[Bob fran]

Recently acquired the above mill, Y servo is burnt and X servo have defective gears of the encoder. The gearing is to compensate for the metric Leadscrew. I'm planning to use newer servo motors and new controller. I will no longer use the gearing for the encoder. Needing your opinions whether I'm on the right track. I'm comfortable with metric system. :drowning:

[Al_The_Man]

What type of controller are you thinking of using? All of the modern controllers I use, it is not necessary to gear an encoder because the ball screw is metric, you just enter the amount of encoder pulses per distance unit of measure.
Al

[unterhaus]

You are on the right track.

As an example I have never seen a linear encoders that didn't have metric spacing. They just convert units in the the dro or control. It doesn't hurt that there are exactly 25.4 mm per inch. Gearing is a bad idea, they were compensating for a shortcoming in their control.

[HuFlungDung]

Summit Dana is Bandit, is it not? Even that control could use metric. However, if the two screws were different pitches, that would account for them attempting to patch the installation with gears because I don't believe circular interpolation would work if the XY were different.

That control may not have even used encoders, but resolvers instead.

You might as well get right into a new retrofit of it, if the rest of the machine is decent.

[Bob fran]

Al/Unterhaus/huflungdung,

Thank you, I'm begining to see the light at the other end of the tunnel. I plan to use either Rutex or Gecko to drive the servo motors. Any suggestion of what size of servo motor to use? Will use whatever software you guys recommend. Could anyone shed light on the number of encoder pulses required for a 5 mm pitch ballscrew to be readable also in English. So I can have both worlds, Metric and English.

Summit Dana is Bandit and all three motors have gearing on the Resolver(not encoder). The mill is mechanically in good condition, ballscrew is quite tight and the ways have only 0.001 differences. Leadscrew is 5 mm pitch.

[Al_The_Man]

It makes sense now you mention it is a resolver. Usually the reason for gearing a resolver is because of its low resolution, if you convert the motors to encoder, they can be driven direct from the motor shaft.
Al

[HuFlungDung]

BobFran,
Your metric screws should be just fine. Since the ratio for converting metric to inch is exactly 25.4 mm/inch, this works out to 5.0800 turns of the screw to move an inch. Multiply this by your encoder count/rev and you will end up with a nice whole number. For example, a 1000 line encoder may give 4000 counts per rev, so your counts per inch will be 20320.

In most cnc controllers, this counts per inch is a one time entry. If it were metric based software, they might ask your for counts per revolution, instead of counts per inch.

If you choose to work in inch or metric after that, the software takes care of the conversion for you. There is no need to alter the parameters after the machine is correctly set up.

As for cnc software, if you are on a tight budget, you could try what the other guys around here are using, which is Mach2. I honestly wish I could see an installation using this to see how it rates with professional cnc software. Its not expensive to try out, I guess.

If that is not to your liking, then look at the Ajax cnc or the Camsoft cnc.

[Bob fran]

Thanks Al / huFlungDung

With the new knowledge you gave me I will go ahead with the plan of retrofitting with newer motor and ENCODER. I have 18 / 19 Bobcad to use on Mach2 as you suggested. Will use a pot to control Spindle speed for now, Ajax will be considered later. I will get back to you guys along the way.