Tajima machines has many plastic parts in order that machine will run much quieter that other machines.Sound of TAJIMA machines is something special and it can not be compared with noise of other machines like SWF of ZANGS.
Even so,all this plastic parts(reciprocator,take-up lever Cam,Sprial Bevel gear)are very durable(longer that metal parts on other brands)and consistent.It prevents further damage on machine if mistake is made(non lubrication,hitting the hoop etc.),and machine is moving very smoothly.
In my oppinion Tajima is the best machines,but therefore it's a reason why they are very pricey when new.