Random stuff, reduction, servo motors, ideas and thoughts

the 5V on the BOB seems to not stay on all the time. just when first turned on for some reason? the bob as two LED's and while the two are on the 5V shows up but only stays on for about 15 to 30 seconds then goes off after that. the one LED has relay marked beside it and that seems to be the one that goes out but noticed there is a jumper built into the BOB to switch between the use of a 5th axis or the spindle control with the built in relay. i'm not sure if that has anything to do with the 5V not staying on or not?

i will have to mess around with it some more tomorrow. China strikes again probably would have been easier to pick up something better documented. glad it was only $10 seems like the computer has the needed 5V source if i can get it to stay on i think i found a PDF on this BOB or the one it was copied from anyways

not sure what i did but it works now one thing i did notice about this cheap board was the screw terminals are junk and don't work very well. but what do you expect for $10

going down to 48V is noticeable from 70V but it is what it is i guess i'm moving under power at least so as long as the computer provides a good 5V these work without the dedicated 5V supply but this kind of set up is about a thing of the past honestly

if it is not one thing it is something else. got everything moving to later discover binding on my long ball screw. ripped that apart to find some issues with the ball nut. with the first nut it had 3 circuits with the plastic returns so when problems began those got messed up. the silver lining was the soft plastic gave room to keep the screw from harm but the nut was toast.

i guess the moral of the story is maybe grease is not good for linear motion slides and a way oil might be better suited? i think the grease kept the balls from rolling and caused some problems. i also seen some bad signs on the bearing blocks for the long axis, looked like the plating on the ball bearings was starting to flake off. so since i had to rework some stuff i went over that with a fine tooth comb to avoid it from happening again. put a new ball nut and new bearing blocks on this thing.

this is turning into the never ending build from hell

long story short i pushed my spindle to hard one to many times and killed the driver board i think. which in turn got the wheels turning and is usually where i dive down a rabbit hole and come up with a half baked idea Youtube is great for this seen some people doing some interesting stuff with treadmill motors and the MC-60 drives. it started off with the knife guys making belt sanders from them and then lead me to find some guys using them on mini mills which is basically what i have on a gantry machine. i just happen to have a treadmill pushed in the corner doing nothing so i tore into it to see what kind of goodies i could find inside

what i found was the MC-60 speed control board and a 2.5 hp DC motor only problem is this thing is old and the manufacture is not around anymore as far as i can tell? i was trying to figure out how much torque this motor has? taking the info from the ID tag i'm guess it is rated at somewhere around 2.5 Nm ? does this sound about right ? and the original mini mill motor i was putting at about .9 Nm

looking at a way to drive things i can reduce the speed to about 4000 rpm from 7100 rpm or do 5500 from 7100 rpm if this thing is big enough to do away with the high and low range. i would like to do a 1 to 1 ratio and get the full 7100 rpm but i doubt i would have much luck in the torque department in slow speeds?

it was interesting to see the two motors side by side since they are close to the same size but as you can see the specs are quite different

i was looking at things trying to come up with a starting point that was not to involved to start with. i have a motor pulley that can be bored out to fit the bigger motor but the original low range gets cut away doing this since the mini mill motor has a 9mm shaft and the treadmill motor has a 17mm shaft. if i go by what that is rated for it's still a step up from the original 4200 rpm to 5300 rpm,

i did not even think about direct drive so i will look at that option so thanks for the input. i'm not sure if i can do it or not though since the flange at the base is so big on this treadmill motor.

any kind of spindle speed gain would be a huge bonus even an extra 1100 make a big difference in material removal rates.

if things work well at 5300 then your idea would be he next step.

had some rethinking to work out but this is what i ended up with in the end. the drawbar was an issue because this motor has a big flange at the base so i had to cut some clearance for the drawbar with a burr tool by hand. the entire motor mount plate had to be remade and the bottom plate had to have some extra stock added for some mounting point for the swing on the belt tension radial grove. took a while to make since i had to do things old school with a rotary table on the Bridgeport mill. everything works well so i an happy with it as is.

so if this new motor has enough torque on the bottom end it will be a single pulley set up rather than the step pulley like the original and should top out at around 5,300 RPM. should be a safe starting point to play around with i hope so on with the pictures that's what everyone likes anyways

i did happen to come across this high speed drive kit for a different mini mill than the one i modified it could very well work if the bores are the same? i will have to look into it some more and see if it could work? what i have now will work for now but the timing belt drive seems to be a better choice i think for power transmission. this particular kit is a 1:1 ratio so that would loose some torque but take the spindle speed up to 7,100 rpm. i did look into what kind of bearings this head has and it has the 6206 bearings so that's a plus most of them seem to fall in the 10,000 to 12,000 rpm range and the worst one i could find was 7,500 rpm. the higher end brands were rated as high as 25,000 rpm so there is room to work with in that department.

figured i would post a picture of the drive system i was thinking so see if anyone had any feedback.

machinedude wrote:

what i found was the MC-60 speed control board and a 2.5 hp DC motor only problem is this thing is old and the manufacture is not around anymore as far as i can tell? i was trying to figure out how much torque this motor has? taking the info from the ID tag i'm guess it is rated at somewhere around 2.5 Nm ? does this sound about right ?

2.5 hp ≈ 1.86 kW
7100 rev/min ≈ 743.5 radians/s
1.86 [kW]/743.5 [radians/s] ≈ 2.0 Nm - so 2.5 Nm was a good guess!

The power on the nameplate is probably electrical (input) power, so you need to reduce the torque accordingly. If the motor is 90 % efficient then 1.8 Nm.

then that's pretty good for the type of machine it is. deflection will probably be an issue before running out of power at the spindle becomes an issue. i will get to play around with it this weekend since the rotary pot came today so it's just a matter of putting things back together and finishing the wiring which is not to involved at this point. i know the real test is going to be at slower speeds. the old motor was not very good on the low range so running faster worked but was hard on carbide inserts. got my fingers crossed and hoping it makes me giggle just a little bit