9x20 Lathe CNC conversion

jumps4

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today i made a riser block from 1"x4" bar stock for the quick change tool post and the new breakout board got here, $1.95 on ebay it's perfect nothing but a plug and terminals. the numbered points in the center of the card are for volt meter testing each pin. this will solve my slow speed problem letting my go from 25000hz to 100000hz 4 times the speed or higher microstepping for smoother motor movement. when i get the old one out i will post a pic of it so if your reading this to do a build you wont use that one. i installed the tach pickup for threading and even at the speeds i'm running i could thread. the sensor i have is acting up though so i'm waiting for a new one then i'll post a vid of the lathe threading. thats the real test for a cnc lathe, "threading" if you get that working good everything else will work good.
with acme screws the lathes backlash is .002 with ridged couplings and i set mach3 to compensate. the spiral couplings were too weak for the tight gibs and were flexing giving me .010 backlash. the way i built the z axis the screw is supported by the nut and thrust bearing on the other end so a ridgid mount worked well there also.
if the steppers will be fast enough after the new breakout board to do course threads at 145 rpm i wont need to change to a dc motor.
steve

DSCF0421.JPG DSCF0422.JPG DSCF0425.JPG
 

okent

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Looks great! Also looks like it's working. Is that a piece of brass in the chuck that you have turned?
 

jumps4

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everything is working but i didnt turn the brass since it has been cnc. i leave that in the chuck to protect the face of the jaws. i will install the new board today and retune the motors. then i want to make some shields for the motors and screws and a backsplash before i start using it. i am going to use flood cooling on the lathe once it is done.
steve
 

jumps4

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I replaced the breakout board today and boosted the speed to 100000hz i took before and after videos.
the $cheap board is 4 times faster
all i need now is the new irsensor for the index/tach and i can thread, it's working now but the sensor is not trustworthy
i made a few test cuts today and i show a pattern in the cut in time with the screw threads so i ordered a zero backlash shaft coupling $60.00 for two. the leadscrew is from the xz45 mill and a few thousands off center shifting the carrage .001 as it turns, darn chinese lol if the coupler does not correct the problem i'll have to sleeve the ends and regrind them true to the threads.
steve

before i replaced the board
[video=youtube;DWM-9EL636U]http://www.youtube.com/watch?v=DWM-9EL636U&feature=youtu.be[/video]


with the new cheap board (no chips)
[video=youtube;c-JsSNlUv9o]http://www.youtube.com/watch?v=c-JsSNlUv9o&feature=plcp[/video]
 

jumps4

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if you order a cnc kit, motors and drives and they send this breakout board throw it away it's junk ( bottom pic )
the one i show with no chips is the one i used the drives are opto isolated so this was fine for my system. ( top one )
steve

DSCF0425.JPG DSCF0428.JPG
 

8ntsane

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What a differance in speed. The first vid seemed to be slooow motion. After you fixed the problem seems much better.

What puzzles me is how did you know that was the problem? Common thing, or just my lack of understanding?
 

7HC

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What a differance in speed. The first vid seemed to be slooow motion. After you fixed the problem seems much better.

What puzzles me is how did you know that was the problem? Common thing, or just my lack of understanding?


I've met Steve, he's got a good understanding of electronics and he's pretty smart at figuring stuff out.


M
 

8ntsane

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I've met Steve, he's got a good understanding of electronics and he's pretty smart at figuring stuff out.


M

I wish I had better understanding of that type of stuff. Im wanting to learn, but find CNC in general can be very overwelming to get your head wrapped around the basic stuff.

I guess if it was easy, more guys would be doing it. ;)
 

jumps4

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it wasnt very technical to figure out the problem. the cnc lathe and my zx45 cnc mill i just finished use the same pc and uc100 usb controler connected to a"abcd" printer switch to switch from machine to machine so i knew the pc was putting out 100000hz, but at that speed the lathe would do nothing. the lathe has the same brand of drivers an power supplies as the zx45 mill so i knew it wasnt them so i checked the output on the breakout board and i have pulses going in but not out. the board had the 5v to power it. so it had to be slow optocouplers, i reduced the speed of the uc100 to 25000hz and it started working. so i purchased a breakout board with no optocouplers and everything was fine.
i have had my father visiting so i havent been working on the lathe and i'm waiting on two parts to finish it. i still have to make splash shields and a coolant pump system also. when i get it the best it is going to run i'll post a video of it threading or making something else. if it is too slow to make course threads then i'll purchase ballscrews and start over. but right now it looks like it's speed will be fine.
steve
 
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