home made large bore indexer
Posted: Wed Jul 05, 2023 3:56 pm
I'm not sure if I've picked the correct forum to post this question, so please move it if need be.
I have retrofitted a SWI Trak DPM to Centroid ALLIN1DC control and want to add a 4th axis indexer to spline shafts. Here's the twist: I need to be able to pass a 2" diameter shaft thru the indexer bore. I don't need simultaneous rotary/linear motion, I will be using the 4th axis for rotary positioning only.
I have a Cushman Super Spacer with an 8" 3-jaw chuck that would be ideal to hold the workpiece, the challenge is how to drive it with a servo. My thought is to use a HTD pulley set and belt just like the drives for the linear axis ballscrews. I recognize there won't be any mechanical gear reduction normally supplied by the ballscrew. Has anyone built an indexer similar to this, and if so, what is the minimum ratio required to achieve typical indexer resolution? I assume the higher the ratio the better, and I was hoping to find a source for HTD pulleys at least 6" OD, preferably closer to 8" with a tooth count of something above 144. They don't seem to be available in the 5mm belt pitch size (the size I was hoping to use). I would not be opposed to having a pulley custom wire EDM'ed but, again, I am having trouble nailing down accurate geometry to draw up a CAD model to give to a shop to make one. Anybody who can point me to that data would be my hero.
I envision replacing the master index plate with that pulley, and driving it with a servo with the smallest available pulley on it's output shaft. An air cylinder could be used to actuate the Super Spacer's spindle brake and activated by a spare M code. ( Actually, I would probably set it up as spring applied, air cylinder release for failsafe operation.)
Does this sound feasible? If you read between the lines, I'm trying to do this on somewhat of a modest budget, especially since I already have the Super Spacer and the alternative is a rotary table in the 210 mm platter class to get a thru bore over 2.000". I haven't seen any of those go for less than about $4k used on auction sites...too rich for my blood at this point.
I welcome any helpful data or component leads anyone might be able to give.
I have retrofitted a SWI Trak DPM to Centroid ALLIN1DC control and want to add a 4th axis indexer to spline shafts. Here's the twist: I need to be able to pass a 2" diameter shaft thru the indexer bore. I don't need simultaneous rotary/linear motion, I will be using the 4th axis for rotary positioning only.
I have a Cushman Super Spacer with an 8" 3-jaw chuck that would be ideal to hold the workpiece, the challenge is how to drive it with a servo. My thought is to use a HTD pulley set and belt just like the drives for the linear axis ballscrews. I recognize there won't be any mechanical gear reduction normally supplied by the ballscrew. Has anyone built an indexer similar to this, and if so, what is the minimum ratio required to achieve typical indexer resolution? I assume the higher the ratio the better, and I was hoping to find a source for HTD pulleys at least 6" OD, preferably closer to 8" with a tooth count of something above 144. They don't seem to be available in the 5mm belt pitch size (the size I was hoping to use). I would not be opposed to having a pulley custom wire EDM'ed but, again, I am having trouble nailing down accurate geometry to draw up a CAD model to give to a shop to make one. Anybody who can point me to that data would be my hero.
I envision replacing the master index plate with that pulley, and driving it with a servo with the smallest available pulley on it's output shaft. An air cylinder could be used to actuate the Super Spacer's spindle brake and activated by a spare M code. ( Actually, I would probably set it up as spring applied, air cylinder release for failsafe operation.)
Does this sound feasible? If you read between the lines, I'm trying to do this on somewhat of a modest budget, especially since I already have the Super Spacer and the alternative is a rotary table in the 210 mm platter class to get a thru bore over 2.000". I haven't seen any of those go for less than about $4k used on auction sites...too rich for my blood at this point.
I welcome any helpful data or component leads anyone might be able to give.