[pete from TN]

Hey guys,
I finally am getting around to starting the work on my RF45 Lathemaster mill conversion. I got the Gecko G320s here, got my ballscrews and nuts and I am about to start machining them. I tore apart the whole mill now since I have another small mill here ready to do backup duty. I had one helluva time getting the z original screw assembly out of the machine's column. I noticed it has a lower bearing mount and it might even be a place to lift from but I did not investigate it all that well. I figured it all was gonna be replaced anyways. I am using a 3/4 inch screw for the z axis and I am gonna machine my own plates to mount motor and fix the ballscrew end. Just wondering of those on here with this same type of machine did you fellas remove this lower bearing mount or use it to steady the ballscrews end and fix the top and drive the top from the top of the column? The lower mount on my machine is cast iron and pretty heavy duty so it would be alright to use it but I suppose I would still drive from the top and support the weight of the head from the top plate as well. I would think of the bottom mount much the way the undriven end of the x axis will be with just a snug fit of the ballscrew thru a bearing to add support to keep it from wobbling around. Is this the correct thinking on this or am I way the hell off? I am really excited and I experimented with the ballscrew stock yesterday in the lathe and despite the hardness of the screws outer area my 12x36 lathe and my favorite carbide cutter made short work of the screw material and I am now gonna be machining them once I receive my bearings in from the supplier. My kit is gonna be loosely based on the Homecnc conversion but I want to try to beef things up wherever possible. Not that the original designs are weak just that I think they were designed with a little smaller machine in mind.

I took off the millhead by myself yesterday and I gotta tell you that baby is no joke!! A lot heavier than I thought it would be and if you met me you would not think me a wimp!! About blew a gasket taking it from the mill to the table next to it to get to the column stuff behind it. I gotta rig up some kinda crane in here someday.

This should be some kinda adventure I think and hopefully at the end will yield a nice machine that is capable and accurate but we will see. The machining of the z axis lift block I will call it to accept the ballnuts I am supposing I will do in my lathe on the four jaw and attempt to center the threaded original hole with the lathes centerline as best I can and then machine thru with the boring bar followed by a single point thread operation to get the ballnuts to fit. That should be interesting...

Any ideas as to the best way to center the ballscrew stock in the lathe for machining. It looks like I am gonna have to machine for about 1 3/4 inches of screw area to get the bearing surface, the threaded area, and the little shank to accept my rotary encoders. That is gonna certainly need to be machined with a center in the tailstock and with as little of it stickin out the jaws as possible for this hard stuff. I heard someone say that they would zero it in the four jaw off the grooves in the screw not the outer edge to ensure that it was concentric with the actual centerline of the ballnut. They put their DTI in the groove and setup the lathe to machine a thread that is equal to the screw pitch so the screw would turn and drive the table holding the indicator along with it to better yield a true zero. Is this necessary or have most of you just gone with the outside edge and had good accuracy out of it. What say ye?

I lucked out recently and was able to buy a nice desktop computer with an all black case and monitor that is pretty fast to run the show out in the shop while I do all the design work on my laptop here in the den. Should make for a nice setup as it is an e-machines unit and seems to run very well. I also have a nice box that I am gonna be using to house the electronics for the machine and will be starting that build also soon.


Anyways, I hate to call this my build thread as I sometimes do not get much time to work on my own things so it might be all winter or longer before I get this finished but I will try to post here whatever progress I make and ask whatever questions I may have of you nice cnc gurus!! http://www.cnczone.com/forums/images/icons/icon6.gif
Cool
Peace all....

[pete from TN]

Just when I was getting ready to start this baby I go to the Industrial hobbies site for some inspiration and to see the way they machined that bearing in the z slide so I can make something like it, their website is down or something and I cannot look at the pics. Was hoping to use some of that information on my build as I think they have the best setup for this type of machine that I have seen so far. My machine is basically the same one as theirs except the table is a little smaller. Anyone got some pictures of that bearing setup they did that attached the screw block to the z slide. Mine was all kinda loose just like they said on their website when I could view it so I am gonna hafta do the same thing on mine. Any help would be most appreciated!!! http://www.cnczone.com/forums/images/icons/icon11.gif
Red face

Thanks in advance guys and wish me luck....

peace

[SCzEngrgGroup]

Pete,
My advice on the ballscrews is don't try to machine them yourself. It's harder than you think. First, just grabbing them is difficult. It really takes a collet of the correct size. Even then, they're a bugger to hold onto, because they're so smooth and hard. Next, you'll find out just how hard they are. If these are good quality screws, you'll have a bugger of a time cutting them at all, much less getting a good, accurate surface finish. The proper way to machine them is either grinding, or anneal the areas to be machined.
After spending several days attempting to machine a piece of Nook XPR 1" screw stock for my mill, and acommplishing nothing, I finally sent them off for machining, for all of about $50/end. And that was on a very nice, big Emco lathe, with good carbide tooling. They came back beautiful. Here's the guy that did mine:

Robert Spalesh (or maybe Palesh)
(440) 813-0920
[email protected]

He does very nice work, about one week turn-around. He just did a set for a friend of mine as well.

Regards,
Ray L.

[SCzEngrgGroup]

Oh, one more thing. You mention machining a small end on the ballscrew for the encoder. Unless you're going direct drive (which I think would be a mistake), the encoder NEEDS to be mounted directly to the motor shaft. There must be ZERO backlash between the motor and encoder, or you'll drive the servo nuts.

Regards,
Ray L.

[pete from TN]

I was actually going to put the encoders on the shaft of the ballscrew because my motors do not have a shaft on the end and I do not wish to make one there as I have seen some others do. Looking at Industrial hobbies machines they use the same setup with the encoders on the end of the shaft and apparently it works for them. With the timing belt setup there is not supposed to be any real slop anyways. Have you tried this? I also have a friend locally who has them on at least one axis this way without problems? I was talking to him tonight about bearings and belts and such and we actually talked about this but it is possible we are wrong I suppose as I have never built a machine like this before. What do you recommend? peace...

Pete

[TOTALLYRC]

I was actually going to put the encoders on the shaft of the ballscrew because my motors do not have a shaft on the end and I do not wish to make one there as I have seen some others do. Looking at Industrial hobbies machines they use the same setup with the encoders on the end of the shaft and apparently it works for them. With the timing belt setup there is not supposed to be any real slop anyways. Have you tried this? I also have a friend locally who has them on at least one axis this way without problems? I was talking to him tonight about bearings and belts and such and we actually talked about this but it is possible we are wrong I suppose as I have never built a machine like this before. What do you recommend? peace...

Pete

I would check with Gecko directly since you are using the G320. I think that I read somewhere that they specifically recomend against this.
If you have a lathe that will take the proper collet to hold the ballscrew, many people are rigging up a grinder in the tool post to cut thru the tough outer layer and then cutting the rest with a good lathe tool.

On my rolled ballscrews I was able to cut thru with out grinding. It took awhile and several inserts, but it was a lot cheaper than $50/ end and since you need to do both ends of each screw, that is $300 for all three.
Of course, if you screw it up, (pun intended) You could spend more.


Mike

[pete from TN]

I have as I said in the initial post tried to machine on the ballscrew stock just for a test and was able to machine the threaded section off down to the less hardened middle of the screw without any drama. The screw stock is hard but not too bad really. I used my best carbide insert cutter but I think I will use some cheap carbide brazed ones to do the actual machining as they are cheaper if they break. We will see how it goes but I was looking for input on how you held the screw in the lathe?

I do not understand why you could not put the encoder on the shaft as it would I assume be a more accurate representation of the table position. The point may be moot however since I was telling my wife of the potential problems I am going to be having with these motors since they have a 5/8" shaft only on one end and finding a 2-1 pulley setup that will be boreable to fit that size shaft is turning out to be a real needle in the haystack so she surprised the hell outta me by saying why don't you just get some new motors with the right size shaft. I told her it would be expensive and that I might be able to get some with encoder included at additional cost and she said that it would be fine I think mostly because she has seen my enthusiasm for this little adventure and also the possibility of making some cash with the finished machine eventually. I am hoping to maybe find some nice servo motors with attatched encoders that will work for my purposes IE with enough power to lift the head and move the table easily. Any advice or ideas or sources would be most appreciated. Thanks and peace....

[Jason3]

The encoder attached to the ballscrew shaft would give a more accurate representation of actual position, yes. The issue is that any backlash or compliance in the connection between your motor and the ballscrew will usually mean your motor resonates, since the drive attempts to maintain position based on the encoder signal. The more compliance you have, the worse it will be. It will be difficult to tune the servo, and the damping required to keep it stable will likely mean that the system response is adversely affected.

Are you thinking of going with brushed or brushless servos?

Regards,

Jason

[pete from TN]

I know they use the encoder mounted on the ballscrew and the motor is a servo setup with a 4-1 ratio? How come they do not have resonance issues? Am I missing something. I am looking for another set of servo motors right now in case I cannot find a pulley setup that will fit these motors I currently have. What is the recommendation here? peace...

[TOTALLYRC]

I know they use the encoder mounted on the ballscrew and the motor is a servo setup with a 4-1 ratio? How come they do not have resonance issues? Am I missing something. I am looking for another set of servo motors right now in case I cannot find a pulley setup that will fit these motors I currently have. What is the recommendation here? peace...

Your best bet is to call or email gecko drive directly on whether to mount on the motor or the ball screw.

2. The way I have seen people mount an object like a ball screw in a lathe is either a collet like I mentioned in the other post or bore a sleeve, alum or brass,that has an Id = to the od of the screw. Then slit the sleave into three pieces and use these in your three jaw chuck.

[LUCKY13]

I know they use the encoder mounted on the ballscrew and the motor is a servo setup with a 4-1 ratio? How come they do not have resonance issues? Am I missing something. I am looking for another set of servo motors right now in case I cannot find a pulley setup that will fit these motors I currently have. What is the recommendation here? peace...

Hey Pete, I am from TN also (bristol). Anyway, if I understand what is going on right, the reason they get away with the incoder on the ballscrew (IH) is because they use something like a 2000 line incoder instead of a 250 or 500.


If you think about it, with a 4to1 ratio, the motor would have to turn quite aways to register a line on a 250 or 500 line incoder with a 4to1 ratio. This could be what would cause the resinance becasue the motor would have to go farther than a step/microstep to get a responce out of the incoder. SO by the time the mtor moves far enough to get a response out of the incoder it has went beyound its normal movement, then it has to start hunting or bouncing back a forth between line on the incoder to try and keep the motor where it wants it. WIth a 2000 line incoder (or even more) this would make up for the lost resilution from the 4to1 drive and screw mounted incoder.

This would get the drive the info it needs to keep the motors in check on a screw mount setup if I understand correctly. But now you had better be able to send enough step/dir signals to get enough IPM out of the setup so the Gecko 340's, or something like a CNCBrain or smoothstepper would probably be needed to get enough signals to drive this very high res type setup. If not it would be limited on speed because of Mach3/2 limits.


I believe I am thinking correctly on this, but I am not expeiranced enough to know for sure so comfirmation/correction from others would be a good thing to have.


On the Z axis mod, If you go to Bob Warfields site I believe he has documented this proccess on how to do this. He also shows the Z ball nut mounting with this info. The IH site has not offered this info in a very long time, If I am not misstaking, if you read the site it explains this and suggest that he would send this info to anyone that needs it (on CD), that has "bought" a IH mill. I dont know if they would send it to someone that just calls up and ask.



Jess

[pete from TN]

I am starting to understand what is the problem with the idea of using the encoders on the ballscrew. I have not yet abandoned the idea and when time permits I will check with maris on the idea and what his recommendations are. I am also looking at purchasing the motors with encoders attatched for the axes and be done with it with some presumeably more powerful and new motors but the money issue is gonna be close so I will see what gives soon. In the mean time I an going to continue on the buildup and see how I can get along without motors or encoders for now until I am ready for them, my design can be built either way so it is a non issue.

Jess, where are you in bristol? I am in Maryville, just south of knoxville. What are you into for your own cnc adventures? Are you converting a machine or do you already own one? I as yet have never seen a running living breathing cnc home shop mill and I would love to meet someone relatively local that is into the same madness I am..... If you ever wanna chat cnc gimme a call at 865-363-9218. Peace my friend...

The Lathemaster mill is looking pretty naked right now since I stripped all of it's parts off and now there is just a bare column there. I am very excited about the idea of getting the machine running and have some issues with the oiling system that I intend to install on it. Looking around at some of the personal websites I have linked to from this forum I have seen oiling systems done a myriad of different ways but the majority of them seem to use the bijur oilers and a manifold of some type with these push lock flexible plastic tubing. My issue seems to be that for the main part of the table, I E the x axis travel there are two button oilers on the part one on the front edge of the table just above the original stops for the power feed unit and another in the same place on the rear of the table. It would seem to be in the way to simply tap these out and install the connection for the oiling system but I suppose I could do that. However the cleanest looking systems I have seen employ system that is basically all from ports under the table and out of the way of movements and motor mounts and ballscrews etc. I suppose I could just drill and tap from the underside in an appropriate area and then drill thru from the way area then machining the distribution slots on the way surface in my small mill. Is this the way you guys would go and forgo the idea of using the existing button oiler passageways? What say ye? thanks and peace...

[pete from TN]

well guys as I said before I got the mill all torn down and I am starting to make some chips on this conversion. The z axis was a bear to take apart and I got the z axis ballnut mount out of the column and took the power head lift feature off the machine so now it is just a bare column sitting there. I took out the ballnut mount and put it in the four jaw chuck and machined it to fit the new ballnut with a boring operation followed by a single point internal threading operation in the 12x36 lathe and all went very well. The nut fits nice and snug and bottoms out perfectly perpendicular to the mounts surface so I guess I did it right. I am waiting on a second ballnut to go under the mount to go along with the one I already have that goes on top to preload the ballnuts together. I intend to drill and tap a setscrew perpendicular to the threaded bore to lock them into position once they are threaded and preloaded together. Tonight I am going to try to bore the z axis slide for a bushing that will attatch this mount to the slide. Bob Warfields site has some pretty good pictures and explanation on this whole setup so I did not take any progress pics. Maybe I should just for posterity I guess. Anyways, I am still trying to decide on the motors and encoders wether or not to keep these for the other mill and buy the Homecnc motors and be done with it. We will see how it goes....

I am glad to be finally starting on this instead of reading about all you guys doing what I wanted to do for so long.... gonna be real cool.....peace

[SCzEngrgGroup]

I would check with Gecko directly since you are using the G320. I think that I read somewhere that they specifically recomend against this.
If you have a lathe that will take the proper collet to hold the ballscrew, many people are rigging up a grinder in the tool post to cut thru the tough outer layer and then cutting the rest with a good lathe tool.

On my rolled ballscrews I was able to cut thru with out grinding. It took awhile and several inserts, but it was a lot cheaper than $50/ end and since you need to do both ends of each screw, that is $300 for all three.
Of course, if you screw it up, (pun intended) You could spend more.


Mike

On *good* ballscrews, even rolled ones, you can't get "through" the hard part. We cut my 1" screws down to almost 5/8", and they were still too hard to machine nicely - measured at Rc60. They had to be annealed to get an acceptable finish. These were Nook XPR screws.

Regards,
Ray L.

[pete from TN]

I have machined a couple test setups now and my lathe has had no real problems machining thru the hard outer layers. I suppose they are not good screws but they sure look good. I got them from Roton and they were not that expensive so I guess they must not be good ones but I just hope they will be reasonably accurate ones. If they do not prove to be accurate within reason I suppose I will have to get different ones but for now these are all I have. I have two internet friends who have used them and have had good luck with them and they also were able to grind the screw stock a little to get to the soft stuff and then they were able to machine them on their lathes. I have not actually machined them yet as I am trying to decide how I want to orient my bearings and the locknut and washer and whatnot to be in my mounts. My Z is going to be the first one I do and I know that most do it last but I already have another small mill to do the machine work on and I am going to use it. The z is pretty nice with the square column mill and there were a few surprises I found tonight. I took the ballnut mount for the Z as I said and machined it and went to machine on my Z slide after looking at the pictures on Bob Warfields site and found that not only did I not have to machine a concentric shoulder in the center of the ring that mounts the head to accept the different bushing I machined tonight because it already has a hefty shoulder but the Z slide also was made from the factory with oil channels milled into the way surfaces the branch out from the button oiler passageways. That is two things I did not have to do to my machine now that I was getting ready to do. I machined a steel bushing that is a tight fit into the bore of the z axis slide with a shoulder to accept the step in said bore and drilled and bored thru for a snug fit of the lock bolt. All I have to do now is take it out of the lathe and cut it off in the saw, put it back in the lathe backwards and face it off and machine the counter bore for the rather massive socket head capscrew that it uses and I can assemble the z axis slide assembly. I still have to machine some motor mounts for it but it is nice to be nearly finished with that part anyways. I noticed that my ways have a nice ground flaked pattern to them I do not know what you call this but it looks to hold way oil and make for a nice smooth surface. This machine is an early Lathemaster and from what I have seen is nothing like the ones he is currently selling. I have been very happy with it as a manual milling machine and I am sure to be even happier with it under cnc control.

How about a concensus on the size of the angular contact bearings you guys used. My little kit here uses a 12mm and I was just wondering what you guys are using. The Z will be a 3/4 inch screw so it will have to be a larger bearing I suppose so I will try to figure out what size I can get away with on it this weekend and get it ordered. This is kind of a fun project now that I am getting some stuff done on it. Thanks again guys for you support and ideas....peace

[pete from TN]

I just received my new CNC4PC C11G breakout board and I also received my angular contact bearings as well as some other stuff. I also purchased from shars some nice m2al carbide endmills, an eight piece set in 2 flute and an eight piece set in 4 flute as well as a carbide 1/2" rougher. This weekend should see some serious time in the shop machining my screws and working on the mounts and such so I am getting pretty happy now!!!

Anyone out there with a C11G board that has it running? Got any pointers or advice about it's setup in a servo system? thanks guys....peace

[ataxy]

if you got the roton rolled ballscrew then yes they are pretty easy to machine mine were also easy to machine on my 11x27 lathe

[pete from TN]

I do have the roton rolled ballscrews on the x and z but I also have a very fine ground ballscrew that came outta a Mitsubishi EDM machine on my Y axis and I just recently finished machining it on the lathe with little problems. The cutter does get real hot and the insert is definitely struggling to cut it but as long as I do not let it stick out of the chuck too much and put my center in there right behind it nice and tight I can machine them okay. This weekend will be the deciding factor tho as I will try to machine them and thread them in the lathe now that I have the angular contact bearings here to ensure a good fit. This is starting to look like I can do it as I also just found a nice website about some homebuilt routers that goes into great detail about the controller setup and whatnot. Now all I have to do is decide which motors I am gonna buy and get the appropriate power supply for it and I should have everything here to complete the buildup sans cables and the pulley/ belt setup which will be decided soon..... thank and peace....

[LUCKY13]

Your Z axis surface sounds to me like its been scraped. This is designed to true up the surface (perfectly flat and striaght) and it also addes a bearing surface (which does hold oil and lower resistance).


If you was to take blue dykem and a surface plate and test/check that surface it will show that its not touching in all spots. So this is what leaves the room for oil (little pockets), and reduces the resistance/drag ( less stick/slip). Ofcourse that is if its really a scraped surface.



I wise you could add pictures to your build. I will be starting mine this week and I hope to be able to document the build as I go. It is the same mill as yours (except Enco brand) so maybe I will find some nice surprizes such as you have found. Mine is a older machine also but it was a NOS until that was built in year 2000. I still had to clean the shipping grease/wax off of it when I bought it. SO it will be taking a brand new machine to do my convertion on. I have already seen a few things that I know is better than the machines being sold now. It trammed up perfect, real easy, and was factory with inch screws and dials, plus came with a 2hp motor. And if I am not mistaking it also aready has the shoulder in the head mount as you have found.

I will be starting soon. Making a big order monday for Drives, servos,CNC Brain and a few other things but I have a lot of doctor stuff going on at the first of the week so I want get anywhere with anything until the weekend ( except going over electrical stuff and figuring out wiring) as long as I feel up to it.


Keep us informed, and get some pics going if you can.


Jess

[pete from TN]

Yeah I think my machine is somehow scraped but I doubt it was done manually, it looks like the old bridgeport finishes with like little snowflakes everywhere. The z axis slide looks to be a nice design and rather large with the shoulder as I said but I realized that the actual ballnut mount is only held on with the large shcs that goes thru. I will try to take some pics of it tonight and post them here. I am thinking I will have to machine a recess in the ballnut mount to allow my new bushing to protrude past the back of the slide and the ballnut mount will fit over it closely and then the shcs will go thru and tighten everything together hopefully that will be more than enough to make for a solid joint between the two. I am talking to a fellow right now that has some motors for sale that I think would be nice for the machine and if I can negotiate a good price I will definitely get them from him and these are some very strong and slightly faster motors than I was using initially. Only problem is I will have to machine all new mounts for everything since the ones I have here will definitely be too small. The mill itself has been a very good machine for me for several years and has taken some serious abuse under my heavy hands at times with aplomb. Now that is will be a cnc mill hopefully I can design in enough rigidity and take out as much backlash as possible to make for a nice cnc mill.

The day yesterday was used for some machining on some drive assemblies much like Bob Warfield used on his conversion. I took some 3/8" plate and milled a bunch of 3/16" slots for cooling and then machined them into four little plates to mount the geckos on like bob is doing. My machine initally came as a 110v unit and I have since converted it to 220v and the 110v control box is now going to serve as my control unit for the cnc housing the geckos and the power supply. It will be a little tight but it is painted the same color as the mill and is pretty heavy duty steel, that and it has a mount on the back of the column to go on makes it a no brainer. Right now my tablesaw table is all covered up with the parts of the mill and all the cnc stuff I just got and it is to be honest a real mess out there right now. I will admit I am not the neat freak that some of you fellas are when it comes to working in the shop as I have used it for many years now to make some money to help support my family and this whole cnc gig is also not simply a hobby to me but I am hoping a way to increase my income from working it home on some projects I have been manually machining to make extra cash. This is why I am trying to invest in the known good components such as the geckos and semi closed loop servo control and everything else I think I can afford to make it hopefully end up being a machine I can depend on. I am enjoying it as well and the learing curve is also something that I hope to enlarge my capabilities to make money in the long run. Just looking at some of the stuff that you guys make with these machines makes me think that there is definitely some money to be made with the completed machine. I am into airguns and motorcycles and friends are always asking me to machine something for them or custom build goodies for these hobbies. A good decently accurate machine has the capability to do that I think( I hope) and if that means that I can sit out in the shop and tinker having fun while all the time making some extra cash it will be worth the trip for sure. Thanks to all of you guys on here who have been a great inspiration and I would not even attempt to do this without this valuable resource..... peace....

Pete