- Joined
- Jan 20, 2016
- Messages
- 602
After a few months of fiddling with CNC on my X2 mill with mixed results, I decided to try my hand at making a new X and Y axis to get rid of the dovetails. Its the same old story where the dovetails are rough and not too accurate so to get all 8 inches without binding, the dovetails are so loose there is chatter in the middle. In recent months I have found a somewhat happy medium where I can machine light but fast cuts in aluminum (.375" deep, .025 wide, .375 endmill, 60 IPM cutting) while rapiding at 100 IPM. I can hear the motors groaning while in the last 15% of each end of travels and I had to drop to half stepping to make sure they have enough torque to maintain that.
First, the plans and goals of the project.
Goals:
-Increase X and Y travels to at least 14 and 6 inches respectively
-Reduce binding while maintaining rigidity
-Maintain or improve accuracy
-Rapids at 350 IPM
Plan:
-Use aluminum stock to make new table, saddle, and base
-Mount linear rails for accurate and friction free motion
-Make new ballscrew and motor mounting hardware
-Bolt to existing mill base and add extension to maintain rigidity
I am sure the time and effort would be better spent fixing this mill a bit, selling it, and getting something better, but thats not as fun. I figure the worst case scenario, it all goes to crap, the accuracy and rigidity of the new table is garbage, and I go back to where I started out a few weeks of machine work and whatever stock I used for it. Since all the components can be removed and put on something else, there is almost no risk.
I started with a model in Fusion360 and I got it as dimensionally accurate as I could. I found a bunch of 3/4" aluminum plates at a recycling center near me that I am 85% sure is Mic 6 or similar (it machines like cast aluminum, nothing like the 6061 I normally use) and ground. The finish on it was almost mirror like with long swirls and the thickness was incredibly uniform throughout. Checked on a surface plate, most of the surface was within .003" flat and parallel. I used some ink and sandpaper to get it down pretty close on each part.
The components I will use are:
-2 22" 25mm Thomson Accuglide rails with 4 bearings (X axis)
-1 20" 20mm THK HSR20 rail with 2 bearings to be cut in half (Y axis)
-2 IKO MLFG24 19" Rails with 4 bearings (Z axis)
All were ebay deals that I got pretty cheap. The cost was $150, $80, and $68 respectively.
Here is the latest model I am working with. It has been updated as I go and things change.
Here is one of the hauls I made from the recycling center. You can see the big aluminum plate in the middle with that reflective surface. That part will become the table. I pay by the lb there and paid about $120 for all of the stuff in the picture. The piece on the left is 1.5" thick aluminum, 30" long and 5" tall at the smallest height.
The first part I made was the table. I cut it to a little over 22" long and 8.5" wide. I machined the ends square and I might machine the sides at some point, but fixturing 22" is tough on my little X2. I made a little drill guide to spot the holes for the rails. To do that, I drilled the first hole of the first rail and tapped it, lining up the rail to a scribe line as best I could. Then I secured the first end. I then clamped the other end down and spotted the last hole for the first rail. That hole was then drilled and tapped. Now with both ends secure, I spotted the remaining holes and drilled and tapped. I then loosened all the screws but the first one, clamped the rail against my surface plate and tightened the first 4 screws. I then moved the surface plate down, clamped it so half was against the already secured portion of the rail and tightened 2 more screws. I did this until I got to the end.
Next I got working on the saddle so I could use it to secure the second rail parallel to the first. I used the mill to drill and countersink 16 holes for M8 screws. Once I finish that, I secured the saddle to the bearings while mounted on the first rail. I finagled it a bunch until I thought the second rail was pretty close and clamped it down. I did a similar procedure where I drilled and tapped the first hole, secured the rail, moved the saddle to the other end, drilled and tapped the last hole, secured the rail there, spotted the remaining holes, drilled and tapped, then moved the saddle along, tightening the screws as the saddle was right next to them. Once I finished this, the saddle moved back and forth the full length with little resistance. Checked with an indicator, the rails were within .002" parallel over 22" and within .001" height over 22". Thats good enough for me.
I followed a similar procedure doing the Y axis. The saddle was drilled and countersunk for the M5 screws the HSR20 bearings needed. The rail mount/base was drilled on the mill, then tapped using a screw I cut flutes into because I couldn't find an M5 tap anywhere nearby and I didn't want to wait for one to ship. That worked surprisingly well, but I had to power tap with a drill, otherwise I couldn't get it to start. The Y axis moves with so little friction that lifting the base enough to put a pen under one side causes the whole assembly to slide all the way down. I am still not sure if the 2 bearings on the Y will be sufficient, but if they aren't, I will get new rails with 4 bearings and remachine the saddle and mount. Though for now, it feels plenty rigid. It also weighs at least 25lbs more than the original table.
Here is a picture of the saddle sitting on the Y axis with the X axis bearings installed. The caged balls helped a ton with assembly since the table could be slipped off to get to the screws underneath.
Here it is with the table installed.
A view of the goodies underneath.
Here is the left end of the X travel.
And the right end.
In those pictures, it looks like the table is dipping a little bit, but it isn't. Its a trick of the light and the slight bending of the desk the assembly is sitting on.
With that part squared away, I got started on the hardware mounts for the X axis. I need two bearing blocks for the ball screw, a motor mount, and a ball nut mount. With the table ready, I took some measurements and got started.
Here is the stock I started with for the 2 blocks.
Rough cut with the stock that will be used for the motor mount. I like these small components because I can use the cut offs from other projects. The X motor mount will be made with the leftover from cutting the ends off the table plate.
I got the first block mostly done. I squared it up as best I could, then cut the 2 important surfaces (top and bearing face) in the same set up to make sure they were as square as my mill is capable of. The machine cut the bearing seat a little small the first time, but I had the toolpath cut with -.002" stock to leave and it cut it for a nice snug fit.
Thats where the project is now. I am looking at 15" of X travel without overtraveling the bearings, and I can probably get away with 2" on each side for getting around stuff, but not cutting. The Y axis has a little over 7" of travel and I had to buy a new leadscrew, since the old one needed to be cut down to fit and would only allow for 5" of travel.
Next, I need to do the other bearing block for the X, the motor mount, and the ball nut mount, then the same deal with the Y. Then I will drill and tap the X2 base to take the new table and if all goes well, the Z will be after that.
First, the plans and goals of the project.
Goals:
-Increase X and Y travels to at least 14 and 6 inches respectively
-Reduce binding while maintaining rigidity
-Maintain or improve accuracy
-Rapids at 350 IPM
Plan:
-Use aluminum stock to make new table, saddle, and base
-Mount linear rails for accurate and friction free motion
-Make new ballscrew and motor mounting hardware
-Bolt to existing mill base and add extension to maintain rigidity
I am sure the time and effort would be better spent fixing this mill a bit, selling it, and getting something better, but thats not as fun. I figure the worst case scenario, it all goes to crap, the accuracy and rigidity of the new table is garbage, and I go back to where I started out a few weeks of machine work and whatever stock I used for it. Since all the components can be removed and put on something else, there is almost no risk.
I started with a model in Fusion360 and I got it as dimensionally accurate as I could. I found a bunch of 3/4" aluminum plates at a recycling center near me that I am 85% sure is Mic 6 or similar (it machines like cast aluminum, nothing like the 6061 I normally use) and ground. The finish on it was almost mirror like with long swirls and the thickness was incredibly uniform throughout. Checked on a surface plate, most of the surface was within .003" flat and parallel. I used some ink and sandpaper to get it down pretty close on each part.
The components I will use are:
-2 22" 25mm Thomson Accuglide rails with 4 bearings (X axis)
-1 20" 20mm THK HSR20 rail with 2 bearings to be cut in half (Y axis)
-2 IKO MLFG24 19" Rails with 4 bearings (Z axis)
All were ebay deals that I got pretty cheap. The cost was $150, $80, and $68 respectively.
Here is the latest model I am working with. It has been updated as I go and things change.
Here is one of the hauls I made from the recycling center. You can see the big aluminum plate in the middle with that reflective surface. That part will become the table. I pay by the lb there and paid about $120 for all of the stuff in the picture. The piece on the left is 1.5" thick aluminum, 30" long and 5" tall at the smallest height.
The first part I made was the table. I cut it to a little over 22" long and 8.5" wide. I machined the ends square and I might machine the sides at some point, but fixturing 22" is tough on my little X2. I made a little drill guide to spot the holes for the rails. To do that, I drilled the first hole of the first rail and tapped it, lining up the rail to a scribe line as best I could. Then I secured the first end. I then clamped the other end down and spotted the last hole for the first rail. That hole was then drilled and tapped. Now with both ends secure, I spotted the remaining holes and drilled and tapped. I then loosened all the screws but the first one, clamped the rail against my surface plate and tightened the first 4 screws. I then moved the surface plate down, clamped it so half was against the already secured portion of the rail and tightened 2 more screws. I did this until I got to the end.
Next I got working on the saddle so I could use it to secure the second rail parallel to the first. I used the mill to drill and countersink 16 holes for M8 screws. Once I finish that, I secured the saddle to the bearings while mounted on the first rail. I finagled it a bunch until I thought the second rail was pretty close and clamped it down. I did a similar procedure where I drilled and tapped the first hole, secured the rail, moved the saddle to the other end, drilled and tapped the last hole, secured the rail there, spotted the remaining holes, drilled and tapped, then moved the saddle along, tightening the screws as the saddle was right next to them. Once I finished this, the saddle moved back and forth the full length with little resistance. Checked with an indicator, the rails were within .002" parallel over 22" and within .001" height over 22". Thats good enough for me.
I followed a similar procedure doing the Y axis. The saddle was drilled and countersunk for the M5 screws the HSR20 bearings needed. The rail mount/base was drilled on the mill, then tapped using a screw I cut flutes into because I couldn't find an M5 tap anywhere nearby and I didn't want to wait for one to ship. That worked surprisingly well, but I had to power tap with a drill, otherwise I couldn't get it to start. The Y axis moves with so little friction that lifting the base enough to put a pen under one side causes the whole assembly to slide all the way down. I am still not sure if the 2 bearings on the Y will be sufficient, but if they aren't, I will get new rails with 4 bearings and remachine the saddle and mount. Though for now, it feels plenty rigid. It also weighs at least 25lbs more than the original table.
Here is a picture of the saddle sitting on the Y axis with the X axis bearings installed. The caged balls helped a ton with assembly since the table could be slipped off to get to the screws underneath.
Here it is with the table installed.
A view of the goodies underneath.
Here is the left end of the X travel.
And the right end.
In those pictures, it looks like the table is dipping a little bit, but it isn't. Its a trick of the light and the slight bending of the desk the assembly is sitting on.
With that part squared away, I got started on the hardware mounts for the X axis. I need two bearing blocks for the ball screw, a motor mount, and a ball nut mount. With the table ready, I took some measurements and got started.
Here is the stock I started with for the 2 blocks.
Rough cut with the stock that will be used for the motor mount. I like these small components because I can use the cut offs from other projects. The X motor mount will be made with the leftover from cutting the ends off the table plate.
I got the first block mostly done. I squared it up as best I could, then cut the 2 important surfaces (top and bearing face) in the same set up to make sure they were as square as my mill is capable of. The machine cut the bearing seat a little small the first time, but I had the toolpath cut with -.002" stock to leave and it cut it for a nice snug fit.
Thats where the project is now. I am looking at 15" of X travel without overtraveling the bearings, and I can probably get away with 2" on each side for getting around stuff, but not cutting. The Y axis has a little over 7" of travel and I had to buy a new leadscrew, since the old one needed to be cut down to fit and would only allow for 5" of travel.
Next, I need to do the other bearing block for the X, the motor mount, and the ball nut mount, then the same deal with the Y. Then I will drill and tap the X2 base to take the new table and if all goes well, the Z will be after that.