Diminutive, a small EDM prototype

For the last little bit I’ve been working on a small EDM prototype for use on large parts, pipe sections or for use in the field. While they do make and sell these things, the vast majority of them require the use of vibratory assistance, aren’t terribly accurate and are relatively low powered. I intend to make one that is accurate and could potentially be used as a ram EDM in a pinch. Also, I’d like it to be able to use copper and graphite electrodes so polarity reversal is necessary.

This is the linear drive of the small EDM. It has 8 inches of travel and is surprisingly rigid and play-free. I was going to use a gear motor on the top with a rotary encoder but since the loads are quite small a stepper should be OK, even at higher speeds.
This is the linear drive of the small EDM. It has 8 inches of travel and is surprisingly rigid and play-free. I was going to use a gear motor on the top with a rotary encoder but since the loads are quite small a stepper should be OK, even at higher speeds.

I’m currently trying to come up with ways to mount this guy on magnetic bases but also allow for small amounts of fine adjustment so that if there is a need for precision work, the unit can be dialed in. Right now the coupling is made of two pieces of steel. I’m going to replace one of them with nylon to reduce noise. I was going to use a spider coupler with rubber in between but I didn’t have one kicking around on the weekend when I was making it so I just made my own.

It's all made from 7075 aircraft aluminum. Pretty strong stuff. The movement was initially pretty stiff because the screw, which is just hot rolled, was a little bit out so I had to run it back and forth to wear in the brass acme nut. I may put two acme nuts into the travel block simply to take up play, as it stands though right now there is less tan .0003" of play, even with significant force applied.
It’s all made from 7075 aircraft aluminum. Pretty strong stuff. The movement was initially pretty stiff because the screw, which is just hot rolled, was a little bit out so I had to run it back and forth to wear in the brass acme nut. I may put two acme nuts into the travel block simply to take up play, as it stands though right now there is less tan .0003″ of play, even with significant force applied.

So next things next, the prototype electronics. Right now I’m simply going to use what I have laying around, so a TM1638 display, a cheap chinese stepper driver with a toshiba stepper driver and I opted for an Arduino to drive the motor. I will be making a full fledged PCB that will nicely fit in a box but I need to get the pulse generator and sensory circuits working first, then I can integrate them fully on to one PCB.

Just a rough testbed for the motion control and a simple interface. I would like this thing to be nice and easy to use.
Just a rough testbed for the motion control and a simple interface. I would like this thing to be nice and easy to use.

Well, anyways, I have quite a bit more work to do for this project. Even a single axis CNC can be a little more tricky since it’s doing more than simply positioning. A ram EDM is a dynamic machine that reacts to the sensory input to keep the cut running smoothly and with appropriate voltage and gap settings.

More later.

The magic of EDM machines

The other day we were asked to remove a section out of a valve. It’s not a huge valve but milling it would’ve been difficult all the way to the center so we put it on the EDM to blast out the side to make the inside visible. through to the stuff on the inside. Here are the images.

another view
another view
EDMing of valve looking from the top
And a view from the top. gotta love the clean edges with the rough gritty surface.
EDMing of valve looking from the side
Here's a look at it from the side

This was all burned at 150 amps which is max for this machine.

A look as it was being burned, not much to see

Nothing crazy interesting, but I thought it may be neat.

Happy 2011! uuh, I guess a bit late though.

It’s been well over two months since I last posted. Frankly, not a lot has happened in the meantime anyways. Work is going well and life is pretty good. That said, I’ve begun to regain my inspiration for electronics again and I’ve been going hog wild building stuff in the evenings. Just some stuff to touch on I guess…

My Lab

Well, again I have a secluded labratory in the shop I work at. It consists of 2 desks, two shelves and all of my equipment. It’s nice to hang around and listen to music and stuff while having access to all of the manufacturing facilities I could ask for!

Here’s a picture of my lab as I was setting it up.

The new lab as of 2011
The new lab as of 2011, this is an early picture. there is more equipment, parts and shelves now

It’s a real treat here and I’ve been sitting up here for many hours on my projects lately. Yay!

A veroboard planner PDF

Not really a project per say, however, somebody might want it. It’s for printed pcbs from PCBIran which have a ground loop on the outside and sets of rows and columns. Somebody may find it useful. I dunno.

BOARD PLANNER 01

The Shop

The shop I’m at is investing in new technology (IE. CNC mill and CNC Ram EDM) and I figured it’d be neat to take an overview picture. Sure is crowded though. 🙂 The mill, as was stated earlier, is a Haas VF-5 with a 40 taper and the Machine is a large CHMER EDM, more on that thing later in the post

Shop Growing
The shop I work at is growing, but not in floor space. 🙂

It’s actually much tidier now, this is when we were installing the EDM.

Rotary Table and CHMER EDM

I am developing a rotary table interface for the CHMER Ram EDM. The fools at CHMER decided that the machine requires NO extra M-codes for interfacing to external hardware… WHY!!!??!?

So now I have to monitor the outrush current of the pump, turn it on and off a prescribed number of times and then the rotary table can index. I’m still kind of in shock that nobody has ever presented CHMER with this problem. Weird!

The TI Launchpad

I have just ordered the TI launchpad for $4.60 or whatever it cost. TI is attempting to break into the hobbyist market something fierce. unfortunately, after looking at the development tools available, they are all way overpriced.

While they do provide a code-size limited version, which is useful for most things, I think people like to have unfettered access to their chips and what kind they use from a particular vendor. When the development tools that allow this are in the $500 range, that’s simply too much.

Perhaps there will be some good 3rd party support like Atmel and Microchip has and they can really take their MCU’s to the next level. It’d be very cool. 🙂

The Rest

Well, there is probably still more to say after such a long hiatus but I can’t think of it now. I do have some other ideas banging around in my head like a new design of the coolant refractometer which won’t foul. A robot that is machined beautifully and function on sonar. And a new coolant nozzle design that will kick Spider Cool’s ass from here to main street (I’m actually pretty stoked about this one).

Some changes, some improvements, some fun.

Yes, it’s been some time, again. Every post I make seems to say the same things. anyways. Here are some things I’m working on and also no longer working on.

Viscometer

No, nope and no. They bore me now and plus I don’t think there’s much of a market beyond a select few. meh. No lonjger working on it

In-line refractometer

I’ve been slowly working on this. I had a sample of a special coating and tested it. Sadly it didn’t work as I had expected. The only way for me to figure this out would be for me to make the coolant into a mist or to pour it somehow.

EDM Wire Chopper

This is a relatively new idea for me. the Chmer CNC wire EDM here at work doesn’t chop the wire that comes out the back. Already I’ve had it bind up on me. So I’m developing a new chopper that doesn’t pull on the extra wire that comes out.

There are some criteria that are important here. The electrics of the chopper must not meet the wire and the frame of the chopper must not be conductive to the frame of the machine. Here are some pictures of my idea thus far. There is some work to do on it, no doubt, especially the chopper cutter, could be a bit more sturdy.

EDM Wire Chopper
A view of the inside of the prototype chopper module

EDM Chopper assembly wireframeEDM wire Chopper assembly drawingCNMG Facemill

I was thinking about this idea for a while. Since so many shops use CNMG432 for general turning, it’d be nice to be able to use the obtuse side of the insert for something. While there are turning tools that utilize the obtuse side, they are usually only for facing or OD turning. Not very convenient. So I designed a facemill for use with CNMG432 obtuse side inserts.

This particular design is of course only for facing, no shoulders allowed 🙂 Here are some images of this cutter.

cnmg432 facemill 4

cnmg432 facemill 2
Another rendering of the CNMG facemill. Of course the arbor mount isn't correct

Anyways, things being what they are, I should have some new and interesting things to post in a few weeks since I have access to EDMs and soon CNC mills on a more unfettered level. YAY!