[stockdancer]

I am getting a web on the outside corner of a part. How do I set blocking to eliminate the web? I have attached a picture to clarify what I mean...notice the crease (webbing). I have also included pictures of the problem area. Let me know what you think. Thanks!

[wendtmk]

you might get a quicker answer if you asked this in the vacu-forming & thermo-forming sub-forum. This forum is for general woodworking.

Mark

[zool]

It looks like the damage is due to heat being concentrated [building up] in one small area coupled with tool pressure coupled with the material being abraded by machining on the area when it is overheated.

To be more specific [details details!!!]:

To grasp the following, think of all the activities that are taking place when a piece of material is machined.

First, think of the "webbing" as fractures in the material. [Webbing = fracturing.]

Now, think about:

The Physical Items Involved

The Material
The chemical composition of the material
The physical composition of the material

The Machine and Tooling
The machining process
The spindle and its condition
The tooling [Diameter; How many flutes?; Spiral or straight; Up cut or down cut?]
The condition of the tooling [Is it sharp?!!]
The feeds and speeds

The Machining Process
The interaction of the material and the tooling
The various processes that are taking place when the tooling interacts with the material
a. The initial tool strike
b. The separation of the material [the cutting process]
c. The movement of the removed material from the cutting site
d. The condition of the materiel that remains

The Result of the Material/Tool Interaction
What has happened to the tool
What has happened to the collet
What has happened to the spindle
What has happened at the precise site of the material/tool interaction
What is the relationship of the portion that is being shaped with the larger piece of material
What has happened to the material
a. that was removed
b. that remains

What has happened chemically and physically to the remaining material, and how and why?

What is the most common physical result of machining any material? HEAT. [If you would like the chemistry and physics of this process I would be happy to share it .. but maybe later.]

Therefore, what is the effect of heat on the machine, the tooling, the material that is removed, and the material that remains?

To get to the core of the matter [finally!!]: If you heat a solid and them hit it over and over, what happens? It changes shape, and if it continues to be struck as it cools, it breaks!!!

In Summary:

The area in which there is damage [webbing/fracturing] is prominent from the majority of the material being machined, therefore has less attachment to the surround material [think of the material surrounding the area being machined as a heat sink], hence the ability for heat being generated by the machining process to be transferred away quickly from that specific area being machined is limited by the lack of surface area contact, which results in heat buildup in the prominent portion, which coupled with the friction and abrading [pressure or being struck], raises the temperature to a point that the material begins to decompose chemically and physically, then when it is struck by the rotating tool machining the material continually, this causes the webbing/fracturing to appear, as the chemical composition and physical integrity of the material has deteriorated because of the heat buildup and the abrasion.

The Cure:

Ultimately the solutions are:

1. About feeds and speeds
2. Removal of heat

Feeds and speeds are not my strong point, so I leave this to be answered by someone wiser and more experienced than I. Why: I caused a piece of wood to burst into flames when I first started.

Removal of heat I can handle though.

Metal workers flood the area being machined with a fluid, this lubricates and removes swarf, and keeps the materials being machine and the tooling cooled.

I am guessing you do not want to flood with water, so that leaves air. [Both are "fluids" actually .. but I digress]

Using the same device to direct coolant [those flexible hose thingies] as a metal worker does, direct high volumes of air [does not even have to go through a dryer .. actually undried air might be better] onto the site being machined.

Then the following actions will be taking place all at once:
a. area that was machined is being cooled
b. area being machined is being cooled
c. area to be machined is being cooled
d. tooling is being cooled
e. swarf, which contains heat, is being quickly removed [along with the heat it contains]
f. swarf, which dulls a tool as it is waste being cut again if not removed, is quickly being removed, thereby keeping the tooling from unnecessarily dulling from unnecessary use, which means the tooling stays sharper longer, which means it will cut cooler longer.

And we all live happily ever after.

THE END.