Help With Indexing Servo Drive

[MachineryE 0]

Hey Guys! New here and for that matter very green when it comes to modern industrial electronics. I come here as most new members do...with a problem! I am getting into making gun barrels. One of biggest hangups now is with my rifling machine. This is a button rifling machine, and to generate the twist rate of the rifling, the machine uses a helicaly machined bar with a follower setup which turns the tool as the hydraulic ram pulls it through the barrel. The big problem is that I have such a range of barrels that I want to make, its going to take alot of helical bars to cover all the twists. The bars are not very easy to make. Plus, with all the mechanical equipment, it reduces the pulling range. I was looking last night at the manual for an indexing servo drive and it talked about "electronic gearing" how you can vary the input pulses to output pulses that drive the motor via ratios. Hmmm... This is would be the cats meow if I could get an encoder or a linear scale on the hydraulic ram to provide feedback for that axis, let's call it "X" Then for tool rotation axis let's call it "C" would be driven by a servo motor driven by the indexing servo drive. Using the electronic gear ratio, vary the pulses from the encoder on the X axis via the electronic gearing to generate the twist that is generated by "C" turning. So for example, if I need a 1:16 twist, the ram would move 16". If the encoder has a resolution of 100 pulses per inch...Drive takes 16,000 pulses per revolution of servo. So would be a 1:10 electronic gear ratio. I don't know, Like I said, this is new stuff to me, and I am looking to try to learn something, really would appreciate any thoughts or input!

[drforsythe 15]

MachineryE: This is a common 'following' or 'gearing' application for a servo system. For linear applications, I have used linear encoders by Sony (MagneScale) and Northstar, but there are many reputable manufacturers out there with resolutions MUCH higher than 100 pulses per inch. The key thing to do is to find a reputable integrator or vendor in your area who can help size your system and ensure that the right components are selected and a properly designed system is created. Developing an application with multiple programmable gearing ratios should not be a problem for someone who works in motion control. Make sure that whatever vendor you choose that they have local support who can help you through the initial specification, startup and runoff. As with any new system, take some time to put your wants and needs on paper so the scope of work can be properly developed. If you let me know your locality in the US, I may be able to suggest a company or two. If you want, you can send a private message.

[MachineryE 0]

Good thoughts drforsythe! I sent you a PM, that would be great if you could suggest some companies that can help out. Also great idea on making up a list of requirements so its more clear. Very good to know what I'm thinking is possible! If anyone else would be interested in doing this project let me know! I think it would be alot better to get someone to do it instead of trying to figure it out. I need to get going sooner rather than later.

[Peter Nachtwey 15]

We do this sort of thing all the time. The hydraulic cylinder can use Temposonic or Balluff MDT rod for the position feedback. These rods go into the back of a hydraulic cylinder. http://www.deltamotion.com/pdf/technical/tn_fluid%20power%20basics.pdf You can see the MDT rod at the back of the cylinder. These MDT rods can provide feedback resolution as fine as 1 micron. 2 and 5 microns is common. Our controller can control both the hydaulic and the servo motor. This is important for accuracy because gearing ( following ) to an external device is not as accurate as following an internal target. It is best if the motion controller generates targets for both the hydraulic cylinder and the servo drive. The dart touches the ballon but doesn't pop the balloon. http://www.mtssensors.com/news/r-series-sensor-balloon-domonstration/index.html The RMC75 controller can be found here http://www.deltamotion.com/products/motion/rmc70/ The demo will be at an upcoming trade show. I forget which one now.