IH Mill Prep for CNC Conversion: One shot oiler, Z-mod, etc.

[BobWarfield]

Been a long time since I got to post on the CNC conversion work. Tin Falcon's and other's recent CNC posts reminded me to get back after it now that the Team Build parts have been mailed out and before I get knee deep in the next team build. I was just thinking how fast those crankshaft bearings would go if I had the mill up and running: DOH!

I didn't get as much time as I would have liked this weekend--it is a family time after all, and I had to fix a car and my air compressor, but I did get on to the next step.

The last little bit involved finishing up the base epoxy granite fill with provision for a large connecting bolt as well as making some hockey puck feet. I still can't get over how sturdy and how dead the filled base seems compared to the original!

Next step is to set up the column to receive that large connecting bolt. To do so, I epoxied a thin metal plate in position at the bottom of the column. The casting is pretty rough so I used sand in conjunction with epoxy to fill the gaps. I let that cure over night and then I used a hole saw to make way for the piece of pipe that provides the bore for the bolt in the column. The pipe is not an exact diameter that works for the hole saw so I went one size too small and then broke out the air grinder with a little drum sanding attachment to tune up the bore to a nice sliding fit.

Lastly, I dimpled the end with a punch so the pipe would sit without falling through. I quick couple of pumps of epoxy and a chip brush later I had the epoxy laid for the pipe:

I think the whole works is "water tight". I'll let the epoxy cure all week and then hopefully next weekend I can flip the column and fill with the epoxy granite mixture around the pipe. I'll be filling almost 10" of the bottom, so it should add quite a lot of mass and dampening to the works. I had considered dealing with filling all the way up the column, but it's quite a lot more work and I've decided to forgo it in the interests of getting on with the rest of the CNC conversion.

I still need to finish the one shot oiling system--a few holes to tap, manifolds to be made and mounted, and I need to engineer oiling for each of the 3 ballnuts.

After the column is filled and the one shot is done, I'll need to thread the Z-axis bracket shown at the beginning of this thread for the Z-axis ballnut. I've ordered a nice threading bar from Enco (along with a 1HP buffer--you guys don't get to have all the bling!) for that task, so that'll be interesting as well.

Once all that is done it's time to bolt up the mechanicals kit I have from Industrial Hobbies. I got in a set of servo motors from Homeshopcnc, so hopefully that all goes together pretty well. I'll also need to build the electronics, but that isn't too bad. I've done it once before for my lathe project and will do something almost identical but with a bigger DC power supply capable of driving 4 beefier axes. I've got a nice big NEMA enclosure available to house it all in.

Lots of work but hoping to make steady progress going forward!

Cheers,

BW

 

[CrewCab]

I had considered dealing with filling all the way up the column, but it's quite a lot more work and I've decided to forgo it in the interests of getting on with the rest of the CNC conversion.

Bob .............. good work and thanks for posting all the info

Just a thought ......... (and I apologise beforehand if this is a "teaching Grandma to suck eggs senario")

If you drill a series of holes up the column, pump epoxy in the second one up till it flows out of the first and third, then move up to the 5th and pump till it flows out of the 4th and 6th ............. etc ............. not a long job really, providing the epoxy flows well


hth .............. if not please feel free to ignore me :

CC

 

[BobWarfield]

Crew Cab, no need to even drill holes. The column is open the full length on one side and the leadscrew goes inside. What would be required is to either make a male mold to reserve space for the leadscrew, or possibly pour each of 3 sides separately. There's not an awful lot of room left for lots of epoxy granite anyway. Probably not more than 1 to 1 1/2" of thickness against the inside of the column. I dunno, I may relent and do it anyway.

We'll see,

BW

 

[BobWarfield]

This morning I got up bright and early to finish the fill on the bottom of the column. I flipped the column upright and masked off the top of the pipe:

To access the narrow slot and feed in the epoxy granite mixture I used an ice cream scoop I got at the hardware store for $4. It worked really well!

I filled with my normal E/G mixture to about 1/2" from the top of the pipe. Then I switched to a mixture of just sand and epoxy. I added enough epoxy to the sand to get something halfway between the thickness of creamy peanut butter and gelato, so it flows very nicely into all the cracks and crevices:

After a couple of hours I checked and nothing had leaked out the bottom. I love working with this stuff. It's so easy!

Now I'm back down to the garage to see which part of the CNC conversion to work on next. I'm torn between doing more one shot oiling and building the DC supply for the servo motors.

Cheers,

BW

 

[derekm]

A few questions /suggestion
what cleaning surface preparation did you do to the surface of the cast iron to get a good bond?

Did you consider putting reinforcement?
e.g. laying up the inside of the base with carbon fibre

Did you consider making the bottom a box section by bonding in a plate or bonding in fixings for a plate?

when/if you fill the column is it possible to put in steel or carbon fibre rods?

 

[BobWarfield]

Derek, I simply degreased the cast iron with brake cleaner. I was careful to only do this inside the castings where I wanted the bond. After degreasing, I applied a thin coat of oil to the outside areas such as the ways with a paper towel. The epoxy bonds best to rough cast iron anyway. It has a harder time with smooth steel plate, for example.

RE the carbon fiber, I didn't consider it. None of the literature I've seen on polymer concrete for machine tools has used any carbon fiber. Given that the primary goal is dampening, not an increase in strength (although there will be some of that too), I think any continuous piece of material, carbon fiber or otherwise, is at odds with that goal. The reason the epoxy/gravel/sand mix works so well is that the epoxy has to flex through a very amorphous mass of much harder material whose only connection is the epoxy. The resistance to this flexing can absorb considerable vibrational energy--multiples of what the same amount of cast iron will absorb, in fact. The same principle is at work when a drag racer fills part of the water jacket of their engine block with concrete (usually a special mix that is also said to work well in this application). They're trying to dampen the vibration from all that horsepower (and especially detonation) to increase the life of the motor.

The other point I would make is gravel and sand is cheaper than carbon fiber. :big:

Cheers,

BW

 

[BobWarfield]

I finished up another component of the one shot oiling today. This is the Y-axis ballnut mount:

It goes on the underside of the saddle. The little hole in the center allows oil to drop down onto the ballscrew.

Details on the machine work are here:

http://www.cnccookbook.com/CCMillYMount.htm

Finishing that mount allowed me to get on and make some more significant progress. Here is a teaser:

Cheers,

BW

 

[BobWarfield]

Quite a bit of progress since I reported in. This weekend I got the column up on the base, so now all 3 axes have ballscrews installed. I also made a cover plate which will be used to mount the one shot oil pump, and I did some tricky measuring and calculating to spec out a new couple of pulleys and different sized timing belt from stock, as the stock pulleys were too small to fit the big shafts on my servos. Doh!

Here are a few photos.

Starting to look like a mill:

I knew there was a reason I owned that big Bozo-the-clown sized calipers!

(I'm using them to figure out the shaft to shaft distance so I can figure out a new belt and pulley)

That servo looks beefy there!

It's an 850 oz in from HomeShopCNC. It'll be interesting to see how it performs.

Working on a mounting plate for my one shot oil pump, but didn't finish:

More details on my page here: http://www.cnccookbook.com/index.htm

It was a good weekend's progress. Had to get my brother's day off to get that column up there.

Cheers,

BW

 

[wareagle]

Bob, it's coming along! Everything is looking great.

 

[BobWarfield]

Fellas, I've declared the one shot oiling done. There are some minor tweaks I may make, but it works pretty darned well. Here are a few photos:

Saddle plumbing is the most complex. It is nearly all hidden (and protected) under the table.

Z-axis uses plastic tubing to feed either way. The copper pipe goes up and dribbles oil down the leadscrew inside the column.

Here is the pump mounted on the column. You can see there are no flow control valves on the Z-axis. I got so many emails from people protesting the flow control valves were not needed and made the system too bulky I thought I would try one circuit without. This was the best circuit because it is so symmetrical flows ought to be pretty equal. In the end, I would have liked 1 flow control valve to balance this circuit versus the other, and to provide a check valve at the low end near the pump. What I find is the Z-axis plumbing drains from gravity very quickly. I waste a fair amount of oil on the X-Y circuits just trying to pump up before any flows to Z. My conclusion is the system needs to metering to be adjustable, especially in the saddle, and the check valves built into the flow control valves are also very helpful. I will likely buy another valve and plumb it into the Z-circuit.

Meanwhile, I waste a couple pumps of oil, but it sure is nice to be able to oil everything so evenly and quickly!

I'm now finished modifying the mill from stock except for the CNC portion, so that's where my attention will be focused. I'll start another thread so you can see how that goes.

 

[wareagle]

Bob, thanks for sharing the progress. I am tucking this info away for another day. Eventually I will be jumping in to the CNC realm and every little bit helps with knowing what needs to be done and more importantly, what not to do!

I am eager to see this thing in action! :bow: