Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Bhohbein on January 31, 2015, 01:24:56 PM
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How can i make my machine more precise. y axis is running longer than my x axis. Ive done motor tuning and step calibration. I used a very pointy bit and drew a line on a piece of wood and used a micometer to measure and its still off. I need to be more precise then this. I do have a chinese router with the blue controler. Im using windows 8 and a uc100 motion controler.
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The machine normally will be as accurate as YOU set it up to be in Motor tuning. IF you are loosing steps OR you have set the steps per incorrectly then you machine will be OFF.
There are volumes here on setting up Motors step per. Same with lost steps.
(;- )TP
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ive done searches on lost steps and precision and the read is too technical for me to understand.. haha ive tried to set the machine up as exact as i can but im still off almost an 1/8 in on an 11in circle and a 4 bolt hole circle wont match up when 2 diffrent cuts are matched up.
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You could use a yard stick to measure and get better accuracy than 1/8". ???
Use the axis calibration feature which can be found on the Settings screen (ALt 6) lower left corner fo the screen.
The axis move you make shoud be as long as possible with backlash removed. Refine to hearts desire........
RICH
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Ok tried a better way of measuring my steps per unit and tried setting backlash. Still trying to figure out how to measure backlash more accurately had it set to .005 on y and .004 on x and still was off alittle reset my kernal speed to 25000 was at 35000 and retuned motors and now the the stepper motors stall and jerk while running x and y at same time while jogging. Does not matter motor speed or accel. Rest set to 35000 kernal speed and still haveing the same problem am i doing something wrong.
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If you guys dont already know Im new to cnc and machining and not very good with computers haha. I was a mechanic for 16 years so Im pretty good at figuring stuff out but this is too much to learn all at once trying my best though
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Turned off backlash and reset system is working fine now turned back lash back on and the motors stall and jerk again is my backlash set to high its only at .004 inches ill try and recalculate
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Take a look at this video & see if it helps. https://www.youtube.com/watch?v=A27nOkTFYDY
I had trouble until I reset the settings like Hoss shows.
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thanks that did help. Now when im measuring backlash i type in a g0y1 g0y0 code and measurehow much its off correct does it matter what direction im doing it, Should i be checking a larger or smaller distance
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does it matter what direction im doing it, Should i be checking a larger or smaller distance
In general:
A short distance is fine and you only move in one direction and then measure the non movement (backlash) of the axis when going in the opposite direction.
Some things and refinements to be aware of:
1. Steps per unit need to be correct for best accuracy of backlash measurement.
2. Backlash can vary some due to mechanical items.
3. There is no such thing as ZERO backlash, may be small but it is there, just a matter of amount
4. Bearing preload can affect backlash location along the axis since you need to apply opposite force to load up
the bearing. You need adjust / remove any play in the bearing and yet minimize amount of torque used post adjustment.
5. Backlash can vary due to the quality of the screw / nut. You will have what you got. Some screws are not linear, IE
+- accuracy over say 3 feet, but that +- can be happening in say a 12" section of the screw! Or the screw pitch can be slightly
different in the opposite direction.
6. Belt tension, quality of belt/pulley/gears / rack etc come into play etc
So rather easy to get the backlash down to some small amount,but, to really minimize it you got to get very meticulous
about everything. Thus in the end you got what you have and overall mechanical system affects backlash.
RICH
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I went overthe hole machine to make sure everything is tight checked backlash. Had no backlash on x and .002 on y. Reset steps and motor tuning Checked steps on y to 11 inches and was exact on dial indicator. ran a 5 inch circle cut y cut to 5.034 and x cut to 5.014. cut a 3 inch square y cut to 3.004 and x cut to 3.023. Can the program be off im useing mill wizard.
Also when the program end i move the gantry out of the way a few inches then hit go to zero and its not in the same place. My machine is chinese should i get new drivers if so what should i get. Im getteing shielded wire and im going to redo all my cables
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does anyone else have a problem with the mill wizard gcode . Just trying to figure out why stuff is not coming out right
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then hit go to zero and its not in the same place
Not sure what you mean by not in the same place.
Off a little or a lot?
Go To Zero - axis will move to the current offset if there is one........
RICH
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When i set a piece to cut,i bring the router over to the center and zero the dro. When the program is finished i move the router out of the way put a new piece of material in and hi go to zero. The dro goes to zero but the routers off between .030 and .070 most times not all the time
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If your steps per unit are correct, backlash is set correctly, the axis mechancs are of reasonable quality and your velocity / accel
vlaues are proper for you machine, then I would guess that you should do better than what you are seeing.
What more can I say................
RICH
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Try reducing the X & Y axis's Velocity and acceleration settings by 50% then retest. It sounds a lot like lost steps.
(;-) TP
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I will try the motor tuning again. I have the chinese controler and would like to up grade to equipment that will work best for me. I just dont know what to get. Do you guys have any suggestions on what i should get. What drivers and motors and mother board thing do you recomend.
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I ordered a g540 and a new power supply and new stepper motors and cables. Hopefully this will make me more accurate