe test.

As far as making "U" instead if a sharp "V", i think it's a setup problem also, if the steps per unit are correct then it's
mechanical problem, and the lathe test will show it.

Hope this helps,
RICH

      
  

5945

G-Code, CAD, and CAM discussions / Re: Editing a Pocket?

« on: August 12, 2009, 01:20:16 AM »

You will not find any any "specific" info on the cutting directions in the manual other than definitions in sect 8.4.2.
May be in the upcoming  rev 1.
I want to address the lead-ins / out's  in the manual along with cutting direction in one shot / tutorial. I am not sure what rules LC is following or if it's not restricted. Maybe Vmax or Chip can elaborate more. I don't remember what is in the video , if anything.

Till then,
RICH

5946

General Mach Discussion / Re: Machturn threading problem

« on: August 11, 2009, 10:28:39 AM »

I don't have that problem, but then also don't have my lathe setup for homing. I assume you are
using the standard screens of Turn.

Here is something from another post:

"Is it possible to shift the X origin (zero position) to the outer diameter of the starting stock so that

setup operations whether using wizard or LazyTurn G-code are similar? "

 Most all programs have X=0 as the origin for their code because it can be a repeatable place to easily

find / reference to, along with a number of other reasons. There are a lot of ways of accomplishing

what you ask. Depends on how "you" want to work and your understanding of Mach3 Turn.

For now here is MY suggestion for when in MACH3Turn:

Zero world  X and Z which ( cancels any G54 so there are no offsets ) and set home somewhere away

from the piece, move the tool "controlled point" to where the gcode for the part was created, click part

zero X & Z, ( now machine=program=part cords at the same point ) move the tool to where you want

to start cutting, cycle start the program and all should work just fine. That's a mouth full, but, just one

way of working.

FWIW,
RICH
 

5947

General Mach Discussion / Re: Support Question: Motors stall after powering down during long perpendicular run

« on: August 11, 2009, 09:39:29 AM »

Unfortunately, your problem is HobbyCNC / their system, and they need to address the issue. Mach or any controlling  program delivers the pulse and the controller ( power supply, drives, and associated electronics ) should respond.

 Maybe you should think about a different drive to better suite what you are doing?
 
Kind of like driving down the road, and the motor is automaticaly shuts off , you go to pass someone, and can't!

Ask Hobby CNC why they "designed" their driver like that and what "they" recommend as a fix and also "their"   definiton of intended use of their product.

Just my nickle for what it's worth,
RICH

5948

LazyCam (Beta) / Re: I cannot figure out what LCam is doing?

« on: August 10, 2009, 10:52:14 PM »

It won't for long. 
It's just a non-curable disease that can only be fixed by a full LC dose of medicine! 
RICH

5949

LazyCam (Beta) / Re: I cannot figure out what LCam is doing?

« on: August 10, 2009, 10:46:29 PM »

Already in the works, for rev1. 
RICH

5950

Tangent Corner / Re: Not a Spambot

« on: August 10, 2009, 08:08:45 PM »

Not me anymore, used the last one i had to polish the neigbors brown car. 

RICH