# LMS 3960 X-axis Power Feed (the powerglide experiment)



## Tio Loco (Sep 17, 2019)

Just thought I'd share my mad scientist project. As with many other things about this hobby, I'd convinced myself that I 'needed' a power feed for my 3960. Two issues: first, sticker shock, second I just don't have room to add ~6" to the left side of my mill. Most of the home grown solutions mimic the layout of the commercial one, so I set out to design a compact one.  It seems like these things always start out simple, and then take on a life of their own.

I found a suitable motor on Amazon, and came up with a design, but struggled with how to engage and disengage it from the lead screw. After about a week of half baked ideas, I happened to remember how strong RC car steering servos are these days. Here's the design:


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## Tio Loco (Sep 17, 2019)

Of course that led me to the issue of controlling everything. One thing led to another and I settled on a scheme to use a servo controller that monitored the voltage going to the power feed motor, and use that to activate the servo and engage/disengage (hence the name Powerglide, apologies to the classic GM transmissions).

A few of the build photos.


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## Tio Loco (Sep 17, 2019)

Finally on Sunday, the first chooch test:






Still needs refinement, maybe a more powerful servo. Still need to add limit switches to the ways, but I'm thinking that overall, the concept might actually work... time will tell. But hey, I'll always have the joy of creating something vs. buying something.

Your comments and suggestions are welcome


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## hman (Sep 17, 2019)

VERY nice engage/disengage method!  I think you've got yourself a winner.


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## markba633csi (Sep 18, 2019)

Nice- be sure to fit a cover to keep chips out
Did you do the anodizing yourself?
Mark


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## mattthemuppet2 (Sep 18, 2019)

very neat! Do you have to turn the speed to zero to reverse? The motor seemed to be moving back and forth a bit on the guides on the return, but not the other way. Any idea why? Maybe a rigid servo arm might help keep the bevel gears meshed fully in reverse.

Very impressed with both the mechanics and the electronics.


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## Tio Loco (Sep 18, 2019)

hman said:


> VERY nice engage/disengage method!  I think you've got yourself a winner.



Thanks, still plenty to do. Always a work in progress.



markba633csi said:


> Nice- be sure to fit a cover to keep chips out
> Did you do the anodizing yourself?
> Mark



Photos below with her shiny new acrylic cover in place. I ordered a sheet of 2mm aluminum for the cover, but while she's in shakedown mode I wanted to see what was going on under the hood. Turned out kinda neat, so I may keep it for a while. I'm sure after a while it will get scratched and dulled with swarf splooge and I'll want to replace it with the aluminum.

The parts are powder coated not anodized. Another new skill that I've yet to master. Photo below of my high tech powder coating booth.  
A/C filter in the back and box fan minimize powder dispersion.



mattthemuppet2 said:


> very neat! Do you have to turn the speed to zero to reverse? The motor seemed to be moving back and forth a bit on the guides on the return, but not the other way. Any idea why? Maybe a rigid servo arm might help keep the bevel gears meshed fully in reverse.
> 
> Very impressed with both the mechanics and the electronics.



Thanks Matt. No, the reverse switch and motor will happily change direction at any speed. If I switch off the power switch while the servo is in the engaged position, it stays engaged, so that's another, less abrupt, option for changing direction (power off - change direction - power on).

As for the motor wobble, there are a couple of issues that I'm looking at. First, the nylon gears are not super precision, not terrible, but not what I was expecting. Part of that may be my lead screw adapter. It slips over the lead screw with a rolled pin which fits into the slot of the lead screw. Then it's turned down to 8mm with two flats to fit the gear. Since I don't have a lathe yet I made it using round stock and turning it down using a boring bar on the external face. I'm sure a lathe turned adapter would be more precise. 

See the photos for the new servo arm and linkage. The video was the proof of concept test.

I'm thinking I need to change a couple of things. Any time that the PF power switch is on the servo constantly twitches. After a couple of minutes powered on, even though I'm not using the PF, it gets hot enough that it can't engage/disengage. (Or maybe it's just tired from twitching.) Switch the power off for a few minutes and she goes fine again.

I used a PWM controller for the motor, so that's the first thing I'm going to try to change. I know that they are more efficient than just using a potentiometer, but the voltage sensor never sees a constant voltage from it and will occasionally engage/disengage the servo at random times. Electronics is definitely not my strong suit, but if I understand the way a PWM works, I believe the voltage sensor, being digital, is occasionally seeing the 'gaps' in the wave instead of a steady voltage that the DC motor sees. I tapped this down considerably by adding a 750ms delay to the script of the servo controller, but I think that is the reason for the constant twitch.

I also may just need a more powerful servo. This one is considered a micro-servo with a torque about 1/25th of what a RC car servo can deliver. Of course those servos are bigger so I'll have to machine a new rear plate if I go that route. In that instance I'd probably mount the servo 90° clockwise, putting the linkage lower and parallel to the end plate on the ways, which would let me attach the linkage to the motor mount directly between the inboard rails and closer to the axis of the gears. The current location is causing some binding just because it's pulling/pushing from the very top of the mount.  I'm sure that the ideal pressure point would be dead center of the three rails (on the back of the motor gearbox), but that will require considerably more real estate on the back side.

The adventure continues. Again comments and suggestions are welcome. I'm just making this up as I stumble along.


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## Tio Loco (Mar 5, 2020)

Just a quick updated on this experiment. After using it for a while, the motor gearbox was not up to the task. The brass spur gear driven by a worm gear gave up the ghost.

V2 is rumbling around in my head using a more robust motor and servo.


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## Shootymacshootface (Mar 5, 2020)

From what you have shown us so far, I'm sure that you will come up with a solution. 
Looking forward to see it.


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## toysareforboys (Apr 2, 2020)

They make stepper motors with pretty beefy 90 degree gearboxes already attached (with all metal gears), i.e.: https://www.aliexpress.com/item/32875110441.html






Could be a more robust option for you. Not sure how you could do a disengagement setup with that though.

I just installed a stepper motor as the main drive motor on my lathe, love it lots 

-Jamie M.


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## Tio Loco (Apr 2, 2020)

@toysareforboys thanks for that. I've been noodling that around for a bit. I picked up a stepper motor (no gearbox), and one of the automotive power seat motors that a number of guys have used for power feed, but still haven't hit on how I want to attack the next version.

The gearbox on the one you pictured looks suspiciously similar to the one that I trashed. I'm curious if 'all metal gears' includes brass (worm gear), which is what failed on my  first version.


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## toysareforboys (Apr 2, 2020)

Tio Loco said:


> The gearbox on the one you pictured looks suspiciously similar to the one that I trashed. I'm curious if 'all metal gears' includes brass (worm gear), which is what failed on my  first version.



Ahhh. I didn't see you had a similar motor/gearbox, I thought you were just running a straight stepper with the bevel gears. The one I linked, the worm gear is brass. The only ones I've seen with all steel gears are the gearboxes with heatsinks.

-Jamie M.


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## Tio Loco (May 14, 2020)

I know you thought that you'd seen the end of this project, but it's just been simmering. It takes me a while to let the ideas gel, and I've found that it I take a break and not consciously think about a problem, things will come together in their own sweet time.

So, a couple of issues with the first try, motor was underpowered, servo was underpowered, electronics were ok, but I wanted it to be super skookum. New plan, use two stepper motors and a couple of rails with linear bearings and a lead screw like a 3d printer. After many, many hours in Fusion 360, I'm ready so start construction, just waiting on one more stepper motor driver and some screws.  Here's the plan:






Still very compact 60mm x 150mm x 111mm. The modular design will allow removal of the entire mechanism with just two screws, while leaving the table end, lead screw, bearing and gear in place if needed.





I didn't model the cog belt, I know, I'm lazy...


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## toysareforboys (May 14, 2020)

Looks beefy, nice work! Can't wait to see it in action 

-Jamie M.


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## homebrewed (May 15, 2020)

Are you planning on using an open-loop approach to get proper engagement of the gears?  The stepper/feed screw arrangement could apply a lot of force to the gears if over-driven.  On the other hand, you probably won't need a very beefy stepper for that part of the design.  And once the gears are properly meshed you likely won't even need to keep the little stepper powered up.  That's a very creative approach!


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## Tio Loco (May 15, 2020)

If you mean a loop cog belt, yes. The stepper controller I'm using will let me set a position when energized if I understand the documents correctly. It's very little movement, but I'll just have to dial the mesh in manually.  I ordered an Arduino board today, just to play with using it as a controller vs just the stepper controllers. I think I will be able to achieve a smoother engagement and speed ramp up/down that way.


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## GunsOfNavarone (May 24, 2020)

@Tio Loco I have been playing with the idea of "learning" Arduino based on some comments on this board. A couple things for Lathe and mill, but also I could bring to fruition, some things knocking around in my head for work the last 6-7 years.
As far as controlling steppers, reading sensors/servos, how impossible would this be for a noob? Am I biting off way too much? I did download the program and looked over examples, but I don't know what its limits are for the aforementioned wish list.
Nice work!


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## toysareforboys (May 24, 2020)

GunsOfNavarone said:


> @Tio Loco I have been playing with the idea of "learning" Arduino based on some comments on this board. A couple things for Lathe and mill, but also I could bring to fruition, some things knocking around in my head for wok the last 6-7 years.
> As far as controlling steppers, reading sensors/servos, how impossible would this be for a noob? Am I biting off way too uch? I did download the program and looked over examples, but I don't know what its limits are for the aforementioned wish list.
> Nice work!


Can't wait to see how you do! I'm building an Arduino based automatic firework controller for 64 cues (fireworks), will have colour touchscreen, play music, etc. Going to be tricky no double. Anxious to hear how you do after you start!

-Jamie M.


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## Tio Loco (May 25, 2020)

@GunsOfNavarone I'm probably not the best person to ask about Arduino. Got a taste about 5 years ago getting the TouchDRO set up, and promptly forgot everything I learned, but from what I've seen, writing sketches (scripts, I don't know why they are called sketches) for the Arduino is pretty straghtforward and pretty basic.

I'm using (hopefully) small stepper controllers from Pololu.com, and they have a library available for Arduino integration, and pretty extensive documentation about the process, so it will be just a matter of beating my head against the wall until I figure it out.

I'd also suggest DroneBot Workshop on youtube. He's very good about distilling the voodoo down to layman level.  https://www.youtube.com/channel/UCzml9bXoEM0itbcE96CB03w

@toysareforboys I can't wait to see that bad boy run...


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## GunsOfNavarone (May 25, 2020)

I’m not sure if your use, but I’ve decided to go Clear Path SPHD stepper motors with the drive built in. Maybe take a look at those, I think it will surpass some headaches down the road.


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## Tio Loco (May 26, 2020)

@GunsOfNavarone Thanks, those are pretty cool, hadn't seen them before. I already have the stepper motors and controllers, so it doesn't make sense to buy more (unless the current ones don't work), and those are pretty pricey.


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## toysareforboys (May 26, 2020)

Tio Loco said:


> @toysareforboys I can't wait to see that bad boy run...


Thanks man! I bought a commercial 15 cue ignition system but I'm not happy with it. If you want it done right you gotta do it yourself 






New one should be awesome! Can't wait to work with Arduino, all my parts should arrive by mid nextweek at the latest.

If there's no pyro there's no party!

-Jamie M.


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## Tio Loco (Jun 22, 2020)

Time, OK, past time for a progress update. Get some popcorn, this will be another long post. 

New V2 end cap for the mill table. The lip facilitates and supports the modular power feed assembly which can be easily removed (3 screws) for service or adjustment.







One issue with the V1 was the short aluminum adapter from the lead screw to the bevel gear allowed excessive gear wobble. For V2 I designed a deeper bearing housing allowing for a longer adapter. The sealed bearing is retained with an internal c-clip (another new adventure). The slot in the bottom allows access to the set screw on the adapter.






 V2 adapter is 1144 instead of aluminum.











Transmission (NEMA 17) stepper motor to engage/disengage the drive (NEMA 23) motor.






Transmission nut mount






Linear bearing carrier.






Transmission test fit.






I wasn't happy with the standard linear bearing mounts commonly used on 3D printers. Too blulky, bearings were rough and noisy, and 16 mounting screws made a smoothly sliding alignment a PITA, so I printed more svelte ones. The bearings are a perfect press fit, so no c-clips needed, making for a shorter mount.











Full V2 assembly






And the electronics.  Clockwise from top right: 2-line LCD display for status of the motors (and eventually feed rate display), drive motor driver, transmission motor driver with limit switches attached, slide pot for speed direction control, Arduino Uno micro controller. In the far back at 12 o'clock position is the Arduino Nano, which will be used instead of the Uno for the final installation.






I have the preliminary sketch (program) written and functional, still needs a bit of tuning. There will just be two controls, an on/off switch will power the motor drivers, which will power the Arduino, and the slider for direction and speed. Center of the slider is neutral. Moving it in either direction will activate the transmission motor to engage the gears, then spin up the drive motor. Vice versa for moving the slider to neutral.

But.... There are several things I'm not happy with. As my better half told me, "That's why they call it prototyping".  

The cog belt arrangement works, but it's needlessly complex, and I'm not overly confident about long term reliability. I was also struggling with the location for the transmission limit switches. My preference would be to keep them, and the requisite wiring out of the mechanical area if possible.

So, on to V3. Minor changes the design of the left plate, linear bearing carrier, drive motor mount and transmission motor mount will allow a change to direct drive of the transmission assembly.


















Haven't completed modeling the electronics box, but each circuit will be on a slide-in tray.




The link from the drive motor mount and passing thru the transmission motor mount is a brass rod, threaded on each end, and will replace one of the drive motor mounting screws. This will allow the limit switches to be housed inside the electronics box out of harms way.






That sums things up as they stand today, but the end is in sight. Still noodling how to mount a magnet to the lead screw spur gear, so I can read the RPM's, and from there I can calculate the feed rate. 

Now back to the mill to create fresh aluminum swarf... stay tuned.


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## toysareforboys (Jun 22, 2020)

Absolutely amazing, can't wait to see it run in anger  

Thanks for sharing all the sketches and photos!

For the RPM on my lathe I epoxied a N52 magnet to the chuck shaft then used one of those hall detection RPM sensors and it works flawless, right up to my maximum 2400rpm!

-Jamie M.


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## Tio Loco (Jun 22, 2020)

@toysareforboys Thanks!  That's my plan. I'm thinking a collar for the lead screw bevel gear that will put the magnet to put the magnet out close to the electronics box, and mount a hall effect sensor in the electronics box, again I don't want any more wiring out in the mechanical zone than absolutely necessary.


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