encoder count recomendation

[johnscnc]

hi just wondering what brand,type, and line count you recomend for use with the viper 200. i have motors rated at 4500 rpm with 2-1 belts to a 5tpi ballscrew for x and y. the z is 1-1 on the belts with the same 5tpi ballscrew would like to be able to command to .0001 and rapid around 200ipm. i think this is possible with mach 3 and a 4x step muliplier with 1000 line encoders or would 2000 line with 8x step multiplier be better? any info would be apreciated. thanks, John

[TOTALLYRC]

5tpi*2:1 =10motor turns/In.*2000cts=20,000cts/in.
20Kcpi*3.3ips(200ipm)=66k cps or 66ksteps/sec


20ksteps/in =0.00005"/step which is half of what you are looking for so using a 500line encoder in quad will give this resolution.

A 1000 line encoder in quad will give 0.000025/step. Which is 40k steps per inch x 3.3ips(200ipm) = 132khz

132/8=16,500khz which is well within mach3's range of output thru the pport

2000 in quad is double that so it would be 32khz which mach3 should run on a good computer or a smooth stepper or other pulse generator.


I had to take my shoes off to do the math, so maybe somebody can check it for me.

Mike

[johnscnc]

thanks totallyrc the math loks good to me. i was more wondering what resolution i would need for a good error following range "window".this a 9 x 49 mill with ballscrews so there shouldn't be excessive inertia. and would i want the same on the z or half the count?

[TOTALLYRC]

On my machine I use 500 in quad =2000 oer rev with a 5tpi screw and I can command .0001 jog moves. But since there is .003 backlash in the screw currently, I am content. I have a 500 step following error, which I am going to probably decrease as I get a better handle on the servo tuning

I would use double the encoder count on the z to keep it to same on each axis.if you use 2000 on the X and Y use, use 2000 on the Z to keep it the same.

Mariss of Gecko has switched all of his test equipment to the amt-102/103????? capacitive encoders that you can get from Digi-key and highly recomends them. They also offer adjustable resolution via dip switches on the encoders.
I am currently using the renco encoders from ebay and they are working well for me at this point.

When I order encoders for the lathe conversion soon, I will give the amt's a try.

[johnscnc]

thanks totallyrc those look like interesting encoders problem is the motors are set up with shaft couplers and self contained drc encoders model 77L-11-A13-635AH of unknown resolution and possibly single ended they also say 6vdc so i dont think they will be useable maybe al knows somthing about them?

[Larken]

Mariss of Gecko has switched all of his test equipment to the amt-102/103????? capacitive encoders that you can get from Digi-key and highly recomends them. They also offer adjustable resolution via dip switches on the encoders.

Thats a single ended encoder and one of my customers had to add differential line drivers to drive a 10' cable reliably, but they worked ok after that.
You can't a beat US digital differential encoder though.

[johnscnc]

thanks larken. if those are single ended do you think i can use the ones already installed or would that 6vdc not work with the viper ? i'll check the number of wires and any other info in a few days if i can the mill is at my brotherinlaws at the end of a really really muddy section line driveway and i don't have a 4wheel drive maybe you've seen north dakota in the news lately it's not a pretty sight. What model from us digital do you use they have quite a few models .thanks again, John

[Larken]

6Volts ?? Its probably 6 volts max, but will run on 5 volts.

BTW, Don't be wiring up those vipers while your standing in 2 feet of water.

[johnscnc]

thanks for the reply maybe i'll have to try them there are 10 wire connection screws on them only 5 labeled and only five currently used though. ch A, ch B, ch Z, v+, grd. any way to tell what resolution they are? we are in western nd northwest of bismark 35 miles no river flooding here just 6-10' snow banks yet just got done with another blizzard i think i heard there is another planned for thursday or friday though. 2 more inches to be record snowfall for a winter! it's getting old.

[Larken]

Whats the model and part# of the encoder ? It woulod be best to run it in differential mode.

[johnscnc]

hi the model on the encoders for the x & y are : DRC 77L-11-A13-635AH the AH lettters are only on the y. the z has what looks identical but relabeled by tri-onics, the original converters of the mill, i didn't take any numbers off of it though.any help would be appreciated. thanks, John