Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Shwagiedo on November 04, 2013, 10:33:43 PM
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Hello all,
I am new to the cnc game and thought id try mymhand at it. I have recently converted my harbor frieght 7x12 mini lathe to cnc. I am useing the stock motor and motor controller with a G540. I can controll both axis's no problem i just figure out how to gain control of my spindle via mach and a pulse index card for threading purposes. Problem i am haveing while still in my testing phase is that if i turn on thw spindle then try to jog my x axis thenspindle speed increases and then decreases if i stop jogging. I am not sure where i went wrong im betting its a settings issue any help would be greatly apprecieated. Thanks for your help in advance.
Shwagiedo
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Can you attach your xml and also what exactly does the speed controller consist of? Is it a VFD?
Hood
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Hello All,
My machine is a harbor freight 7 X 12 mini lathe with a Stock FC250J/110V Motor controller, I am using a Gecko G540 to control it. I am under the assumption that the Stock motor controller is a VFD since it has a POT to control it. Here is the xml file I am currently playing with and thank you guys for any help or direction you may be able to push me in.
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weird wouldn't let me post xml for a while
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Are you controlling the spindle speed via the pot?
Hood
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Hood,
No I have the vfd wires from the G540 in the P1 , P2 , and P3 pot connections on the motor controller board.
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Ok do you have any idea what the controller for the spindle is? Can you take a pic of it ?
Hood
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yea np here is a pic of the controller I believe it is made by SIEG, also here is a pic of my spindle speed pick up, and how I setup my X axis. Thanks again for your time and help hood
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ok so I did some testing on my setup if I unplug the X axis from the G540 and manually Jog the X axis the spindle speed does not increase nor decrease, but if I put in the S200 command I am actually seeing 400 RPM on spindle speed with 2.429 volts out of the G540.
Now if I plug back in the X axis the spindle speed increases if I jog the X axis and decreases when I stop jogging. now just applying the S200 command and turning the spindle on while X axis is plugged in I am seeing a spindle reading of 103 RPM & voltage of 2.317V out of the G540 with out jogging and a RPM of 400 & 2.42V while jogging.
I am sure my speeds are off because I do not yet have the pulleys setup correctly in mach, how ever I was able to determine my maximum low and high gear speeds for the spindle via a Tachometer on spindle. I have not figured out the ratio between my drive motor and the spindle I will need to pick up a hand held Tachometer sometime this weekend. That's all the info I got atm thanks for looking guys any help or ideas would be greatly appreciated.
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Sounds like you have some sort of interference with your wiring, ie the spindle controller wire is picking up noise from the motor wires. All wiring in low voltage systems should be shielded and the shield properly grounded.
Hood
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Hmmm I never thought about that, I have my VFD wires coming out of the G540 and going through a Db9 connector I mounted on the outside of the controller box and inside the box are none shielded wires to the motor controller. Do you think I could be getting the interference inside the box ? I am assuming the serial cable I bought to use for the Db9 connections is shielded. and I only have about 18" of lead wires coming off the X axis until it has a db9 connector attached to it. that I am hooking up to the G540. Hood would you know a good way to check for electrical noise ? via DVOM or some other instrument?
Thanks again for all your help hood
Shwagiedo
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Ok so I got a few mins to play around again after work, so I wrapped the 4 lead wires coming out of the stepper motor in some wire shielding I got from work which did not help at all then I wrapped the motor and still no change. so I decided to use my Y Axis in the X axis port. now the Y axis is not mounted to the machine yet, so I give a S400 command spindle speed is almost on the money and I start to jog the X axis using the Y stepper and cable which is sitting on the shelf below the machine, and the spindle speed does not change at all. So I thought let me bring the stepper closer to the machine and motor controller board, and no change in speed at all. Then I touched the stepper motor to the Mount for the X axis on the machine and the spindle speed dropped. I pulled the motor off the mount and the spindle speed increased. I touched the stepper to the frame of the machine and the spindle speed dropped then I jogged the stepper and the spindle speed picked up again. I am a little baffeled at what is going on here I am hoping someone could shed some light on this for me.
My X axis mount is mounted directly to my X axis lead screw support bearing bracket. here is a pic of the setup again
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ok was bugging me so I thought I would give it a try before I went to sleep I fired everything back up and gave a S350 code and had the X axis hooked up spindle was running slower than 350 RPM. So I got the idea to run a ground wire from my 48 volt power supply for the G540 to the frame of the machine and would ya know it the spindle smoothed out to near 350 RPM. but if I jogged x axis the spindle speed still increased but only slightly. Any thoughts anyone ?
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Sorry couldnt reply yesterday as the topic was locked for some reason.
Anyway, ideally all wiring should be shielded, especially low voltage wiring but also shielding mains and stepper motor wiring can help. The current thought is to have the shield connected only at one end (usually controller end) and all shields should go to a single point and that point be connected to Earth.
Hood
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Ok so I used a spare wire in the DB9 connector and went from an earth ground inside my BOB enclosure to the the earth ground on my machine and it cleard up the spindle issues. My only question as i am puzzeled is if the machine is earth grounded by the wall receptical and the BOB enclosure is earth grounded by another wall recepticle why must i run a ground from the BOB enclosure to the machine. Probably a dumn question but i am doing my best to learn these issues and how to solve them. :) Thanks alot again hood for your help you helped push me in the right direction. Im sure down the road ill have some more issues to work out lol. Btw would anyone know how i could measure backlash i know i have some in my x axis but not sure how to determine exactly how much to let mach know.
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Getting rid of noise can be problematic at best and basically can just be a case of trial and error. Industrial machines solve this issue by having 24v I/O rather than 5v and thankfully quite a few controllers are now on the market which utilise 24v. Previously on my machines I had to do the conversion to and from 24v myself but now it is done for me and makes for a much neater system.
Regarding backlash, if you have a Dial Indicator you can place it beside the axis you are checking, jog onto the point then zero the DRO in Mach. Make sure you are in step Jog mode then back off the point whilst watching the needle, as soon as the needle moves you stop jogging and the value in the DRO in Mach will be your backlash.
Hood
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I am amazed by how many problems we see here from electrical noise and poor shielding. I was extremely careful shielding everything on my machine and having just one common grounding point. My configuration has very long wires, about 12 feet for every cable, and I spent a fortune on shielded cable, even though I got a pile of cable for free. However I have had absolutely no glitches with anything, so I think it was worth it.
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Don't know if anyone can help me on this next issue I am trying to calibrate the spindle and for some reason I can not get the spindle to start up when using calibration menu in mach. If I give a S500 command I am seeing 331 RPM, then I shut the spindle off S key, then go to calibrate spindle menu give a control of 200 "my minimum speed" then click spindle on/off nothing happens and I can see the screen states PWM bumped to minimum setting. Any clue guys?
Hood thank you for the back lash instructions Z axis is all dialed in now thanks again.
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ok so I can go into spindle calibration now and tell it to use pulley #1 my minimum speed now is 0 and I tell it to start at 200 rpm, then I click spindle on/off. the spindle starts up and is 170-185 ish then I click Autocal and the spindle stops and the calibration seems to keep going but the spindle just stops and nothing happens. I watched a video on youtube of a guys doing this and seems to work fine for him not sure as to why my spindle seems to shut down and not go through the calibration process. here is another copy of my latest XML file.
Any ideas would be greatly appreciated thanks again guys.