Lathe DIY - Lead Screw - Stepper motor

[mischmerz]

Howdy folks:

I was wondering if there is good combination between lead screw pitch and stepper motor specifications to get as close as possible to a perfect spiral. I am thinking about buying a 8mm pitch lead screw stage and power it with a stepper. My first calculations boil down to about 4 steps/second for a 33 1/3 cutting process - but I am unsure if this is good enough?

mm.

[EmAtChapterV]

Some folks here have reported success using stepper motors, but others (myself included) are concerned that the steps could show up as unwanted noise in the cut - 4 Hz is about the bottom end of cartridge and tonearm resonances, and bumping it up by a factor of 10 for lead-ins and banding is 40 Hz which could be audible rumble.

[mischmerz]

I am aware of this problem. I will try different size stepper motors driving a belt to reduce noise - so that shouldn't be a problem. I am more concerned about the motion of the cutter head. A 'normal' motor will spin continuously while a stepper motor will pause between steps - it's just a semi 'continuous' motion. I was wondering if there is something like a minimum of distance / steps to produce acceptable 'pseudo continuous' linear motion.

mm.

[rsimms3]

I'm going to be looking into this subject soon. What are the alternatives? DC motor with PWM adjustment? I bought a lathe with fixed LPI but mechanically controlled spiral controls via a 4 speed pulley system. I'm looking to replace the motor system for the lead screw to something modern and practical. I'm thinking I'll continue with a belt but make the motor speed adjustable. I'm not so concerned with a wide lead out as much as spirals between tracks as well as variable LPI.

[Gus]

I am aware of this problem. I will try different size stepper motors driving a belt to reduce noise - so that shouldn't be a problem. I am more concerned about the motion of the cutter head. A 'normal' motor will spin continuously while a stepper motor will pause between steps - it's just a semi 'continuous' motion. I was wondering if there is something like a minimum of distance / steps to produce acceptable 'pseudo continuous' linear motion.

mm.

i do not agree that with the motion of the cutter head because as you can see on the picture the fairchild overhead drive mechanism has gears like a stepper motor. i had modified my fairchild overhead with a stepper motor and it works very nice the only problem is the rumble at lead in - out grooves.

[mischmerz]

i do not agree that with the motion of the cutter head because as you can see on the picture the fairchild overhead drive mechanism has gears like a stepper motor. i had modified my fairchild overhead with a stepper motor and it works very nice the only problem is the rumble at lead in - out grooves.

I see - thanks. Well, I am going to try a fairly small stepper .. and if this little buddy won't pull the sled. I am going to use a NEMA 14 stepper. Everything else would probably be to big and to noisy. I will also use a tooth belt to reduce the amount of noise fed to the feed screw.

m.

[opcode66]

That should work just fine.

[mischmerz]

That should work just fine.

LOL - hope so. This lathe is designed to control your cutter head

m.