Working on a new winder. . .

[axeman6]

Nice work. Hi everyone My name is Art I have been wanting to build my own pickup winder for some time now. This is a great forum were I can learn and finally build my winder with some help, I hope. Anyways I've build quite a few Marshall amplifier clones and many guitars utilizing parts from Warmoth and really enjoy building things that are related to music.

Nice to meet everyone here.

Art

[walcen]

I Love Open Source!
Keep it free, that would be Great!
I am Windoz Free, running Linux Mint 14!
T

I'll second that I am Windoz Free too.

[Lucas]

why not use the unipolar controller and motor?

[Lyrebird Steve]

why not use the unipolar controller and motor?

I started with Arduino/EasyDriver before changing to Phidgets controllers. This was because I got a great deal on some hyprid linear/rotational steppers that were bipolar.

Corresponding Phidgets controller for Unipolar is significantly slower in terms of max velocity

[kayakerca]

why not use the unipolar controller and motor?

You can, they just generate less torque.

[Lucas]

I will have to look at spec for max velocity.
Do you need much torque for a winder?

[kayakerca]

Do you need much torque for a winder?

You need enough torque that you can't stop of slow the stepper motor out of sync or it will lock up and you will have to reset the your controller(s) are restart your wind. Rotary steppers are very inexpensive. Here is the one I use for the rotary winding part of my winder.

Phidgets Inc. - 3303_0 - NEMA-17 Bipolar 48mm Stepper

It works fine and costs $15.

[kayakerca]

Well, a number of months and a 100 or so winds later, I have a few observations about my rudimentary homemade CNC winder.

1. Bipolar steppers by their nature are finickity little creatures. There want to run at speeds they want to run at and not others. I like to wind at ~ 1,100 - 1,200 rpm. So at 85 - 100 tpl on a Strat bobbin, the traverser is happy. But, if you want to turn that down to the 35 - 50 tpl area, the $200 bipolar stepper becomes very unhappy and can just sit there and complain about it. Solution is simple, just reduce the winding rpm to a point where the traverser becomes happy. Hindsight being 20/20, I probably would have used a linear actuator for the traverser that was 2 - 3 times lower in its resolution. I used .00012" per step. Maybe a resolution in the range of .00024 - .0003125 would have worked a little better. Can't be sure and I'm not going to invest the $200 to find out.

And beyond too fast or too slow, anything even approaching their resonance frequency makes it very unhappy as well.
Here's what Wikipedia has to say about that. . .

"Ringing and resonance

When the motor moves a single step it overshoots the final resting point and oscillates round this point as it comes to rest. This undesirable ringing is experienced as motor vibration and is more pronounced in unloaded motors. An unloaded or under loaded motor may, and often will, stall if the vibration experienced is enough to cause loss of synchronisation.

Stepper motors have a natural frequency of operation. When the excitation frequency matches this resonance the ringing is more pronounced, steps may be missed, and stalling is more likely. Motor resonance frequency can be calculated from the formula:

f=\frac{100}{2\pi} \sqrt{\frac{2p\cdot M_h}{J_r} }

Mh Holding torque cN·m
p Number of pole pairs
Jr Rotor inertia kg·cm²"

2. A CNC winder is more accurate than the bobbin dimensions or how square it mounts on the winder base plate no matter how careful and precise you try and be. Any number of things like warps, uneven lacquer thickness, forbon pressed ridges, etc. all can cause the bobbin mount to be less accurate than the CNC winder wind specs. Not a problem, I just interrupt the wind every couple thousand turns to see that the wiring is laying down the way I want it to and if it's not, I make an adjustment. Not a problem, just an observation.

3. The computer operating the CNC winder has got to stay focused. If it decides it wants to search and load updates for Windows (I know Terry. . . Windoz ;-) or antivirus software or whatever, it can forget what it is supposed to be doing for a bit (which has happened about 3 times). If it lets things between the app the the CNC controllers get interrupted for just a millisecond, the winder can go off and do it's own thing, which isn't pretty and ends up sending a lot of wire in the garbage bucket. Seems the solution for me was. . . turn off the WiFi, remove all anitivus software and anything else you don't need. I use a little LG mini notebook (see below) that was used by my daughter when she was doing volunteer work in Africa a few years back. It works fine, so long as it stays focused on the task at hand!

That's about it. Taking the time to dig in and learn what I had to learn to design and build the winder was absolutely worth the effort (a career's worth of finance and accounting skills didn't bring much to the table).

Truth is, that puppy works great and the players using the pickups wound on it are happy as clams with what they're hearing.
So I give the project a big. . .



I can hardly wait to see what Steve ends up with with his software build for his.

[David King]

The "mid-band' resonance issues have been addressed by Gecko in their drivers. Their drivers are a little more expensive than the higher end phidgits one but can operate at 48V and put out 7A per phase (granted that's massive overkill for this project). Gecko usually has a sale right around Thanksgiving where they knock 10-20% off their products.

Just as an aside Jim, I'm not sure if twisting the stepper leads together is such a great idea. Isn't there all sorts of potential back emf and hash getting generated and cross-talking through there?

[kayakerca]

Just as an aside Jim, I'm not sure if twisting the stepper leads together is such a great idea. Isn't there all sorts of potential back emf and hash getting generated and cross-talking through there?

Hi David:

A career in finance and accounting doesn't teach you much about this. So you are suggesting I would be better off to unbundle the motor leads and run them parallel to each other from the controllers to the motors rather than leaving them braided together (which I did just to clean up the wiring mess)?

[David King]

Well, I just did a little googling and in fact twisting the wires reduces electro-magnetic radiation so keep them twisted.

[Lyrebird Steve]

3. The computer operating the CNC winder has got to stay focused. If it decides it wants to search and load updates for Windows (I know Terry. . . Windoz ;-) or antivirus software or whatever, it can forget what it is supposed to be doing for a bit (which has happened about 3 times). If it lets things between the app the the CNC controllers get interrupted for just a millisecond, the winder can go off and do it's own thing, which isn't pretty and ends up sending a lot of wire in the garbage bucket. Seems the solution for me was. . . turn off the WiFi, remove all anitivus software and anything else you don't need. I use a little LG mini notebook (see below) that was used by my daughter when she was doing volunteer work in Africa a few years back. It works fine, so long as it stays focused on the task at hand!

Yes !!! This happened to me too. The USB just stopped sending/processing seemingly randomly. I have set the process priority to High and avoid using a USB hub. Haven't had issues since ... oh and turn off the power saving / screen saver stuff too

[walcen]

Hi Jim and other guys, I'm not real smart with this sort of stuff and this may sound dumb but I'll pitch in anyway. Could you add a lever, fulcrum, to the traverse stepper bracket to increase it's travel thus increasing it's frequency by say double and then make adjustments via the software? It may cheer up a little then.

A simple no will do

regards

Walt

[Lyrebird Steve]

Hi Walt,

Short answer is YES ... long answer is shouldn't be required with a larger stepper resolution

there are 2 limits to consider with the traverse stepper.

(1) How frequently the controller can send step commands - the older phidgets 1063_1 controller can send about 2048 full step commands per second, the newer 1067 gets to 15,625 full steps per second

(2) How far does your motor move in a full step.

eg Jim's motor moves 0.003048 mm per step so he has a max traverse of about 6mm per second. If he is winding a 12mm strat bobbin he takes 2 seconds per traverse (layer). If he is winding at 100 Turns per layer ... he maxes out at 50 turns per second or 3000 RPM

This is not taking into consideration time to decelerate between changing direction and calculating limits etc.

So 20 Turns per second seems a comfortable speed to go at (ie 40% of max)

[kayakerca]

Hi Jim and other guys, I'm not real smart with this sort of stuff and this may sound dumb but I'll pitch in anyway. Could you add a lever, fulcrum, to the traverse stepper bracket to increase it's travel thus increasing it's frequency by say double and then make adjustments via the software? It may cheer up a little then.

A simple no will do

regards

Walt

Hi Walt:

Simple answer is Yes.

However, it would kinda defeat the point of going the CNC route. You could never get a mechanical lever arrangement to equal the accuracy level of the bipolar linear actuator as a traverser on its own . The lever would kinda be going backwards in precision. So long as the stroke and resolution (distance of linear travel per step of the bipolar stepper motor) of the linear actuator exceed your requirements, your would really never have any need for any other mechanical intervention such as a lever. It's just expensive to figure what resolution is best for pickup winding without actually trying our a number of different linear actuators with different resolutions to actually see which resolution works best.