Messages

2631

General Mach Discussion / Re: z axis moving up

« on: May 31, 2012, 06:31:30 AM »

DRAY,
You should properly support the lead screw with a bearing. The stepper motor has axial play and you'll have backlash along with putting
unnecessary loads into the motor. The bearing should be preloaded to minimise backlash and also needs to aligned properly.

Consider that when microstepping you reduce the motor torque probably in half, then the torque required to raise / lower the Z axis, headroom for cutting, reduced power requirements ......thus skipping is just waiting for the right condition.

Your going to have varied values when you measure because the screw is floating.

Now on to the coupling between the motor and screw.........What kind are you using?

I didn't see any recomended step or direction pulse durations for your drive and you may want to ask Mechatronics what they recommend.

Just a quick test you can do:
Mount  a ring ( can be made out of paper) about 3 to 6 inches on the motor shaft along with a stationary index. With the motor energized make a fine mark. Do an up and down movement for say 1". The index should be in alignment with the mark after the moves.  Doing this will isolate the motor from the screw and thus eliminate the mechanical influence of the axis. You can also calculate how many steps for a given movement and thus measure steps within reason.
 
So the poor mans step counter works like this:
- 6" dia x 3.14= 18.85" circumference
- 18.85" /200 ( steps per rev of motor ) x 8 ( micro steps per )= .012" of circumferential  movement per sent step
So a fine mark could be around .005" and you can see or even measure steps to see if there is an electronic issue.
(BTW, one of the reasons I like motors with dual shafts)

RICH





 

2632

General Mach Discussion / Re: z axis moving up

« on: May 30, 2012, 07:14:30 PM »

Your steps per unit for the Z are calculated correctly.
Now test the Z axis movement accurately using a dial indicator. Do this at vel setting of 10 and accel of 2 and over a larger movement
of 1". The movement should be in the Z downward direction. Bring the Z all the way up and then move it down say .5". Now move the Z in the downward direction via MDI. Record the distance for the move as shown on the indicator. Do another downward movement of 1"
and again record the indicator ( you may need to reset the indicator). If the two moves were 1" each your steps per are ok. If not
adjust the steps per until the moves are correct as indicated by the indicator.  

You may want to also try the reverse of the above and see if screw has a different pitch ( small maybe but it can add up) when the Z goes up.

With the steps correct, you should now check for backlash. So just raise the Z all the way up and down again but for 1.5".
Set the indicator and jog the Z up in .001"  movements. The number of jogs required to just move up .001" up is your backlash.
How much is there? You can use backlash comp to deal with, not ideal, but may serve you well.

----------------------------------------------------------------------
Do you have specific info on your Z motor?
Are your ther steppers the same?

Your power supply is 31V @ 2.42 A. That is is not adequate for your three steppers. If all the steppers are the same then the min required
amps maybe around 3 x 2.8 amps per stepper x .7 = 5.88 amps.

Don't know the basis of  your motor torque rating but will say that the microstepping, reduced amperage available will reduce the the available torque and speed of the steppers.

---------------------------
Can't see how your motor is attached to the screw and how the screw is supported in the pic you posted.
Can you post another pic showing that?

Post back,
RICH

2633

Mach SDK plugin questions and answers. / Re: Phidgets USB and Mach3, need a Post Processor

« on: May 30, 2012, 07:07:58 AM »

CROB09,

Besides what is wrong with giving a person some direction?

Absolutely nothing and hopefully some of the 1000's of users on this site will respond.

Rich, I was looking for some simple direction not some link to a person I have to pay to get the run around.

Since there were no replies to a number of your posts, requesting one on one support for developement help was an option
given for your consideration.
 

you are the kind of person that exploits peoples ignorance and because you don't want to share any information

The requested info you seek is not my expertise so can't give what I don't have.

Relative to your perception of me........time spent reconcilling it would be better spent helping others.

RICH

2634

General Mach Discussion / Re: z axis moving up

« on: May 29, 2012, 05:51:29 PM »

I echo what others have replied about the accel and velocity.  Post back with the results but do the testing in logical way.

I would recomend that you set your velocity to 20 IPM with an acceleration value of 2.
- ? When you jog does the Z motor run / sound smooth?
- ? How much are you gaining after the loop test?
Swap the x or y axis drive and do the same test with the same settings. Report back on those results.

POST the following:
- Pic's of your Z axis
- The xml you are using
- Pic of the driver test graph
 
Now give us the following info:
- Windows system -?
- Description of your pc...on-board graphics, PP,
- Mach version-?
- Screen set your using-?
- Type of drives-?
   - amp, voltage,micro step or any other settings
- How is the motor wired?  
- Name / description of any BOB's
- Power supply you are using / specs

Yes , I am asking for a lot, but then would like to know what your system is composed of and would rather review what you have than say a whole bunch of things that can cuase what you are experiencing.

RICH

2635

Show"N"Tell ( What you have made with your CNC machine.) / Re: Tweakie's De-Mag.

« on: May 29, 2012, 06:31:54 AM »

Thanks All,
Found an old bulk tape eraser. It's a transformer mounted in a metal box but the sides and top of the box is plastic. Has a momentary switch to turn on the
AC to the transformer. The transformer is different than a conventional one since the core is U shapped thus putting out a directional magnetic field / eddy current.  Not sure if it will be strong enough but worth a try.

Never throw out good junk...............
RICH

2636

General Mach Discussion / Re: z axis moving up

« on: May 29, 2012, 05:59:00 AM »

Make sure your steps per unit are correct.
How is the Z axis driven ...... any backlash?

RICH

2637

FAQs / Re: Steps per JACKED!

« on: May 29, 2012, 05:48:21 AM »

Did you save the configuration after you used the axis calibration?
RICH

2638

Show"N"Tell ( What you have made with your CNC machine.) / Re: Tweakie's De-Mag.

« on: May 27, 2012, 07:10:10 AM »

Any insight on what to do if the mill table is becoming magnetized.
Interestingly a friend mentioned that after milling a lot of hardened material using a carbide fly cutter his table, vise etc has become magnetized.
I have seen this happen with the chips, but never the whole table.

Any thoughts on the matter??

RICH

2639

General Mach Discussion / Re: Zeroing the work piece Question?

« on: May 27, 2012, 06:58:56 AM »

There are two parts to setup,namely, where the user wants  to start and how to get to that starting point.
You need to think about where you want to start early on and the selected start point should include how the material is mounted,
how your going to touch off to the part, the intial tool move into the material, how the part will be machined, accuracy of setup, etc, etc.

In many cases common sense will dictate.
RICH

2640

General Mach Discussion / Re: touch probes

« on: May 25, 2012, 06:55:28 AM »

dont know much about this stuff so play it by ear and see what happens

Your not alone....in general:
You will be using a probe to digitize the part using the wizard.
-Z travel height should be higher than your part.
-Z Probe depth is how deep you want to go. I think setting it to 0 would be the bottom of your part.
-Stepover is the spacing of the point grid.
-Feedrate is how fast to probe. Don't probe too fast, or the probe won't be able to stop when it's tripped. It has to decelerate after it makes contact.

Do a search and you will find info on digitizing. Gerry posted the above.

After the collection of points Mach Cloud will convert the pont cloud to a stl file. The stl file is a mesh which basicaly creates a surface by connnecting all the points ( not a solid). There are other porgrams that can be purchased or used to create the mesh. Some programs can manipulate the mesh some can't. Maybe you'll want a solid to work with.

The stl file is used by a CAM program to generate the  gcode so it can be machined.

SO in general :
Digitize the part, generate a solid or mesh for use by a modeling program, cam it, cut it.
I have an expensive probe,never used it and certainly don't want to damage it. So over time want some insurance on functionality of the digitizing. Depending on what you want to do you may need or want to
modify the steel file. ie; how are you going to do the checkering for the grips. Guess i am just saying that
one needs to get the right mix of software ( and hardware ) to accomplish the task without breaking the bank and miniizing the learning curve.

RICH