Metallographic Individual vs. Central Automated Polishing

Metallographic Automated Polisher - Equipment

Metallographic semi-automated polishing machines are available with individual/ single specimen loading or with a fixed central holder. The main advantage for using a central force holder is that the overall specimen flatness is better. The primary advantages for individual specimen holders are fewer required grinding/ polishing steps and the ability to repolish samples without the need to re-planarize the specimens.

Return to top

Individual vs. Central Force Automated Polishing

Individual Force: The force is applied to each sample individually. The main advantage for single or individual sample preparation is the elimination of the planar grinding steps. The primary disadvantage is that the specimen plane is not fixed in a rigid position during grinding and can result in loss of flatness across the specimen.

Central Force: For central force holders the specimens are locked into a rigid position or fixed plane so that the specimens cannot rock during sample preparation, especially the planar grinding or coarser grinding steps. The advantage is that the flatness across all the specimen mounts is better than individual force sample preparation. The main disadvantage is that 1-2 more planar grinding steps are required using coarser more damaging abrasives.

Advantages

Individual	Central
Reduced number of preparation steps and lower cost for consumables	Flatter specimens
Sample can be re-polished without having to planarize specimens in the holder	Specimens can be polished in both the contra and complementary head / base directions

Disadvantages

Individual	Central
Can result in loss of flatness across the specimen if heavy duty grinding is required	Minimum of 3-sample are required in the holder
It is recommended that the grinding and polishing steps only be done at matching head and base speeds with the rotation being in the same direction	Typically requires 1-3 additional coarser grinding steps to planarize all specimens
	Additional grinding steps increase both consumables cost and total preparation time
	Coarser grinding can result in more surface and subsurface damage to the specimen
	Need to planarize specimens again if they are removed from the fixed holder

Individual vs. Central Force Preparation Requirements

Step	Individual	Central
Planar Grinding	n/a	120, 240 grit SiC
Rough Grinding	360, 600 grit SiC	360, 600 grit SiC
Fine Grinding	800, 1200 grit SiC	800, 1200 grit SiC
Intermediate Polishing	1 micron polycrystalline diamond on a woven pad	1 micron polycrystalline diamond on a woven pad
Final Polishing	0.05 micron NANOMETER alumina on a napped pad	0.05 micron NANOMETER alumina on a napped pad

Individual Force Automated Polishing

Individual Force: Individual specimen force can be applied using the Quick Release Chuck system by screwing down the outside of the coupler so as to lock the specimen mounting plate into a rigid plane. This set-up allows for the individual holder to be removed and cleaned. This holder also eliminates the need to replane the samples if they are removed from the holder.


Individual Force Pistons in the off position.		Individual Force Pistons in the on position - Force is applied to each specimen individually.

Central Force Automated Polishing

Central Force: The individual pistons apply the polishing force to the landing pads and pushes down the holder through the spring loaded central male coupler (patent pending). For central polishing a minimum of three samples locked into the holder is required; however, flatness is then fixed over all the mounted specimens.


Central Force in the off position.		Central Force in the on position - Force is applied to the rigid specimen sample holder.

Autopolishing Heads for Individual and Dual Central / Individual Polishing

Polishing Wheel Size	Individual Force only	Dual Central / Individual Force
8 and 10-inch diameter wheels	FEMTO 1100	FEMTO 1500
12 and 14-inch diameter wheels	FEMTO 2200	FEMTO 2500