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Fred Derf

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Everything posted by Fred Derf

  1. Thank you Kratmel for the input. The ubiquitous CAN bus has survived for quite some time for a reason. With my clean slate approach I thought I’d ask those who have experience with the Unitronics products. As for grounding, I’m often in a situation where there is no real Earth or line ground. These welding applications are Hard Surfacing or Weld Rebuild. Portable trucks with engine driven welding power supplies that do not offer any practical ground. Undesirable energy must be dissipated internally. It is not a fabrication application there is no need for high accuracy or interpolated movements. Its mostly bang bang servo control with some dynamic speed variations. The goal of these welding applications is to rebuild with molten metal as fast as possible. Sometimes with six torches simultaneously welding in excess of 150kW total. The V700 is a great inexpensive controller for these simple tasks. I do it now via analog and relay signals. I just need to do the same via network communication.
  2. I realize this might be like asking what's better, Ford, Chevy, or Dodge, and the opinions are likely as varied. I ask here specifically because I am designing a new multi-axis welding system for my current employer. We build automated welding equipment for environments that are extremely prone to EMI noise interference. Besides relay logic and proprietary circuit boards, I've used the Samba and V700 to control our equipment. Those products have worked extremely well for us. Control has been done via analog out for speed and relay logic for Enable/Direction to simple SCR drives powering 0-90VCD gearmotors. I'm old enough to have witnessed the transition from tubes to transistors and have spent a lifetime mitigating EMI in our control designs. Part of that design mentality was to never design around a network centric control system. A good portion of our business has been replacing such controls that just could not reliably operate in such a noisy environment. Now I must design a multi-axis servo controlled network system. The welding systems are often portable and have to operate from regular North American 120VAC outlets. That unfortunately prevents me from trying the Unitronics line of servos and their Unican. I don't need to have fast communication with the drives, I need reliable communication. Axis travel speeds are measured in Inches/Minute. So considerable latency will be acceptable. The V700 seems very versatile and can use several protocols. Ethernet TCP/IP, RS485/RS232, MODBUS TCP, SNMP*, CANopen, CANlayer2, UniCAN, BACnet, KNX and M-Bus via gateway. Initial servo drives are likely to be from Applied Motion Products. Unless someone has another suggestion. Their drives are available for many different protocols. Given the current design parameters, what is the best network communication protocol for this type of an application?
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