Machining Solid Carbide 1

[mechedoc]

So, I made a critical error on specifying some cutting tools and now we have 30 solid carbide tools that have a taper that is 0.334" too long for our customer's machine.

While the interim solution is to use adapters to make them work for now, long term that is not something we would want out in the field.


The taper on the left hand side of the attached image is 0.925" and should be 0.591".
The center has to be maintained as that is how the tool is sharpened.


Every vendor we have talked to has no problem with taking in the length of the tool (usually with wire EDM), but none have committed to putting the center back in after the operation.

Internally we talked about center grinding after the shortening, but are having a hard time sourcing the proper tools.


My question to the group is what other options would we have for salvaging these?

Thanks

 

[HGMorgan]

A Sinker EDM could do it.

Harold G. Morgan
CATIA, QA, CNC & CMM Programmer

 

[btrueblood]

The problem is how to get the sinker edm aligned to "perfect center" on the existing taper profile. Or, does the angle of the taper change when the tool is shortened, i.e. does the taper need to be reground anyway?

One way might be to center the tool in sinker edm using existing centers, and sink the small diameter some .5" or so deeper, then wire off to the .591, and re-center with the small diameter to re-cut the center taper.

 

[mechedoc]

Thanks for the replies.

Luckily the taper angle and gage diameter are correct, it's just too long - so we don't have to regrind the entire taper.

The basic method of making the center pilot deeper, then wiring to length, then recentering was our original thought - but most of the suppliers we talked to seemed to prefer wiring first then recentering off the taper. I have a feeling that's more for reducing the number of operations - but can't confirm it.

I'll have to look into the sinker edm process and see if we have an approved vendor for it. Am I correct in thinking plunge edm is a different name for sinker edm, or is that another variation on the edm process?

 

[HGMorgan]

A cut & paste:
Plunge EDM, which goes by many names including conventional EDM, sinker EDM and ram EDM, produces parts by eroding materials in the path of the EDM tool using electrical discharges, or sparks that can generate heat anywhere from eight to twenty thousand degrees. The piece of material to be worked on is connected to a power supply and then an electrode is used to create a conductive path and cut the material into the desired shape or pattern. There is no actual contact between the electrode and the work piece as the erosion takes place as a response to the electrical current being produced. The process takes place in a dielectric fluid, allowing electricity to be conducted. The fluid is always used to flush away the debris from the process allowing for clean and burr free edges. Plunge EDM is ideal for applications such as injection mold tooling, micro hole drilling, keyways, washers and scientific research apparatus. Industries served include aerospace, medical, tool and die, automobile and military. It is able to achieve high tolerances on complex geometries and patterns. Unlike wire EDM which uses a pre-drilled hole to feed the wire into for the process, plunge EDM does not require a hole. Common plunge EDM electrodes include machined graphite, copper tungsten and brass.

One of the two major types of EDM, plunge EDM differs from its counterpart wire EDM nor only in terms of the type of electrode used but also because plunge EDM has 3D capacities while wire EDM can only produce 2D parts. Furthermore, plunge or ram EDM can be applied to hard materials including stainless steel, copper, graphite, and exotic metals that would cause difficulties during conventional machining. The process of electrical discharge machining typically takes place in a shallow bath of dielectric fluid, which prevents premature sparking and flushes away debris. For high precision pieces, CNC EDM is used in which CNC machines are used to guide, monitor and control the machining process, as well as CAD and CAM software to ensure the highest tolerances. One disadvantage to using this process is the extra time and costs involved with fabricating the electrodes necessary for the specific procedure. These can be costly and can wear down easily due to the intensity of the electrical process. Therefore, it is important to take this aspect of EDM machining into consideration before committing, however, the tight tolerances and minimal product damage remain as advantageous benefits to using EDM.

Bottom line:
EDM can do it and to very tight tolerances. It is not cheap.


Harold G. Morgan
CATIA, QA, CNC & CMM Programmer

 

[mechedoc]

Thanks for the detailed response HGMorgan.

While some of that information is available in bits and pieces elsewhere - you brought it together succinctly.

 

[capnhook]

.....except for the part that says "...wire EDM can only produce 2D parts"

A good WEDM can produce parts with 3D draft, typically up to 25 degrees.

Proud Member of the Reality-Based Community..

[green]To the Toolmaker, your nice little cartoon drawing of your glass looks cool, but your solid model sucks. Do you want me to fix it, or are you going to take all week to get it back to me so I can get some work done?[/green]

 

[HGMorgan]

capnhook is correct, there are multi-axis wire EDM machines that can cut a SIDE angle shape.
Since that wouldn't work & didn't apply to this situation, I didn't edit the cut & paste.

Harold G. Morgan
CATIA, QA, CNC & CMM Programmer

 

[capnhook]

Yep, that's the problem with cut and paste...

Proud Member of the Reality-Based Community..

[green]To the Toolmaker, your nice little cartoon drawing of your glass looks cool, but your solid model sucks. Do you want me to fix it, or are you going to take all week to get it back to me so I can get some work done?[/green]