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Author Topic: Some basic setup questions  (Read 3828 times)

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Offline Kristin D

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Some basic setup questions
« on: April 27, 2008, 03:08:32 PM »
I finally got all the bugs worked out of my HobbyCNC Pro driver board, got XYZ humming along and getting ready to connect some motors to my Taig lathe. So now comes the questions, I can set full, half, quarter step on the board and also see something in Mach where there is a Shereline half step mode and probably other settings I have yet to discover. For some reason Dave over at HobbyCNC seems to suggest half or quarter step settings on his board, if I understand it this reduces the available torque from the motor.

So since I am now thoroughly confused I'll start with the cross slide, the leadscrew drives that .050/rev so do I set the motor tuning to 20*200 or 4000 steps/inch? What is the pulse for step and direction do or control? I think once I have a clear picture of how all these things interact I'll be able to transfer to the carriage drive, I have two options there, I can drive it via the rack that is standard which moves something like .596"/rev or I have a set of worm gears and a spur gear to reduce it to .051/rev which I have yet to have built up(I was hoping to CNC the parts for that). The Z axis for the milling table would be the same as the cross slide.

I know read the manual, well as soon as I can I am going to have it printed out so I can, just can't seem to follow it reading on screen it's easier on paper where you can stick post-it notes to the important pages.

Kristin

Offline Hood

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Re: Some basic setup questions
« Reply #1 on: April 27, 2008, 05:48:23 PM »
Its usually best to set to the highest microstepping that you can, well up to 10 I think, over that I am sure I remember Mariss saying its not worth it and if Mariss says that then you know its true.
 So best probably for you to go 1/4 if thats the max of your drives. Setting the stepping to 1/4 wont affect the torque adversly, it will make things smoother.
 The steps per on the details you give above would be 0.05 per rev so to go one unit (1 Inch) you will need 20 revs, your motors if 1.8 degree steppers will have 200 steps per rev and with 1/4 stepping it will be 4 times that so 20 x 200 x 4 = 16,000 steps per unit.

 I know what you mean about the manual and reading on screen, I am exactly the same.

Hood

Offline Kristin D

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Re: Some basic setup questions
« Reply #2 on: April 27, 2008, 06:32:24 PM »
Thanks,

I can actually set jumpers for 1/8 and 1/16 step on the board but if Mariss says over 10 is not worth it, from his lips to god's ear! What is the pulse width setting, I am still not clear on that my board seems to work with it set at zero or 10 ms??? I am about to go back and set up a motor to drive the cross slide so I will "play" with the settings and see what it looks like, or sounds like running a static dummy program so nothing can crash. Might get to the printer tomorrow but sometimes they are backlogged with printing forms for the town or county and just can't do a job right away, well once they copy the file I'll just have to go back later in the week and pick it up unless the owner who lives nearby will deliver to my gate.

I am actually getting pretty excited about getting this all running although as I just bought another Taig micro lathe the other day I may wait a week and modify that one as the CNC monster as I will not feel so bad about drilling and tapping holes in a less pretty older model for mounting brackets and will not have to worry about making it so the motors are removable to convert to manual operation when I need it.

Kristin

Offline Hood

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Re: Some basic setup questions
« Reply #3 on: April 27, 2008, 06:47:28 PM »
Where are you seeing pulse width? if its the Step Pulse then some drives need a slightly longer pulse time than others, if yours works fine at 0 then leave it there, if you hae random missed step issues then bump it up a bit. If you still have issues then Sheline Half Pulse might help. Dont worry about them unless you have problems ;)

As for converting back to  manual operation, you will probably find you never do that. About 4 years ago I converted a manual Bridgeport to CNC, I was determined that I would keep the crank handles as I thought I would use the mill maybe 50% of the time manually. After a few months I had never even touched the cranks so I got out the angle grinder and chopped them off :D If its just a quick one off face or whatever its easier to use the MDI line than crank handles and if its a bit more then the wizards do most things.

Hood

Offline Kristin D

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Re: Some basic setup questions
« Reply #4 on: April 27, 2008, 07:07:57 PM »
Well just as an experiment I set up at 1/8 step, 32000 steps per inch and about 75" a min with a moderate acceration, sing went the motor and stopped turning, cut back the feed rate and acceleration since the top of the curve was off the chart and they seem to work reasonably well, I think I will stick with half or quarter step as the old finger on the gear torque test seems to show a loss of power at 1/8 step no matter how slow I set the feed and acceleration, but it's been educational.

Thanks for the step & dir pulse answer, apparently my board is happy with zero as it seems to work all right there. Not wanting to go to the calculator I suppose longer pulse and higher step rate must cross paths at some point and stall the motors also.

Thanks for your input and not telling me to "RTFM" as I have gotten on other forums when asking questions, I ususally try to read or at least skim over the manual but somtimes if you don't know the right terminology it's impossible to look up the answers.

Kristin

Offline vadude

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Re: Some basic setup questions
« Reply #5 on: November 16, 2009, 08:10:27 PM »
Hello everyone,
Does anybody has a dxf file for a spur gear or at least direct to where I can get one without having to draw in autocad myself?.I am working a hobby project that requires a spur gear.I am hoping to modify the propective dxf file it to suit my application
No Pain No Gain

Offline Tweakie.CNC

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Re: Some basic setup questions
« Reply #6 on: November 17, 2009, 04:01:10 AM »
Here is a link for the spur gear:-

http://www.forestmoon.com/Software/GearDXF/


Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.