Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: thedude on April 28, 2009, 10:00:27 PM
-
Hi all.
Using Mach3 Turn for the Lathe...
I have a strange motor speed happening when I reverse direction on my Z axis.
I do not have this issue when using mach3 Mill software tho.
I was going to try to explain it in words,,, but I could not,,so I took a video to show it.
(Build history)
Lathe is the 7X14 Sieg (micro mark Mill.) http://www.micromark.com/MICROLUX-7X14-MINI-LATHE,8176.html
I am using the hobbycnc pro driver board.
When I first started to convert the lathe to CNC,, I set up the X axis to drive the carrage only from the threading lead screw and used the Mach3MILL software to make some cuts..... This worked well with backlash compensation, no problems.
I am using backlash compensation, .0135" on that leadscrew at backlash speed of 100%. I do close and restart the program with any adjustment here.
Ive since mounted a motor (now the X axis) on the cross feed, and I have mounted the Z axis motor to the Z feed.
Motors are in 1/2 step and tuned properly per dial indicator verifications on each axis.
Now I am using the Mach3Turn software as I should be.
Here is the problem when using backlash compensation in Mach3Turn vs. Mach3Mill
http://tdracingrc.com/machining/Strange.wmv
In the video I jog, in one direction a few times,,, the velocity and accel work fine,, BUT when I reverse direction I get the strange movement.
I have made a few part with it this way,,, and accuracy is good on most features,, but,,,, this delay is causing some issues as the X takes off while the Z is winding down,, or up....
Can anyone offer some advice on this?
Any help is appreciated
I have changed accel rates and velocity rates to troubleshoot this issue. They do change, per new inputs, but still the reversing motor speeds are still weird.
-
I have looked at the video and - yes - it does seem odd.
Reading your text, I wonder why you only have the system on 1.2 step ( which I assume means 2 microsteps) . It will work more smoothly if you work on 8 microsteps, or - for example - my Ghecko drivers work on 10)
I would increase the number of microsteps, then go to motor tuning, and make the appropriate adjustment to your steps per unit. Your motors will be 200 step, if you use 8 microstep that will be 1600, you appear to have about a 2 to 1 reduction, so that will be 3200, then what ever your leadscrew is. Mine on the lathe was 10 turns per inch so this would be in the order of 32,000 per inch - do not worry, Mach can take it.
My lathe was 60,000 turns per inch - and Mach coped very well. I have now gone metric, with a 5mm ball screw, so I am down to 1200 per mm - but it is, in effect the same motor speed.
As regards you motors, if they are eight wire, they will be much faster if wired in parrallel. I wired mine in series at first, with disappointing results - only 4 ins per min.I wired mine in parrallel, and I shot up to 10 times that figure. I have eased it back to 24 ins per min to keep accuracy. My next move is to increase the voltage.My Ghecko drivers will take it, but my Z drive is limited to 24 volts so I am stuck at the moment.
-
Thanks for the reply,,
I'll change the steps, maybe to 1/4, try it, then to 1/8, play around with it a bit. I chose half step from the advice from the hobbycncpro instructions.
Mainly it was a recommendation as a good place to start. Also, they mentioned not to use microstepping to increase accuracy. I suppose if I don't run the motor faster than needed, I shouldn't have a problem with missing steps.
There isnt a problem when I do not use backlash comp, (or set it at zero.) ie. Backlash comp is on, X set to zero and Z set to .0113. The X doesnt have the issue (as seen in vid) but the Z does. but if I add say .002 to the x,, it has the same issue.
This problem never occurs when I use the machMill program, only the Machturn.... I'm wondering if it might be a software issue???
I'll change the steps and try that first..
Thanks again!
dude..
-
Check that you have the same shuttle accel value in Turn as you have in Mill.
Hood
-
Check that you have the same shuttle accel value in Turn as you have in Mill.
Hood
Checked it,,,, they are not the same.
Shuttle Accel.
Mill .004
Turn 1
This could be it huh?
-
Almost definitely :)
Hood
-
I will bow to Hood, who knows a bit more than me.
To go back to the microsteps issue. Hobbycnc are quite right, you do not use microsteps to increase accuracy - although you would think it would. It does, infact, but the reason that advice is given is that the distance between microsteps is not even and you cannot guarantee that say 5 microsteps of a 10 micro step driver is exactly in the centre of a motor step. It does, however, give the maths of Mach more to go at when making the divisions necessary to drive complex fractions of measurement. Mach works to a 0. (12 figures) of accuracy - althoug only 4 are shown on your DRO's.
The reason you use microsteps is for smoothness of running, and you will find that 8 is a good smooth run with most motors and drivers.
-
I assumed the "shuttle Accel" was a setting for the MPG,, which I do not have.
MAN! I hope this is the problem. I will check tonight when I get home.
Thanks!
-
Worked like a charm!!! So much that I spent the evening in the shop playing and making a few trial parts.
Thank you all and thanks Hood for your help. Nice to know there is a dedicated and helpfull forum of the software for us new to CNC.
I did change to 1/8 step and reset the steps, etc. I do like the smoother action and sound of it this way.
Some "motor banging/EEEGHRRRR!" sounds when changing direction, but I got it worked out through velocity and accel in motor tuning.
Although when rapid jogging in Z,, then adding X jog during the Z jog,, caused some bad motor noise and disruption in steps.
I wonder if 1/4 step would be a happy medium for the hobbycncpro board and my setup?
I also found this in a document other than the manual,,,, just after hood suggested it, of coarse.. haha
"Shuttle Wheel Setting (Shuttle Accel.____ Seconds)
Determines how much time is allowed for the backlash takeup movement to take place.
For my servo systems I set this to a VERY small value (0.00001). This will prevent the
backlash motion from affecting the smoothness of the machine because the step pulses
are sent out as fast as possible (to the limit of the kernal speed). A large number may be
required in stepper systems to prevent lost steps. I also find it very helpful to set the
backlash distance to some HUGE visible number (10mm), then it is easy to see how the
different backlash settings affect machine motion."
-
You will probably find the "motor banging" (although that sounds a bit harsh) on reversal is the backlash compensation system, which you say you have turned on. There is very little you can do about it. The backlash seems to (as you reverse direction) - start in the reverse direction - suddenly realise this and stop - apply backlash (at whatever speed you have indicated) - stop - start again to complete the move
I have my backlash comp speed set at 50% (although I recently fitted ball screws and got rid of most of the backlash) and I found this reasonable. It's not too bad when you realise what it is - and it certainly works very well. The problem is, of course, on some moves you have to apply backlash on both axis, and these have to be independently applied to each axis. It is quite fun to listen to.
-
Hi All,
Just my 50-50-50 pitch ( easy to remember).
BACKLASH - set at 50%
Motor Velocity - set at 50% of the velocity they would start to skip steps
Shuttle Setting - set at .0050 or .050 value ( .5 is slow )
These are start values and then tweak upward. They all work in harmony.
RICH
-
Thanks Rich, I'll try that and see how it works out.
The motor "banging" wasn't the backlash comp. I had the accel too high, or at least when I lowered it it stopped. It happened mostly when I was jogging at start.
I made a part with a series of turned DIA at different lengths (-Z). The final DIA were off by anywhere from .021 to .007" .... I rechecked the motor steps with a dial indicator and jogged in .100" inc.... Moved .050" everytime, in either direction,, steps and backlash are good. I made several parts,, rezeroing x at the DIA each time,, and each time it was off. If I use MDI,,, the DIA are still off.
Last night I purchased the software registry codes and will work with it some more.
I'm still trying to wrap my head around a few setup tasks;
1.) Setting the machine coord home (without home switches)
2.) The MASTER Tool #1, Use it only to setup part stock? Set every other tool from its location coord?
Question.
In the manual screen-- The program, machine and part coord buttons/LEDs. They are buttons for dro displays of the coord, NOT buttons for setting up each coord?
ie. If you are setting your part coord, z 0.00 and x DIA of stock, the part coord button does / does not have to be activated during this setup? And same for setting X and Z home limits? Any of them can be activated when doing this.
What confused me was in the manual in the section of setiing up the machine home coord. After setting my x and Z away from the part, the screenshot shows you to click the x and z home buttons,,, but in the screenshot the "program coord" LED is lit......?
Thanks again for everyones help
-
thedude,
1.) Setting the machine coord home (without home switches)
I just posted a little how to on this in "Members Docs". For a mill.
As far as all the other questions i'll get back later on.
RICH
-
Thanks RICH.
I'm also going to post a better description of my setup, config and a few more questions. I'm going to run some trial parts tonight and post the code and the measured results to be more clear.
Thanks again.
-
thedude,
Just a few comments.
Walk before you run. Make sure that motor tuning is right, steps per unit are correct, backlash is set setup properly.
Play around some with the lathe doing some simple stuff .........without any sophistication....................................
like fooling with the tool tables, setting up homing without switches, etc.
If you don't have an indexer, a repeatable tool changer the value of all that sophistication will only make doing something simple into a barrage of questions on why something is not comming out correctly.
What i am alluding to, is that if you make one of a kind stuff, constantly changing tools / the angle of the tool changer etc you can find the sophistication to be a pain in the neck.
RICH
-
Thanks RICH for the replies and help.
I should although be more clear about how I arrived at where I am on this. I have made several parts, just playing mostly. I've set the drives per calculations and verified with a dial indicator, also using it to verify backlash. So far, I'm setup retty tight on steps and backlash as verified through a dial indicator,,,,,, but still,,, have a few lost steps through different actions taken through Mach3turn.
I spent some time tonight troubleshooting everything. My wife stood by and took notes as I spoke what I was doing.
Here is some trials I was doing tonight. This is only a part of what we did,, but I wanted to keep the post short,, and add as needed.
(Tool #1)
Setting Tool in Tool Table
Turning diameter = .7085 Z0
Turned to a DIA of .7085 Clicked touch X
Faced the end, Clicked touch Z
DRO Access coordinates reading: X offset/X wear and Y offset/Y wear are all 0.000
Quit tool table screen
Returned to manual screen
Clicked Home X and Home Z
*SUCCESS* (as best I can tell, it moved near where I originally set home limits)
To Verify part coord after tool setup.
MDI
Z0 X.7085 (diameter from setting part zero x)
Tool was right on the OD and the end of the part. (Visual)
To check programmed DIA cuts.
On manual screen: MDI to X.670
Manually jogged Z to cut
Diameter = .670
On manual screen: MDI to X.650
Manually jogged Z to cut
Diameter = .650
Opened tool table to check tool info, closed and went back to manual screen
On manual screen: MDI to X.60 (From last DIA of .650)
Manually jogged Z to cut
Diameter = .631 ?????
*FAIL*
Re-zeroed part in X
Made facing cut
Diameter = .609
Typed in .609 in part zero
Clicked part zero X button
On manual screen: MDI to X.580
Manually jogged Z to cut
Diameter = .597 ?????
*FAIL*
Attached Mechanical Dial Indicator to measure movement of X axis (NO Part Machining)
Jog increment = .1 inch
Diameter mode, result should be .050
Jogged positive X 6 times and each time resulted in .050 each time
Jogged negative X 4 times and each time resulted in .050 each time, (backlash comp verification,, set correct)
Verifying turnings with Dial indicator attached. (Part Machining)
On manual screen: MDI to X.609
X.609
zero the indicator.
MDI X.58
Should go .0145 inches but it went .0055 (DIA Mode)
Told it to go back to .609 and it went to 0
Went back to test this in jog increment of 0.100
Indicator Readings
1. X.048 ????
2. X.091 ????
Zeroed indicator and repeated jog increment 4 times 1) .050, 2). .050 3) .050 4.) .050
Moved to Home X and Home Z. Home X crashed slightly in negative.
I have no conclusions to any of this.....
My settings are below.
Current Config Setup.
Motors
Both motors are 4.2v, 3 amp, 305 oz/in
X axis = 1/8 step, Direct Drive of a 20 TPI Lead screw, (.050 per turn)
Steps per revolution = 32,000
Velocity = 30
Accel = 1
Step pulse = 0 (I never set this)
Direct pulse = 0 (I never set this)
Z axis = 1/8 step (Using threading lead screw on lathe, 16 TPI, two timing pullys 1:1.5, 38400 calculated, Indicated to 38,360)
Steps per revolution = 38,360
Velocity = 25.002
Accel = .75
Step pulse and Direct pulse = 0 (?)
Backlash Comp
Backlash X = .0012 (Per Dial Indicator)
Backlash Z = .0185 (Per Dial Indicator)
50%
Both motors are 4.2v, 3 amp, 305 oz/in
Shuttle excel = .1 second
Motion mode = Constant velocity
CV Control
CV distance tolerance = 60
G100 adaptive nurbs is checked by default
Stop CV on angles is unchecked
Distance mode = absolute
IJ mode = incremental
Ports & Pins
Port enabled is checked
Kernel speed = 25,000Hz
EStop Checked,,, Low active Unchecked
X and Z axis Low active and Step Low active both Unchecked.
Hope I have provided enough info for a guru to see the problem,,, any questions please ask,,,
Thanks! Any help is appreciated greatly.
-
I hope I haven't worn out my welcome with that last post. It is long, but I wanted to give enough info to promote a fix.
The short of it is that,,, when Inc jogging, by .100 in this case, the X axis is dead on. When using MDI it varies. Also, not listed in my post is running a program, it varies too.
Again,, thanks for everyones help thus far,,, and I hope some suggestions will continue.
Thanks again.
duder,,,
-
thedude,
You have not worn out your welcome. I would have to carefully look at what you posted
and see if i could find the problem. Right now I'm just caught up in a problem myself
( at least your machine is running ). ;) Others will chime in.
RICH
-
Tonight I decided to run a rew more trial pcs.
The part was a series of DIA, each cut in less -Z.
Basically, the part looked like a mini DEVO hat,,, Whip It!! haha. Simple.
The DIA were finishing at .020-.026 oversized each time.
I decided to adjust my X axis stepper setting from the calculated, 32000. (1/8 step, 20 TPI) and see what happens.
Here is my workflow.
Part stock is .75" DIA Delrin
I'm working in Diameter mode.
Tool 0 (as I am setting the part zero manually)
Load the stock.
Make a facing cut
Type zero, enter, click zero part Z.
Make a turning cut.
Measure, type the measured DIA, click zero part X.
Run program.
Measure.
.020-.026 more than programmed DIA.
Adjust Stepper setting a bit, repeat. (several times, adjust, repeat. I must have made 15 mini Devo Hats tonight)
Strangely,, it would get within .006 to DIA,,, then,,, when I tweaked just a hair more to dial it in,,,,
It would go back to giving me an error of the .020-.026" !!!! Regardless of the stepper setting.
My stepper setting ranged from 32500 to 31025 during this troubleshoot.
I'm wondering if I have narrowed it down to my hobbycnc controller box??
Anyone think that I should now mount the "Y" axis motor, reset the Y pin outputs to the Z outputs and retry???
Any help,,, thanks
-
Wondering if I should abondon this thread. I've taken everones advise so far and it has proved to be helpfull. Now I'm stuck on the X travel Variance issue.
I will keep reading, troubleshooting, and searching.
Thanks everyone for your help thus far.
-
I am sending you a personal message.
RICH
-
It is certainly always a good idea to try swapping hardware around one bit at a time to see if the problem follows the hardware.
Hood
-
thedude,
- Your steps per unit: Use the calculated values Z=32000 X=38400
Yes, you can use a different value, don't want to confuse ( only when you know why you are doing it ).
When you checked your steps / unit you were jogging in small incremenntal steps. It would be much better to
jog a longer distance ( at least an inch ) and use that to confirm settings. Once the steps / unit are confirmed
then find the backlash setting.
Reading this post you said you had .0135" backlash in the X and then somewhere else it was .0012" so i am
confused.
- What settings for the pulse & dir time in motor tuning are appropriate for your drives?
I could not find any recomendations on the Hobbycnc Site and additionaly no instruction sheet for your driver.
That sucks HOBBYCNC!
So if the steppers are working fine with the 0 value, use it . By increasing the value your giving
more time for the computer pulse to be seem by your drives.
- Your driver has an idle current setting such that it will reduce the current 50% after 10 seconds.
I could not find how you change that setting on your driver board. Is there a jumper or something
on the driver board to change that setting ? I couldn't tell from the pictures of your drives posted on the
Hobbycnc site but it does say it can be changed.
Some time ago, someone else had a problem with that driver and changing it such that there was no current
reduction solved a backlash and or missed step problem. Just don't remember. It was in the last year or so.
Can you post your xml file? It's located in the subdirectory where you installed Mach3. Change the file extension to
.thedude for posting.
RICH
-
Rich,
I won't be able to get to the shop tonight. I will make some notes and look at my hobby cnc info here.
I will be in the shop tomorrow. Let me know if you have any time.
Hood,
I'll change out the motor tomorrow and rerun the gcode program.
Thanks everyone.!!!
-
I didn't want to post such a long file so I converted to pdf.
DARNIT!! DO NOT USE THE XML FILE ATTACHED,,,,(I removed it)
I'm sorry, got in a rush and posted the wrong one. I hope this hasn't caused any trouble.... :-[
This is the backlash comp.
Backlash Comp
Backlash X = .0012 (Per Dial Indicator)
Backlash Z = .0185 (Per Dial Indicator)
50%
Idle Current Reduction (From the hobby cnc instruction manual)
Idle Current Reduction
Jumper J4 controls this function on each axis. This allows the current to be reduced to @50% after no
movement for approximately 10 seconds on that axis. This may reduce stepper motor heating. Each axis is
individually settable. Remove J4 jumper to enable this function. Install jumper on J4 to disable it. A word
of caution is in order. Idle current reduction MAY cause lost steps IF your software settings are very
aggressive for the start rate and accel rate. It takes a few microseconds to restore full power when
commanded to move from an idle current reduced condition. Experiment a bit with this.
As an alternate to the 50% reduction, substituting R2,R4,R6,R8 with a 4.7K value (not included) will
allow only @30% current reduction. (3A down to 2A for example). This may allow more aggressive software
se~ups. Note that 20K would allow @75% current reduction.
Synchronous and Asynchronous Mode
Asynchronous function is active for all stepping modes. Approximately 10 seconds after last movement
the stepper driver will automatically switch to synchronous mode. This helps prevent stepper "hiss" when not
moving. The time delay is directly related to the idle current delay resistors (100K) installed in step #2. This
function is always active and is independent of idle current enable/disable J4 jumper setting.
-
thedude,
You sent me xml info for the MILL and we are working with the lathe.
That's all right for now.
Can you call me?
RICH
-
thedude,
Suggest the following:
Create a new xml file for the lathe. One that has no homing, tool offsets, etc. because
you should start all over again, as if you were just setting up the lathe for the first time.
I think, and could be wrong, that the iddle current reduction caused you missed steps
which screws up your setup.
1. Disable the iddle current reduction
2. Set your steps / unit at the calculated values
3. Disable backlash
4. Check your x & z movements based on calculated values, if required, change accordingly
5. Check backlash to find values, then set at 50%
6. Retune your motors, find where they start to skip using an acceleration value of 3, then use a
use a value of 50% of were they skipped for the velocity, and also use a shuttle acceleration .05.
( You can tweek the system later on )
7. Enable backlash
8. Run some repetative gcode programs to confirm that the movements are repeatable
and tweek the backlash if necessary.
9. Test some actual cutting.
10. Tweek the system based on your experience.
Hope this solves your problem,
RICH
-
Thanks Rich, (yeah, I know I posted the wrong xml file,,,,sorry I edited the post mentioning that but not in time,,, )
Adjusted and troubleshooted your suggestions and it is now cutting DIA within .002" Not too bad, but I imagine it could be better??
Heres what Iv'e done,
1.) DISabled idle current
2.) Retuned the X to 31900 after cutting and measuring DIAs and tuned with trial and error. (Many more Devo Hats!)haha
3.) Checked backlash by cutting DIA NOT using my indicator. Turns out there is ZERO backlash on X. baclash on Z is same and set to 50%
4.) Switched to exact Stop Mode.
5.) my motors speed and accel are 20 and 0.45. (I'm sure I could increase the accel but taking it slow for dial in.)
I'm going to make a few more parts working with your step 6 suggestion to have a good accel setting. (All that "whining up and down was annoying).
I'm going to check the parts and see if anything else is off. Maybe tweak a bit more.
I'm very happy with the setup now. You guys have been GREAT Help!! I thank you all very much!!!
-
:)
RICH
-
Thanks again RICH,,, and Hood.
Feels motivating to be confident in the machine.
I increased the motor velocity to 30 and accel to 1.5 and it was stable and smooth.
I also decreased the shuttle accel from .15 to .05 (per RICH suggestion)
Worked great.!!!
My motors never got hot.
I also went to radio shack and bought a game controller and set it up for my jogging to setup the part. Now that is REALLY nice to have for manual maching.
Anyone know what the hotkeys are (if any) for setting x and z part zero?
Made a few parts tonight using the wizards,, nothing special, but rewarding for me.
I know it is silly to post pics of such simple parts,, but for me it was a milestone moment in setting up the lathe.
Yes,,, thats the "Devo Hat" in the pic. A bit larger than the last 25, and made from aluminum, not delrin.
they are attached.
-
Hey Dude, Happy to see you're getting under way.
Don't know if there's a hot key to zero the axis but there is Ctrl X and Ctrl Z that will highlight/select the DRO, then hit 0 or whatever value you want and hit ENTER.
This is the way it is in MILL so I set my TURN the same way with Screen4.
You could assign any key or combo you like but be careful because many are used for other functions in the system.
Wayne would be proud of you and your little Devo hats. he he he
Let er' rip,
RC