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ExCello power knee info

V

Vector Warbirds

Member
Greetings! I have an ExCello 602 mill and I am thinking about installing a power knee servo. From what I have seen these mills need a more powerful unit than the run of the mill and hand cranking the ExCello compared to a Bridge you can tell the knee is harder to lift. Servo Company makes the 200 series but its over $1000 so no dice there. Does anyone here have an ExCello with a power knee and if so I would appreciate your input. I am pondering the use of a gear motor and making my own. Have been looking at E bike motors of DC 24v 250w and chain driving to the knee shaft. Ca Lem did a convert on his Bridge and looks like it works. Just kicking around ideas at this point so your thoughts are appreciated. Have watched all the Tube videos and not impressed with the cheap drives.

Cheers!
 
Welcome. John installed an Align/clone? power feed on his BP mill as well as his prior mill. I can't say how comparable that would be to your Excello. There might be some other posts but this one rings a bell. There are also some Youtube vids (Clough42 maybe?). There's a few things to be aware of going into the project.

canadianhobbymetalworkers.com

New 10" X 54" mill ordered.

Could it be that the base is taller than on other BP clones? The height above the floor pads / foot mounting looks substantially beefier than even on my real BP.
canadianhobbymetalworkers.com canadianhobbymetalworkers.com
 
I used a Ex-Cell-O #602 knee mill for years in the 1990s.
Last year, I met a fellow who has done dozen of rebuilds of these mills.
His business focuses on the #602 mills.
He may have some direction for you.

PRESTON REBUILT MACHINERY
Roy Weidinger - Cambridge, Ontario
P. 519-621-4258
 
I have an Align unit on my bridgeport clone. It's also a 10x54 and has no problem at all lifting the knee with a 150# rotary table, 60# vice, and more. Should be easy enough to adapt. I had to adapt mine too.
 
I'm using a 750W Bergerda AC Servo. I started with a 1200 oz-in stepper and it was way too slow for me and at higher speeds stalled. Then when the Gecko DC Stepper drive failed I tried a crappy Leadshine stepper driver off Ebay that had a horrible whine. So I went with the servo. Haven't looked back.


And I've run this with a lot of weight without issues and now have proper metal pulleys and AC servos instead of the DC servos on X and Y.
WeigthonZ.webp
 
A friend of mine with a the next size up of our mill (his has horizontal spindle and larger X sized table) but we both have the heavy pivoting X axis mechanism. Anyway, I believe he used a wheel chair DC motor at 24VDC. He's not done CNC on this mill so it's just a power feed to make cranking it up/down easier.

reduction.webp
 
Put a digital torque wrench on it and measure the effort required to turn the crank. If that's not available, use a wrench and fish scale and calculate the torque. Once you have this this is the absolute min and is not recomended, I would use at least 1.5 that number if not 2.

Now you can determine the motor (stepper/servo or dedicated system you need). Most of the motor systems are between 120-200inch/oz which is only (0.625-1.04ft/lb) With servos (and stepper begrudgingly) you can easily direct drive without reduction.
 
Degen said:
Put a digital torque wrench on it and measure the effort required to turn the crank. If that's not available, use a wrench and fish scale and calculate the torque. Once you have this this is the absolute min and is not recomended, I would use at least 1.5 that number if not 2.

Now you can determine the motor (stepper/servo or dedicated system you need). Most of the motor systems are between 120-200inch/oz which is only (0.625-1.04ft/lb) With servos (and stepper begrudgingly) you can easily direct drive without reduction.
Click to expand...
I did the same thing to determine the torque requirements for the lathe and the mill knee.
For the mill I started with Size 34, 600 oz-in running on about 50VDC and 3:1 belt drive. I found that although it was useful for slowly up and down and easier than winding by hand it had very little speed.

I changed up to a 1200 oz-in with the 3:1 ratio. Now I had better speed and still enough torque based on the motor curve drop off at speeds above 250 RPM.

If you think about it, a stepper motor that pulls 6A per winding at 50V is 300W x 2 but in reality by the time you get a decent velocity the current is far less. Assuming you did get at least 3NM at speed that's just over 2 ft.lb.

I may well have been off base using 3:1 for torque increase at the cost of lower torque at higher RPM. Might have been on the wrong side of the curve and direct drive would be better.

Now with the 750W servo and 3:1 I get decent speed and still adequate torque.
 

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Degen said:
This is the reason I used servos, 260in/oz with a peak of 1100in/oz.
Click to expand...
Yes. And they are so quiet too. I have 3:1 on my X and because the Y has to carry the extra weight I have 4:1 on it. I'm finding 180ipm a bit scary actually. So easy to run into things.
Mine are 180 oz-in peak 538 oz-in and on X that means 540 oz-in and 1614 oz-in peak.
 

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Mine are direct feed, no reduction and run peak of 100ipm, most machine is done at 20ipm won't go much beyond that as column stiffness and motor hp become an issue.

ClearPath SDSK Models | Teknic, Inc.

ClearPath servo motor specifications for Step & Direction NEMA 23, 34, 56, & 143 SDSK models. Compare Torque-Speed curves, solid models, and power ratings.
teknic.com teknic.com
 
@jcdammeyer how are you getting 180ipm with your setup?

I assume you are using 0.1"/rev for your screws, you max allowing for reduction at 1000rpm (3:1) is about 100ipm at 750rpm (4:1) drops to 75ipm.

I have yet to change out my ACME screws to ball screws and depending on the pitch will change my top ipm. It is on the list as driving the machine the way I do the screw nuts won't last.
 
LenVW said:
I used a Ex-Cell-O #602 knee mill for years in the 1990s.
Last year, I met a fellow who has done dozen of rebuilds of these mills.
His business focuses on the #602 mills.
He may have some direction for you.

PRESTON REBUILT MACHINERY
Roy Weidinger - Cambridge, Ontario
P. 519-621-4258
Click to expand...
Thanks much, trying to make contact. Might be best for me to just buy a crane scale and have an exact number, then I can use the scale to weight pipe dream fish;) Cheers!
 
Degen said:
@jcdammeyer how are you getting 180ipm with your setup?

I assume you are using 0.1"/rev for your screws, you max allowing for reduction at 1000rpm (3:1) is about 100ipm at 750rpm (4:1) drops to 75ipm.

I have yet to change out my ACME screws to ball screws and depending on the pitch will change my top ipm. It is on the list as driving the machine the way I do the screw nuts won't last.
Click to expand...
I'm also still with ACME and the knee is 0.25" per rev (4 TPI). X and Y are 5 TPI (0.2" per rev). The knee moves up at a max of 120 ipm, Y at 150 ipm and X at 180 ipm. So when I tell it to do a tool change it goes really quickly to the tool change position. I'm likely wearing out my ACMe screws.
 
jcdammeyer said:
I'm also still with ACME and the knee is 0.25" per rev (4 TPI). X and Y are 5 TPI (0.2" per rev). The knee moves up at a max of 120 ipm, Y at 150 ipm and X at 180 ipm. So when I tell it to do a tool change it goes really quickly to the tool change position. I'm likely wearing out my ACMe screws.
Click to expand...
Hehehehe I have the rapids on my router set to 9000mm/min or about 350 IPM :D
 
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