Messages

31

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 04, 2008, 01:55:23 PM »

Hey I'm ready to cut but want to drill a hole through my work table.

When you use the Wizards in Mach 3 such as circle cut and hole drill, do you position the Z axis bit down and just kiss the surface to be cut then press the Zero axis button and then Press Start??

Thanks

32

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 04, 2008, 11:12:29 AM »

Here are the test procedure and results from measuring the X and Y axis.  As you can see all the results from moving 1” came out to be 0.996” on all three tests that were ran on each axis.  I am using ½” 10 TPI 1 start Acme rod.  All three axis were cut from one piece of rod.   This is not a high precision piece of iron.
After setup I did not have to touch the indicator, it came back to zero every time.

I will try and attach the spreadsheet with test details.

What do you think of the test results? 
What would be my next step?

Regards

Hager

33

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 04, 2008, 09:35:28 AM »

Jim,

Thanks for taking the time to explain accurately and in detail.  It is always best not to assume that I know anything, in this case you are correct.  He He

I am using Acme 1 start ½” 10 TPI, direct drive.  Stepper motors are 200 oz/in with a 24V PS.

My configuration is a fixed gantry so I don’t have to push a big heavy gantry around. 

Thanks for the detailed step by step instructions for eliminating backlash and getting accurate results on distance traveled. 

When you say “Gradually increase the speed on each axis.” Do you mean air cutting or cutting the typical material that I will be using?

Regards

Hager (AKA Mr.Chips)

34

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 04, 2008, 12:10:10 AM »

I am not too concerned about the actual size of the squares that I ran at 4,000, 8,0000, 16,000 because I was using a ball point pen that was loosely floating inside a piece of copper pipe with a weight on top, and it had quite a bit of wobble which in itself will make the size of the squares inaccurate.  When I actually put a known size bit in and cut wood that will be the proof of the pudding.  And yes I will cut the largest square that will fit on my table.    Then run ¼ table size squares in each corner, this should be a good test.

The 4,000, 8,0000, 16,000 were the same in the X and Y direction, however when I upped the speed to 32,000 it made a rectangle, one of the posters said that to run at 32,000 you needed a PC with a high GHZ rate, I really think that was the problem when I tried to run at 32,000.  Anyway around 16,000 is the ballpark I need to be in not 32,000.

I really want to avoid using the Settings utility where Mach 3 takes the number you actually measure after a fixed move and it sets the step rate.  This utility has caused me many problems, the last time I used it the steppers would not jog more than a couple of revolutions when holding the job button down.   Another member also cautioned me about the utility.  When it is time to set the steps I will do it by trial and error until I find the magic number for my machine.

Today I installed the table hold down track and sacrifice table and made a crude dust shoe, and cut my first piece of wood with a ¼” Zip bit and a “V” shaped router bit.  Things worked as expected.

Tomorrow I start to work on my dust collector, dust, especially fine dust in the 2 3 micron range is a killer.

Thank you all again, I had all my questions answered.

Mr Chips

35

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 03, 2008, 12:02:08 PM »

I always hit the enter as well as the SAVE SETTINGS button. Had trouble early on with settings not "Taking".
RC

YES hitting "Enter" is the trick!!!

Now I have another question now that the "Motor Tuning, Steps Per" is working.

I wrote GCode to draw a 1" square.  Results below.
Why is the 32,000 run way off size and a rectangle.  I was expecting it to be 2"  Any ideas.  I know this is off topic, and I know how to draw a 1" square now, but it doesn't make sense.

At 32,000 it draws a square that is 1.026" X 1.104  Not square
At 16,000 it draws a square that is 0.986"
At 8,000 it draws a square that is 0.489"
At 4,000 it draws a square that is 0.224"

THanks

36

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 03, 2008, 11:21:14 AM »

I am setting the steps in "Motor Tuning, Steps Per".

Is this the correct place to define the steps?

37

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 03, 2008, 10:16:19 AM »

1/8 step should be 16,000 steps, btw. 8 x 200 x 10

I am so Confused Stupid or Both.

Start settings:
1/8 step at 32,000 steps settings  X1 draws a line 1" long

I go into Motor Tuning and change the steps/unit to 16,000 for all 3 axis, saving each axis.

Now i get:
1/8 step at 16,000 steps settings  X1 draws a line 1" long

What it wrong?  At 16,000 steps/unit shouldnt the line be 1/2" long??

What am I doing wrong???

38

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 02, 2008, 09:47:48 PM »

When I moved from full to 1/8 step I could no longer run the Y axis at 100 had to drop to I think 60. Why would that be?

Because Mach3 can't output steps fast enough, unless you change to a faster kernel speed.

Where does it show the kernel speed?  And what are my options?

Hey Gerry you really get around.  Guess that happens when you are knowledgeable and in demand

Thanks

39

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 02, 2008, 09:28:49 PM »

MrChips,
The power supply min amperage should be at least equal to the sum of all the amps required for x,y,& z
along with proper voltage output. That said:
 
Would set the X and Y at the lower speed of the two. Think I am correct in that Mach will default to the lower speed of the two axis's when doing circular moves. Reliable movements are more important than speed. If there are minor differences in the acclerations between two axis set the x & y  at the lower of the two.
As the stepper speed increases the torque goes down. It is a trade off, faster speed with less torque or slower speed with more torque. So if you are cutting some wood  and say you hit a knot you'll need  some power to get thru it. Power is 
a function of speed and torque. So you run at a feed rate which leaves some reserve while cutting.

As far as acceleration goes, start low, increasing by 2x until your motors skip, then set at say 60% of that acceleration value, then tweek up or down to refine.
Just some thoughts ,
RICH

When you say "until your motors skip", you mean loose steps don't you?  What would be a good test for this?  Cutting MDF (because of the consistant composition) at say 1/4" deep with a 1/4" 2 flute bit, and I'm guessing 20 IMP with my setup.

Thanks Rich

40

General Mach Discussion / Re: After using the “Steps Per Unit” in “Axis Calibration” my CNC wont run properly

« on: September 02, 2008, 09:19:22 PM »

Nice looking machine! Mid-band resonance occurs at moderate speeds, and when you hit it, motor torque falls drastically. One way to deal with it (sometimes) is to just power your way through it - accelerate fast enough that you get through it, to higher RPM, before the motor has a chance to stall. But, that isn't always practical. Mechanical dampers are another way to deal with it, and can be quite effective. Micro-stepping can also help, as it reduced vibration. From what you've described, I do think this is likely your problem.

Regards,
Ray L.

I have changed the step from full to 1/8 step and changed my step units to 32,000.  (With my Probotix drivers I can go down to 1/16 step would this be considered Micro-stepping)  On a command of 2" it moves about 2 1/4"  I am afraid to go into the “Steps Per Unit” in “Axis Calibration” because this is where I ran into trouble last time.  I can just test and measure until I get in shape.

When I moved from full to 1/8 step I could no longer run the Y axis at 100 had to drop to I think 60.  Why would that be?  I also lowered the acceleration to 20.   Also in the Motor Tuning page is Step and Dir Pulse, it says 1-5, currently it is on 0, as it was the default, what should this be set to?   There are so many options in Mach 3 and I tried watching the videos, but seems some are missing, I printed the manual but what I would like to see is a typical setup for a machine of a given machine type.

I know high speed is just bragging rights, but I was kind of using speed as a proof of good alignment and i would like to have a not too slow jog speed.