# Strange Pockets



## Crosetti (Mar 21, 2013)

Hello there!
Strange cuts have been occurring & I don't know why. Is it the machine, is it the program?
Pockets are not flat. I have tried different strategies as in offset, raster, climb & conventional with no luck & router has not slipped in clamp. 
1st pic is uneven pocket
2nd pic is random non-level sections

Any ideas?

Thank You!!


----------



## 4DThinker (Feb 16, 2014)

How are you clamping your boards down? If you can flex the board after clamping, then when the bit comes down and depending on the direction it is moving it can dig deeper or shallower relative to the board. If there is any flex in your router mount that can also lead to the symptoms you've posted. Upcut/downcut spiral bits can push a board down/router up or pull a board up/router down as they move forward or the density of wood changes. Sharks are known for flex in the gantry/router mount. You might try a slower feed speed with the same pattern in the same wood and see if that helps. 

One thing that solved many problems we were having with our HD 2.0 was adding the aluminum back plate to replace the plastic back. Our plastic back had seriously deformed under the load of the cantilevering router, and I could manually flex the router up and down relative to the bed, despite being tight in the clamp. 

4D


----------



## honesttjohn (Feb 17, 2015)

Perfesser 4D,

You are a man of logic, as well as smarts!!!!! Makes a lot of sense. 

On mine, I've noticed the bit "pushing down" the material, if there's any warpage or it's not level. One way to help even it out is to cut a little deeper when it's allowed.

HJ

Don't get me started on the clamping part


----------



## bgriggs (Nov 26, 2008)

If you lean on the spoil board to get a better look, you can also get these height changes.


----------



## MEBCWD (Jan 14, 2012)

4DThinker said:


> How are you clamping your boards down? If you can flex the board after clamping, then when the bit comes down and depending on the direction it is moving it can dig deeper or shallower relative to the board. If there is any flex in your router mount that can also lead to the symptoms you've posted. Upcut/downcut spiral bits can push a board down/router up or pull a board up/router down as they move forward or the density of wood changes. Sharks are known for flex in the gantry/router mount. You might try a slower feed speed with the same pattern in the same wood and see if that helps.
> 
> One thing that solved many problems we were having with our HD 2.0 was adding the aluminum back plate to replace the plastic back. Our plastic back had seriously deformed under the load of the cantilevering router, and I could manually flex the router up and down relative to the bed, despite being tight in the clamp.
> 
> 4D


The Shark HDs are notorious for problems with flex in the gantry because of the added weight of the larger routers they can use allowing the bit to raise on the material as the gantry moves to the back leaving uncut material and flexing down as the gantry moves forward making the bit cut deeper than it should. These problems do not always show up because of different clamping, different feeds and speeds, differences in wood density, or internal stresses in the blank itself. 

Your feed rates may not be allowing the bit to completely cut the material and is trying making the bit ride up on the material leaving uncut material behind.

I have an original Shark Pro with the MDF bed that is limited to use of a Colt router, and an HD1 With the capability to use the larger 2.25hp routers. I do not see as much flex in the Pro as I do in the HD1. I have not replaced the gantry back board yet but have a rail clamped to the back of the gantry to eliminate some of the flex. It helps when the gantry moves forward more than when it is moving back. I do plan on changing the gantry someday when I can afford the materials and find enough time.

You can clamp a stiffener to the back of the gantry board to see if this gets rid of some of your problems, if it does then you might consider reinforcing or replacing the plastic board.


----------



## bgriggs (Nov 26, 2008)

Did you surface your spoilboard at any point?


----------



## Crosetti (Mar 21, 2013)

Thanks guys!!!!
4d: I screw my boards into the spoil board. But I did notice yesterday that the spoil board came loose in 1 corner & was raised 1/16" to 1/8" in that corner, so that might be it right there! (haven't had time to fix & test, but will soon)

Bill: Good point about leaning on spoil board, but I'm careful not lean on the machine in any way.

Mike: I will do the gantry stiffener even if my problems are cured without it, I like this idea. On feed rates, I program my feeds @ 100 ipm then use the FRO to slow it down. Usually end up around 40-60ipm with down cuts & 60-80ipm on upcuts depending on the design & wood density ... too fast??

Thanks, 
John


----------



## MEBCWD (Jan 14, 2012)

John,

Your speeds and feeds will depend on bit design, material being cut, and how much vibration you have in your setup.

Actually the pictures look like the problem I described about the flex in the gantry and I think you should find that stiffening the gantry will make a big difference in the cut and allow you to use a little faster feed rates depending on you setup.


----------

