Hi anybody made any CNC sinker orwire EDM from Camtronics plans?
I am looking for his help/suggestions.
I made two EDMs from Robert Langlois & Peter Rawlinson plans.
But these are non CNC machines.

Thanks.
Hobman

You may not get much response since a true full cnc edm machine is more complex than might appear at first blush. Certainly many more obstacles than a mill/lathe/plasma, etc. If you are determined to do it, and think it would be more fun than frustrating, I'll be glad to give you some of the problem areas for consideration. I should also point out you will not achieve the accuarcy or production levels of factory built machines.

Regards,

Roy Solomon

Roy, I'm interested to hear what the challenges are and also what you think are the differences to expect on factory tolerances vs diy?

I'd heard Robert Langlois was at at one point working on a wire edm, don't know if it was cnc, but he's very knowlegable about electronics - be great to get some guidance or at least a heads up on where the problem areas are.

McGyver, The first problem would be driving the servos relative to the gap condition. Modern edm's use adaptive controls to monitor the stability of the burn and speed-up/slow-down/reverse-direction based on the feedback loop. They also use special routines to maintain the integrity of sharp outside corners, or remove sufficent material on inside corners. This includes changing power settings, flush pressure, wire tension, and wire path.
Which naturally leads to the next bits of fun, controlling wire tension and flush pressure(and having enough pressure properly fed in to the kerf). On the older machines, tension was created with a jockey pulley and a weight. This limits the range of adjustment, and precludes changing it on the fly via program control. Modern machines do this with a brake motor that creates tension electronically. Likewise with flush, the older machines use needle valves and volumetric flow gages to set flush pressure. You could need upwards of 12 bar depending on how high a part you want to be able to cut. Most of the new machines cut submerged in addition to the pressure flush. Which would lead to the next bits of fun, but I'll stop here for now to let you digest.
Still want to know more? Be glad to help.

Roy Solomon

I Want To Know More! (There are probably a lot of us who would like to know more about this)

How about a primer on the whole EDM process?

Patrick, I am flattered that you think it sounds like I know what I'm talking about! Based on the number of views for this thread, you may be right. I don't have time for daily chapters, but perhaps a weekly post would be possible.

First some disclaimers. I'm just another guy in the shop, like most of us here. I happen to have learned a lot during my 25 years in the trade. My opinions are mine alone, not my employers, or any machine manufactureres. Everyone is welcome to take them for what they are worth, or ignore them.

The bible for edm is "The EDM Handbook" by E. Bud Guitrau, the true master!
There are also some very good articles and a forum at http://www.mmsonline.com/edm/index.html

Although this forum mostly favors plasma, there are at least a couple of other edm guys lurking, and I would welcome their additions to this thread. I would expect the discussion to be reasoned and respectfull.

That being said, if no one tells me to go to hell, and the thread keeps getting posts and views, I'll start adding more info. Any feedback on specific topics is welcomed.

Roy Solomon

Roy thanks very much for stepping forward on this - I'm very interested to learn. you certainly made your point that there are many complexities here!

for others, here's a few more links that cover the basics.

http://www.jjjtrain.com/vms/other_edm_basics.html
http://www.agieus.com/Academy/

as a diy're, my priorities are accuracy and feasibility, not speed/production rate. Of course my priorities aren't everyone’s, but I'd guess most of those interested in a cnc diy edm are less concerned about production rates or they'd buy a commercial unit.

As some of these complexities are there to achieve combined objectives of speed & accuracy, if a home shop guy didn't care about speed, could some of the complexity be eliminated while maintaining accuracy? i.e. just run it really slowly at a lower voltage?

Roy, can you give some detail of the cutting movement/action....at what frequency does the unit spark, is the motion fairly analogue or is it spark/wait/step?

I suppose at some point it comes down to how accurately you can control the axis? If the best resolution you can get is .001, then that constraint will set the minimum voltage you can use?

With the low feed rates of an edm, I think it would be possible to make a home machine that you could control to a 10th of a thou. this is accuracy beyond normal diy stuff but with linear encoders reading to a few microns (my fav, http://www.newall.com/), high tpi screws and geared down servos, why not? If this was doable, and using a slower, low voltage approach, I'm wondering what class work you think is possible?

McGyver, you are correct that many areas can be simplified if productivity is not the concern. For example, the aforementioned tension method of jockey pulley and counter weight is much simpler than an electronic brake motor, and very effective. Also in that category would be submerged cutting and high pressure flush.

Moving the table accurately is about 1/3 of the final result. You will also need to guide the wire, (more on that later), and control the overburn.

The links you gave are good. I have run Agie’s and they make an excellent machine. The Virtual Machine Shop looks like a potential black hole time drain; I had to tear myself away from a lot of interesting reading. I did find two points in the edm chapters I would take issue with. One is they say copper wire is common; in fact brass is almost universally predominant, although there are some other materials being used in special applications. The other is their recommendation to use kerosene as a dielectric fluid in a sinker edm. This is never done anymore, kerosene is too volatile. Most machines use synthetic oil with a much higher flash point. I sent Ron Smith an e-mail regarding this; it might be nice if they could adopt a “wika” concept for open editing.

Now back to your questions. The state of the art is .0001mm steps, (4 millionths), or 10 millionths inch resolution. The general concepts for linear guides, rotary encoders, stepper motors, etc, is the same as the more conventional machines people are building, just to a higher order of magnitude. Your part will always be some amount less accurate than you can position your table, so this is the first order limitation. You don’t need much speed or thrust, so you can use whatever techniques (gear reduction, etc) that help towards that end.

As to the forward motion, the spark generation happens thousands of times per second, depending on the settings for off time and on time. At the same time, the gap condition (open gap voltage) is monitored and adjusted thousands of times per second. This is an interesting debate ongoing between machines with ballscrews that sense the gap more often, but have to deal with lost mechanical motion and limitations to acceleration, versus machines with linear motors that sample the gap less often, but can respond and accelerate the table quicker. Also toss glass scales into the mix. Some machines use closed loop feedback; others rely on the rotary encoders.

For a Diy system, you could use a forward feed low enough that you would not have to sense or respond to anything. Early machines were like this, and the next step in evolution was to stop the machine in response to a short circuit.

I think the next installment would focus on the wire drive/guide system, and the impact of dielectric fluid (deionized water) delivery/control.

Roy Solomon

Are you able to mill a PCB with EDM? If not, why not?

Klpauba,
If you mean PCB as in "printed circuit board", the answer is no, because you can only EDM(the term would be "burn" as opposed to "mill") conductive materials. If you happened to mean PCD as in "poly crystalline diamond", the short answer is yes, this is being done by some people.

Roy Solomon

thanks again Roy.

Resolution to 0.0001mm, one ten millionth of a meter is currently beyond my ability – but not by much! One could theoretically approach 1 micron resolution (1/1,000,000m), and cheaply to boot. I say theoretical because things like the rigidity of the machine, linear bearing clearance, etc seriously come into play when you’re talking 1/100,000 of an inch!

How to accomplish this bodacious claim? I think it would be possible with fine tpi lead screw, geared down servers, and a closed loop system with Newall linear encoders. These have 1 micron resolution and can be used submerged and supposedly are tolerant to magnetic forces (is there much emf or other interference generated by edm?). Heck, fine ready rod with a plastic nut and simple anti-backlash would do – the positional accuracy is from the encoders. This idea would have to be linear – rotary encoders or steppers wouldn’t work, at least not with ready rod

http://www.newall.com/LEDs/leds.htm

basing the system on the prepackaged accuracy of the Newalls and using really inexpensive components to drive the motion is a unique opportunity presented by the EDM characteristic that 1) motion slow and 2) involves no cutting force.

Now I don’t really think I’m going to be cutting to 1/100,000”, but that there is a strategy to get this kind of resolution and its only 10x of what is state of the art, gives me encouragement that a high class machine could be built (or at least as far as the first 1/3 goes!)

The VMS is a great project – bunch of guys putting a lot of work into something for the betterment of all. I’m sure Ron would welcome another contributing editor ;) …or maybe we’ll just collect all your posts and send em to him

Mike

Hi McGyver, It sounds like you’ve got motion control covered. I’ll point out that the OEM’s use precision ground ball screws, and a final laser compensation for greater accuracy. The majority of factory built machines are 4/5 axis. This includes U/V for tapering, and a power Z axis. I’m guessing you’ll be satisfied with a 2 axis machine. The machine will create a fair amount of EMI. The Swiss machines come with full enclosures like you would see on a machining center, in this case, it’s just for dampening emissions to the CE(European Union) standard. I would not worry about this from a safety standpoint. You do need to use shielded cables for communications, such as RS-232, or CAT 5 cables for Ethernet. This is only a concern while you are cutting. I do not know what they do to shield data flow to/from the scales and encoders. I imagine you buy shielded cables, or do it yourself to standard cables. You won’t be able to listen to the radio while you’re sparking! :frown:

The next consideration for accuracy is driving and guiding the wire. Starting from the used end, you will be pulling the wire from the supply side spool. This is done with two steel rollers, one fixed, one spring loaded to pinch the wire between the two rollers. One roller is driven by a variable speed motor, the other idles free. The speed is increased to accommodate taller or more accurate parts. After these rollers, the wire can be collected on a take-up spool, dumped into a collection bin, or chopped into small pieces and collected. The new machines all use choppers.
The tension on the wire can be done several ways. The most basic and least consistent is to simply create drag on the supply spool. I’m sure you can imagine several ways this could be done, and the drawback to each. The most accurate method is to use a brake motor and a strain gage sensor to monitor and adjust the tension electronically. The intermediate method is to use a counter weight and jockey pulley arrangement. This requires another set of pinch rollers, a drive motor for these rollers, and a sensor on the jockey pulley to increase/decrease the speed of the take-up side motor to keep the jockey pulley in the center of the travel. This would be similar to a press feed supply loop sensor if you are familiar with that concept.

I have seen pictures of a diy machine with no wire guides, just strung between the pulleys. The pulleys are not very precise, and the distance between them too large for accurate work. Guides can be round, 3 point “V” contact, or open “V” design. The guide material has to be hard. OEM’s use diamond, ruby, sapphire, or carbide. Since your machine would not have U/V motion, the guides need to be mounted so the wire is square to the table, either by design, or with some adjustment. All the machines I've run have U/V travel, so I'm not sure how this is done by OEM's on a 2 axis machine. Anybody else want to chime in on this or anything else so far? Come on you lurkers, get off the back bench! :stickpoke If the guide is conductive, it has to be insulated. In conjunction with the guide, consideration has to be given to getting power to the wire, and ideally, flush to the workpiece co-axial to the wire.

I have attached a couple of jpeg's to help clarify.


Next on the list would be the dielectric fluid requirements, and how to achieve them.

Roy Solomon

Yeah, I meant Printed Circuit Board.

The copper clad board is conductive, no? I would think that you could burn the traces through the copper coating clear down to the fiberglas board. If it could work, I bet it would be too slow.

Thanks, I appreciate your sharing the knowledge!

Roy, another great post - keep ‘em coming!

you are being kind saying the movements all figured out, but with the lack of cutting forces i think some good stuff could be done. I agree a home shop probably won’t need the U/V motion but might want a rotary axis on the table.

The picture you gave shows the wire going through a round guide, then the electrical contact cylinder, then a guide that looks like its made up 4 balls in forced in contact with the wire. I'm guessing it has to be something this complex because unless it was an interference fit, just running the wire through a round guide would introduce movement or error = clearance between the wire and the guide?

With the example you gave of the wire being held between pulleys, once the wire is in tension between the pulleys, and the pulleys are on good preloaded angular contact bearings, are there additional forces acting on the wire? ie resonance from somewhere, or does the spark causes the wire to move, etc? I guess I'm wondering if, without the U/V requirement, it could work well between pulleys or does that approach doom the machine to second class work from the start.

Can you describe a typical case of wire size, feed rate, tension etc., say to cut a gear in 3/8 thick mild steel. Is the tension just to create shortest distance between two points, or are you actually stretching the wire – i.e., why the need to adjust tension, or is that done at set up for different wire sizes?

Mike

Excellent back and forth, Mcgyver and roysol.

Mike - sub-micron placement with rotary encoders is not all that difficult as you likely know, but I agree that linears would be more suitable. Temperature compensation should not be an issue - if you expect TRUE sub-micron tolerances, then you are in a climate controlled environment - like it or not.

Roy - keep it coming. I for one appreciate you sharing your obvious expertice...either you are one hell of a sales guy or you do this for a living. I am thinking EDM is your life!

Ich liebe es!

Scott

Hello all, thanks for the feedback.

Scott, I have been in manufacturing most of my adult life. I have never done any sales. I currently am responsible for one wire and one sinker. I have 7 years experience on cnc mills, 5 on cnc lathes, about 10,000 hours on wire edm, and 5,000 hours on sinker edm. Philosophically, edm is not my life anymore than any job would be. But I do love my job!

Mike, I have some pictures I'll post next week of a diy machine that relys on the rollers for guiding. The guide I posted is more complicated than it has to be. I'll post some simpler ones also. The deflecting forces are the current, which creates "wire lag",the actual wire position is behind the gap, and flush pressure(which may not be that high on a diy machine). The tension adjustment is for lower pull during rough cutting, and maximum pull during trimming. Also to allow for different size wires to be used. In all cases you are NOT stretching the wire.

I mostly use .010 or .012 wire, sometimes .008, and I have cut with .004. They make machines currently capable of cutting with .0008" wire(no that's not a typo!).

The machine I run at 4 years old cuts 12 linear inches per hour. In 3/8 steel it would cut 32 inches per hour. The newest machines cut upwards of 35 square per hour, 885 inches linear per hour in 3/8 steel.

Cheers everyone, and have a great weekend!

Roy Solomon

That last line should read 85 inches per hour!

Roy, with Sqin/hr fairly well established, what do EDM's usually ballpark in $/hr?

$50? $100? $200?

Thanks!

-Jeff

Your knowledge of edm is super.

A. Why can't a typical Bridgeport with its motor belts having additional gear reduction from IPM to inches per hour thus fitting in the edm world?

B. Arms to hold upper and lower wire guides to be fabricated to fit the table for xy motion.

C. The task is now to control the burn.

D. Not looking for a 4 finish, not looking for diminensions within thousanths. (.015 is fine)

E. Not looking for 4 axis.

F. Looking to rough a part closer to finish than plasma or waterjet as a prep for machining.

G. Run a large enough wire so breakage is not a problem.

H. Presently machining unfriendly material like nitraloy135M etc. So to rough remove material is the needed result.

I. Who is out there capable to do the electronics, wire feed, amperage, etc. ?

Roysol:

What happened to the EDM thread that seemed to be going so well? I would like to hear more about this.

Jerry

Hi there,

I'd also like to hear more - I don't have much to contribute, but am very interested in these machines...

Regards
Warren

To answer a question posed in this thread earlier, EDM could be used for 'burning' PCBs (printed circuit boards), using the EDM sinker method, in which a negative of the board is milled into the face of a chunk of graphite (preferred for multiple burns at high accuracy) and the sinker merely plunges into the copper, eroding it electrically, much as a wire edm goes through conductive metals. the copper on the other side (assuming a double sided PCB) would probably not be affected, but there could be some problems in making sure the PCB was perfectly flat, so that a proper burn was achieved.
A pretty expensive way to go about it i suspect, but entirely possible nevertheless. nevertheless.

Hello all, my apologies for being away from this thread for so long. I had every intention of continuing, particularly since I received several requests to do so. An extreme upsurge in activity at work and a major personal distraction(I bought a house and moved) conspired to keep me away from here. My boss is very tolerant of my on-line actions, as long as it does not interfere with real work, an entirely reasonable position.

As pcroxford points out, you can burn the traces(remove copper to leave a path) from the surface of a pcb with the method he describes. I also saw a thread at yahoo groups home built edm, here, http://groups.yahoo.com/group/EDMHomeBuilders/ , indicating they were successful using a round electrode and cycling up and down burns with small xy stepovers, like you might do in certain applications on a milling machine, for example, with a boring bar, to make an oval slot.

Untill I get back to the origional focus of this thread, here's an inquiry from fran h regarding used edm equipment versus new, and my response.

Good morning,

I'm part owner of a very small machine shop and as such there is always the opportunity to try to enhance the bottom line. Since we are concentrating to do government replacement parts in a timely fashion, Usually 2 to 50, this niche allows us to compete with the big guys. Alloys such as AMS 6470 and 4140 are common. 6470 eats carbide inserts like a child eating M&Ms. This, after consulting with tooling engineers and their metalurgests (sorry no spellcheck). NOW an edm can get me in the ballpark and leave me a .03 final cut to be rid of the recast would be wonderful. Also some parts could be a lights out operation.

What advice can you offer as to a used wire edm ?(not looking for great accuracy) and what is your opinion about Mustang EDM as a refurbursher of used edm's. (Mustang is being sold on ebay). What is the most forgiving edm for neophites?

email me at fhutchins@myeastern.com

Thanks in advance

FranH


Hello Fran, sorry for the slow reply, I’ve had some actual work lately that’s kept me busy. Although edm was developed for producing tooling of high accuracy in hardened high carbon steel, it has gained wider acceptance in production applications. In my current job, this is most of what we do. The great thing about edm is that the hardness/toughness/heat resistance of the material is irrelevant to the edm process. What does matter is that it’s homogenous, with a minimum of non-conductive inclusions. In other words, the “cleaner” the better. Low carbon steels of poor quality do not edm well. Aerospace materials such as Inconel edm fairly well.


As to machine choice, it’s a bit of a catch 22 for a neophyte wanting to get a foot in the door. New equipment is easy to run, and comes with substantial support, but is quite expensive, as you may already know. Used machines can be a good bargain, but the learning curve is steep, some manufacturers such as Mitsubishi charge a registration fee before they will support a machine purchased used. You might be buying someone else’s headache, and the productivity of edm’s has soared dramatically over the years, so you might not be competitive quoting head to head against people with newer machines.

The Mustang you inquired about is actually an Agie, which has been restored/retrofitted by Techstar. This is a Swiss built machine from the mid 80’s that is incredibly accurate. They were slow in cutting speed, even back in the day. Techstar stepped in to boost the productivity of these otherwise fine machines. I have run a variety of Agie’s, they are well built. I have done business with Techstar; they have been around a long time and have a good reputation. An aside about the evolution of wire edm, virtually all modern ones have auto threaders, this machine does not.


In general, the Swiss machines like Agie and Charmilles require higher maintenance; the Japanese machines like Mitsubishi and Fanuc are more forgiving. The Swiss machines tend to be more accurate, the Japanese machines tend to cut faster.


The opinions I express are mine and mine alone. They do not represent my employer’s or any manufacturer’s. Others may disagree. Use them for what they are worth.

Hopefully this is still useful to you even with the slow response. If you have further questions, feel free to post at cnczone, e-mail me direct, or call.

I will be posting to the homebuilt thread at cnczone to let people know that I’ll be continuing our discussion there. I would like to post your questions and my response until I have time to get back on topic, if that’s alright with you. I would withhold your info if you prefer.

Regards,

Roy Solomon
Edm Department
Mri/Prompton Tool Inc.
120 Sunrise Ave.
Honesdale Pa 18431
570-253-4141 ext 237
Fax 570-253-0548
rsolomon@promptontool.com

Roy, good to see you back, congrats on the house. I look forward to learning more when those annoying distractions like a job and home and a life don't keep you away from the computer :)

having second thoughts about the whole PCB via EDM sinker idea.
The reason being that since the traces are usually isolated islands of copper, they may not be able to sustain the electrical connection once the island is formed. I am no expert, but I suspect that the heat might have an adverse affect on the plastic substrate and cause it to peel. it would be an interesting project though.. outta my league, but interesting... I wonder how many burns you could get from one electrode....... someone should move this message and the others to a new thread..

Thanks roysol .. you've been an encouragement.

I was going to try and cut through 40mm Diameter 17-7PH Stainless hollow bar stock to make springs that look much like Die Springs only with variable pitch and variable guage using diamond impregnated wire. The cutting widths of the wire vary from 0.18 ~ 0.43mm and the surface finish achieved on SiC crystal is normally <1micrometer.

When cutting with EDM what sort of surface finish could I expect to achieve? Can you enlighten me a bit about this area?

Also can you detail the "sparK" aspect of the process? - If I could organise to hold the hollow bar, immersed in a bath of the correct fluid, and I had the correct wire running into it, held properly - what black magic do I need to induce in the wire to make it do its job?

Thanks again for your insight and willingness to share.

i was reading the posts in the thread and this sound like a fasinating subject.
i always woundered how an edm worked.i did a search in yahoo groups and found a group called edm_cnc.
http://finance.groups.yahoo.com/group/EDM_CNC/
the info is very good to help the newbe learn what is going on.the machines those guys are building look very simple and produce some pritty good results.in the files section there are even cuircit explination and a few diagrams.
don't know if this would help any.

do you use distilled water, it doesn't conduct electricity. My work needs a edm to cut square corners, how much would the average home built 2.5 axis CNC sinker cost?

Hi Dear Friends
I have a Wirecut Agie 200 and I want to work with Esprit 2007 , unfortunately I have n't ASC file which is Post Processor for Esprit 3007 and it does need it, please help me how can I write a Post Processor for Esprit 2007.
Best Regards
Majid Madadi

Hi,

I found this guy on another forum who's built his own wire edm machine and uses it to build QCTP holders.

http://www.outbackmachineshop.com/

Hope that helps.

gentlemen,

after reading thru this thread i see that no one is aware that Linux EMC2 software has a working wire edm function built into it.

i retrofitted a Charmilles/Andrew EF330 with this software.

i removed the dec pdp8\a from the machine and installed a plain vanilla pc loaded with emc2.
i also added some new servo drives, a Motenc Lite servo board, and my own custom i/o.

i had suggested to the EMC coders that they should give EMC2 the ability to vary the feedrate while executing g-code, and the feedrate had to vary in reference to an analog input voltage...

well the EMC2 team cam thru big, as the new edm function works flawlessly.....

test cuts on the old Andrew edm were successful.

well that is it in a nutshell, we did this about 2 years ago, and i was suprized
that i have been the only person reporting that wire edm for the home type guy is here......

feel free to ask any questions....

mdynac,

We have an unregistered Mits DWC-80 with a servo error. I think the problem is actually an interface board but since we're not registered I cant get any info from mits. I would like to retrofit the machine. The motion control seems straight forward. My issue is with the power unit. How does it interface to EMC? Did you have enough documentation to interface to the power unit with your old machine? Also what does the control do on contact? The old mits would backup a short distance to clear the wire path then return. At first glance the EMC2 looks like it would be the best choice.

Any help would be greatly appreciated.

well the Andrew has a manual generator, so no computer interface required.....

no the EMC2 software does not backup......yet, i had the coders get the feedrate control
working properly first. The next logical step would be to incorporate a "backup" function to emc. but we have not gone that far yet. maybe now we can.

interfacing the generator will be a cool thing to do......but it will take some time.

the mits is a good choice for emc, as it is a nice machine tool.

keep me posted.....

gentlemen,

after reading thru this thread i see that no one is aware that Linux EMC2 software has a working wire edm function built into it.

i retrofitted a Charmilles/Andrew EF330 with this software.




!!!!!!!!!!!!!!

I have this exact machine. I've got it running with the original control. Well, sort of, some of the buttons are broke and i can only burn a short while before breaking the wire.

I plan on refitting this machine. You could be a HUGE HUGE help here. Any assistance you could give would be GREATLY appreciated.

Karl

mdynac,

How do you handle a broken wire or contact with the EMC2? Also, what is a manual generator? The DWC-80 power supply is setup manually (on time, off time, power) but I will have to reverse engineer how to make it work with a retrofit.

Thanks

Hi guys...

I am finishing up my ME degree at the university of utah, and for my senior design project, 10 of us are designing a 2 axis wire EDM for a professor's research.

This is where it gets interesting:

We need sub micron precision over 25mm travels (thank god the travels are short!)
Must feed 15 to 100 micron wire
18" cubic overall maximum
Must flood as well as flush- high pressure flush not neccessary or wanted, the parts he is making sometimes break even from gentle flushing.


We are currently considering options- our plan right now is granite slabs precision ground with crossed roller rail sets, extremely geared down servo's with GOOD rotary encoders.

It is in a climate controlled lab, and we are considering putting the fluid through a heat exchanger as well, i think this would help control the temperature of the frame and cutting head assembly more actively.

Some people on the team are looking into wire routing schemes at the moment. We will most likely be using an extra axis powered brake- the software the professor has written has feed rate optimization already. Well, I think one of his masters students did that hahaha.

How do the commercial choppers function? He is using an assortment of wires including tugsten and moly, coated steels, i think whatever he can find that small. In either case, we are throwing around ideas with a cone shaped reciever right after the drive wheels / pinch and then a cam or quick return linkage driven shear blade. Another idea is to put the wire down a chamber that narrows to a rotating end mill at the end. I'm worried the end mill might pull it around in circles and wrap it up if the clearance isn't ~ nothing.

The scariest thing is that the budget for this is $3-4k. Now- that said, I think our professor has connections, and lots of spare parts sitting around- and we get free machine / grinder time and of course 10 not quite mechanical engineers on it haha.

Finding crossed roller ways / rails / any sort of off the shelf linear motion to this precision has been tough. I posted on the general mechanical -> linear forum, and basically just got guys telling me we are crazy. One guy suggested IKO CRW or CRWM crossed roller slides. Their PDF suggests precision down to about 1micron straightness at 100mm travel, but the data does not go any lower in travel then that- I'm going to call.

Anyways, none of us have any experience with precision machine design or EDM's, although 4 of us have lots of experience running / using / setting up cnc mills / lathes. Our professor does a lot of this, but right now is being fairly tight lipped as he wants us to go out and do research.

So, I'm real interested in anything / everything you guys have to say- well, except i'd rather skip the "impossible" speeches. :violin:

-Pete

Here are some home built EDM's
http://www.practicalmachinist.com/vb/showthread.php?t=152388&page=2

Jim