Hi All,

This is a 'lengthy' posting, so am forced to split into many…

SO- post-1

The Main Panel:

The Sub-Panel:

I had previously posted in this Forum on the start of this project and have progress quite a ways. I thought it better to start a new thread (!) though, since things did change a lot along the way!

The aim of this was to create a simple Electronic threading aid using a small microprocessor reading a spindle encoder wheel, and driving a stepper motor attached to the main lead screw. The encoder provides 4096 edges on two quadrature channels, and an index pulse , per rotation. The 4096 pulses are 'divided' down, using a DDA computation, to give the required Stepper pulse rate, taking into account the chosen thread pitch, leadscrew pitch and stepper to leadscrew drive pulley ratios. The single index pulse is used to synchronise the start of the stepper pulse ( and movement) to the lathe spindle, so that the thread always starts in the same place each threading run.

The process is :

Select thread ( Imperial or metric) and pitch required on the main panel.

Move the tool to a thread start point around 1 or 2 thread pitches away from the thread start. ( allows for leadscrew/half nut backlash takeup). Press THREAD_START BUTTON. Use the jog wheel or joystick to move the carriage and tool to the thread end point. Press the THREAD_END Button.

On the sub Panel, press DONE-REWIND, and the carriage and tool moves to the thread start point. Press Start Thread. Put on cut, and start Spindle.

Once the index pulse is seen, the stepper drives the tool along the cut till thread end, and stops spindle and stepper. Retract tool, press DONE-REWIND and the tool goes back to the starts. Put on cut and repeat till done…Works for RH and LH threads, up to 6mm pitch on my lathe.

The Spindle motor is fitted with a VFD that is programmed to stop the spindle within 150milliseconds in threading mode, below 300RPM max. The MicroP controls the VFD as well for FWD, REV, stop with brake or without, etc. The rapid stop allows threading to take place without worrying about stopping the spidle before the thread end, or pulling the tool out at just the right time – fewer clean underpants required. – I have threaded a 2mm thread at 350 RPM up to a shoulder with Disdain…

Auto-feed also is implemented, and can feed FWD and REV obviously.

This 'ELS' cannot do pseudo CNC stuff that the others seem to do – that over-complicates the use of a basic Lathe in my opinion – GO CNC if you want that! This does threading VERY well, and Auto Feed as well.

Next Post (2)

And now POST – 2….

Here are some pics of the fiiting to the Lathe.

The lathe is in the process of re-furbishment and will be stripped for new leadscrews, nuts, bearings, etc, as well as new full-cover Swarf guards and a DRO – the DRO may be the subject or a new post..

The 'original' Lathe:

Modifying the housings for new electronics:

Wiring the Electronics in:

Uses a NUCLEO (Semi-Arduino compatible) STM 32bit process module and code all in C. Processor runs at 124MHz

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Next up, a 1mm pitch Thread cut, and then a 2.5mm Pitch.

Joe…

POST-4 – Cutting a 2.5mm Thread.

Shows nicely the rapid stop at thread end – no over-run.

The threading process works very well – Start 1 thread pitch away from start, stops right on the entered thread end point, no-over run, clean underpants all the way, even at 300RPM / 4mm pitch thread…

Main Panel Setup again for 2.5mm Pitch, and set start and end points:

The Start Threading:

End point reached with rapid stop.

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Mark the stop point:

And repeat after putting on more cut:

Threading stops om the spot!

Now finish threading:

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Final Cut:

Always stops on the spot!

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I made a video, but the motion from one button to another and to the tool tip, and the thread start and end – makes me ill !!!!!

All worked well, so now I must make all the swarf guards, fit the DRO, modify the cabinet for drawers and doors, and strip, Paint, fit new parts, and reassemble neatly..maybe I will post that lot as well…>>

Joe

John, yes , a sea-sick video is not pleasant, but I fear your dig re the tripod is a little glibly over-simplified perhaps? I have a few tripods and nowhere to place them for this video – it turns into a major nether Pain –>>

The camera needs to pan from the top left panel to show jogging and thread pitch selections, thread start and end point selections, and between each the view must move to the tool tip at start point, then at end point then move the view to the sub panel ( lower left) to show the rewind and then watch the tool rewinding and the the start threading button and spindle on, the back to the tool and watch the threading and the quick stop, etc, etc…The operator is in the way of the camera when viewing the tool and if the camera is overhead the tool it can't see the control panels, and the like…Just describing it makes me ill…

It is not an issue of keep the camera still when viewing the specific panel or area of interest – my tripod did that fine, but it is the panning from view to view that is nauseating!

>I also tried making separate videos – do just the main panel, then the sub panel then the tool movement and cutting, with a tripod and the camera not moving. Then I tried editing the bunch into one and attempted to get the sequencing correct. After three or four attempts, because the choreography was not always nicely sequential, and the gaps or jumps looked silly, I gave up…The panning still was to much..>

Panels and buttons and tool tip all over the place – from top left to bottom left to mid right overhead and back again…

Hi Mechman – Sorry, the intent was not to sound clever…just kind of what came out of my head.

Basically all this thingy is , is an electronic implementation of the very neat single point mechanical Dog Clutch that has done the rounds on this web site, among others. The index pulse from the encoder wheel is exactly the electronic equivalent of that single point in the clutch. The 'Quadrature pulses' ( 4096 pulse per chuck revolution) are then simply coupled to the stepper driving the leadscrew, in a ratio to give the required thread pitch, as would be performed by your lathes mechanical gear box or Gear Change set. And Bob's your uncle…

Joe