Hey Peter,
This is a frequently asked question. Unfortunately yet there is no working User’s FAQ in this forum.
Yes, you need one for ModBus/RS-485 communication between CNC Controller and VFD, but if you forgot to order it at Onefinitycnc.com, this an item you can find everywhere. Search for DB-25 breakout adapter at a good electronics supplier.
For this, read the information in your VFD manual and your spindle manual.
Usually you will need 2+PE if your VFD is made for single phase input and for output you will need shielded 3+PE for the three phase spindle. Cables especially made for drag chains are e. g. LAPP ÖLFLEX® CLASSIC FD 810 CY or IGUS chainflex® .
As for choosing the wire’s cross-section area (or diameter aka gauge ), it is dependent on current (i.e., ampères).
In my VFD manual, it says:
– Source: Omron MX2 User’s Manual
Note that if you use 115 Volts, for the same power (kW/HP) double the amperes than with 230 Volts do flow and therefore you will need wires with the double cross-section area then.
- See also: Comparison chart of AWG (blue), SWG (red) and IEC 60228 (black) wire sizes (hover mouse over a field to see dimension)
You may also be interested in this, this, this, also this, and see here and here.
The shield of the shielded cable should be clamped to ground (see picture) or grounded with a grounding cable gland.
Both earth portions of the shielded cable must be connected to the earth point by cable clamps.
– Source: Omron MX2 User’s Manual
The other day when discussing connection of both ends of shield, Mike @mchoonmaker linked this paper that I can recommend:
PS: Note that the link in the article is broken, the working link is here: Begin with the End in Mind — Proper VFD Cable Termination