Chester Conquest mill power feed

[John Rudd]

My motor for my power feed came today...

It's an ex Ford Fiesta wiper motor and should do admirably...

There was no scientific process involved in the selection guest a wild stab in the dark...

After all experimentation is what it's all about...

Here's a picture

[John Rudd]

Having got the motor, I'm going to fit it to the left hand end of the mill table...No particular reason, just feels more comfortable for me.

I've tried ot remove the handwheel, but it's a bit stubborn..I may need to warm it with my hot air gun..or maybe resort to something a bit more brutish..

attaching the motor necessitates a plate mount to pick up on the two holes that hold the end plate to the mill table...2 hex steel pillars with an M6 thread should see to that...

Another picture...

[John Rudd]

How to power the motor...I cobbled together a pwm speed controller using a 556 timer chip and a mosfet.

The 556 is a dual 555 timer, the pwm frequency is around 300Hz, annoyingly it makes the motor buzz at 0%...A little tweaking is needed to prevent this as it causes the mosfet to become all hot and bothered...Suffice to say when built it will have a heatsink attached...

An issue I identified with the circuit is the high component count, also there are no safety features...if the motor should become stalled, something is likely to fry...

So, current limited output or limit switches on the table?


So many choices and so little time....decisions.. decisions....Time for a lie down!

[Darren]

 Looking good so far, how many leads does your motor have, mine had 3.

I knew there was another reason I shied away from a timer circuit. I have mentioned it before but forgot to say when we last exchanged posts on this subject.

Some motors don't like timer/freq circuits cos it makes their windings "bounce". That's what you can hear buzzing. Not only can it heat the windings it can also damage the insulation.

Coils and transformers/chokes can have the same problems unless designed for PWM circuits.

Not trying to teach you to suck eggs, I just knew there was something I was forgetting to mention before.

[John Rudd]

My motor has two wires...single speed...flat out!...


I think to over come the buzz at 0% pwm, I'll use a switched pot to kill the power to the electronics...

Still mulling over( not milling... ) what to use for speed control, 556 or pic micro...Pic version will use less components and mean an easier pcb to design...

[Darren]

I did consider pic, but it was way too far into new territory for me.

Now that would make an interesting write up to follow......

[raynerd]

Nice going John, I`ll keep watching with interest as this is the same milling machine I own.

I have reading  few thread on here about mill power feeds, I think Darren also has a thread. Why do you guys use standard electrical windscreen motors rather than hooking up a stepper motor? Electronics isn`t my strong point - but I just thought you`d have more control with a stepper?

Chris

[John Rudd]

2 reasons for going with the wiper motor....it was £6...

I'm a tight wad...tight Northern git whatever..

and pwm speed control is easy to do...

Steppers can be expensive and need a stepper control circuit...slightly more complicated...

[raynerd]

OK - I understand. So basically a stepper would do the same job just at a greater expense.

 Good luck with the rest of the mod, I`ll be watching!!

Chris

[Darren]

John, what do you mean by 0%?

zero voltage or full voltage output?

Or should I say fully chopped or full intact wave?

[John Rudd]

Ok,

Things have moved on slightly on the speed control front...

The 555 timer thing is pants...Try as I might I cant get it to control the motor speed at a decent rate...Changing some of the component values makes things worse..

A change of tactic is required...

So, on to a redesign....

[Mike K]

Darren, I think John is referring to duty cycle.

Mike

[Darren]

Ah yes, that's would be it,

Thanks Mike...


John, do you think that maybe there could be a miss match here between the DC motor and the AC signal you are feeding it?

[John Rudd]

Err....probably...My guess would be the inductance of the motor is having some sort of effect....

[Darren]

Yes, that sounds plausible,

Do you have a simple dual voltage secondary transformer? If so why not give it a go with just two voltage outputs and switch between them?

I'm sure you know what I'm suggesting, but for others, mains-fuse-transformer voltage in 240V-transformer voltage out 6/12V-rectifier to DC,

The outputs will be slightly higher due to being rectified but close enough. I really don't think the actual speed of the wiper motor is that critical from my exp, just so long as you have a fast and a slow speed for convenience.


I must rig this up sometime and test it in real life as I promised to sort something out for Stew. But I think it will work fine and would be rock solid reliable (unlike fancy electronics)

Just a suggestion.

[John Rudd]

Having spent some time pondering at the mill....I'm wondering whether this is a viable and worthwhile project..

I removed the handwheel to access the X axis leadscrew bearing support plate...a quick measure up and the bolt holes for it are very close to the mounting holes for the motor....

My intent was to make a mounting plate that picked up the two bolt holes for the bearing support plate and make some long spacing bolts that would replace the existing bolts, the new mounting plate fitting on the end of the new bolts...

So a rethink...do I continue or bin the idea? Choices choices choices.....

[Darren]

Bit difficult to tell from here John, a picture of the problem may help....

[John Rudd]

Ok,

Here are some pictures of the leadscrew bearing plate, motor mounting points and where the bearing plate fits.

As you can see, the bearing plate is secured with two M6 cap head screws to the table, the distance that these are apart is say X mm, nowlook at the motor mounting points, two appear in a straight line( the top onse...) they are Xmm plus a bit apart...

[John Rudd]

My intenton was to mount the motor on a plate that would bolt to the table using the existing tapped holes...


Driving the leadscrew next...I was thinking of a sliding dog clutch, the fixed part on the leadscrew and themoving part on the motor...Sorry no pictures of that as yet....its all in my head as they say..

[Darren]

My first thoughts are an off set threaded rod?

Take a bar say 15mm (aprox) off set it by half the plus a bit and thread it 6mm.....?

[John Rudd]

I thnik I know what you mean...
I could thread one end to screw back into the table, the other end of the bar tapped offset....yes?

[Darren]

Second thoughts, you don't need two fixing points as the leadscrew becomes one itself.

Bit like this

[Darren]

I thnik I know what you mean...
I could thread one end to screw back into the table, the other end of the bar tapped offset....yes?

Yes that sounds like what I was thinking...

[Darren]

I made a dog clutch originally for mine, didn't stay with it though. No real reason as it worked well enough but I just got carried away

Have a look here and scroll down a bit....http://madmodder.net/index.php?topic=1050.msg8336#msg8336

[John Rudd]

So a potential solution, a question tho'

The pillars are threaded to go into the mill table, the other end s are tapped but offset..

How do I know that when the pillars are screwed home into the table that my threaded holes at 'tother end will line up to meet the motor mounts?

[Darren]

I'd suggest threading the pillars in, turn them to set the required distance for the motor mounts and use lock nuts to clamp the bars tight to the mill.

[John Rudd]

Second thoughts, you don't need two fixing points as the leadscrew becomes one itself.

Bit like this

Ahhh, that seems to be a better approach...Nice idea..

[Darren]

I'm sure a member on here has done it this way, well before I even gave doing mine a thought...

Can't remember who though, hopefully they'll chime in with some tips for you.....

[John Rudd]

Ok,

Spurred on by Darrens comments and suggestions, I've decide to pursue this..

A slight deviation from the original scheme is required. I'm going to make a new leadscrew support plate and drill/tap some new pick up points for mounting the motor.

Why? Because I dont want to modify any of the existing mill parts...

Will you be watching?....tune next time.




More to follow...

[bogstandard]

That looks to be a very good option John.

I think you are like myself. You like to be able to put things back to how they were, just in case.

After having used power feeds for a while now, I would recommend to anyone that you should at least fit an X axis one, no matter how basic. The quality of finish you can obtain has to be seen to be believed, with no aching arms.

I used to play about with DC electrickery a few years back, and found that car battery chargers, picked up from car boot sales for a couple of squid, make wonderful power supplies for projects such as this.

Bogs

[Darren]

Glad to have provided some encouragement....

Like Bogs said, you will never look back once you have this sorted. The improvements are too large to be measured...

And you'll feel less tired.....

[John Rudd]

Ok guys,

Some progress today in the garage..after a bit of diy in the house ( we're redecorating...oh boy what a chore that is


So,

After deciding how to progress this, I made up the shaft for the motor coupling that the driving dog is going to slide on...

Here's some snaps...

I cut a piece of EN1 about 40mm long using my trusty bandsaw...Saves a lot of un-necessary grief..

After making a lot of swarf, I have made the shaft that will attach to the worm gear..The idea being that the driving part of the dog clutch will slide on the shaft...

[John Rudd]

I need to cut a keyway for a 3mm key to locate the driving dog..the dog clutch I intend to make from some 38mm 6082 ally bar that I have,but that's something for tomorrow...more pictures...

Tune in next time folks...


More to follow..

[Darren]

That's a good start, once you get going it will all fall into place....

keep the pic's coming, I'd like to see how you tackle this...

[John Rudd]

That's a good start, once you get going it will all fall into place....

keep the pic's coming, I'd like to see how you tackle this...

Cheers Darren...

I need to dust off the angle grinder and fire up the gas axe....for the next stages.. (only kiddin' )


Nah really, I think I got it sorted I might have to machine a bit off the body of the gearbox to reduce the overall profile  so that too much doesnt stick out at the lh end of the machine...

[John Rudd]

Ok, A little more progress albeit slow...more diy done today...SWMBO is laying the law down  

I sketched up a few dimensions on how I thought the dog clutch was going to look...excuse the scrawl, I know it looks like something a 3 year old had drawn but I'm not into CAD drawing and it would take longer to do than machine the parts...

Also a picture of a piece of Ally bar 60mm long and 32 dia marked out for the dog's ears...cutting them will be interesting as I've never done this before...I found it easier to use the centre finder to draw the radial lines on the end...

Any advice chaps before I waste mor metal?

Are you keeping up so far? I hope I aint boring you folk...( no pun intended...this is a machining forum after all  )


More to follow...
 

[bogstandard]

Wrong John,

This isn't a machining forum, it just looks like it. It is a project forum, which is slightly different.

Your sketches are fine as they are, except you need to upgrade the the now web famous Bogstandard C-o-C (Crap-o-Cad) system.

The upgrade consists of black felt tip rather than ball pen or pencil, it makes it easier for people to see, and for the deluxe system, colours can be introduced when you have mastered the basic version.

Bogs

[Darren]

John,

Take a 10mm milling cutter and run it straight through the work off set by 5mm. (so the outside of the cutter runs through the centre)

Turn work 120 deg and do the same again,

Turn another 120 deg and same again

You will now find your dog matches the part on the miller....

[John Rudd]

John,

Take a 10mm milling cutter and run it straight through the work off set by 5mm. (so the outside of the cutter runs through the centre)

Turn work 120 deg and do the same again,

Turn another 120 deg and same again

You will now find your dog matches the part on the miller....

Darren,

I thought I was reasonably versed in machining but this is somewhat of a challenge...A faint heart and all that..I'm not put off but a little confused by the statement you made...

Here's what I think....

I have six radial lines, if I align the outer edge of a cutter with line 1 and cut thru to centre, next mill thru line 3 and so on...Right?

Thing is I'm having to do this twice...so accuracy is the requirement of the day..I'll make the first then machine the second to match..

Good so far on this then ?

[Darren]

John,

I think the way you are trying to do it would be quite difficult.

The way I have suggested you only have three straight cuts to make, each at 120deg.

It's very simple to do once you understand the results it will give. Accurate every time.

I'm not sure how else to explain the method, anyone else wanna have a go?

[John Rudd]

Darren,

I just read in this month's MEW....

The penny has dropped I think..

If I centre the piece directly in line with the axis of the cutter, then offset by 1/2 of the cutters dia...then just mill thru'...Correct ?

[Darren]

Bingo, that's the one....

What's in the rag?

[John Rudd]

Bingo, that's the one....

What's in the rag?

A power feed for a  Chester Conq...   Sealey SM25 mill like yours I believe...
A cnc router spindle motor, Clarkson sharpening  article, modifying the X1...

Pump centre for a mini lathe...Looks interesting...might make one of them..

[Darren]

Pump centre sounds interesting....