New PM-25MV Mill

I think I figured out how I can make some way covers for between the saddle and column. I want something that would keep chips and coolant off of the ways and ballscrew, without collecting chips until it jams everything up. The stock set up with the thick rubber sheet worked ok, but it collected chips, and kept getting bunched up so that any time I worked on something larger than 3" wide, the vise would rub against the cover until it ripped. The according style covers seemed ok, except that they caught chips like crazy and were difficult to keep clean. The ones on the Z axis also ended up tearing after the vise rubbing it too many times.

What I really want is some of those sheet metal telescoping ways that you see on the real VMCs. They seem to protect well, easy to brush off the chips that gather on them, and last a long time. The problems is that bending and welding sheet metal covers like that so they slide well while not having excessive clearance requires skill and equipment beyond my capabilities. I tried to come up with something that I can reasonably make that will work well. Since I am a lot better at machining than bending and welding, I tried to stick to machining as much as I could.

What I came up with is basically aluminum blocks that slide on rails with a piece of sheet metal attached to the top. This way I can closely control the clearance between the parts and control their movement. The blocks will have little pins sticking out of them that will ride in the a slot of the adjacent block. This way, when the first segment reaches the end of its length, the pin will reach the end of the slot and start pulling the next one. Then when that one reaches the end, it starts pulling the next one. When they go the other direction, the table will push the first all the way back in, then the second, the third, etc. I will use either felt or rubber as wipers for the covers to keep chips from getting under them between the spaces. The two end segments will be fixed to the saddle and the column. I am planning to use "tight tolerance stainless round bar" from mcmaster for the rails.

Here is a picture of the top.
4PMrB0F.png


Here is a picture of the bottom.
DOZPKk0.png


I have also designed the covers for the X and Y axis motors. The X looks very similar to the way Tormach covers their motor. Its just a box that surrounds the motor to keep chips and coolant off of it. The Y axis has a sheet metal box that mounts to the motor mount specifically to protect the motor, then a moving section attaches to the saddle that will protect the ways when the saddle is moved toward the column.
KLjXFPq.png


Any thoughts, feedback or suggestions are welcomed and appreciated!
 
I like the idea! Do you think the rods are necessary? If you already have the tongue and groove on the inside of the plates AND you are bolting to the saddle which has to move perfectly straight out, then I'd think it would keep itself straight?

If you do use the rods, I suggest you install small oilite bushings in the plates. This will get your rods running through much more smoothly and less likely to bind in the hole.
 
macardoso said:
I like the idea! Do you think the rods are necessary? If you already have the tongue and groove on the inside of the plates AND you are bolting to the saddle which has to move perfectly straight out, then I'd think it would keep itself straight?

If you do use the rods, I suggest you install small oilite bushings in the plates. This will get your rods running through much more smoothly and less likely to bind in the hole.
Click to expand...
I thought they would rotate around the pin too much without the rods holding them in place, but now that I think about it, they could only tilt forward, and they would be resting on the section in front of them so they can't tilt forward. So maybe it can be done without the rods... Worst case, it doesn't work and the rods can be added after the fact.
 
I made the new Y axis motor mount and bearing block. This one does a better job protecting the coupling from chips and coolant, but it comes at the cost of decreased access during assembly. I also switch from the original bearing block with a flange to hold the bearings in place to a configuration where one bearing goes in on each side of the bearing and preload is set by tightening the lock nut. It is 3 different parts and I used alignment pins so they will go together easily and line up perfectly. I am hoping they also add a little bit of rigidity to the set up.

Here is a lock at the mount with the bearing block closest. You can see how the coupler will be completely covered from the top. The enlarged portion on the back where the motor mounts will also mount a cover for the motor. That will be made of sheet metal and should do a good job of protecting the motor connections from coolant.
oSvijXs.jpg


Here it is from the motor mount end. I enlarged the holes that mount the bearing block to the base which will hopefully allow better alignment once installed. The 4 larger holes here attach the motor mount to the spacer, then the smaller holes on the outside corners will be used to screw the motor on.
doljxCL.jpg


Here it is from underneath. It looks like there is more space between the parts because I did a very light edge break chamfer on them. The finish on the spacer isn't fantastic. I left .01" after roughing with the insert end mills to clean up with a regular end mill, but it wasn't enough. I am wondering if there is run out in the holders of those end mills, so they went in farther than they should have and then there wasn't enough to clean up after. I will increase the stock to leave for those tools so hopefully things look better in the future.
W5B3KfU.jpg
 
shooter123456 said:
I think I figured out how I can make some way covers for between the saddle and column. I want something that would keep chips and coolant off of the ways and ballscrew, without collecting chips until it jams everything up. The stock set up with the thick rubber sheet worked ok, but it collected chips, and kept getting bunched up so that any time I worked on something larger than 3" wide, the vise would rub against the cover until it ripped. The according style covers seemed ok, except that they caught chips like crazy and were difficult to keep clean. The ones on the Z axis also ended up tearing after the vise rubbing it too many times.

What I really want is some of those sheet metal telescoping ways that you see on the real VMCs. They seem to protect well, easy to brush off the chips that gather on them, and last a long time. The problems is that bending and welding sheet metal covers like that so they slide well while not having excessive clearance requires skill and equipment beyond my capabilities. I tried to come up with something that I can reasonably make that will work well. Since I am a lot better at machining than bending and welding, I tried to stick to machining as much as I could.

What I came up with is basically aluminum blocks that slide on rails with a piece of sheet metal attached to the top. This way I can closely control the clearance between the parts and control their movement. The blocks will have little pins sticking out of them that will ride in the a slot of the adjacent block. This way, when the first segment reaches the end of its length, the pin will reach the end of the slot and start pulling the next one. Then when that one reaches the end, it starts pulling the next one. When they go the other direction, the table will push the first all the way back in, then the second, the third, etc. I will use either felt or rubber as wipers for the covers to keep chips from getting under them between the spaces. The two end segments will be fixed to the saddle and the column. I am planning to use "tight tolerance stainless round bar" from mcmaster for the rails.

Here is a picture of the top.
4PMrB0F.png


Here is a picture of the bottom.
DOZPKk0.png


I have also designed the covers for the X and Y axis motors. The X looks very similar to the way Tormach covers their motor. Its just a box that surrounds the motor to keep chips and coolant off of it. The Y axis has a sheet metal box that mounts to the motor mount specifically to protect the motor, then a moving section attaches to the saddle that will protect the ways when the saddle is moved toward the column.
KLjXFPq.png


Any thoughts, feedback or suggestions are welcomed and appreciated!
Click to expand...
From personal experience, I haven't had good experience with AL rubbing on SS because the AL ended up galling. I would suggest look at adding some sort of bushing to prevent this from happening. Although your contact area looks alot more than my previous failed applications, so the stress causing galling should be alot less. My practical experience found that if the stress was above 2-3 ksi, binding would result between the 2 materials.

Have you thought about 3D printing the covers. This would be less expensive and allow you to build a smaller scale to work details.Here are a few pictures my design of 3d printed way covers ( in blue) from my column build/linear rail conversion. The small prototype i've built seem to have promise, but haven't gone full scale. I know that I would have to cover them in thin sheet metal to protect the surfaces from hot chips melting into it. I've has decent luck with the printed material not wearing out too quickly but would considered it to have a finite life. . And it should be pretty easy to design mounting provisions for the wiper.

Column Covers 2.jpg


Column Covers 1.jpg

back side cover 1.jpg
 
vinnito1 said:
From personal experience, I haven't had good experience with AL rubbing on SS because the AL ended up galling. I would suggest look at adding some sort of bushing to prevent this from happening. Although your contact area looks alot more than my previous failed applications, so the stress causing galling should be alot less. My practical experience found that if the stress was above 2-3 ksi, binding would result between the 2 materials.

Have you thought about 3D printing the covers. This would be less expensive and allow you to build a smaller scale to work details.Here are a few pictures my design of 3d printed way covers ( in blue) from my column build/linear rail conversion. The small prototype i've built seem to have promise, but haven't gone full scale. I know that I would have to cover them in thin sheet metal to protect the surfaces from hot chips melting into it. I've has decent luck with the printed material not wearing out too quickly but would considered it to have a finite life. . And it should be pretty easy to design mounting provisions for the wiper.
Click to expand...
If I use the guide rods, I am thinking I will add one of the oilite bushings mcmaster sells. That should keep it from galling. I hadn't considered 3D printed covers as I do not have a 3D printer. Maybe someday I will have one and I can consider going that route.
 
So the boss says "I have a job I think you can handle."

Got the machining for the handles finished. I am not sure if I will keep them this long, but this is the general idea. The end parts were machined on the mill and the middle is just 1.125" aluminum tube I found at the scrap yard. They will just screw on to the doors.

lH8ua6K.jpg


Just sitting on the door frames.
j72sLea.jpg


A little long I think, they will probably need to be shortened a bit.
cEDHH68.jpg
 
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