New PM-25MV Mill

[shooter123456]

Everything is mounted up and tested. So far so good. The spindle threads aren't straight so the top hat wobbles a little bit. I get a little bit of vibration at 5000 rpm now, but it will do just fine.

I tested the drawbar with a 2 inch face mill doing .75" WOC, .1" DOC at 25 IPM and it didn't pull out at all. That is 1.875 cuin/min I was able to make the belt slip and there was no pull out. Right now, the air cylinder can release the tool just fine at 70 PSI, so I can probably tighten the drawbar even more. I just need to seal some air leaks and it will be good to go.

 

[macardoso]

Everything is mounted up and tested. So far so good. The spindle threads aren't straight so the top hat wobbles a little bit. I get a little bit of vibration at 5000 rpm now, but it will do just fine.

I tested the drawbar with a 2 inch face mill doing .75" WOC, .1" DOC at 25 IPM and it didn't pull out at all. That is 1.875 cuin/min I was able to make the belt slip and there was no pull out. Right now, the air cylinder can release the tool just fine at 70 PSI, so I can probably tighten the drawbar even more. I just need to seal some air leaks and it will be good to go.

Awesome job. Can’t wait to get mine finished. That’s a hell of a cut for this mill!

 

[shooter123456]

Well that didn't take long... I had the day off on Monday and spent the day working on the mill and I conked out the spindle bearings. This was expected since they aren't meant to be run at 5500 RPM, it was just a matter of time.

I finished 2 parts that had a total spindle time of about an hour each, let the machine rest for about an hour and half while I went to the store and got some lunch, then set up some new tool holders (ordered some TTS holders, these things are nice!) and started the third part, I stopped it before the first cut after the spindle had been on for about 30 seconds (height offset wasn't right) and it went from 5500 to zero in like 2 turns. It was almost immediate. I touched the spindle and it was burning hot and no longer rotating freely. Luckily, I had a set of angular contact bearings ready for just such an occasion.

Swapping the bearings was relatively simple. I made a simple tool to remove the lower bearing nut and just used a pipe wrench on the top nut. The top nut was terribly machined, its a lock nut and the slots that were cut into it are nowhere near straight. Not a huge deal, but its a rotating part that will certainly need to be replaced if I want to get it moving faster. The spindle was tapped out of the housing with a deadblow hammer and came out pretty easily. The bearing cups fell right out as well. They were a bit of a loose fit which I was surprised by. I thought I would need to tap them out. Since the AC bearings are shorter than the tapered rollers, I had to turn 2 spacers, but those went on with no trouble. The reassembly was easy enough. I stuck the spindle in my lathe and used sand paper to clean up the non contact parts just so it looked a little better and I touched up the bearing seats a little to remove any burrs or raised edges. I stuck the spindle in the freezer for a few minutes while I heated the bearings and spacers with a hair dryer. The bottom one slid right on and got screwed in, but the top one had to be forced in with the lock nut. It didn't take much pressure to get it to slide on, but it took more than just hand pressure. I reassembled and put it back on the machine to let the bearings break in a little bit. I used regular automotive bearing grease to grease them. The spindle wasn't noticeably quieter with the new bearings, but the loudest one is the very top one which wasn't replaced. I have started questioning whether that one is really needed anyway, but it doesn't get hot at all so I haven't been worrying about it. After 45 minutes or so of slowly ramping up the speed, I started machining the third part. There was no noticeable loss of rigidity from the spindle and all of the same cuts were handled just fine. After about 2 hours of total spindle run time, the spindle was noticeably cooler than with the tapered rollers (again, to be expected).

Here are the new bearings compared to the old ones. I thought these were surprisingly small since my X2 used the same size lower bearing, but a much larger upper bearing. It may not matter, but I figured they would be larger.

Unfortunately, the third part was scrapped as well. There was an issue with the tool offset and I messed up a tool path in fusion. I need to figure out how to do the automatic tool height offset with LinuxCNC. The first part had no problem at all, but the second part had multiple issues with the offsets not working right. I also found the X axis slowly and consistently drifting to the right. The first operation is a roughing pass all the way around the part to get the stock to the right size, and looking at the right side dead on, you can see each pass is slightly farther over. Since it is consistent, I am guessing it is probably an issue with backlash, so I will need to check that before making more parts. Another issue I need to address is with the air cylinder. After sealing all the leaks at the connection points, I was able to hear a slight hiss from one of the exhaust in the solenoid when the other channel is open. When there is air pressure going to the retract side of the cylinder, the exhaust for the expand side starts leaking. I am guessing that air is escaping where one of the spacers meets the piston since there is no seal there. If it ends up being a problem, I will just take the cylinder apart, use some silicon to seal those areas, and go from there.

 

[shooter123456]

I couldn't deal with the chips getting everywhere anymore, so I decided to put a short hold on the tool changer to get going on the enclosure. I originally planned to try to do it with sheet metal, but after trying to make a small simple part without a brake and shears, I decided that just wasn't going to happen. Looks like MDF is the material of choice. I used it on my X2 enclosure and sealed with epoxy paint and that held up fine for a year until the PM25 came and that mill stopped being used.

I am not very good at working with MDF or wood, so this might end up being a bit of a hack job. I plan to use plywood for the base and MDF for the body, acrylic for the windows and aluminum for the doors. I am going to machine a 4 piece frame for each door and they will slide on drawer sliders I used on the X2. I am hoping to just use the sliders on the top away from the chips and then something simple to support the doors on the bottom. I ordered 2 LED floodlights to light it up inside and I am planning to make a fogbuster type coolant system to use for the coming months until I figure out how to handle the flood coolant. I will need to do some waterproofing of the electronics before I can do that. I plan to put a chip drawer under the mill to make clean up easier.

As of now, I have all the MDF pieces cut out and almost all of them assembled. I put a quick coat of paint on it before I fully assembled it while everything was easy to access. This thing is already really heavy, so I might stick it on wheels so it can be moved once the mill is in it. The back panel where the tool changer will go is 2 pieces so that one can be removed when I install the tool changer and then when I need to get to it to work on it. The head will stick out the top a little bit, but that seems to be how all of them are. I am going to relocate the control box on the side of the head to the electronics enclosure in the back. I still need to figure out how to control the spindle directly from the computer.

I also made a tool finger to test before I make more of them. The machine cut it fine, but it is too tight on the tool. I will need to make that fit a little bit looser. I also changed the tool finger design so that it will have a spring and lever to hold the tool in place instead of just gravity. This should keep the tools from sliding out if the machine is vibrating, if the tool changer spins too fast, or when it is being pushed into place and retracted.

I solved 2 of my previous problems as well. The tool height issue was user error. When I set the tool off set or touched off, I did the correct T1 M6 to tell it which tool I have, but I didn't do G43 H1 to tell it to use that tools offset. For the lost motion in the X, it was the stepper coupler being a little bit loose. I was able to turn each of the screws in the coupler a full turn and a half so I am guessing it slipped a little bit when switching directions causing the axis to drift.

Here are some pictures.

 

[macardoso]

I couldn't deal with the chips getting everywhere anymore, so I decided to put a short hold on the tool changer to get going on the enclosure. I originally planned to try to do it with sheet metal, but after trying to make a small simple part without a brake and shears, I decided that just wasn't going to happen. Looks like MDF is the material of choice. I used it on my X2 enclosure and sealed with epoxy paint and that held up fine for a year until the PM25 came and that mill stopped being used.

I am not very good at working with MDF or wood, so this might end up being a bit of a hack job. I plan to use plywood for the base and MDF for the body, acrylic for the windows and aluminum for the doors. I am going to machine a 4 piece frame for each door and they will slide on drawer sliders I used on the X2. I am hoping to just use the sliders on the top away from the chips and then something simple to support the doors on the bottom. I ordered 2 LED floodlights to light it up inside and I am planning to make a fogbuster type coolant system to use for the coming months until I figure out how to handle the flood coolant. I will need to do some waterproofing of the electronics before I can do that. I plan to put a chip drawer under the mill to make clean up easier.

As of now, I have all the MDF pieces cut out and almost all of them assembled. I put a quick coat of paint on it before I fully assembled it while everything was easy to access. This thing is already really heavy, so I might stick it on wheels so it can be moved once the mill is in it. The back panel where the tool changer will go is 2 pieces so that one can be removed when I install the tool changer and then when I need to get to it to work on it. The head will stick out the top a little bit, but that seems to be how all of them are. I am going to relocate the control box on the side of the head to the electronics enclosure in the back. I still need to figure out how to control the spindle directly from the computer.

I also made a tool finger to test before I make more of them. The machine cut it fine, but it is too tight on the tool. I will need to make that fit a little bit looser. I also changed the tool finger design so that it will have a spring and lever to hold the tool in place instead of just gravity. This should keep the tools from sliding out if the machine is vibrating, if the tool changer spins too fast, or when it is being pushed into place and retracted.

I solved 2 of my previous problems as well. The tool height issue was user error. When I set the tool off set or touched off, I did the correct T1 M6 to tell it which tool I have, but I didn't do G43 H1 to tell it to use that tools offset. For the lost motion in the X, it was the stepper coupler being a little bit loose. I was able to turn each of the screws in the coupler a full turn and a half so I am guessing it slipped a little bit when switching directions causing the axis to drift.

Here are some pictures.

That's a nice looking enclosure. Would you be willing to share plans for it?

 

[shooter123456]

That's a nice looking enclosure. Would you be willing to share plans for it?

I could do that. All I have is a 3D model, but if you have a way to view it, I would be happy to send it to you. Message me your email address and I can send it right over.

 

[shooter123456]

I am just about done with the enclosure now. It has the inside completely painted and waterproofed and the stand has the skeleton done. Getting the enclosure up onto the stand was a bit of a challenge, but it got done. I made the decision to put the machine into the enclosure before making the doors since they would make a ton of chips and I can mostly contain them even without doors. The windows are going to be .093 acrylic sheets, and I am considering going with something a bit thicker for the doors just in case something gets flung like a broken tool or workpiece pulled loose. That way, if it is thrown toward me, hopefully the doors will stop it. I removed the spindle control box and it will be relocated to the electronics box on the back of the machine.

I can control spindle on and off easily with the computer, but I have not yet figured out how to control speed. Since I run it at full speed 95% of the time, for now I will just leave the pot with the box and walk around to the back of the machine to adjust the spindle speed. I am waiting on a cable track for the head so I can wire it up nicely. The track will carry the lines for the air cylinder, the spindle motor wires, and the mist coolant lines.

Here are a few pictures. Unfortunately, the glass on my camera is still broken (Just got a new one, need to get it installed!) so there is some flaring of the light.

Empty enclosure. There is about an inch of clearance on each side for the machine to get in. I did this just because I don't have a way to cut the MDF accurately enough to make it closer. I will use some rubber sheets to fill the area between.

Machine in place. Getting the table in there wasn't easy, but hopefully I won't need to do it again for a while.

Other side.

Here is the naked head. There are lots of holes in it that I would like to fill somehow. I will try to re use some of them to mount the coolant head, but I want to get rid of the rest. I might fill them with body filler and repaint it.

I am still looking for a new spindle motor, but so far that search hasn't yielded any good results. I don't think it is worth it to spend $500 or so for a DMM servo as discussed a little earlier. I have not been able to find an AC motor that would work either. The ones I have found are 56C, which will not fit. I was looking for some smaller motors, but I haven't found anything that looks suitable yet. I am looking for something 1 to 2 HP, 3500 RPM or higher, less than 20 lbs, and hopefully $400 or less for the motor and control. It seems like that is a tall order. If anyone knows of a motor that would fit those points, that would be much appreciated.

 

[phazertwo]

Looking pretty good. I am patiently waiting to see how your enclosure turns out... I have been dreaming of a sweet enclosure, but also lack the equipment to make something nice out of sheet metal.

As far as a motor, why can't you use a 56C and just let the face be above the top of the mill? As long as the shaft hangs down low enough.

PZ

 

[shooter123456]

Looking pretty good. I am patiently waiting to see how your enclosure turns out... I have been dreaming of a sweet enclosure, but also lack the equipment to make something nice out of sheet metal.

As far as a motor, why can't you use a 56C and just let the face be above the top of the mill? As long as the shaft hangs down low enough.

PZ

Its just one of those things... I could probably invest the time and money and make something really nice, but its a supporting accessory. Something hacked together that looks rough and gets the job done faster and cheaper is fine by me in this case. Now if I bought the mill because I wanted to have a show piece I could be proud of, that would be a different story. But in the end, I want to spend that time and money making parts and adding stuff to the machine.

Referring to the motor, when I imported a 56C model from one of the manufacturers, there was not enough room between the air cylinder and column for the motor to go. With it just clearing the air cylinder, it overhung the back of the head and interfered with the Z axis stepper. The other option was to off set it to the side, but that would require either using 2 belts to route under the air cylinder or redesigning the air cylinder to make it work. Neither of those seemed like ideal solutions if there are smaller motors available. On top of that, the motors I was looking at were 26 lbs, compared to less than 10 for the current motor or some of the servo options. I would like to try to keep the weight of the head down so it can move quickly.

 

[shooter123456]

In hopes of figuring out who makes the spindle motor and finding more details about it, I took the sucker apart. In the end, I have learned nothing.

It is a 2500 rpm Nema 34 750w brushless motor, it has a small fan under the top cover, with 8 wires. 5 appear to be for feedback, 3 for power. The feedback wires are marked +, -, W, U, V. The 3 larger wires did not have any visible markings.

The only markings on the circuit board inside the motor are:
L3155-HL
13/3/23
H13938
P46S24027

Unfortunately, google did not yield any results that give me relevant information. I had asked Matt for some more information about the motor and control board and he wasn't able to provide anything for me.

If you have ever wondered what these things look like on the inside, here are some pictures.

Top cover off. You can see the weird fan on the top.

Side view with wire cover removed. It looks like this thing melted at some point. It may have been to seal the motor or support the wires, but it no longer does so.

Fan removed. It is just pressed onto the back of the shaft. I am not sure how it works with the blades not having much room for air flow, but it might be to draw air over the fins on the outside of the motor.

Rear panel removed giving me a decent view of the encoder inside and rear bearing. You can also see the cooling fins pretty well here.

Here it is next to the 1000 oz in nema 34 that will be going on the Z axis at some point. The spindle motor is slightly longer, but the same face size I think.

Closer view of encoder and power wires. Soldering doesn't look all that clean.

Shaft removed. The magnets are in the shaft and the coils are in the motor body. Backwards from a brushed motor as far as I know.

Picture of the shaft. The magnets in this thing are rediculously strong. It took some care to get it back in the motor without crushing my fingers or breaking the encoder.

That's all for now. If anyone can tell me anything about the motor, that would be great. I may repurpose it once I pick a new motor for the machine. Maybe to keep costs low, I will swap the motor with the one on my lathe. The lathe has a 4000 RPM 750w brushed motor. That should give me the higher speeds I want, about 8800 RPM with my current pulley set up. The 2500 RPM motor would change the lathe low speed from 50-1000 to 30-625. That would give the lathe a ton more torque and the mill would get the speed I want. Decisions decisions.