Why is inertia influencing collision?

edit

Hi,

I am using Gazebo 1.2.5 with ROS Groovy.

I have a spatula whose head has a 0.002 thickness, the problem is that it goes through objects like a hot knife through butter. The erp, cfm, kp, kd constants don't help me in this case (for other objects they work fine).

I give them the approx values:
HARD bodies: cfm=0; erp=0.02; kp = kd = 100000000;
SOFT bodies: cfm = erp = 100; kp = kd = 1;
Like I said these values don't seem to influence the spatula heads collision;

If I comment out the <inertia> tag it works perfectly, but then I don't have inertia, which I need.

Any ideas why is this happening, and how could I solve this without commenting out the inertia?

Thanks, Andrei

EDIT:
Here is the sdf file. The model is composed of one link with more collisions/visuals. The collision I am interested in is called spatula_head_collision.

Here is the inertia commented (not going through objects):

        <inertial>
            <pose>0.000000 0.000000 0.000000 0.000000 -0.000000 0.000000</pose>
            <!--inertia>
                <ixx>0.000019</ixx>
                <ixy>0.000000</ixy>
                <ixz>0.000000</ixz>
                <iyy>0.000041</iyy>
                <iyz>0.000000</iyz>
                <izz>0.000054</izz>
            </inertia-->
            <mass>0.105000</mass>
        </inertial>

Un-commented (going through objects):

        <inertial>
            <pose>0.000000 0.000000 0.000000 0.000000 -0.000000 0.000000</pose>
            <inertia>
                <ixx>0.000019</ixx>
                <ixy>0.000000</ixy>
                <ixz>0.000000</ixz>
                <iyy>0.000041</iyy>
                <iyz>0.000000</iyz>
                <izz>0.000054</izz>
            </inertia>
            <mass>0.105000</mass>
        </inertial>

I don't think the problem is the <inertia> tag because changing the values changes the behavior of the model in simulation.

@hsu could you give me an example for erp, cfm, kp, kd constants values, so the body is the hardest / softest. Thanks.