The Home Machinist!

In an earlier post, Stevec made mention of a power feed he built for his mill/drill. Do you have any details on that, Steve? Has anyone else done something along the same lines? I'm just barely getting started with my Grizz 0619, but I can already see a need there, and maybe on the z axis as well . But just the x axis would be a huge improvement. Thanks, gents.

Dave

Dave, I do. The motive power is a DC variable speed gearmotor and it's SCR based controller.
The handle engages the dog style clutch when rotated left or right via a double lobed cam. At the same time the cam activates the left feed microswitch or the right feed micro switch which in turn energize their respective relay that switch the speed controller power and polarity. The panel has a pilot light, on-off switch, speed potentiometer and a momentary conmtact top speed button for rapid traverse.



Feel free to ask any other questions that come to mind.

Thanks, Steve. Damn, I was hoping it would be an easy, off the shelf project, but I'm not much of an electronics guy . By the time I buy all the parts needed, I could just buy the factory power feed for my machine. Oh, well, some day...

Dave

Dave, sorry to mislead you, of course the gearmotor, contoller, micro switches etc. were in "inventory"
I just thought I'd 'splain a lttle 'bout what I'd done.
My brother-in-law has the "off the shelf" model that seems to work fine, I just wanted to keep everything level with the table in case I ever needed to work on something long.

Looks very nice. could you pls post the circuit diagram of the speed controller?

Amron, I was going to say I'll post the diagram when you fill in your location in your profile, but that's not fair, it's just a bugaboo of mine.
I don't have a wiring diagram of the scr speed controller, it's something else I had in "inventory" .
I believe it's a KBIC.
Try this link. SPEED-CONTROLLER

Nice job Steve! If you ever feel like opening up the lid for a clutch service, let's know - I'd be very interested in seeing your clutch actuator.

Shaggy

Dave, here's one I'm currently building for my Benchmaster. It uses a 12VDC window winder gearmotor and a simple pin clutch between the motor and leadscrew. It will have a variable power supply and adjustable limit switches.

I'm using it in the interim 'as is' with a 15V/3A supply, reversing switch, and series power resistors to drop the motor voltage. It has 4 speeds of roughly 5, 7, 10, and 13 ins/minute.

Shaggy

Lookin' good Shaggy, can you disengage the little gearmotor to permit hand cranking from the other end
or is that mecessary?
I've also seen lots of 12VDC electronic speed controls on Flea-Bay, if infinitely variable control is in your thoughts.

P.S. I dunno how I missed your question about the clutch Shaggy, sorta answers my first question above. I made up what I believe is a dog clutch, it looks like a lovejoy coupling without the rubber insert.
The spring return gearmotor drive side slides on a keyed shaft (extension of the gearmotor shaft) to engage or disengage and I actuate the engagement via a "fork" activated by one lobe of a a two lobbed cam on the lever shaft.
The other lobe of the cam actuates one of the 2 micro switches for left or right drive direction.

I hope that blather allows you to create some kind of picture in your mind, if not PM me (so I won't miss your post (again )

Amazing the number of things that have gear motors in them, once you start looking ! I don't understand the term "pin clutch", can you clarify that? My apologies in advance if that's a dumb question. I'm curious, how big is a Benchmaster mill? I'm wondering just how much motor power one of these things needs, my machine is the Grizzly version of the Seig SX 3. Thanks for the response, you may have breathed new life into adding power feed to my mill . Later.

Dave

Hey Steve. Thanks, that's a good explanation.
At the moment I have to reach under the table to engage/disengage. You can see the sliding sleeve, with slots in each end, that engage in pins through the shafting. A remote actuator would be nice, but would need more head-scratching than I have time for at present. Maybe later. This works well for very little effort.
BTW, I tried one of those cheap PWM controllers, but the motor didn't like it at all - it created a lot of noise and harmonics in the motor at the lower output voltages. It seems better just to build a simple DC variable power supply.

Shaggy

Hi Dave, not a dumb question. It's just a 'dog' -type clutch. Best operated statically, i.e. not under power. Here's a couple of pics showing how it works (also see what I wrote Steve above), and a pic of my mill. The Benchmaster sits around 28" high and is about 24" wide. Table is 6 x 18".
These type of gearmotors should have enough power for any small mill, as long as the gibs are properly adjusted and not too tight. I'm keeping an eye on the motor for heat dissipation. So far, with moderate use it doesn't seem to be a problem.

One tip I can offer based on recent experience is to put some kind of flex coupling in the drive to the leadscrew, like the ones usually seen on CNC stepper motors. The motor will have an easier time, and you'll get a more even feed if there's slight eccentricity in the end of your leadscrew.

best of luck
Shaggy