VH-65 Seal Repair
After rebuilding the VH-65 and mounting it, I kept my eye on the oil level. After a few weeks it fell below the sight glass and I knew I had a leak. I had really fought with the large seal in front and immediately came to the conclusion I had messed it up. Careful observation seemed to show that it was leaking as there was evidence on the front of the rotary.
It's kinda hard to see, but there is some faint staining right below the seal area as shown here.
First up - remove the old seal. Easy - just drill a small hole in the seal and use a slide puller!
My problem the first time was I had no way to evenly pull in the seal. I had tried to gently hammer it in, but I knew at the time I had deformed it. I needed a tool.
When I was scrounging around my local surplus yard, I found a scrap ring of 6.5" ID aluminum. Perfect. For $10 it was mine. All it needed was to a bit of machining to open up the ID a bit and face it. I used the T slots in the face and a couple of scrap plates to rig up a way to pull it down. I carefully tightened each nut so as to install the seal square and even. It went in pretty easy.
I topped it up with oil and I'll keep any eye on it for the next few weeks a see what happens.
When I had purchased the rotary, the Fadal logo plate was missing. One happened to come up on eBay, so I decided - what the hell.
Part 4 - Fadal VH-65 - Found a Leak
It's been a few weeks since I put it together. I haven't used it yet - still working on learning the CAM and tweaking my postprocessor. However I've noticed the oil level slowly dropping and have determined that the big lip seal in the front that I had trouble installing is leaking. Back to the drawing board. The good news is that leak is pretty slow and I've got LOTS of oil. Also this seal is pretty easy to remove. The bad news is I'll need to devise a seal installer tool of some sort. When I figure that out, I'll post the results. I purchased a replacement on eBay for $25, so hopefully will get the tool figured out before the end of the year.
Basically assembly is the reverse of disassembly. I first reinserted and sealed all the set screws I found on the main body. I then lubed the front chuck bearing and inserted it into the body. I rotated the assembly so it was resting on the chuck face.
Next, reattach the brake plates the chuck - noting the correct dish position. Here I had to guess because I didn’t realize they were dished when I took it apart. Based on the marks the screw heads left, I choose have the center higher section toward the rear. It’s hard to see, but the center is higher than the outside edge. I placed it with the highest part to the rear.
Now install the 3 brake piston o-rings in the body (HDW-0176) and the 2 o-rings in the center of the piston (HDW-0167). I used some silicone grease for lube, I suppose oil would be fine too. You probably want something to ease the assembly. Now insert the brake piston.
Next is the back plate (ROT-0033). Install the two outer o-rings (HDW-0172) with some grease or lube. I also greased the nose section that locates inside the brake piston. You want to be careful about screw alignment as it’s a bitch to rotate when its home. Also there are two plugs that go at the top. I then installed the lip seal (HDW-0223). Unfortunately, I screwed up and drove it in way too far. It should be flush with the top of the bore. Remember to use a bit of sealant on the screw threads. At this point I installed the o-ring on the end of the chuck shaft (HDW-0164).
I forgot to take a picture of the preload ring being installed. Since I had no information on what it should be preloaded to - I guessed at 90 ft lbs. I figured the bearings where very large and there might be significant lateral cantilevered loads on the chuck face, so it better be tight. Hopefully it’s close. If you know let me know! When it was torqued up it rotated pretty freely and had no tight spots or “notchiness”. I got to use my tool from Part 1 to torque it up!
Next was inserting the worm (ROT-0037 + ROT-0043), from the motor end. Then sliding the adjuster plate (ROT-0043) on the opposite end. Unscrew the two screws on the top and bottom of the adjuster plate so they are clear of the hole. Push the adjuster plates down so they are resting on the top of the pin.
Thread on the Higgins nut on on the non-motor side. Note that there is a 0.015 or so boss on that goes to the inside.
Now insert the motor drive gear on motor end of the worm, locating with the key. Note: the boss on the gear goes toward the inside. Thread on the Higgins nut, noting it’s boss goes to toward the gear face.
Hand tighten the Higgins nuts. Make sure the adjuster plates are fully down on the tops of pins, to create maximum clearance with the worm gear. You should be able to freely rotate the worm and the chuck should spin nicely with no bindings etc. There will be some backlash, however.
At this point you need to read the maintenance section of the Options Manual. See Options Maintenance Manual. It gives detailed instructions on how to set up the worm, the backlash and tune the amplifier, etc. I’ll cover some this stuff later.
First is setting up the worm. The adjuster plates basically pivot up and down around a locator pin. The other pin is the one between the two screws and is in a hole that’s oversize enough to allow for a range of motion. By screwing in the top screw, and therefore pivoting the adjuster plate upwards, you’re also bringing the worm closer together and reducing backlash. You need to raise both ends of the worm evenly so we reference it off a surface plate.
The procedure is to screw the top screw on the non-motor side in one turn (after just contacting the pin). And screw the motor side one in two turns. Now zero an indicator on the non-motor side (pick a spot that will be same on both ends as it makes a difference. I used an area just outboard of the screw center line.
Now carefully transfer this reading to the motor side and adjust it either up or down to read the same. At this point the worm should be level and backlash should be pretty much out. In my case I felt I had a bit too much backlash, so I raised the non-motor side about a quarter turn and re-leveled the other end. Hmmm, too tight. So I backed it off a bit, re-leveled. Note: you’ll need to push the plate down if you unscrew the top screw - i.e. don’t assume it moved down just because you took pressure off the top. After 3 or 4 attempts I managed to get it so there was a bit of backlash, but it didn’t bind. You should check all 360 degrees. Don’t install the end plate or motor plate just yet.
Now install the large lip seal in the front (HDW-0224). I had a hell of time getting that in, so I won’t relate it. It was just wrong. Probably need to create a ring to be able to uniformly press it in. I can tell you now a small ball peen ain’t the way to do it.
Once that was in and the retaining screws were installed (with sealant), install the zero indicator plate, loosely. I would rotate the chuck so the line is in approximately the correct position and the T-slot is horizontal.
OK the hard part is over! Next is mounting the motor. Replace the 1/4″ o-rings (HDW-0149) on the motor side of the motor end plate.
Lube the lip seal (HDW-0225 - I didn’t replace this on mine as it looked fairly new) and slide it into the motor. Tighten down the 4 mounting screws. Now place the gear and clamp on the motor shaft. Note: the beveled end of the clamp goes against the gear.
Reseal air fitting and run one of the HDW-0162 o-rings around the outer groove. Put 3 more around the periphery. I used Gasgacinch to glue them in and some blue painters tape to hold it until the glue set. It seemed to work well enough. As the British might say, “offer the motor to the body” and secure with the 10 bolts. Don’t forget sealant on the threads (esp the through holes).
Carefully slide the motor cover on and secure.
At this point, you’re ready to mount it in the mill and set up the final adjustments. The end plate opposite the motor should still be off!
After you hook up the electrical cable and air line, there are 6 things left to do:
My amp board was sort of hacked in - that’s why that electrical block is sort of hanging in space right in front of it, etc. Your mileage may vary. Here’s where you adjust SIG2 on this amp board.
I ended up adding a 0.0007 backlash at the control (as in BL,4,7) and it seemed like I ended up with backlash around 0.0003.
Once you have everything adjusted to your liking, mount the end plate and fill with oil. Before you reinstall the top fill plug, run it back and forth and wait at least 10 mins. You’ll probably need to top it off. After it’s settled down and the level is stable, tighten the plug. I would watch the oil level over the next week or so to make sure there are no leaks
Basically I cleaned the whole thing up - Scotchbrite, solvent and elbow grease. I found several setscrews that were sealed with silicone seal at various locations. I also noted that some of the mounting screw holes where through holes and could leak, those had silicone on them too.
Since my application for this would be hobby use, I wanted to spend as little as possible. I knew I was in for seals, but wanted to reuse everything else. I found the main bearings (BRG-0037/BRG-038 and BRG-0035/BRG-0036) where less than wonderful. The races had damage from what looked like corrosion, but I wasn’t going to replace them. I decided to simply polish them with some crocus cloth.
Once I cleaned up the rollers etc. they seemed to spin smoothly enough for me. Other than cost - I also had no idea how to remove the bearing located in the chuck. What kind of puller do you use for that? I also didn’t look forward to removing the races as that would have meant pressing them out and in I’m sure!
Next on to ordering parts - A few things to note. The parts diagrams I found for this showed only two of the HDW-0176, but my rotary needed 3. Also there are 4 1/4″ o-rings that seal the motor mount screws not listed in the diagram, their part number is HDW-0149. Also note there are 3 HDW-0162 o-rings for the motor cover to motor plate seal and the same o-rings are used to seal the end plates - so you need 5 total. I found the large lip seal (HDW-0224) on eBay for $25. Also the o-rings are standard so any decent parts house can probably get em. I found all these at FadalCNC.com aka CNCPros.com. Although prompt, they sent me several incorrect o-rings, which required another shipment. They were very responsive about fixing it and shipped the replacements overnight, no charge!
You’ll need gear oil to refill it. I didn’t realize I could order a gallon from CNCPros, so ended up getting 5 gallons off eBay. The original lube was spec’ed as MOBILGEAR 626 - LUBRICATION OIL ISO VG 68. Apparently Mobil 626 has been superseded by Mobil 600 XP 68. 3 Quarts will run you $15 from CNCPros - Rotary Gear Oil.
Part 1 - Fadal VH-65 Disassembly
Since I’m just a hobbyist, I couldn’t see purchasing a 4th axis for my 1994 Fadal VMC20 for much more than $1000. Since these things seem to go on eBay for more like $3500 and up, I jumped at the chance when one came up for $999. After the bidding was over, it cost several hundred bucks more, but still pretty reasonable.
Since this was an eBay purchase, I had my expectations in check when it arrived. I’ve learned with eBay you get what you pay for, so I figured it would be a good idea to disassemble the easy stuff apart to see what the condition was. Good thing too - it turned out it was a mess. Right off the bat, I noticed the motor cover had a nice dent in the top and several of the screws that held it to the motor mount end plate were cross threaded. This cover had been off before. I wondered what was lurked inside.
BTW - The part numbers I’m referencing come from the Fadal Options Parts Manual, pages 16 - 18.
I pulled the motor cover off and found the first issue. The motor wasn’t actually bolted to the mount plate - it was just sort of rattling around in there. I then removed the bolts on the motor mount end plate removed the motor and plate. Two things became obvious - The four screws meant to fasten the motor to the plate were just missing altogether and there was no gear oil at all. On the plus side, the motor looks like a fresh replacement/rebuilt unit (also the wires had labels on them, like you might do when replacing a motor). I hope the previous owner was in the middle of a motor replacement when they lost interest.
Once the motor was out, I tried to turn the worm by hand. Got about a 1/16 of a turn and that was pretty stiff. What little I could find by searching the web indicated it should be pretty easy to turn by hand, which it was not. Time to dig deeper, so I decided I better take whole thing apart. Whoever worked on this last was an ape - all the fasteners were REALLY tight - way too tight.
My first problem was the Higgins nuts (HDW-0230). The hold the worm in place and they were on really tight. I didn’t want to chew them up removing them, so I made a tool. (In hindsight, this was probably overkill, but when you have a mill…)
If you want the STEP 214 file - HigginsTool.stp
I made two and they really made it easy to get the nuts off (it also helped setting things up on reassembly). Once I had the nuts off and slipped the drive shaft gear (ROT-0280) off, it’s easy to remove the worm by pushing it out toward the motor end. I left the motor end worm pivot plate (ROT-0043) along with gear key as I didn’t need to take it apart any further.
With the worm out, the chuck should be able to spin relatively easily. Not in my case. So I now needed to remove the preload adjusting ring (ROT-0035). It took a while to figure out how this worked, but I finally got it. There are two small set screws that deform a thinner section to create a locking feature (Note: There are two small pins located under set screws, so you only need to loosen - not remove - the screws. In my case, however, the gorilla that worked on this last managed to bend the locking section of the ring so much I couldn’t release it. Time for another tool…
STEP 214 file - preloadnuttool.stp
In my case, I had to resort to an impact driver to get this off. One removed, it became obvious the previous person had way overtightened the set screws and overbent the thin middle sections enough to damage the threads. I managed to bend it back enough and clean up the threads so I could hand thread it back on. (Note set screws partially exposed in the picture. You can also just make out one of the pins just touching the thin section.)
Once the ring was off, I needed to pull the back cover/bearing race (ROT-0033). There were 6 screws holding it on, and once removed, I realized the thing wasn’t going anywhere. I noticed 4 threaded holes around the periphery and decided they were there for pulling. Those holes are 4.75″ apart. I guess I needed another tool…
Although crude looking, it worked. Basically I used 4 screws ( I think they’re 8x32) to mount it to the back cover, and placed a small block of aluminum between the central cap head screw and the end of the chuck shaft. By screwing down on the cap screw, it jacked the cover up. After about a half an inch, it came free. You’re pulling against larger perimeter o-rings, so it’s supposed to be tight.
Once that’s off you can gain access to the 12 screws (HDW-0303) the hold the brake plates (ROT-0036) to the chuck (ROT-0000).
After removing the screws, you can extract the chuck out the front. Before you do that, you’ll need to pull the large front seal (HDW-0224). I drilled a small hole in it, then mounted a slide puller with a screw in the end. It didn’t take much to get it out. You can then push the brake plate and brake piston out the back. There are 3 large o-rings (HDW-0176) you need push them past. Note, the brake plates are dished! I didn’t notice that when I removed them and had to guess as to the way they went back to together.
At this point, it should be disassembled!