Hi Ray, I was just thinking I needed to do an update. I've had company. Some snow bird friends are on their way back up North and stopped here for a week. Beyond that distraction, I've had a terrible case of "You can't get there that way". I put the bearing holder together for the Thompson screw and mounted the table. There was a hard spot when I turned the screw. Same spot every turn. It didn't matter how I adjusted the nut in the saddle, it wouldn't turn freely. So I took the table off the saddle and turned the screw. The free end scribed a circle nearly an inch and a half in diameter. I played with the bearing block for a while, but the inescapable conclusion was that something is bent. Hours messing with the screw, surface plate, and indicators and I'm pretty sure that most of the bend is where the bearing surface meets the threaded part of the screw, but there is also distortion in the threaded part. It was an Ebay screw and I would have sent it back, but I made some modifications to the nut and the undriven end bearing surfaces. The seller didn't fall all over himself to replace it, and I don't blame him. I should have checked it before doing modifications. I know better.
So much for the Thompson screw. It goes in the resource drawer. I have a 1605 import screw on the Y-axis and some other things. I am okay with the performance. The problem is the integral mounting flange. The nut will fit in the recess I cut for the Thompson nut, but the table will not go on with the big flange sticking up. That flange was most of the reason why I got the Thompson. So with the Thompson out of the running, I can either buy a screw and nut from Roton, or do something about the import nut.
I'm cheap, so I attacked a spare (and short) 1605 screw from the drawer. The nut is hard. Way hard. It eats carbide without flinching. I don't have any ceramic or diamond inserts, so I attacked it with the grinder. My coarse wheel is #60, but it ground the nut faster than I expected. I put a plug in the grease port of the nut to keep out at least some of the grit. I now have a nut that will fit in the saddle without rubbing on the table. The present screw is nowhere near long enough, but at least I know that the nut can be fit without excessive grinding time. The ground down nut feels like it digested at least some grit. I'm going to take it apart and see if I can clean it out and put it back together, If I cant get it back together, I'll have to grind down the nut that comes with a longer screw. I'll pump the next nut full of grease before grinding it. That should keep the grit out better.
Now I need to order a 400mm 1605 screw with machined ends and nut. But that will have to wait because I'm going to California and Washington next week.
OK I'm back in the shop. The trip to the coast was interesting, but I like our horrible Florida weather better. I have been occupied training the new puppy and getting one of the older dogs ready for rally competition, so time in the shop has been minimal.
The mounting for the latest X-axis ball screw is screwed. The recess was cut out for the Thompson screw that was bent. Not wanting to get a new Thompson screw or take a chance on another Ebay one, I got the Asian screw and modified the nut. That would be the one in the previous picture. I mounted the table and tried to get the screw and nut lined up with it. No cigar! The screw would tilt down towards the free end when the clamp screws were tightened. Metal removed for the Thompson nut was needed by the Asian nut. Since there is no way to put metal back onto the saddle without incurring a whole lot of re-machining, and a new saddle wouldn't help without just as much milling on it, I had to come up with a better way. I saw a picture of the nut mounted on the outside of the saddle. It entailed making a mounting block that would fit in the original nut pocket and extend outside the saddle to accept the ball nut. That still used the missing metal, but it got me thinking that I could just mount the ball nut onto the saddle directly. The ball nut needs to be pulled against the pocket rather than pushed against the back side. The back side is where the metal is missing. The original clamp screws are 6mm and the holes in the nut are 5mm. The ball nut is really hard. The is no reasonable way to thread the 5mm holes for the clamp screws, To top it off, the holes in the nut do not exactly match the saddle. But I am a metal butcher, capable of making many small pieces of scrap out of big ones, so I clamped the saddle to the mill and turned the 6mm threaded holes into oversized 5mm slots. Now I can use 5mm screws with nuts to pull the ball nut onto the outside surface of the saddle. The slots provide lateral adjustability to line up the table to the screw, and being oversize I get a little vertical wiggle. I put the whole thing together and the table, screw and saddle line up. I don't seem to need any more vertical travel, but I can slot the bearing carrier at the end of the table if I have to. Picture is of the saddle and nut. The bearing carrier is sitting on the table saw while the paint heat cures.
I still need to make a spacer for the driven end piece so I don't loose the 1.5" of travel that the nut takes up. The metal will be here in a few days. Mean time I'll procure a couple of grease fittings for the ball nuts and do final assembly on the Y-axis and saddle.
No pictures. I greased the Y-axis nut, then mounted the saddle to the base. A little way oil and gib adjustment and the screw turned nicely. I then mounted the Y-axis stepper and fired up the control computer. I had to change the motor configuration because the new screw is 5tpi instead of the stock 16tpi. It moves! The stock screw never got over 6ipm before bogging down. The new setup will do 60ipm. Granted, there's not much load on it now, but I is going to be way faster than before.
I machined the spacer yesterday. Tonight I lubed the screw, oiled the X-axis ways, and put it together. I still need to mount the X-axis motor. I'm not sure I can salvage the old motor mount. The new screw needs longer standoffs. It may just be easier to make a new mount.
I traversed the X-axis with a cordless drill. It was smooth with the OEM spec. travel. That is something the machine never did before. The ways are tight without restriction, but I expect them to wear in a little. I'll try my hand at writing a traverse loop when both motors are on. I'll let it traverse both X and Y for a few hours before I lock down the gib adjusters.
New travel for the table is 5.75" for Y and 9.25 for X. I could get 6" for Y if I wanted to diddle with nut clearances, but increasing the effective Y travel by 2.75" is a nice increase.
I got side tracked worrying myself about the head setup. For years I have been coveting tilt and nod in a mill. I have tilt in my bigger G759 +/- 90 degrees. I have used that capability and it is pretty nice. It would have been nice to have the head swivel with a worm drive like a Bridgeport, but I probably couldn't have afforded it if it did. Nod would have been really nice on the G759 when I was cutting gibs, but there really isn't all that need for it.
the little CNC X2 doesn't have enough room to build in useful nod. Hoss put it in his Freak conversion, but he grafted two base casting together to get that much Y travel. I will leave nod for the next lifetime where I may be able afford a really big mill.
Rotating the head on the X2 would solve several problems with the tilt column design. Tram would be a lot easier and more stable. It would also be easier to strengthen the column if it didn't need to move about. I may be able to pull that off. I have added almost 2" of Y travel to the X2. I will need to move the spindle out about an inch to get it back to the center of the table travel. I also found when taking the head apart that there is 2" of dead space in the z saddle. That gives me up to 3" of space to rotate the head. I found a junky 4" rotary table that I had purchase in a misguided attempt to save money. The table is 2.5" high. It should be possible to graft onto the Z saddle and spindle casting. It has worm drive and clamping. It is pretty crappy, but the gears are good, so I could probably toss the tables casting and plate and put my own together.
I have been building a column model in Fusion 360. The saddle even goes up and down the column. I still have a lot of pieces to add to it, but I hope to be able to design the head modifications in the cloud rather than screwing up more stock.
The paint finally dried enough to finish the X-axis. The motors need to be calibrated, but that will have to wait until I get the head finished. The speed is approximately 50ipm.
Video will not upload. Probably too much storage space.
I am thrashing on what to do with the head rotation. I'd like to use a worm gear to make moving the head exact, but the design is a mess for a hobby project. I may just dump the gear part. The cost of 6" diameter stock is also daunting. I'm not sure how my little HF bandsaw will do cutting 6" rounds either. I wonder if I can get away with using aluminum instead of cast iron.
I am thrashing on what to do with the head rotation. I'd like to use a worm gear to make moving the head exact, but the design is a mess for a hobby project. I may just dump the gear part. The cost of 6" diameter stock is also daunting. I'm not sure how my little HF bandsaw will do cutting 6" rounds either. I wonder if I can get away with using aluminum instead of cast iron. View attachment 132774
It has been a fun 2 weeks. I ordered 2 6"X1" aluminum disks for the rotation. I shouldn't have.
Getting the worm/gear set into the saddle was getting to be a bit tedious, then I discovered the real problem. The bolt track around the fixed disk for a +/- 90deg rotation would require a full circle slot. I would need a T-slot milled into the fixed disk to do that. I should have looked at the available T-slot bolts before ordering the metal. The slot would make the outer lip way too thin to reliably clamp the moveable disk. Moving the slot into the disk was not an option because the T-bolt would foul the spindle box. The clamping power of smaller bolts is suspect. I have since discovered motor mount problems, so I'm glad I resisted the temptation to order bigger metal. The question became, do I really need +/- 90? The motor control box is on the left side of the head. The control box would prevent the spindle from getting very close to the table, so counterclockwise rotation was not very useful. Only rotating clockwise reduced the required slot down to 120deg. That would give me 10deg counterclockwise for tramming purposes and 110deg clockwise for horizontal operation.
The object in the center is an acetal axle.
I turned up the studs in only a few minutes on the lathe running at 560rpm. I love my threading clutch.
This is the test fit before I reduced the saddle to put the spindle back in the center of the table travel.
The motor problem I mentioned before? The original motor mount would put the motor where the aluminum disks are. I will have to make a belt drive conversion. I had planned to do that eventually. I guess eventually has become soon.
So when it rains around here, it pours. The spindle bearings make noise. There is a clicking sound when the spindle is rotated by hand. I checked preload and investigated the transmission gears, but it is the upper bearing that isn't smooth.It sorta sounds like there is a loose ball that is rattling around inside. The mill has been terribly noisy for some time. I always assumed that it was gear noise. I'm glad that I found it before it seized up. New bearings are pretty reasonable. I suspect that it is shipped with ABEC-1 bearings judging by what LMS wants for replacements. I ordered ABEC-3 bearings to replace mine. They should be here Friday.
Tonight I took the spindle apart. It went reasonably well.
I had to attach the left ear to an aluminum angle. I could have waited until I could get a larger piece of plate for the base, but I'm getting impatient with the delays. The motor mounting plate is not shown. It was a seat of the pants project. In making the plate I was lucky to plan far enough ahead to notice that the drawings from other belt drive projects were for a different motor than I had. At least the mounting holes for my motor didn't match what I had down loaded. Once I had the motor mounted, I turned my attention to the pulleys. I knew that the pulley designs that I had should fit, but the rotational addition made space tight. I made the motor pulley first. It was the most space restrained. At that point I came up against the metric conundrum us Americans face with these machines. I needed a pulley bore for a 9mm shaft. I could fake that with a #T drill. The thing I couldn't fake was the key slot. None of my imperial size broaches would work, and a $40 broach from the far East hurt my cheap skate mentality. Fortunately we had a get together of Florida machinists and Mr. Ogberi fabricated a a tool to cut the keyway on his S/B lathe. It worked.
With the pulley mounted on the motor, and the motor on the head, It looks like the original spindle pulley design will work just fine, We started the spindle pulley at the meet, but I will have to finish it on my G602 tomorrow. And then, yes, there is another metric keyway to cut. At least the next one is 5mm and the bore is big enough to swallow a standard cut off blade.
The finished pulleys -
I had to do some fudging to get the spindle pulley to work. The main problem is the low cost (cheap) way that the Chinese locked the spindle nut. They used a set screw that bore against the spindle threads instead of a lock nut. The pulley needs to sit up higher with my motor mounting arrangement. Here is what happens to the set screw -
Can't see it, can you? I can make up a spanner to tighten the nut but there is no way to lock it in place. I considered using a thread locker, but I'm nervous about depending on it to keep the 4Krpm pulley on. My plan is to put a steel, keyed washer that is left over from pulling the original bearings, between the top bearing and the pulley. That will raise the pulley enough to clear the deck of the motor mount base. Then on top of the pulley I will put a keyed spacer from the unused gear stack on top of the pulley. The nut can then be run on and the set screw is accessible and able to grab the spindle. -
The belt drive is now ready for a belt and testing. That will have to wait until the belt arrives in the mail. A 2L130 is too short and a 2L150 is a little too long to work with the motor pulley to head clearance. A 2L140 turns out to be special order.
The stain on the pulley drawing is not rust. It is BBQ sauce. You central Florida machinists missed out on some fine food.
I have been working on the Z axis drive. My original slap together conversion of the X2 used the rotating nut, fixed screw design used by Daniel Kemp. I decided to look at other designs since I had the chance to start over. The fixed screw, rotating nut designs are much simpler to execute, but they all have what I consider a serious fault. The screw extends into the swarf generating area. The lubrication on the screw would retain metal particles. The Asian 1605 series ball screws that I am using do have a wiper of sorts, but they aren’t very effective. The X and Y axis are mostly protected by the saddle and table, but the Z axis is not easily covered. The rotating nut is more complicated to execute, but the screw stays above the head and therefore out of the primary swarf cloud.
The axle and bearing stack that carries the drive gear and the ball nut has a problem with backlash in the Kemp design. In the cross section drawing, red represents the axle, blue the retainer plate, and green the thrust bearings. The only way to adjust the pre-load, or lack of, is to change the length of the axle by putting shims between the axle and the retainer plate. That is a bit inconvenient when trying for minimum end play (backlash) and adjusting for wear.
A better way to handle fixing the axle would be using the same way the X and Y axis do.A single nut with set screw or even a double nut that would allow adjustment to eliminate backlash. The top of the axle where the gear and screw will mount is 2.5, the axle is 1.25”, and the threaded portion is 1-14. I didn’t have a nice piece of 2.5” round bar laying around, so I shrunk fit the axle to the top. I heated the top to 275F and froze the axle for an hour. It dropped in a little over half way before seizing up. Being prepared for such an event, I whacked it twice with a #2 hammer to seat it.
This is the Z-axis axle with the drive gear. The gear sits in a push fit pocket to help keep everything concentric. The gear is held with 3 5mm screws that clamp the ball nut, and gear to the axle. Three additional 5mm screws hold the nut to the gear. I am waiting on the screw. It has been in Chicago for a week now. I have received empty boxes in the past when they have been held up this long, so I hope I don’t have to wait for another one to be shipped. I can fabricate the head attachment for the screw once it gets here. Then it’s just a matter of putting it all together. That should finish the mechanical part of the upgrade. It will still need some electronic part installation, but its completion is within sight.
The ball screw for the Z-axis finally arrived. Getting things from asia is always interesting. It arrived in Chicago about when I expected, but then it sat the for 10 days. I was getting fearful that it had fallen off the belt or torn apart by some machine. It finally went to customs. The next day it was on my door step. No trasnfwer from customs, no arrival at the destination post office, no out for delivery. I try not to order international stuff because you never know when or if you will get it.
I drilled and tapped the needed 5/16 hole to attach it to the head. No particular gotcha when I put it all together. It goes up and dow at 60ipm, even without any counter balance. I will probably install something to take most of the weight off the screw. I might even get some more speed out of it.
The last major mechanical work was to put the motor back on. Minor problem. The left support riser was too long. The motor control box wouldn't fit. I happened to have a face mill on the G759, so it only took a few minutes to mill off .120". Motor and control boxes are on.
The spindle spins and everything moves. Hot darn it really works!
I still need to install some limit switches and put the wiring in flexible conduit before calibration.
The electrical work is done, I think. Home switches for all 3 axis. There are connectors for all the cables. The motor and home switch for the X-axis needs some sort of flexible conduit. I got a chunk of Igus link carrier, but it doesn't work right.
The original incarnation of the machine used micro switches for home and limit. Limit switches proved to be of little real value. The micro switches were prone to failure and collected swarf. The switches for this version are mostly sealed and have over travel so nothing gets bent. I originally used intercom cable for motor drive. Solid conductor cable doesn't do well on things that move. I am currently using 4-conductor trailer wire. Over kill as far as gauge goes, but low resistance is always a good thing.
The Z drive doesn't move as fast as the others, but seems reliable. I did not re-install the spring counter because it limited the Z travel. I don't think air springs will work any better. I will set up a counter weight if it has any problems with stalling.
Before I embarked on calibration of the axis, I needed to get the column square and trammed. I couldn't just tram the column to get it square to the table. The rotating head queered that. Instead I mounted a 1-2-3 block on the table. I mounted a .0001 resolution dial indicator to the head so that it bore on the block. I then ran the head up and down whilst tapping the column into alignment. I managed to get it down to .00015 in 2.5", or .0006 over 6". I have no way to check the accuracy of the block, it is probably good enough for anything I would make. I then mounted my tramming device in the head and adjusted the rotation so that the spindle is square to the table.
I had intended to invite Ray over and have some fun calibrating the steppers, but I discovered that I really didn't know how to do the calibration. The original hacked up machine was run with Mach3. Once that machine had passed the smoke test and hadn't fallen apart after a few hours of running, I needed to make a decision on legal software to run it. Mach3 is nice, but I still don't think the few times I will probably make things with it justify the cost. The version 1 machine finished life running with linuxCNC. The ancient PC that I am running the machine with also likes Ubuntu better than the recent versions of windows. So, the ini file to run linuxCNC was converted from the original Mach3 one. That method didn't work now that I had different screws moving the axis. After some experimenting I found the ini parameters that needed to be changed. Only when I was about done with the calibration did I figure out how to use the built in calibration routines. The axis are now accurate to about .0003. I still need to check backlash, but I am putting that of until I solve the next ugly problem.
While messing about looking for documentation for the HAL parameters, I discovered that my version of linuxCNC is 2.5 and no longer supported. The current version is 2.7.7, but you can't upgrade to it unless you do an upgrade to 2.6 first. I don't have networking on the controller PC. Upgrading once is a pain, but upgading twice to get to the current version is not going to happen. I saved all of my custom HAL settings. I downloaded the latest version of linuxCNC and burned it to DVD. Tomorrow I will receive a wifi dongle that is supposed to work with ubuntu. tomorrow afternoon I will lock myself in the shop and reinstall linuxCNC. Worst that could happen is that I have to retreat to 2.5. If I'm really lucky and hold my tongue to the roof of my mouth, while tapping my left foot and singling Dixie, I may end up with version 2.77 and wifi access.
Scraping in dovetails is far easier than upgrading ancient software. I got my wifi dongle. It said it was linux compatible. Well, sorta. It is compatible with the newer linux versions, not my Ubuntu 10.04.
I disconnected the cables and hauled the computer into the office so I could upgrade it. After dozens of re-installs and a new CD drive, I discovered that version 2.7 and 2.6 detect my wifi, but crash starting up linuxCNC. Versions 2.5 and 2.4 don't detect wifi, but linuxCNC does function. In an effort to get wifi, linuxCNC, and a supported version, I bought a refurbished computer and had it shipped over night.
I'm not sure what constitutes 'refurbished' The computer I received beeped like a calliope when I turned it on. The system battery was dead and the hard drive fan was unplugged. And the left side cover latches were broken so the side fell off when I moved the box. It went back. I gave in. I will use linuxCNC 2.5 with no network connection until I get rich and buy a new desktop.
I have the machine running and cut a circular test pocket. It looked round so the backlash compensation is working. It was a 1.250" pocket cut with a 3/8 end mill. It was too small by a few thousandths as measured by a dial caliper, electronic caliper, and a micrometer over a telescoping gauge. I adjusted the pulses per inch and the pocket became the right size.
The ugly problem is that manual moves with the MDI interface are now off by the amount I adjusted the pocket for. Something is wrong with the cam or the post, or 'I don't know'. I snuck away from T-day celebration to do the MDI measurements. I haven't had a chance to look into it. Anyone else have this kind of discrepancy?
measure your end mill. I have noticed that cheaper end mills are typically undersized. Carbide end mills seem to be a very common offender for this. New or otherwise I always measure my end mills before they go into my tool library.
If that's not an issue, post up the Gc0de. should be easy to find out if your cam is leaving extra stock.
I didn't see in your posts above if you are using the parallel port or and external motion controller. Correct me if I'm wrong but somewhere I read that axis calibration only works if you are using the parallel port. Doesn't work with USB or ethernet motion controllers.
Sorry about not doing an update sooner. This is a busy time of the year.
I redid the manual calibration. First I did all 3 axis with a digital indicator over a 0.45" distance. I had intended to do 0.5", but the plunger travel was barely that much and I kept hitting the stop. Next I used a mechanical indicator over 1". I am satisfied that the calibration is accurate and repeatable to less than 0.0005". Since backlash had already been done, I ran the test program again. The pocket was still too small. It acted like the backlash compensation wasn't working.
I then measured the backlash. I still had backlash. So I opened the 'ini' file and added 0.002" to the x-axis. Mach3 is so much easier for setup. LinuxCNC gets its operating parameters from an 'ini' file. While a script populates some of the possible commands, backlash is not one of them. The backlash must be manually entered with a text editor and the program re-started. The command for joint 0 (x-axis) is:
backlash = 0.002
I rechecked the backlash and it was slightly less than 0.002. So I made the backlash value 0.006 and it was still 0.002". After muttering to myself for a while I realized what the problem was. See the command above? Well it is wrong. It should be:
BACKLASH = 0.002
I have written operating programs for real machines doing real testing on real ICs. I would never, ever have made a machines ini file case sensitive. Some day someone would inevitably do exactly what I did.
Anyway -- I measured my 1/4" end mill and it measures 0.0002 over size on 2 calipers and a micrometer.
I still need to find time to get out to the shop to run the test program.