Sunday, 16 December 2012

Progress on the Mill build

Its nearly Christmas,

My mate found time to finish off 90% of the dividing head ( YAY ). I rushed it home with the PC and controller box, attached a power plug that i had been putting off until i had a reason to. Then proceeded to install a copy of ECM running on Ubuntu 10.04 from a liveCD image to a USB key then onto the 4Gb CF card. the motherboard seems to be a little slow booting up so i may sink another $50 into the build and buy a 8GB sata SSD and liberate the processor..

Once I had the OS and EMC installed I Proceeded to attempt to configure EMC. this turned out to be in total a 2 day ordeal. first the problems were getting the LiveCD image to actually boot, just had to find a magical usb key and the right settings in the bios and standing on one foot with one eye closed :).

I purchased the Stepper interface quite a while ago and the exact user manual for my board so i started looking on ebay, i couldn't find the exact seller with the same unit. I did find several that looked the same, but when i downloaded the data sheets for them the pin maps just didn't line up properly, the 5 axis data sheet had the right title and said it was for the 5 axis model but the pin table only showed 4 axis, another had only 3 axis, then finally i found one that had all five axis labeled..

I ran the stepconf program to configure the stepper drivers as per the data sheet, but weird stuff happened, so then i looked at my cable that i have made to go between the par port and the stepper driver, turns out that this was rather wrong, so i turned the ends around about 5 times until i finally got the right orientation so pin 1 is connected to pin 1 and so on. i tested the results and yet another fail, not sure where the problem was i started testing, i grabbed a LED and jammed it in the end of the cable, then clicked on things in the gui and all the pins matched their functions. So then i figured i should probably check the pin functions on the stepper board.. this was a little difficult, i had to first work out which pins would make a led light up then try and work out what that led meant, in the end i managed to get each Axis spinning in both directions when commanded to, some of the axis were being difficult but got there in the end.

At this point in time i have all the Axis responding to the GUI buttons, i have calibrated the XYZ Axis' according to the numbers, leadscrews have 16TPI = 1.558mm/Revolution, 200 steps per rev on the steppers, 1:1 drive ratio and 2:1 microsteps. this results in 251.9steps/mm. for the Dividing head it has 200 steps per rev, 1:3 ratio, and 16:1 microsteps, resulting in 26.7 steps per degree, this should be fine enough for what i want to play with. I should be able to cut some gears and worms, but first on the list is a triple hyena bolt. Arcol from the reprap forums has designed a really nice drive bolt that grips the plastic really well and doesn't clog up, i have asked in the past if he could make me a custom one that has three sets of teeth but at the time it wasn't worth his time as he gets his bolts that he sells made in a workshop by real machinists if anyone is wondering what sort of bolt they should use see Arcol's blog.

Before i have even bolted all the bits on to the mill i already want to program it... I want to write some gcode that will cut my bolt :) there are a few parameters that i will have to get from the Mill itself for the code to be complete but i will write it anyway, have i mentioned before i am an impatient and impulsive sort of person...
next post some Gcode to cut a Drive bolt..


 here you can see the dividing head sitting on the X axis, my mate made me a Angle bracket to mount the head to the bed as shown above, or to have the head pointing up so you could drill or slot a gear as well as cut the teeth.
here you can see how chunky it is compared to the rest of the mill. we should have no bounce or flex when this is mounted in either position. hanging out the side of the bed there you can see the profile piece that is becoming T nuts :)

video
here is a close up of the belt and pulley. in testing i have done on the bench here this little chuck has some torque behind it. the steppers are 269 ounce with a 3:1 ratio on it that should come out at over 60netwons/meter. that could be more torque than on the other axis :)

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