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New from Old / Re: The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
« Last post by awemawson on July 18, 2018, 04:09:31 PM »
Well an extremely frustrating day today  :bang:

I managed, by re-wiring hydraulic solenoids, to unlock the turret, allowing me to turn it manually and set it in the correct position, thus being able to initialise it - hooray. I could then select tools at will, jog where I wanted, and spin the spindle at great speeds forward and reverse.

However, once turned off and back on I couldn't even jog, the control reporting a fault with the KTK Mentor. Now I've been through EVERY wire into and out of the Mentor, documented them and inspected any that might report a fault. None do, and the drive says it's ready on it's front panel.

BUT - if the power to the Mentor is dropped and remade by dropping out it's isolator the fault very occasionally clears :scratch:

Once this fault is cleared I can jog as I wish. So two issues to bottom, the Mentor issue and the Turret issue - I did at least manage to winkle circuit diagrams for the Turret SMCC servo card out of Delta Tau in California today  :thumbup:

I think tomorrow I will log  the voltages on all 41 of the Mentors interface connections with the fault 'ON' and try to clear it and repeat the logging - hopefully that will show how the controller knows that there is a fault  :scratch:

. . . meanwhile I'm going to finish off this bottle of Pinot, I'm sure things will look better after that  :clap:
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Project Logs / Re: Building a New Lathe
« Last post by PekkaNF on July 18, 2018, 12:09:33 PM »
Pekka, you might recall I did a similar Tee-slot table before, though that time I just added the tops of the Tees:

https://madmodder.net/index.php/topic,8900.0.html

Thank you, I remember that one, but it was good to read again.

Pekka
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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on July 18, 2018, 10:46:52 AM »
Pekka, you might recall I did a similar Tee-slot table before, though that time I just added the tops of the Tees:

https://madmodder.net/index.php/topic,8900.0.html
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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on July 18, 2018, 10:41:51 AM »
Sorry Andrew.

Pekka the holes in the cross slide and the T-bars were all done on the mill. Admission: unfortunately the first time I drilled the cross slide I hadn't checked the mill vise from the last time I'd used it, and it was slightly off perpendicular.  :palm: :wack:

But, since I decided that 1-3/8" spacing between rows was smarter than 1-1/2" (because I could use 1" wide bars instead of 1-1/8), I plugged the old holes, indicated the vise in accurately, and re-drilled everything with the altered spacing. Because of the change in spacing, none of the newer accurate holes impinged on the old holes. so it was all in new material. Then I tapped them. So to answer your question, the T-slots should all be accurately parallel with the bed ways.  :med:
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How do I?? / Re: Reversing D.C. Motor Direction
« Last post by Pete. on July 18, 2018, 09:08:37 AM »
No it's shunt wound.
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How do I?? / Re: Reversing D.C. Motor Direction
« Last post by John Rudd on July 18, 2018, 04:07:42 AM »
I dont comoletely understand what you have there, given your description.....

A dc motor has magnets, no wound field coils....it will run on a dc supply only

A universal motor doesnt have magnets, but wound field coils....will run on either ac or dc supply

Any how, in either case, swapping over the wires to the brushes will change the direction of rotation....

Do be careful..... :zap:

My lathe has a DC-only motor with field windings.

Ok, a generalisation, there's always an exception like a car's starter motor

In your case ..presumably the field windings are in series then with the armature? That is the same configuration as a universal motor that can run on ac.....
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How do I?? / Re: Reversing D.C. Motor Direction
« Last post by PekkaNF on July 18, 2018, 03:52:22 AM »
If I understand it correctly you have series connected universal motor.

https://en.wikipedia.org/wiki/Universal_motor

This thread should answer you question more clearly than I can:
https://electronics.stackexchange.com/questions/253867/reversing-direction-of-an-ac-universal-motor

When these motors are run in DC, you just swap polarity and it runs then opposite direction. Obiviously this does not work on AC, there you neeed to reverse the field connection with respect to the armature (often easiest to swap the wires on brushes).

However, there is one caveat: some motors may be optimized to run one direction:

1) Radial fan may have curved blades pull the air more effectively when the shaft it rotating the correct direction. Axial fan is allways designed to cool primary the commutator.

2) brushes might be "advanced" to improve efficiency or increase RPM. You see that easy when you look at the rear of the motor and compare bruches axis with the field winding, if all looks symmetrical you are good to go (same charachteristics, both direction). If the brush holder is rotated or tilted, you will notice different performace. Sometimes the parts can be remounted.

About the brushes this is pretty good introcuction:
http://www.morganelectricalmaterials.com/media/1996/technicalhandbookglobalproof_0.pdf

p.12-15 is good info on how to read bruches or commutator to identify problems.

Pekka
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Project Logs / Re: Building a New Lathe
« Last post by PekkaNF on July 18, 2018, 03:21:41 AM »
I have a big interes on this latest T-slot construction.

I haven been planiing/doodling a new top slide for my small lathe. Original is that shitty that it is next to useless. I use it only when i can't avoid it, other times it is replaced with a rires block on the cross slide - much better and more stable. It also has two holes for mounting this riser, places are defined to maximize working envelope, original fixing point wast not even compromise, it had bad sides from the tool overhang and diameter capacity.

Milling the T-slots is the industrial practice, but not always easiest to do in HMS. And tou need a bigger piece on stock to start with.

Fabricating the pieces gives you more versatility and you can replace the parts. Also looks easier to make on small mill.

You planning to align the T-slots accurately with the top-slide I.E. nearly perpenticular to spinde axis?

Pekka
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Project Logs / Re: Building a New Lathe
« Last post by awemawson on July 18, 2018, 02:51:23 AM »
 :worthless:
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How do I?? / Re: Reversing D.C. Motor Direction
« Last post by Pete. on July 18, 2018, 02:21:25 AM »
I dont comoletely understand what you have there, given your description.....

A dc motor has magnets, no wound field coils....it will run on a dc supply only

A universal motor doesnt have magnets, but wound field coils....will run on either ac or dc supply

Any how, in either case, swapping over the wires to the brushes will change the direction of rotation....

Do be careful..... :zap:

My lathe has a DC-only motor with field windings.
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