Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: tpgolf on July 09, 2016, 10:43:10 AM
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First time post and fairly new to CNC & Mach3
X & A slaved
"Home slave with master" is unchecked
"Ref All Home" script - RefCombination(9)
No limit switches on Y & Z yet
X & A are reversed so they work correctly, home negative is checked for both
X & A are identical in the motor tuning setup
I installed 2 hall effect proximity sensors on the X & A axis - separate pins on BOB (pin 13 & 12 respectively)
When the magnet approaches the sensors the light on the sensor goes out and the light on M1Home & M4Home activates
Problem is when I "Ref All Home" the gantry moves toward the sensors (negative) as it should
one of the sensors will activate, the other side will stop moving, still not activated
the activated side continues moving negative and racks the gantry
What am I doing wrong?
Thanks,
Joe
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What version of Mach3?
Parallel port?
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Im having same problem. I have uc-100 to usb. Cant seem to get it to do the "squaring". I have home neg checked and auto zero, when a g28 is executed the z goes up then both x and y/a slave go home but im not seeing it hit the switch and then back off the switch. I made a couple home switches with pogo pins and nylon nuts, works great.
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Hi,
3.042.020 & parallel port
thanks,
Joe
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Can you post your .xml file?
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Hi Gerry,
I THINK i have it figured out. After trying every possible combinations of every button I could find with no luck I erased the Ref All Home script and typed it again.
it appears to be working now. Being totally unfamiliar with the macro language and formats I'm not sure if ther was rouge space, return, etc. somewhere that was causing a problem.
That leads me to another issue with the proximity sensors. Definately struggling to get any sort of repeatability/ consistency out of them. They are a Chinese NPN NC 3 wire sensor.
I'm chasing to get them to activate at the same time. I get them absolutely perfect, withing .0005", and then the next try they are off by .015". I'm thinking that since I'm trying to square the gantry that the accuracy of them coming off the sensor is more important than when it goes into the sensor. Any thoughts on that?
I've read numerous posts and it's split on whether I need to add a resistor or some other electrical component to make them operate properly.
Do you have any advise on them? Are they supposed to be the most accurate and repeatable of the options that are out there?
Can you also point me in the direction of a good tutorial on the Mach3 macros? Again, I've looked and can only find references to the commands, nothing explaining what they really mean and how to use them. Mach3 macros for dummies (does it exist?)
Appreciate the help
Have a great day,
Joe
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I'm thinking that since I'm trying to square the gantry that the accuracy of them coming off the sensor is more important than when it goes into the sensor.
Correct. Sorry, but I've never used proximity sensors.
Have you looked through this manual?
http://www.machsupport.com/wp-content/uploads/2013/02/VBScript_Commands.pdf
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Proximity sensors don't have anywhere near the accuracy and repeatabilty you are looking for, at least not at a price you'd be willing to pay! Really accurate limit switches are available, and they will likely be normally and forced open as that is generally more repeatable. In thinking about this issue I would be concerned about setting the squareness using microstepping. I think I would set the drives for full step and mechanically adjust the motor to screw or belt position to be perfectly square at full step. I believe they would then be much more likely to move together accurately.
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Can you also point me in the direction of a good tutorial on the Mach3 macros? Again, I've looked and can only find references to the commands, nothing explaining what they really mean and how to use them. Mach3 macros for dummies (does it exist?)
It does not exist. If you do, or have done programming, then the learning experience will be rather quick.
I will be the first to admit that I am not the sharpest tack on macros, but, I learned a lot just by looking at all the stuff you will find posted in the Tool Box or screen sets, etc .
You be amazed at just how dangerous you can become.
RICH
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Hi Gerry, Gary & Rich,
Appreciate the feedback.
I have no programming experience but will definitely look thru the VB scripts and start lurking thru the Tool Box & screen sets. You never know where it might lead me on my quest to figure this stuff out.
It has become apparent that the proximity sensors I bought are not capable of doing what I intended. That said there is little doubt that I am getting carried away with some of the things I'm doing. I built the CNC from SidewinderCNC. Had a blast building it, using it for a bit so far and furthering my knowledge on the whole CNC world. The accuracy of the machine is probably far less than I'm worrying about with these sensors. I plan on building another machine, hopefully much for accurate in the future. I'm using what I have to learn about different things so I can make informed decisions when that time comes.
I'm using the Xylotex controller and motors, is there a way to change the microstepping?
I'll do some reading about microstepping but what are the pros & cons of it? Is accuracy diminished going to full steps?
Can you provide a link or some names of accurate limit switches?
Really appreciate all the effort everyone puts into these forums. They have been a tremendous source of information and hopefully someday I'll be able to repay the favor to someone that needs help.
Have a great day,
Joe
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You can change the microstepping, but I would NOT recommend it. The Xylotex is very susceptible to resonance issues, and running at lower microstep settings can make it much worse.
I've been using one for many years at 1/8 microstepping and get very repeatable homing with homemade Hall effect switches.
To be honest, in almost 15 years of doing this, I've never heard anyone recommend reducing microstepping to improve homing accuracy.
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Hi Gerry,
I'm not 100% sure but i believe the setup I have is using 1/16 microstepping. I remember in one of Dave Gatton's video's he mentions that Jeff made some modifications to the newer controllers. In his video i recall some of his settings for the motors and he had 3200 steps.
Mine is set for 6400 steps per the instructions from Jeff @ Xylotex.
Is 1/8 better? Smoother? More accurate? Not necessarily for the gantry issue but general use
Can i change it?
Do you have any recommendations on an accurate switch or method to square up the gantry?
Thanks,
Joe
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Hi Gerry,
my fingers are going faster than my mind and i hit send to soon.
Do you have any info on your hall effect sensors?
Are you using Xylotex's BOB?
Thanks again,
Joe
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I built my sensors based on this thread:
http://www.cnczone.com/forums/open-source-cnc-machine-designs/101878-cnc-forum.html
And yes, I'm using a Xylotex that I bought about 10 years ago.
I don't know if the kits that Jeff is selling now are using the same board or not?
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Gerry,
I wasn't suggesting running with reduced microstepping. I was simply suggesting that the mechanical linkages be adjusted with a full step holding everything stationary. If the gantry is square at a full step then I think it might tend to stay that way. When my drives power up they always seem to jump to some position. Might be an initial full step? If two drives power up and they had be aligned by microstepping might they not be out when that initial step happens? As I said just a suggestion, based on lots of people seeming to have an issue when two motors are involved. Comes up frequently on the 3D printer forums too.
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Hi Gary,
The issue you are speaking about is what I believe is causing my problem with the gantry going out of square.
Almost every time I turn the controller on the motors "jump" and lock into position. when I'm trying to manually square the gantry I turn off the controller to turn the screw by hand to adjust the dial indicator. when I turn it back on it jumps anywhere from .001" to .005" in either direction. I seem to spend a lot of time chasing this to dial it in so it's square.
Would going from 1/16 step to 1/8, assuming my Xylotex controller gives me that option, help in anyway with this or make it worse?
Any thoughts or this isuue just an inherent problem with steppers?
Thanks,
Joe
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How about optical(opto) sensor type limit switch, will it be better or or at least as well as the said hall effect or inductive type limit switchs?
In my gantry machine, I already installed two pulleys on the axis and mechanical linked them with timing belt to fix the out of squareness problem. The problem is really harassed, if not properly resolved, large current draw and friction force will damage electronic and mechan ical parts...
Thanks