795, 895 (etc) DC motors

Bit off topic (sorry) but has anyone got experience with these smaller 24V DC motors?

This is not for re-motoring the U3 - which I’ve done already, a tremendous improvement - but for an auxiliary spindle.

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I believe the motor designation number relates to the physical size but I’m having trouble finding a general page as an overview of their characteristics. A google search brings up pages of items being marketed.

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Any advice and recommendations resulting from your practical experience would be much appreciated. I guess I’m looking for the best balance of size/weight and power, as it would be mounted on the slide. Quality and reasonable longevity are always good as well !

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I have a 24V supply with two PWM outputs, so that part is no problem.

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Thanks!

Re: Recommendations for stepper motors, controller, software

#63542

That whirling is remarkable - it seems with enough power you can do anything!

The challenge here of course is what can be done on the Unimat… with an ‘all the time in the world’ approach I think (virtually) anything is possible.

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A 3” inch flange with a Whitworth 12TPI thread would be the goal!

Re: Recommendations for stepper motors, controller, software

#63541

Well, that would be one way to do it, but it is not the normal way of milling threads. That would have everything mounted as normal in a vertical mill, and the cutter would enter a pre-cut hole, and do a kind of shimmy as it goes down, cutting the thread. The thread pitch and diameter are all under computer control, so one cutter can cut numerous different threads. Each cutter would cover a range of sizes, but different cutters would also be needed for different thread angles, 47?° for BA, 55° for Whitworth and BSF, 60° for metric and USA, 80° for Pg, and that then leaves the question of threads with rounded crests. However, with the dominance now of Metric and USA threads a small range of cutters would deal with everything. I don't see much happening with cutting external threads. I don't think industry has got used to that possibility yet. Most external threads are cut on lathes still, where again a single point tool can be used for a range of sizes.

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Thread whirling is a little like what you envisage, but they use an external circular cutter with multiple cutting edges. I was offered lead screws made this way. When I asked how long we could have (we needed about 4? metres, roughly 15 feet) they said they used to be able to do much longer than that, but somebody had built an office block where the car park had been, so they were a bit limited now. They had a hole in the wall for jobs too long for the workshop, but our mere 4? metres was no problem. The limit was the distance to the next building, or the maximum length of bar they could get. See https://genswiss.com/whirldata for some idea of how it's done.

Re: Anyone Actively Unimat?

#63540

I have decided to keep my original Unimat DB200 in its original configuration for the time being. As it is the only thing I have modified is the addition of two 150 watt DC motors with speed and forward and reverse controls. This is a huge upgrade from the original motors.

Maybe someday I will upgrade to full CNC but that is not in my plans for now. Most of my carver I spent working with CNC machines so I am very well versed in it.

Dick

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Re: Recommendations for stepper motors, controller, software

#63539

Ah doh, I get it. Sorry, I’m being a bit dense.

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The work is fixed flat on the slide, the main leadscrew and the one on the slide provide the X and Y movement, and the mill is the Z.

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Re: Recommendations for stepper motors, controller, software

#63538

开云体育

Nicely done although I think I’d miss the ability to use a manual down feed for drilling.

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And as for open loop my Electronic Lead Screw kit uses open loop on both my Gingery Lathe and South Bend Heavy 10L. ?As does MACH3 of which there are probably tens of thousands of installations.? And then there are the likely more than 1 million 3D printers reading G-Code and running open loop.

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My CNC JGRO based Router runs open loop with MACH3 on a WIN-XP system with no need to upgrade at this point.?? OTOH, my CNC Mill now does use AC Servos and although I don’t couple the encoders back into LinuxCNC like some do, the AC Servo Drive will create a FAULT signal if the steps in verses encoder feedback drifts past a max deviation.?? So it’s sort of closed loop in that the motor does it for me.

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John

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Show quoted text

From: [email protected] [mailto:[email protected]] On Behalf Of roycegb via groups.io
Sent: August 29, 2024 5:24 AM
To: [email protected]; Peter Brooks
Subject: Re: [Unimat] Recommendations for stepper motors, controller, software

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Peter,

The Unimat is used in the mill configuration with stepper motors on all axes including the Z axis.

The picture shows the setup after milling a dust cap for a French bicycle crank. The 23.35M1 thread had already been cut using a single point thread cutter. Unusual tasks like lense caps are ideal for this setup.

The system is limited by the Z axis range and cutter reach but after that will cut any diameter, pitch and rotation.

There also seems to be confusion on my CNC setup. For simplicity and cost, I use an open loop approach. If the stepper motor does not go where I tell it because it stalled, I need to start over at a lower feed rate. Typical Unimat tasks do not stall a stepper motor.

Royce

Re: Recommendations for stepper motors, controller, software

#63537

It usually takes several passes.

You just set the starting point a bit closer each cut. You can call individual GCodes from within the LinuxCNC position menu so it is simple to do manually. If I were doing more than a one off I would write a full GCode script. That's where things like subroutines, conditional OCodes and named variables in LinuxCNC are great.

The holder is hand made via Mert’s instructions somewhere in the archives. I tend to use small bits particularly for engraving and circuit board milling so brass works just fine. I haven’t measured runout lately but it was good when I finished it. It cut down on very small milling bit breakage.

Royce

Show quoted text

On Aug 29, 2024, at 11:34?AM, g steinback via groups.io <Gsteinba52@...> wrote:

Looks neat. How many passes required to milling threads to depth? And is that a brass collet holder?

Re: Recommendations for stepper motors, controller, software

#63536

Hi Peter:

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The work is fixed, the cutter orbits around the work.

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Thread size and tolerance is all software driven.

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Carl.?

Show quoted text

On 08/29/2024 9:42 AM EDT Peter Brooks <peter@...> wrote:

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What is turning the work in that setup? (I could be misunderstanding here…)

Re: Recommendations for stepper motors, controller, software

#63535

Looks neat. How many passes required to milling threads to depth? And is that a brass collet holder?

Re: Recommendations for stepper motors, controller, software

#63534

Peter - I tried that, it’s a nice design. I got the gears 3D printed but when assembled it suffered from slipping. Maybe I didn’t make it well enough (quite likely:-)

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Don - surely on something like the U3 rotating the work (slowly) would have the same effect as moving the table? Just trying to work it out in my head. The single point cutter would obviously have to advance as well.

Re: Recommendations for stepper motors, controller, software

#63533

When thread milling the work does not turn.? The milling table is moved so that the work piece will follow a circular path around the cutter.? Unlike taps and dies, one cutter COULD be used to mill a variety of threads, either LH or RH, internal threads or external threads, single-start or multi-start.? If you wanted to cut multi-start LH external threads with a 0.5mm pitch on 6" diameter stock - as long as your mill has the X-Y-Z movement capacity, you could do it.? I don't know why you'd want to do it, but you could do it.

Re: Recommendations for stepper motors, controller, software

#63532

I like the Unimat 4? hand cranked threading mechanism (that works well on a Unimat 3 as well)

Show quoted text

------ Original Message ------

From "Peter Brooks" <peter@...>

To "roycegb" <roycegb@...>; [email protected]

Date 29/08/2024 14:42:28

Subject Re: [Unimat] Recommendations for stepper motors, controller, software

What is turning the work in that setup? (I could be misunderstanding here…)

Re: Recommendations for stepper motors, controller, software

#63531

What is turning the work in that setup? (I could be misunderstanding here…)

Re: Recommendations for stepper motors, controller, software

#63530

Peter,

The Unimat is used in the mill configuration with stepper motors on all axes including the Z axis.

The picture shows the setup after milling a dust cap for a French bicycle crank. The 23.35M1 thread had already been cut using a single point thread cutter. Unusual tasks like lense caps are ideal for this setup.

The system is limited by the Z axis range and cutter reach but after that will cut any diameter, pitch and rotation.

There also seems to be confusion on my CNC setup. For simplicity and cost, I use an open loop approach. If the stepper motor does not go where I tell it because it stalled, I need to start over at a lower feed rate. Typical Unimat tasks do not stall a stepper motor.

Royce

ZAxis1.jpeg