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#GR #GR

 

This week
Finished the new Mk 2 gear reduction unit.
Frame CNC milled, gears CNC cut.
Bench tested, surprisingly not noisy.?
Mk1 Gear Reduction gears are nylon, they have never been a problem, but the 125 mm dia mm now being my predominant chuck?
of choice,?the phosphor bronze gears will be stronger on spindle start ups.


--
John
 

Hi John really nice neat job. I am in the process of converting my DB7 lathe to VFD? got the 3 phase 4 pole motor and inverter and waiting on some parts. There is no back gear on these lathes just a series of reduction pulleys with the associated DC motor 0.6 HP with poor torque on low speeds

Regards Les


On Saturday, 23 November 2019, 04:12:28 GMT, John Lindo <bechetboat@...> wrote:


This week
Finished the new Mk 2 gear reduction unit.
Frame CNC milled, gears CNC cut.
Bench tested, surprisingly not noisy.?
Mk1 Gear Reduction gears are nylon, they have never been a problem, but the 125 mm dia mm now being my predominant chuck?
of choice,?the phosphor bronze gears will be stronger on spindle start ups.


--
John

 

John,

Gear Reduction v.2.0 came out very well!? Nice job!

I see that you are in love with your 125 mm chuck...
--
Regards,

Charlie
New Jersey, USA

MURPHY'S CONSTANT:?Matter will be damaged in direct proportion to its value.
 

Reference Mini lathe. 125 mm dia chuck. I use very regularly.
I am still looking for an electrical device to put inline a?"soft start" when turning on the spindle using the 125 mm chuck only, due?to the extra static weight .
I do not want to shock the machine when it kicks in. The 80 mm and 100 mm dia chucks are not an issue.
I understand there are 4 setting? "pots" BIOS ? whatever they are called, on the main board that adjusts the way the motor behaves,
but I am nervous to fiddle with these away from the original factory settings.
As in my past posts, I admit? I am not an electrical engineer, so any help would be appreciated.

Ideal situation would be to be able to isolate the "soft start" when the 125 mm dia chuck is not in use.
But at this moment, as it is not a show stopper, provided? I get into the habit of turning the spindle start on slowly all works OK.

I can post the mounting plate dimensions/drawings of a mini lathe 4" spindle to 5" chuck if of interest.
The Chinese "Sanou" brand of chucks, MAGIC, for quality, price, exceptional, concentric holding on the both sets of
steel jaws incredible accuracy.?


--
John
 

¿ªÔÆÌåÓý

Back in the old days, with tube televisions and radios a temperature dependent resistor was placed in series with the transformer primary to prevent a large current surge that happened as the transformer power supply charged up.? As the current flowed the resistor warmed and the value of the resistance dropped to a value that reduced the voltage drop and the TV/Radio behaved as if it wasn't there.

?

That worked well for those types of equipment because they weren't repeatedly switched on and off.? While hot they wouldn't do what they were supposed.? But for Motor Control systems they don't work because system may be switched off due to an estop or limit switch (or a spindle motor) and while hot you no longer get that soft start.

?

That's why I added a small 8 pin PIC micro-controller to switch the relay in/out based on when AC is applied.? Now each ESTOP causes the same sort of inrush current suppression.

?

Now about the spindle motor.? Putting a inrush resistor on a simple DC brushed motor would probably work.?

?

But a speed controlled motor like on the mini-lathes may not like an inrush limiter on the AC input.? If the motor is a two wire DC brushed motor then something like that might limit the motor current but only when it's cold.? It stays hot while running so if the motor is switched off and then on again there is no benefit.

?

Another possibility, is switching a resistor in series with the motor for a short time and then removing it may work.? But again I'm not sure it will work with the types of motors on these lathes.

?

If you changed to a switch that was momentary in one direction and ON in the other.? Or had two ON positions you could perhaps switch a resistor in series in the one position and then remove it in the second. ?So for the small chucks flip the switch directly to ON.? For heavy chucks and work held in the chuck, switch to the start position which limits the current into the motor and then as the motor picks up speed switch it the rest of the way onto the ON position.

?

Or alternatively switch the motor driver to one that can actually ramp up the motor speed at whatever rate you program.? Especially if it's got an encoder that lets it close the loop and maintain exact spindle speeds at slow RPM.? Useful for threading with a 1PPR spindle sensor and MACH3.

?

John

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of John Lindo
Sent: November-23-19 9:52 PM
To: [email protected]
Subject: Re: [digitalhobbyist] #GR

?

Reference Mini lathe. 125 mm dia chuck. I use very regularly.
I am still looking for an electrical device to put inline a?"soft start" when turning on the spindle using the 125 mm chuck only, due?to the extra static weight .
I do not want to shock the machine when it kicks in. The 80 mm and 100 mm dia chucks are not an issue.
I understand there are 4 setting? "pots" BIOS ? whatever they are called, on the main board that adjusts the way the motor behaves,
but I am nervous to fiddle with these away from the original factory settings.
As in my past posts, I admit? I am not an electrical engineer, so any help would be appreciated.

Ideal situation would be to be able to isolate the "soft start" when the 125 mm dia chuck is not in use.
But at this moment, as it is not a show stopper, provided? I get into the habit of turning the spindle start on slowly all works OK.

I can post the mounting plate dimensions/drawings of a mini lathe 4" spindle to 5" chuck if of interest.
The Chinese "Sanou" brand of chucks, MAGIC, for quality, price, exceptional, concentric holding on the both sets of
steel jaws incredible accuracy.?


--
John

 

John Lindo,

I have emailed you a manual with a description of the ACCEL trim pot function on the mini-lathe.? Its function is to do exactly what you want to do; to slowly (the adjustment range is 1 - 5 seconds) accelerate the motor based on the setting of this trim pot.? There is also a trim pot to limit the inrush current to the motor.? If you change the ACCEL setting, you must also adjust the speed and inrush current settings.? The manual gives adjustment descriptions.

I would not add additional circuitry here if the function that you want is already built in, and only needs to be set.

I suggest you photograph the original settings so you can always return to them if the adjustments go bad.? Also check the maximum and minimum spindle speeds before making any changes, as you will want to readjust these to the same settings after changing the ACCEL pot.
--
Regards,

Charlie
New Jersey, USA

MURPHY'S CONSTANT:?Matter will be damaged in direct proportion to its value.
 

Hi, John,

Further to my post above,..?

The purpose of the ACCEL trimpot on the mini-lathe is to do exactly what you want to do.? Below please find an excerpt from the KBLC manual on the lathe controller.? I believe this manual is for the latest one, but the functionality of the trim pots should be the same.? Under section 7, ¡°Trimpot Adjustments and Control Function¡±, it states (I added the bold type for emphasis):
?
TRIMPOT ADJUSTMENTS AND CONTROL FUNCTIONS
The KBIC? is factory adjusted to provide 0 to full speed range using a 5K potentiometer. Minimum and
maximum speed trimpots are provided to change the speed range from other than 0 to full speed. An
acceleration (ACCEL) trimpot (located directly behind the MIN trimpot) is factory set to provide motor
acceleration from 0 to full speed over a time period of 2 seconds (approx.) each time the AC power is applied.
The current limiting (CL, or torque output) adjustment is factory set to approximately one and a half times the
motor rating. The IR Compensation (IR) is factory adjusted to provide excellent motor regulation under normal
operation. See Figure 1, on page 4, for trimpot locations.

Note: In order for the IR comp and CL trimpot settings to be correct, the proper Plug-in Horsepower
Resistor? must be installed for the particular motor and input voltage being used. Do not attempt to change
the settings of the trimpots unless absolutely necessary since they are factory adjusted to near optimum
settings.
?
IMPORTANT NOTE:
Readjusting the ACCEL time will affect the MAX speed and IR Comp. settings that will have to be readjusted
(see this Section). If the ACCEL time is decreased to the minimum time of 0.5 seconds (6 o'clock trimpot
position), then increase the IR trimpot 25% CW rotation and decrease the MAX trimpot 20% CCW rotation. If
the ACCEL time is increased to the maximum time of 4 seconds (full rotation), then decrease the IR and
increase the MAX as per above percentages of rotation.
The following procedure is presented in required order of adjustment. It should be followed when readjusting
all trimpot functions:
?
7.1 Acceleration Trimpot (ACCEL)
The ACCEL Trimpot is provided, to allow for a smooth
start over an adjustable time period, each time the AC
power is applied or the Main Speed Potentiometer is
adjusted to a higher speed.

The ACCEL Trimpot has been factory set to 2 seconds,
which is the amount of time it will take for the motor to
accelerate from zero speed to full speed. To increase the
acceleration time, rotate the ACCEL Trimpot clockwise.
To decrease the acceleration time, rotate the ACCEL
Trimpot counterclockwise.

I hope this helps...
--
Regards,

Charlie
New Jersey, USA

MURPHY'S CONSTANT:?Matter will be damaged in direct proportion to its value.

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