Servo motor direct drive or under the table?

[Moti]

Can someone tell me what are the advantages of a direct drive motor on the machine than a motor under the table, I most of the time prefer a motor under the table because I like to add a speed reducer or change the pulley to a smaller or larger one according to needs, the question is a motor under the table that is 750 w and a direct motor which is also 750 w equal in power?
Want about the torq if bout are 7 NM is the end result the same?  Or that on direct motor I don't need so much torq? are there other advantages and disadvantages?

 

[kgg]

1 hour ago, Moti said:

Can someone tell me what are the advantages of a direct drive motor on the machine than a motor under the table,

Just my two cents worth:

i) The main disadvantages

   a) To much computer controls

   b) When the motor fails it probably going to be more expensive to replace the motor and controls as it ages. As far as I know you wouldn't be able to bolt up a generic motor and be limited to a setup for that model of machine from that      manufacturer / supplier.

   c) Higher possibility of damage to internals like shafts etc. should something get jammed up. I have not seen any machines with a built in safety clutch and a lot are made mostly for the garment industry. A possible exception would be the Consew 2206RB-14-7-DD. From what I have see it has similar spec as the Consew 206RB-5 however no safety clutch and quite the price difference Consew 206RB-5 costs about $1500 USD verses about $2200 USD for the Consew 2206RB-14-7-DD.

   d) Inability to add a speed reducer.

ii) The main advantage I think would be in a production environment where machines are replaced on probably a set replacement cycle like every 3 to 5 years.

As I like a basic setup: sewing machine, servo motor (I perfer a Brush rather then a Brushless servo motor), belt/belts connecting the servo motor to sewing and maybe a speed reducer. Makes determining the problem, repairing and back running much simpler which generally means less expensive.

kgg

 

[dikman]

kgg has summed it up pretty well. From my perspective as a hobbyist the only possible advantage is a more compact setup - but that is far outweighed by the cost factor. Having a motor under the table (or mounted on the table, next to the head) gives you flexibility in your setup and if you need to replace the motor there are any number of generic motors available at reasonable prices.

A no-brainer, really.