Off by a Mile

[AGMantz]

I'm currently attempting to wire out some ID inserts, 6 to be exact. I wired out the first one and felt like it went smooth, sent it over to our toolmaker to check dimensions and such and to my surprise I somehow managed to mess it up pretty bad. The insert is 3.181 in. long with a hole in the center with a radius of .129. Which means from the center of the hole to the edge it should be about 1.59 inches on both sides. I somehow managed to be out .040 in one direction which is just unimaginable in WEDM. Horizontally I was spot on so that rules out the work piece shifting during cutting. I'm at a complete loss for what possibly could have caused such a huge disparity. If any WEDM gurus out there have any ideas on what could have caused this please share your thoughts.

I'm very new to WEDM so don't have a lot knowledge or experience under my belt. I'm using a Mits MV4800 as my machine and ESPRIT for programming. Only two months in and I already feel like I'm going to lose my mind.

-AGMantz

 

[plastikdreams]

What are you using to pickup center on the part?

 

[AGMantz]

They gave me .19 diameter start holes so I am just doing a center pick up with the wire.

 

[plastikdreams]

Check to make sure the holes are straight...if they are slanted your pickup will be off.

One way to check is pick up normal, zero out, then set the pickup to run 45° from what you just did. The numbers should be within tenths if the hole is straight.

 

[AGMantz]

Just checked all the start holes including the one I already cut from all of them were within a tenth so that can't be the problem. Thanks for the tip I'll be checking all my start holes from now on just to be safe.

 

[OffsetLeft]

I'd start by looking in ESPRIT - is the start point of your program at the center of the start holes, or is one of them set at 1mm?
If you pick up the center of your hole and hit START without moving to that position, you won't get the results you hoped for.

 

[AGMantz]

All of my start points are definitely at the center of my start holes I double checked the code to make sure it has the right coords and everything seems to check out. I'll screenshot a picture of what my ESPRIT layout looks like so you can see what I'm working with.

NOTE: Ignore on the SS that the top 4 are not programmed out I was messing with them trying to figure out what was going on and haven't re-tooled them yet.

 

[WireEDMServices]

Are you burning the center hole as well or just the rectangular shape?

 

[AGMantz]

Just the outside rectangular shape.

 

[WireEDMServices]

My first thought is that the center hole is already off location in relation to the start hole.

 

[plastikdreams]

So you pick up one center hole as your x,y0?

The wire cuts and moves to a clearance hole, rethreads, and then cuts?

If the center holes are not in the correct position then the hole will not be centered in the part.

When cutting multiple pieces with predrilled holes you need to be sure everything is right, especially if you didn't do the work.

It also looks like you are cutting the full path and letting the parts drop out. Are you sure a part didn't snag the lower head and move your workpiece?

What direction was is out?

 

[otrlt]

I'm currently attempting to wire out some ID inserts, 6 to be exact. I wired out the first one and felt like it went smooth, sent it over to our toolmaker to check dimensions and such and to my surprise I somehow managed to mess it up pretty bad. The insert is 3.181 in. long with a hole in the center with a radius of .129. Which means from the center of the hole to the edge it should be about 1.59 inches on both sides. I somehow managed to be out .040 in one direction which is just unimaginable in WEDM. Horizontally I was spot on so that rules out the work piece shifting during cutting. I'm at a complete loss for what possibly could have caused such a huge disparity. If any WEDM gurus out there have any ideas on what could have caused this please share your thoughts.

I'm very new to WEDM so don't have a lot knowledge or experience under my belt. I'm using a Mits MV4800 as my machine and ESPRIT for programming. Only two months in and I already feel like I'm going to lose my mind.

-AGMantz

Hello Mantz,
Don't be too negative on yourself, these things happen allot in EDM. I have found that wire edm can be capable of extremely tight tolerances, but I have also learned to not rely fully on the process. Generally I will provide a "true" start bore on a unfinished blank. The wire contractor does his work, but I complete the job true to his cut.

Essentially, I never bring a finished part for a edm contractor to complete.

 

[SeymourDumore]

Essentially, I never bring a finished part for a edm contractor to complete.

( please imagine that to be a facepalm )

To the OP


Would you mind posting the code?
Seems pretty simple shape and feature with straights and radiuses so it should be no more than a few lines.

 

[otrlt]

( please imagine that to be a facepalm )

To the OP


Would you mind posting the code?
Seems pretty simple shape and feature with straights and radiuses so it should be no more than a few lines.

A .04 error is most likely an error in the set-up process. I would also bet that he could not locate to within .0005 of an existing datum.

 

[plastikdreams]

They gave me .19 diameter start holes so I am just doing a center pick up with the wire.

Reread this, are you picking up on the start hole or the hole in the center of the part?

 

[plastikdreams]

A .04 error is most likely an error in the set-up process. I would also bet that he could not locate to within .0005 of an existing datum.

How do you know what he or the machine is capable of?

 

[SeymourDumore]

A .04 error is most likely an error in the set-up process. I would also bet that he could not locate to within .0005 of an existing datum.

Against my better judgement ...

Yes, it is either a setup or program issue.
BUT!
If your wire EDM is made within the last 25 years and you cannot reliably locate within .0001 to a feature, then you better give it a good cleaning, you've crashed it a few times or you're just ain't made for the cut! ( pun intended )

 

[otrlt]

Against my better judgement ...

Yes, it is either a setup or program issue.
BUT!
If your wire EDM is made within the last 25 years and you cannot reliably locate within .0001 to a feature, then you better give it a good cleaning, you've crashed it a few times or you're just ain't made for the cut! ( pun intended )

Hello Semore,
I have worked with at least 6 different edm contractors and they all have failed miserably. Your statement of locating to within .0001" is laughable.

I'm the prime contractor that has to pass inspection, it's upon my company to deliver.

We no longer take in jobs that require edm.

 

[newtonsapple]

Hello Semore,
I have worked with at least 6 different edm contractors and they all have failed miserably. Your statement of locating to within .0001" is laughable.

I'm the prime contractor that has to pass inspection, it's upon my company to deliver.

We no longer take in jobs that require edm.

When 6 EDM shops have failed, odds are that you are either incredibly good at finding bad shops or you are demanding something that isn’t possible. Most failures in EDM shops I am aware of occur when the customer insists their parts accurate and are square enough or round enough to register off with out any additional work.

By about the 3rd shop, you should have realized that you need to properly communicate a mutually agreeable method of determining success. When you get the parts home and find later decide they don’t work, part of the failure is on you for not clarifying expectations.

 

[otrlt]

When 6 EDM shops have failed, odds are that you are either incredibly good at finding bad shops or you are demanding something that isn’t possible. Most failures in EDM shops I am aware of occur when the customer insists their parts accurate and are square enough or round enough to register off with out any additional work.

By about the 3rd shop, you should have realized that you need to properly communicate a mutually agreeable method of determining success. When you get the parts home and find later decide they don’t work, part of the failure is on you for not clarifying expectations.

Hello newton,
All of my edm debacles have a in depth Zeiss metrology inspection report documenting the failure in detail. We communicate very well with our costumers and contractors.

The problem that I see with all of the edm contactors that I have known, is that their work has never been inspected to this level.

We have a near perfect record of quality, over 99% of our work passes inspection. I want to get back to 100%.