KMB1 Conversion

[GT390]

Hi Bob,

Your Inbox is full

Also with the Lube pump there are actually two timers in the original setup, one that triggers every 15min or so (mounted on the side of the right cabinet) which drives a time delay relay (mounted on the relay board right cabinet) which actually drives the solenoid for the lube pump. I am trying to work out the delay on the relay as I bet that is also what you are missing.

Cheers

Chris

This makes sense to me, I have the timer like you have Bob, the 15min mechanical one, but everytime it fires off the contactor bangs in and out a few times as the micro-switch comes off and on the cam, I was thinking that it sounded like it would be really hard on the contacts in the mico-switch, I had even thought of installing a timer relay, did not realise the standard setup had one. I think I still have all my old relays, must dig them out and take a look

[GT390]

Bob, did your machine have the mechanical hand wheel speed control with two speed gearbox on the head ? I started to get some noise from the head will doing a job today, sounded like a bearing had gone, I have pulled the whole thing apart today but cant find anything worn enough to be the cause, the spindle bearings seem fine, the noise did seem to be coming from high up on the head near the speed control, and there was a lot of heat up there too. I am going to replace all the bearings up there anyway, looks like there are three or four, all just regular ball races. I do hope its not the spindle/quill bearings. Did you have yours apart after yours failed Bob ? If so, what are the spindle bearing like, are they some special one-off type, or do you think they may be available at reasonable cost ? now would be a good time to change them while everything else is apart, can you offer any advise Bob ?

[Bob La Londe]

No, mine was just a direct drive 1:1. There is another bearing though. The one in the drive pulley that drives the splines. Atleast on mine there was.

[GT390]

Ahh, my machine is a kmb-1x so the head is different, there is a bearing that sits inside the brake shoes held in a cast iron carrier, I have managed to break the carrier whilst trying to extract the bearing, looks like I am out of action for a while till I can find one, or make a new one

[Bob La Londe]

Ahh, my machine is a kmb-1x so the head is different, there is a bearing that sits inside the brake shoes held in a cast iron carrier, I have managed to break the carrier whilst trying to extract the bearing, looks like I am out of action for a while till I can find one, or make a new one

Youch. I so feel for you. If there wasn't a continent and a pond in the way I'ld suggest you pop over see if any of the part's I've removed would work for you.

[purple_jeep]

For completeness here are the drawings from the manual I have showing the Lube Time delay relay.

[GT390]

After having another look at the bearing retainer when I got home from work today, I have realized that it will be a simple enough task to turn a new one up on the lathe. still unable to find the cause of the noises I was hearing from the spindle drive, but I have the whole thing apart so am replacing all the bearings in the vari-drive head anyway. After taking a good look at the part I was machining, it appears that chatter may have been the cause of the noise, now that I see the way that the high and low gearbox gearbox engages the spindle, I am pretty sure any chatter could translate to some serious noise at the top of the head. A closer inspection of the "feel" of the spindle bearings themselves has me more concerned, I can detect no movement in them, but when I rotate the spindle by hand, now that all the drive is disconnected from it, I can feel a very slight "knotchy" feel to it. I guess now is the time to change them while its all apart, and now I know everything is going to work, I may as well get the mechanical side of things as good as it can be. Looking at the parts book, it looks like the spindle has a set of angular contact bearings at the bottom, and a single roller at the top. I am really hoping that these will be of standard type/sizes that will be available from the local bearing shop. Anyone reading this changed kmb spindle bearings before ? The parts book I have is for a SM-1 but it looks the same, it only gives hurco part numbers for the bearings though

[Bob La Londe]

There are 4 roller bearings on the carriage that ride on the front and back of a rail. Chatter when cutting can cause noise to come out of the head if these are not adjusted to contact lightly and roll against their rail when the quill goes up and down.

[Bob La Londe]

When you get them out you may find another manufacturer on the bearing and bearing numbers.

ACBs? Really? Is your mill rated for higher RPM than most (mine)? Mine was rated at 3600, and when I spoke with somebody at Hurco once they said, "DO NOT RUN THEM FASTER." LOL. I never looked that far into my quill, and never will now since I am totally changing my machine. I would have thought they would have precision tapered roller bearings.

Anyway, if they are ACBs or any other kind of bearing you can measure them and find the right size, then its a matter of choosing quality replacments and getting the preload right when you install the new bearings.

[GT390]

The speed dial goes up to 4000rpm, so I guess it must be a little faster, I hopefully will be able to get the bearing sizes from a contact I have tomorrow, the parts book I have is for an SM1, but it looks just like my machine, mine is a KMB-1x, I think its the same as a KMB-1m also, they dont have the roller bearings and guide in the quill as far as I know, I have it apart and cant find them...

[Bob La Londe]

Yours does not have the big square head does it?

[GT390]

No it has the vari-drive head, looks the same as the later hawk machine

[Bob La Londe]

So there is no stabilization for the quill other than the sleeve?

On my KMB1 the carrier clamped onto the back of the quill, and then up above the carrier had 4 rollers that stabilzed the whole thing against rails built into the head.

I would think light fast cutting rather than heavy hogging should always be your method of choice then.

[Krell33]

My KMB-1M manual has a parts list for the head assembly which lists 6203 and MM9306WI bearings. I did a quick Google search and see these are Timken numbers but should be easily cross-matched. I can scan the page if you need.

Dan

[GT390]

My KMB-1M manual has a parts list for the head assembly which lists 6203 and MM9306WI bearings. I did a quick Google search and see these are Timken numbers but should be easily cross-matched. I can scan the page if you need.

Dan

Yes please Dan, that would be great ! I have also read today that a VFD can drive a motor much faster than the motor is rated if it was running on direct mains power, if that is correct I will have to rig up some kind of tach to calibrate the speed, not being well educated in these things, I had thought that as the motor was rated at 1425 rpm, that that would be it`s maximum speed when hooked up to mains, or by being ran flat out by a VFD, it appears this is not the case. As my machine also has a gearbox and a vari-speed head I have no idea what RPM the spindle is actually making. If the machine is labeled to run at 4000rpm max, with a 1425rpm motor then the gearing must be 2.8:1 at top speed, if the VFD can run the motor up to 50% beyond the rated speed, as I have read, then the set up has the potential to turn the spindle at possibly almost 6000rpm, I dont think that would do it much good !!

[Bob La Londe]

Most VFDs can generate frequencies up to 400 (some higher) which would 6.667 times over speed your motor. The motor would likely not hold up at that speed.

[GT390]

Most VFDs can generate frequencies up to 400 (some higher) which would 6.667 times over speed your motor. The motor would likely not hold up at that speed.

Yikes, that means I have a potential flat out speed of 26,600 rpm at the spindle ! I am going to have to rig up a tach to see what I am actually spinning the spindle at

[Bob La Londe]

A tach on the spindle can be handy if you are running software for things like rigid tapping or turning threads on a CNC lathe, but for general milling real time feedback isn't really necessary. A hand held optical tach and a white paint marker is all you really need. Its not going to vary once its set. On a CNC mill you would use a breakout board with a speed controller of some type. Whatever your VFD will accept. Usually 0-10VDC signal voltage. Then you adjust as needed so you are fairly close at any commanded RPM. On my Hurco motor it had a cooling fan motor inside the main spindle motor housing, and it was rated for 3hz to 120hz which was 96 RPM to 3600 RPM. I programmed those limits into the VFD. I was never dead on for RPM, but I had a couple sweet spots.

An induction motor does a fair job of self correcting for speed under load, by drawing more current. You will get consistent repeatable speeds based on the frequency you feed it. They can experience motor slippage, but its only really significant if you are loading your motor near its max at a particular speed.

If you are using Mach3 you can set a max speed for each pulley. The way to find that max speed is to put the spindle in that gear, and feed the motor the maximum frequency you intend to, and then read the speed with your hand held tach. Enter that number in Mach 3 for that pulley number.

Most quality 3 phase motors can handle from half speed to about double speed. An inverter duty motor may be able to handle a wider range, but probably not much slower unless it has an independent cooling fan since it will not self cool at slower speeds. Remember at slower speeds it will have less torque and less power. Its why big VMCs have 15-30HP motors. So they still have decent power at low speeds. A Chinese high speed spindle motor for example likes 8,000 RPM to 18,000 RPM. Some may say 0-24,000, but 24,000 is really fast for the bearings, and it won't have any torque at all at slower speeds.

[Krell33]

Attached is a scan from the KMB-1M manual. Hope this helps.

I need to update my build thread as I'm making progress, albeit slow, on the retrofit.

Dan

[GT390]

Thanks Bob, for the explanation, that is helpful, and thanks Dan for taking the time to post the diagram, I have the machine back together again with the new bearings in the head, I realized that the spindle can be removed from below without taking the head off, so decided to rebuild the head today, made the new cast bearing retainer on the lathe last night, and it worked out just fine, accurate machine were wanting $285 for a used one ! So I am back up and running again, but do intend to do the spindle bearings when I can source some. With the new bearings in the head and drive the machine is now much quieter. Here are a couple of photo`s, excuse the state, its just done a bit of work !