Milling power feed

Hello, I'm growing tired of turning the wheel to traverse the table on my milling machine so I thought a power feed would be a nice treat. However, buying one off the shelf is going to be expensive, the DIY route would most probably be cheaper but I'm not exactly the best person to figure out electrics (unless I have some serious help!)

My mill is a WM18, going through the forum and online I was people have successfully built their own power feed for this machine, but most of the times the details are not there such as the harware you'll need and wiring (what connects to where)

From what I could gather, stepper motors are mostly used with some sort of controler to control speed and direction.

Can someone kindly help me out to determine what I would need and how to connect the wiring together please?

Thanks

Chris

Edited By Brian Oldford on 23/09/2018 19:35:25

Chris,

I think you nicely represent the target audience for the video that I linked in this recent thread: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=137671&p=1

MichaelG.

.

Edit: Closely followed by this one:

https://www.model-engineer.co.uk/forums/postings.asp?th=137731&p=1

Edited By Michael Gilligan on 23/09/2018 19:49:30

Thanks for the links Michael, the first video although interesting lost me half way through when he started mentioning mosfet and codes.

The video in the second link by myfordboy is more like it, so I should be fine with the items listed in the description. The problem is what he connected to where.

Edited By ChrisB on 23/09/2018 20:16:39

Myfordboy had a great you tube video on this. He even posted a shopping list.

Hello Chris,

I am building a new power feed for my milling machine.
The items I am using are as follows:
- An Arduino Uno (Amazon: £ 6.95).
- A 12 volt 6Amperes power supply (Ebay: £ 17.60)
- A stepper motor similar to that used by Mr Myfordboy acquired years ago in the ArcEurotrade, double shaft (£ 84.00). Remember you need a powerfull engine!
- A TB6560 driver (Amazon: £ 5.19).
- One 10kOhm potentiometer

My motor is already running very well.
The connections are very simple.
If you want I can draw the schema and post it and a small video of the set.

Best regards
Dias Costa

Re using a stepper motor: bear in mind that you *will* still want to move the table manually - perhaps more than you might think. If the stepper is permanently connected, this means the stepper puts a considerable drag load on the leadscrew and I can attest that it feels awful. In addition, back-driving the stepper means it acts as a generator and I was left in no doubt on another (stepper) forum that it was a bad-thing-to-do. My suggestion of simply opening the winding connection with a switch was pooh-poohed too.

Not being, by any means, an expert on stepper technology, I couldn't say but I believe I have severely weakened a stepper in another situation by driving the shaft manually.

My simple totally unsophisticated milling machine power cross feed consists of an up/down car window motor, these motors are designed to rotate in both directions unlike some windscreen wiper motors. I used some gears from a discarded photo copier and made a dog clutch so that I can still use the hand wheel.For speed control I used a small circuit published in Model Engineer 21st September 1990 and inserted a small push to give rapid travers. So, by my reckoning its worked without failure for 27 years and all the electronic components we were pre-used. Total cost less than £5. John

Dias Costa I'm also interested in your video and circuit details please let me know when and where they/it will be available.,

Hi

Check out my thread of last week stepper motor speed control and connections, it shows how I fitted x control to my mill using Myfordboys guide and connections, works a treat!

The wiring diagrams and driver settings are opened at the end of Myfordboys video by clicking on the down button and going on to his blogspot.

Whilst scrap components will work, you have to first source them, and then hope they are ok.

Car scrapyards in this day and age are not the source they were in my younger days and there is a lot to be said for buying new components on the net

Ian

A good solution when using direct drive steppers is to incorporate a simple clutch between the motor and leadscrew. I did this with mine and it works well. Another good idea is to use the enable input of the stepper driver to eliminate any drive current from the motor when it is not in use. This makes manual movement much easier even when the clutch (if fitted ) is engaged.

A lot has been said about the wisdom of manually turning a stepper due to the back emf produced possibly damaging the driver, but I have been doing it for years with no problem so I think modern stepper drivers have sufficient protection for this.

Doug

Hi Chris, have a look at...

**LINK**

**LINK**

George.

Thanks for all the replies, all have been helpful. I think I'll go for the Myfordboy setup - it seems simple enough for me to follow, worst part looks the wiring, but I now I found the schematic ( thanks Ian ) I probably will pull it off.

Regarding manually turning the table with a stepper motor directly connected - I was thinking that when there is no input to the motor it would be free to turn, no? I would want to avoid clutches and couplings etc, that's why I'm not considering geared motors.

If you are nervous about switching stuff on and off by electronics, you might consider using a simple toggle switch each side of the table, fixed in the slot where the end stops go. Then all you need is to put the switches in the right positions, and switch on - when it gets to the 'end', click, and it stops. Next step might be to use an on-on switch so that automatically the traverse is reversed. Etc. Nothing complicated, and when it does not do what you expect, you do not need a degree to work out where you went wrong. And if you drive your feeds via toothed belts it is easy to arrange a dog clutch to disconnect for manual feed, and you have the safety feature of a stripped belt when the irresistible force meets a sold lump of cast iron. And plain DC motors are a lot cheaper than steppers.

Mine works OK for me. Tim

Take a look at the pic”s in my album using a simple sliding flexible coupling as a drive.

Using the circuit with the driver connected as in Myfordboys circuit the hand wheel drives as normal with no drag, but if you want to disconnect it is a straightforward job.

Free to turn with no input? No, afraid not. When you turn steppers they do work and generate. I doubt they make enough volts to damage a driver if turned manually at hand speed but I haven't tried it.  Don't blame me if it does!

There's a noticable rather than strong resistance to turning the shaft with the motor disconnected. Being multi-pole devices the resistence to turning has a gritty feel to it. If I expected to move the table a lot by hand I would consider fitting a simple dog-clutch.

An advantage of a stepper motor rather than ordinary types is the controller can (usually!) jog and/or move the motor slowly in very small steps. Hand operation might not be necessary.

Dave

Edited By SillyOldDuffer on 24/09/2018 19:53:50

As stated in my last post, the handwheel turns smoothly with no drag, trying to turn a stepper shaft by hand will feel notchy, but not in practice on my mill.

Ian

I tested a spare nema 17 stepper and with nothing connected it turned freely but if i put a jumper wire across the pins for each coil creating a closed loop or really two separate closed loops the resistance was substanially more .

I know that with my 3D printer when the power is switched on the motors lock - possibly the driver is supplying some current through the coils to cause a braking effect , if i turn the power off i can move the steppers easily .

I'm guessing you will be using an arduino to supply a variable frequency square wave to a stepper driver or possibly one of those cheap pulse generators from China ? so if you wire it up so the main power switch is also the activation switch ( power is supplied to the Arduino which boots up and starts supplying the square wave and power is also supplied to the stepper driver with this switch ) you have a separate potentiometer or rotary encoder to set the pulse frequency ( travel speed ) and a forward / reverse toggle switch . You could also use a pushbutton nvr set up to activate the unit and add limit switches to shut it off at a set point but i have never used the limit switches on my power feed so don't think they are really necessary .

I have also heard that a driver can be damaged by turning the stepper over with no power supplied but as SOD also mentioned the voltages would never get high enough besides that there should be protection diodes in circuit to stop the voltage spikes created by the coils in normal use , i have zipped my build table of my 3D printer back and forth all over the place and fast enough to generate enough power to light up the lcd screen even though there was no power connected and it hasn't failed yet ! I think this rubbish came about because of cheap dodgy drivers that were around a few years back and i think they have improved a bit over recent years .

Took the plunge, and ordered a 1 axis nema 23 cnc kit and a 24v 4.5A power supply from stepperonline - should have the parts next week. The pulse generator ordered from ebay - China, that will take a while I guess.

Next I need to order a pair timing gears and a belt, any suggestions what I should go for size wise and if both should be the same size?

Hi Chris

Dont know what size gears you need, but just a heads up on the circuit that is shown from Myfordboy, the switch will need the unused connection on the on off side of it connecting to the other opposite end connector on the same side, or the motor will only run in one direction as the feed to the relay will not operate.

Hope this makes sense to you.

By the way the controller is on the bay from a UK supplier and arrives in a week, mine f rom China took ages, but I bought a spare and converted it as per Myfordboys design as I found I did not know in which dir ection the table would start with my push button design.

Ian