Another 8x DC conversion

[Zap]

Finally got my DC conversion done. A few bumps along the way but it turned out pretty good and I am very happy with the performance. I used a KBIC-125 controller and 3/4HP Leeson 90VDC motor. Cost was about $150 for the conversion using a brand new motor, controller, and belt. I have no plans of going to 220 volts (I live in a rental) so I have no need for the 240D controller that seems to be the popular choice.







I fit the controller in the original control box. Used the original switches and the reverse works. Still need to make a nice graduated knob for the pot control. AC comes in thru the power switch. DC goes out thru the forward/reverse switch. Took a little work to figure out how to wire it with no diagram. Added a breaker in the back hole for some extra protection. I mounted the control box under my bench instead of on the machine. I probably don't need it but an old Pentium 2 heat sink fit nicely in this configuration. I drilled and tapped a couple 10-32 holes in the heatsink to mount it. I took the board off and used heat sink compound between everything that transfers heat. Being a pack rat has its advantages! My old motor ran hot and noisy as hell and flickered the lights when I fired it up. This set up doesn't even break a sweat at any RPM or load that I put on it so far. I ran it at full speed for an hour unloaded and it never even got warm. The old AC motor would have practically burned me to touch it after running that long.








The motor is Nema mount so I had to make custom brackets. They were cut freehand on my vertical band saw from 1/4 aluminum plate. I have the bottom bracket mounted to the bench temporarily with some pieces of scrap. When I convert to CNC I will connect the lower bracket to the bed with another bracket and build a new machine stand with an enclosure. I can run it under 20 RPM and the controller does a great job compensating for load. I cannot stall it and the amps ramp up to match whatever load is put on. I have to say I am impressed with this controller! Max is 2600 RPM in this pulley configuration. It's basically a 1:1 ratio in these grooves. The motor is rated 2500 RPM @90V. I use a laser tach to measure spindle speed until I can get a permanent tach hooked up. There is some vibration at certain speeds and I suspect the pulleys need some love. Sooner or later I'll do a little balancing to see if I can smooth it out or perhaps make new single groove pulleys out of aluminum. For now I just have to avoid those speeds. It's just a couple of spots in the speed range and it's not all that bad.





I had to shim the pulley a little on the shaft and used a set screw to lock it on. Just some aluminum foil in there for now until I can find my shim stock. Pack ratting has it's disadvantages too. Can't find anything! I drilled the 10-32 set screw hole in the middle groove and used a little anti sieze to keep it easily serviceable. Nothing like stripping out a set screw socket when they sieze! I had to do a little work on the cover to clear the bottom bracket. Thought the cut would take a long time but my old dremel chewed thru it in no time. I burned thru a few grinding disks in the process. They did not last long with my shakey hands. A little deburring with a diamond coated tip and the finished job turned out great!

I love not having to change the belt to adjust speed!!!

[Al_The_Man]

Nice Job, looks identical to the LatheMaster.
You will find the tach will give you nice precise speed control, When you make the enclosure, make sure you include a cover for the motor! It is right in line with the the chuck.
I used a 1:1 timing pulley set up.
Note the 2"+ square hole shown going under the bed, I installed a 2" piece of rigid conduit right to the end of the bed to bring all the CNC cables over to the enclosure end.
Al.

[TroyO]

Weird...I just posted a replay and it looked like it went through but no post showed up... anyway, sorry if it double posts.

I like it! I especially like how you fit the controller in the existting box. I considered trying that but ended up taking the easy way out.

How do you like that link belt? I was considering that upgrade..I have one on my table saw and it made a huge difference. You can't reverse with those belts, can you? (Not that I find myself reversing much.)

Here's a graduated dial if your interested. I used one with an aluminium knob. (I just had the knob but I think Radio Shack carries them.... if you can find one with more than Cell Phones.)

http://www.mouser.com/ProductDetail/...S5u7ASxw%3d%3d

[Zap]

Reverse works fine with this belt. Doesn't seem to run any different forward or reverse. I only use reverse with my tool post grinder so far. Haven't used reverse with this motor other than testing but I don't expect it to perform any different than before. Easy enough to flip the belt if needed but I haven't had any problems running it backwards in the past.

The belt doesn't seem to make much difference on the lathe. I just feel better using it because of my mill. On my mill it made a HUGE difference. It has bigger multiple belts and smoothed out some of the vibration nicely. I might eventually do the same conversion on the mill. But I don't change speeds very often on that machine so it's not a big deal. Top speed for everything but steels! I tend to stay away from steels as much as possible anyway because I hate the swarf.

I mostly got this belt for the lathe because the idler pulley was way off from the factory. almost .200" of run out! There is enough stretch in these belts so you don't need the idler at all. The extremely handy adjustable length is really nice too. If it happens to break I only have to replace the broken link and I'm back to work. I have enough extra to make another complete belt if needed. Judging from my mill, I will never need to replace it. Over 6 years on those belts and no signs of ever wearing out. The stock belts on both machines started showing wear immediately. However, they were pretty cheaply made belts.

I'm going to make a knob from scratch. Works great as is without a knob for now. I just want to put some numbers on so I don't have to break out the hand held tach all the time. If my cheapo tach project works out then I will likely leave it alone.

[TroyO]

Hahaha... it never occurred to me I could just flip the belt over even if it was directional, LOL.

They don't cost a lot and maybe will dampen some vibration anyway... I think I'll get one next time I see them. Hmmm, actually I'll get a couple... drill press, jointer, lathe could all use them.

I'm interested in how you make the knob... your going for a graduated type dial, right? I considered trying a method I saw once of making a guide on the PC with the correct divisions and the diameter of your chuck, then taping it around your chuck and rigging a "pointer" from some wire. Turn one division, the use a 60 degree threading bit installed sideways to gouge a mark in the dial using the carriage.

Not super accurate, but the division of error going from a 5 inch diameter to a 1.5" or so would help.

Come to think of it, if yours is marked in RPM it probably won't be a straight linear progression.... I don't think, anyway.

In practice I use mine a bit more organically.... if i get chatter I try cranking it up, or down and see if it goes away... LOL. I have a constructed Shumatech DRO with the tach working and don't really bother to turn it on.

Someday I will get those scales mounted, though....

[Stirlingbuilder]

I have seen the link belt at Harbor Freight. Seems the cost was under 10.00 bucks if memory serves. I know my drill press has a very tired belt... Maybe I should get one insted of trying to figure out what size that 20 year old belt is?