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vladdy
08-01-2007, 05:49 PM
looked around the shop two weeks ago, and figured I may as well make something out of the leftover steel that was stacked up...about 15 hours over two weekends, wound up with an appx 4'x4' cutter table, probably will wind up with an oxy/acetylene torch head...
hard out of pocket costs were $10 for two steppers, $26 for a pair of controllers, about $15 for wiring, and half a box of welding rods..:0
later this week will grab an old pc out of the pile, and try kcam...

plans??? not even close, tape measure to make sure table was square, rest was 'hold up and mark', more often just 'about three fingers wide'...

can't feel any play with just pushing on the axis, surprising with the quality [or lack thereof], in the components...

might be able to try a test run this weekend, and see how close [or how far out] it is from a square cut...:)

enjoy..

Weldtutor
08-01-2007, 07:44 PM
looked around the shop two weeks ago, and figured I may as well make something out of the leftover steel that was stacked up...

Very resourseful Vladdy!:)

That must have been a valuable "stack of steel" you raided for the table.
Do you have skate type bearings on tubes for the long rails?
What type of drive system will the motor & cross shaft power?
Keep us posted on your progress, you might end up with the lowest priced table build on the CNC ZONE!

All the best, for the weekend test.

vladdy
08-02-2007, 01:22 AM
not sure what kind of bearings, there were a bunch of them in the one bin, just under 1", fit a 3/8 bolt very snugly...washers for shims / spacers...total of eight, 6 on drive side, two on 'coast side', none for hold down, shoudn't need it with a 100lb cross assembly..[without torch head]

was going to try a gear reduction setup, but ran the steppers at 1.125a [30v], and they were pretty tough to stop just by grabbing the output shaft by hand...so made up a couple of seamless pipe adapters [5/8 to 3/8] and stuck them on the end of shafts, just 3/4 bulk threaded rod, left over bearing block from a small grain cleaner, endplay adjusted with judicous taps of a 'medium' adjusting hammer...:)
the travel nut [notice I didn't say zero backlash], is just a 3" long coupler nut with a cut taken out of it to give some 'squeeze' to reduce freeplay, the lock setscrews that hold it inside the pipe also double as tension screws..
the steppers were 1.4v 8a, running them at around 30v 1.125a, forget what brand of drives, 'think' the model was 2035 or something, max is 2a out, will try to see how it runs at 'half power' initially..
spent an hour tonight, wired up the steppers, found a 'reasonable cost' cable guide, just 1/2" steel strapping, seems to move ok, not sure how long it will last though..used flat 4 conductor trailer wiring cable, and figured may as well use the trailer connectors as well...

vladdy
08-18-2007, 01:50 AM
finally had some time to spend on the table and did some tests yesterday..
with kcam v4.00?? ran about 6 ipm onth heavy axis, 11 ipm on the cross axis, pretty slow, rough and ragged sounding at higher speeds..
loaded mach3 trial version, didn't run from start, for some reason had to set 1/2 pulse mode..? 25kz core on p667 box...
ran up to around 40 ipm on both axis, but relatively weak at higher speeds, set the drivers to max 2.0A output, and firmed up some...
torque was measured by hand [literally], and with gloves it takes a pretty firm squeeze to stop the steppers, should be sufficient for plasma or torch usage..
loosened up the bearings a little, just so that they 'just about' turn by hand when under compression, runs a little smoother, quieter, but no extra torque noticed..
an appx 10lb sideways pull on the far end of the cross axis will allow the beam to deflect just around 1/32", there "shouldn't" be that much cross torque while running, so I'm assuming that's acceptable..

to get higher than 40 ipm I'm assuming that I would need stronger drivers as the stepper are rated for up to 8A and I only have 2A output max right now...I noticed that around 25 ipm the torque was quite a bit stronger so might look into some kind of replacement screw instead of the 8tpi 3/4 allthread rod that is on there right now..easiest replacement may be 3/4 acme rod as all that would require retrofit would be the rod and nuts, and an hour of lathe time or so...
tried adding a 3lb gear hub to the far end of the screws, to see if it night possibly remove some 'harmonic' speed limitations, but didn't seem to make any difference on max ipm, was a bit smoother sounding though...?
later on this week might get time to mount some home switches, and wiring out to a solenoid for a small gas ax head...

Oldmanandhistoy
08-18-2007, 03:36 AM
to get higher than 40 ipm I'm assuming that I would need stronger drivers as the stepper are rated for up to 8A and I only have 2A output max right now...I noticed that around 25 ipm the torque was quite a bit stronger so might look into some kind of replacement screw instead of the 8tpi 3/4 allthread rod that is on there right now..easiest replacement may be 3/4 acme rod as all that would require retrofit would be the rod and nuts, and an hour of lathe time or so...
tried adding a 3lb gear hub to the far end of the screws, to see if it night possibly remove some 'harmonic' speed limitations, but didn't seem to make any difference on max ipm, was a bit smoother sounding though...?
later on this week might get time to mount some home switches, and wiring out to a solenoid for a small gas ax head...

Yes that is correct; you are only using around ΒΌ of the motors available torque at 2A. Also higher voltage will give you more torque at higher speeds.
Sounds like you def have probs with rotor inertia have a look here for a possible fix. http://www.cnczone.com/forums/showthread.php?t=32284 or find a more suitable motor.

John

vladdy
08-19-2007, 02:48 AM
just wondering if the steppers are maxed out, as far as PPS is concerned, by my calc, 40 ipm with 8tpi rod means 320rpm, and single step with these 1.8 degree motors 64,000 ppm, or 1066 PPS, from what I have been able to tell by searching through the posts here, I may be close to the limit for these steppers..