[chich2]

Yesterday I removed the dovetail ram and spindle assembly like last time and then removed the knee. I placed the knee on some card board out in the yard and marked out where I need to cut away from the knee to fit the pneumatic cylinder. Once I cut out the bottom I then took several small cuts into the 25mm web that runs up the back of the inner knee. I did this with a 4" angle grinder fitted with a 1mm thick cut off wheel. It was just a matter of several light taps with a small hammer until the web pieces broke away. I did not want any stress cracks to develop into the good part of the knee so I used many cuts and only light tapping with the hammer. Once the web was removed I ground the web flat and smooth and then painted the bare cast iron.

The next step was to put the machine back together. Once I got the knee on I adjusted the gib and then lowed the knee onto a piece of hard wood. Next to go on was the Y axis dovetail. Now that I can secure the Y axis I set up my boring head and machined the hole that holds the Y axis lead nut deeper. I needed to do this because I made a much more solid retaining washer and a bigger bolt than the standard one. (There is a photo of it in a previous post).

I then assembled the Y axis lead screw, bearing mount and then tightened the antibacklash nut tightly to the machine. I placed a light preload onto the angular contact bearings and gave the Y axis a go by hand. I am very happy with how smoothly and easily it moves. Keep in mind that there is almost no weight on it at the moment so it may stiffen up a bit when the X axis and swivel is sitting on it too.

Chich

[macona]

Hey, I put up a post with my progress on the refurb of my mill:

http://www.cnczone.com/forums/showthread.php?t=28668

On the bottom there is a picture of the air assist ball screw.

[chich2]

Great thread macona. You have certainly got a great project there with your supermax. The air assisted ball screw is a good set up.

Keep up the good work,
Chich.

[chich2]

Haven't had a post in a while so here is an update on my cnc conversion.

I ordered a precision pressure regulator from SMC. It is acurate to the set pressure setting within 0.5% and repeatibility of 0.2%. I have made a mounting plate that the cylinder rod pushes on and bolted it in firmly to the under side of the knee. When I say underside I mean directly under the Y axis slide ways. Basicaly the cylinder gives me full stroke of the Z axis. I have cut a hole in the casting through the top of the coolant tank and sat the cylinder on the floor of the coolant tank. The floor of the coolant tank casting is about 20mm thick with some very heavy webbing so there is plenty of stregth there. The cylinder is set up to run parallel with the Z axis dovetail slide. I milled off some of the aluminium from the sides of the cylinder ends and I also milled quite a bit off the Z lead screw post. In the photo's you will also see half of the Z axis servo aragement coming together. You will see the servo pulley grub screwed with 2 M6 grub screws 90deg apart. I milled 2 small flats on the screw boss to take the pulley grub screws. I piped the regulator up with brass gas compression fittings and copper tube.

When it came time to try it out I backed the regulator off and turned on the air supply. I then slowly screwed up the pressure on the regulator and the handwheel on the knee became easier and easier to turn. Now when I raise the knee, the regulator fills the cylinder and when I lower the knee the regulator vents the excess pressure. The regulator has a very controll over the pressure in the cylinder.

Here are some pictures.

Chich

[chich2]

Today I made and installed a chip cover over my Y bedway. This should keep most of the chips and swarf off the beds. There are 2 photo's. A before and an after shot.




Chich

[chich2]

I have noticed that the HM-52 has only 1 gib adjusting screw on the knee. What happens is when you make a very small up and down movement on the knee you will see the gib actually stay's still for a very short moment as the knee moves, then the adjusting screw hits the jib and starts to moove it allong the dovetail. This leads to three things. First one is uneven wear. Second is that when the knee goes down the gib is slightly loose. when the knee goes up the gib get's slightly tighter. The third thing is that there will be a tendancy for the front of the knee (where the handwheel is) to drop down very slightly. It wont be much but the top of your knee will no longer be square to the colum of your mill untill you either travel the knee up or tighten the locks on the side of the slide.

I have fixed this problem by adding a second adjuster to the bottom of the knee. I had to chip away the bog filler from the underside of the knee and file it flat with a course file.


Chich

[chich2]

Here is the start of my servo mount. I milled some mild steel down to 20mm thick then bored a hole in 52.02mm diameter to house the bottom Z angular bearing and oil seal. I will try to show all this at a later date when it is all installed.



Chich

[FPV_GTp]

hi

Nice work chick2

cheers

[chich2]

Thanks FPV GTp,
I am at work at the moment and will be back home this friday. I will be adding some new post's to this thread during the next week.

Chich

[chich2]

Here are some more pictures of my conversion. Next step was to mount the servo motor to the mounting plate. I made the servo mount to bolt securely to the flat surface I milled under there, back when I turned the knee over. I set the preload on the 2 angular contact bearings I put on Z axis lead screw (as shown in a previous post). Once this was done I then slid the servo mounting plate over the bearing clamped the plate tightly and marked the holes that secure the plate to the flat milled surface. I then removed the plate and drilled and taped the holes. This eliminates any binding issues caused by an incorrectly positioned mounting plate putting side load on the bottom angular contact bearing. Keep in mind that this mounting plate also doubles up as a bearing and lip seal housing for the Z axis lead screw.

The drive belt has to be tentioned, so the plan was to make the servo able to be slid back and forth allong the mounting plate on slotted holes. This was achieved by milling out 2 pieces of 25mm RHS box section. This can be seen in the first photo. The belt had to clear everything so if the belt did ever slap I had to make sure there was plenty of space for it to run in.

The rest of the photo's are pretty straight forwarward except for photo 5. Because the boss diameter on the small 14 thoothed pulley is so small and the shaft size on my servo is 10mm, I was concerned with how little wall thickness I had for the grub screw to hold into. Because of this I had to (very unwillingly) also add a grub screw hole in the cogged section of the pulley.(wedge) I cleared away any burs and made sure it sat down deep enough that it would not touch the belt when it runs. Guess I'll see what happens when it's running.

Chich

[epineh]

Looking good Chich, make sure you leave enough room for the tool changer!!!

Russell.

[chich2]

Khaa Haa! Yes russ I WILL!! Definately have to use one of your micro controllers for that one! I just read your thread and find it VERY interesting.

Good work!

Chich

[chich2]

Today I finished the Z axis servo mount. It was a matter of setting the pressure on the air cylinder and locking the Z axis dovetail clamps to lock the knee into position, then disconnect the Z lead screw form the machine and screw it down. Once the screw was low enough, then came re-mounting the Z screw pulley with it's 2 grub screws and passing a new belt over the screw. I then put it all back together and adjusted the preload on the Z angular contacts and mounted the servo and released the dovetail clamp locks. A quick belt tension up and we're in buisness. I wanted to see how it would go so I connected the 24volt servo to a 12 volt battery, quickly checked the air pressure to the cylinger and give the motor a quick tickle up with 12volts. BAM! up it went! Switch the wires over and down it went. Pretty crude way of testing but I could hear the precision regulator doing it's thing very quickly adjusting to the pressure rise and fall in the cylinder as the knee moved. Can't wait to see it going by CNC!!!!!! :banana:


Chich

[chich2]

Because my air asist cylinder goes through the base of my mill and sit's on the floor of the coolant tank, there is a good chance chips and swarf will get into the coolant tank. So I made an oil resistant neoprene cover to go over the gaps. This was firstly done by measuring it all up and cutting out a cardboard template. Once the template fitted, then the cover was cut out of neoprene.

Chich

[chich2]

Today I started the X axis servo mount. The first step was to make something to support the end of the X axis lead screw when the table is fully traversed to the right. In this instance the only support the screw has is the 2 anti backlash nuts mounted to the swivel. I have about 600mm of unsupported screw that needs to be held as the servo belt will be pulling sideways on the lead screw. I decided to firstly bore out the cogged pulley and slide it onto the shaft. This allowed me to see exactly where the servo motor would and wouldn't fit. Following that a few measurements of the rectangular box pipe that I have in the rack for the mounts, I came up with a quick scketch.

I cut a piece of steel, milled all the rust off it and milled it to size. Drilled the 2 bolt mounting holes and used my boring head to bore a hole in the plate for a slide fit on my steady bearing (6004 2RS). Bolted it on and gave it a go..... Good thing!

Chich

[chich2]

Today I continued work on the X axis servo mount. Firstly I cut 2 lengths of 150 X 50 RHS 270mm long (6" X 2" Rolled Hollow Section). The servo shaft needs to be parallel to the lead screw so an easy way to do this is to machine one side of the RHS flat and secure it to the machine and attach the servo to the same side. I removed the limit switch for the standard Hafco power feed unit as it is no longer needed. The table travel stops were removed as they are also no longer needed, and one X axis table lock handles removed (one will do). Next was to drill and bore all the holes and bolt it on. Hopefully tomorrow I will attach the motor and give it a test run.

Same old story, just hover your pointer over the picture thumbnail to get a description of the photo.


Chich

[chich2]

Yesterday I ordered my drive electronics. I purchased everything I need from CNC Teknix in Oak Flats near Sydney, Australia. I spoke to a bloke named Dave. He was very helpfull. I purchased 4 Tek10 - 15-80V 25A Servo Drives, A breakout board and registration for Mach3.

Chich

[FPV_GTp]

hi

Chich2 very nice work , love the pneumatic cylinder assisting in the lifting of the heavy bed ( Z direction ) of the milling machine.

Still trying to work out how you eliminated the play in the lead screws of the X and Y axis , i will have to read these posts several times to understand what you have done.

Tek10 - 15-80V 25A Servo Drive $324.50 drivers not cheap at all but a good choice , any reason you chose Dave's drivers over some of the other units out there. Say Gecko , Rutex and so on.

I will follower this thread to the end as i have a Pacific FT-2 universal milling machine i will be converting soon.

Keep up the good work

cheers

[chich2]

FPV GTp,
Thanks for your post. The anti backlash nuts are different for the X and Y axis. The X axis is like screwing 2 nuts together on a thread. As they touch each other, one nut will be pushed up against the flank of lets say the left side of the thread and the other nut will push up against the right flank of the thread, thus eliminating backlash. Some people put a spring between 2 nuts to do the same job.
The Y axis is almost the same but instead of screwing the nuts to move their position along the thread helix, the Y axis nut has jacking screws between the 2 nuts and I simply adjust the 2 nuts apart via the jacking screws to eliminate the backlash.

The CNC Teknix hardware must actually be going up in price. The Tek 10 I actually purchased was at last years price of around $280AU or round about there. Babinda01 here at the zone does CNC conversions as a living and literally lives a stones throw from my place. I believe Babinda01 and CNC Teknix have a long working relationship and they are currently working on a system which will give encoder feedback back to the PC. This means the PC now knows exactly where the position of the machine is and doesn't just assume that the servo drives made it in time. It also allows the user to power down the servo drives and make a manual handwheel movement and the PC will know the position the table is now in. The new system will also be a true DRO. Dave informed me that I can upgrade to the new system for $300AU when it is released. I just seperate the 2 cards on each servo drive and send them the top one and they will send me the new ones and new controll card. The new system is interfaced via USB.

My system requires frequent adjustment as the lead screws in the machine wear the brass nuts away quite rapidly. I am only doing it this way until I can find cheap ball screws to install (which I have just found)

I personally like the Pacific mills. You are lucky to have one.

Chich

[FPV_GTp]

hi
Chick2 , ok understand some of the reasons , but was going to ask why didn't you use ball screws from the start.

I found most bearing places here in Australia are asking a fortune for ball screws.

I got in touch with www.nookindustries.com and was quoted far cheaper like 3 times cheap delivered to my door from overseas than what i could buy here in Australia . Bloody amazing someone is trying to make a packet.

Out of curiousity what brand of ball screws you planning on using and who did you source them from ?

cheers