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Open up Photoshop and create a new layer and name it base. Right Click on base layer and select Blending Options. Go to bevel and match the following settings (opens popup)

Bevel Settings

Now Duplicate the base layer either by right clicking it and choosing duplicate layer, or by dragging the layer into the folder icon. Move the new dot slightly to the top-left. Then right-click on the new layer and choose mergedown to merge with the original base layer. This will form the base of the robotic arms.

Once this is set, select the Photoshop Paintbrush Tool and select a fairly thick circular brush with hard edges choose a light grey as your color, I am using 15% grey or RGB (218, 218, 218) and just make a 'dot' on the canvas

Take the merged base layer and Duplicate it, name the new layer segment. In the segment layer notice that the layer style has also been duplicated, discard the layerstyle by dragging the photoshop 'effects' sublayer into the trash can icon. Your segment should now look something like the one shown in the picture. Place it slightly offset from the position of the base layer.

Duplicate the segment layer and move the new layer so that its position is slightly different from the position of the previous layer. Then Duplicate it again and again till you start building up chains of segments which start to look like a metal robotic arm

Now you can create layers on top of the arms to add things to the arms.

The hands you see in the example were quickly created with the pen tool and shaded with dodge and burn, if you do this for a serious project you should probably add some more detailing. You can try placing pictures on top of the arms, like I did with the shallow bowl that you see in the example to your right.