Epoxy Tearout on New Planer

I think it has more to do with how a insert head cuts.
Or I should say scraps it has very little forward rake. If your not understanding look at it like this the insert has a 30 degree facebevel. It is acts just like a chip breaker and curls up the chip.

Port orford cedar is a soft wood but kinda on the brittle side.
My hh head doesn't do as well as my jointer knives. The tops of the ridges do well but the tips of the inserts where all the cut starts and ends not good.

Helical bryd head

Jointer knives

+1 The helical head geometry is not an asset cutting soft materials.

Looks like typical soft wood helical head cutting issue? Known fact helical heads are not greatest on soft woods.
If the epoxy was not hard enough, would create same effect.

+1 How long was it cured?

FWIW - Casting (river) epoxies are extremely slow curing to avoid heat generation and yellowing typical with large mass of resin. Casting epoxy typically requires 30 days at room temperature to reach 95-98% cure point. If temp is lower, then add several weeks to cure time.

The extra small uneven divots in the groove(s) is excessive tear out. Shows the epoxy was weak or soft in those areas, which could be due the pigments or pearl additives?

Also see wood fibers and epoxy residue stuck into epoxy surface. Would have to either: not be cured, or be heated too high; for resin to get sticky and hold particles.

+1 Not to entirely blame the state of cure and/or the machine, it could be the epoxy used was 'flexible' resin system; that may never get rock hard?
Would need epoxy brand, mix ratios, time since mixing; to draw any hard conclusions?

Apologies for more questions, than answers/help.

Cheers!

+1 The helical head geometry is not an asset cutting soft materials.

Looks like typical soft wood helical head cutting issue? Known fact helical heads are not greatest on soft woods.
If the epoxy was not hard enough, would create same effect.

+1 How long was it cured?

FWIW - Casting (river) epoxies are extremely slow curing to avoid heat generation and yellowing typical with large mass of resin. Casting epoxy typically requires 30 days at room temperature to reach 95-98% cure point. If temp is lower, then add several weeks to cure time.

The extra small uneven divots in the groove(s) is excessive tear out. Shows the epoxy was weak or soft in those areas, which could be due the pigments or pearl additives?

Also see wood fibers and epoxy residue stuck into epoxy surface. Would have to either: not be cured, or be heated too high; for resin to get sticky and hold particles.

+1 Not to entirely blame the state of cure and/or the machine, it could be the epoxy used was flexible resin system; that may never get rock hard?
Would need epoxy brand, mix ratios, time since mixing; to draw any hard conclusions?

Apologies for more questions, than answers/help.

Cheers!

- CaptainKlutz

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I disagree with your analysis. The reason is this. Inserts cutting head rely on curling a chip out of wood. It does not scoop out wood in the same fashion as a simple knife head planer or jointer.
The hard brittle epoxy doesn't bend the way a wood fiber.
Now if the op had a Oliver with a itch head he might have been successful.
Let look at the difference between a Oliver itch head with no face bevel on the knife.
And a bryd head with a facebevel. And very little forward rake.



Clearly we can see the 30 degree face bevel on the bryd head that scraps out wood if it didn't have the slightest tilt Im betting the power factor would be up up and away.

AJ2 - Disagreement is OK. Have formulated and dealt with machining issues on polymers for decades.
But I am not a machinist, and more than likely am not describing this accurately; which makes it easy to disagree?

What bothers me is your base assumption

The hard brittle epoxy doesn't bend the way a wood fiber. - Aj2

Click to expand...

Based on pictures and my experience, I think the epoxy was not hard, but SOFT.

Let me explain why this is problem:

A polymer is not metal or wood. Any polymer mixture as bowl of mixed sized objects (example: Popsicle sticks, gravel, grass, string, and paperclips). The ingredients have different densities, sizes, and strength. These are attached to each other tightly on the 'ends', and occasionally on sides. There are many areas not attached to each other, which is part of what makes a polymer softer/harder; and defines how the polymer chains move against each other. Hard rigid polymer have short chains, with many more cross links. Soft polymer has lower cross link density, and usually much longer object lengths.

When machining a soft polymer: A wide area in front of the machine cut moves slightly, and cutting edge lifts the polymer vertically instead of cutting it. The long soft chains also may not cut at contact point, they stretch and tear at weakest point; unless you exceed the heat capability of polymer during tearing and melt it apart. Due to the movement, the cut is not straight across the (hopefully flat) surface, but goes below the surface.
That is why I called the divots, tear out.

The best method for machining soft polymers is to make short stroke cuts with zero rake angle and larger relief angle, removing smallest width bite possible per cut, while taking a deep enough cut to force cut and not surface tear. Usually adjusting the speed to ensure minimal self heating. Any time you use steep rake angles or long angular cuts you exaggerate the polymer movement/tearing, and increase tear out. Best version of this method is grinding with small abrasives.

Personally, would never use helical head planer to machine a SOFT polymer. A hard polymer might can work, but not soft one.

IMHO - the best tool for flattening river table is router sled with fly cutter/spoil board cutter, or wide belt sander with large grit to avoid clogging the paper.

The issue for this entire discussion is we have no data on 'softness' of epoxy polymer as cured to know if it was source of tear out? Which makes all of this typing simply an educational exercise.

Cheers!