CNC Lathe Servo Spindle Upgrade


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Feb 8, 2014
It's time to upgrade our CNC lathe spindle motor. This has been in the planning stage for the last year or so. When we did the controls retrofit on the machine a couple of years ago we lost what C axis capability we originally had. The lathe has live tooling and can do some light milling. A ''C'' axis is the spindle rotational axis and has the ability to index the spindle accurately, or coordinate the rotation of the spindle axis with the X and Z axes for milling shapes. Without the C axis we are limited to simply stopping the spindle at some random position to do any milling or drilling operations with the live tooling. This has worked well for us for quite awhile, we just designed the parts to be compatible with our capabilities.

The lathe originally had sort of a C axis, at least it had some indexing capability to 1 degree increments. We knew that we were going to lose the C axis when we did the retrofit, but deemed it to not be an issue due to the design of parts we were making for our Stable Camper products. At the time we were buying a specific ball joint to use as a hinge. That supply dried up about a year ago and we were forced to redesign. We literally bought out the entire world supply of those particular ball joints and nobody is making more. We had to come up with a new design on the fly and get it into production.

Just to put these parts in perspective:
The ball joint screwed into the end of the 1'' all thread and mounting bracket

The other end of the tube showing the ball end, we'll get to this later.

And how it installs on a truck camper

These are the ball joints we were buying at $0.78 each. 1/2-20 threads.

This is the current hinge design, riveted together, 303 SS. Works great, but really time consuming and expensive to build.

The new hinge design required a lot of secondary processing that couldn't be done in the lathe. The secondary processing was done in the mill, but this required an immense amount of time and parts handling. Keep in mind that a run of any particular part is several hundred pieces. The parts could have been done in a machine that has both a Y axis and a C axis, along with a sub-spindle. In other words a full on 7 or 9 axis mill/turn machining center. We don't have enough power to run a machine like that, and after costing out a new 3 phase power installation, about $40K, and a used mill/turn machining center, about $100K :eek: We decided to revisit everything, there must be a better, and less expensive way.

So first is a design review of our entire product with regard to the turned parts: What can we change to make it easier to machine and assemble, and more importantly, utilize the capabilities that we currently have? We should have done this design review a long time ago, but were too busy making parts. o_O So I sat down with our current parts and spent about 2 weeks redesigning both the hinge and ball end related components, starting from the perspective of our lathe capabilities. The goal is to drop finished parts out of the lathe with no secondary operations required. Currently almost every turned part requires a secondary operation. In this case a secondary operation is any operation where we would fixture and make chips, other than minor deburring.

First the ball end. Both parts require a secondary operation, the ball needs to be flipped over and the ball finished in a second operation, and the cone needs to be counter bored to accept the bolt that secures the ball. The cone is 6061 aluminum, and the ball is 303 SS.
This is a PITA to build

The new ball end design, doesn't look a whole lot different than the original

Until you look inside, the ball is just threaded and screws into the tapped hole in the cone. No secondary operations required.

But why does require a C axis you ask? Well this part doesn't and this should have been done a long time ago, would have saved many hours of work. :faint:

But this thread is about a C axis, so on to the next part.

So on to the new hinge design. Doing the turning and mill the slot is all done in the lathe as it exists, no problem. Then rotate the spindle and cross drill the pin hole at 90 degrees to the slot. Wait a minute, the lathe won't rotate the spindle 90 degrees.... Big Problem. :eek: Ok the cross drilled hole could be done in a second operation on the mill or even a drill press, but the goal is to have no secondary operations. So add a C axis to the lathe to be able to drill 1 hole in one part. Seems like a pretty radical move until you multiply that by thousands of parts, then it starts making sense. Keep in mind that for the most part, you load a stick of material into the lathe, press GO, and come back in one to three hours and load another stick. It just runs hands off, cranking out parts with no human intervention, I love my lathe. :cheerful:

So next was to find a 7.5kW (10HP) servo motor to replace the original 7.5kW spindle motor so we can index the spindle. Oh, and do this without having to take out a second mortgage to buy it. Large servos are expensive, the last one I bought many years ago was a SEW Eurodrive, 7.5kW, about $15K for the whole package. This is not something I'm going to buy off of eBay, I want local support and good documentation. So I settled on a Delta servo, a mainline Taiwanese manufacture with a large USA presence, and has manufacturing and a distribution network in the USA. So about a week ago I finally located a Delta distributor in California and got a quote for everything needed, about $6800, with 16 week delivery. Not good, but I can live with that. Then the following Monday, Automation Direct launched their SureServo2 line. Guess what? They are selling Delta servos under their brand name, about $3500 for the whole package, everything is in stock, and FREE 2 day shipping. I expect I'll have it all by Friday (today is Wednesday). Great products, documentation, and support from Automation Direct, that's why I buy from them.

So I'm replacing this Fanuc spindle motor. This BTW is the last part on the lathe that says Fanuc on it.

With this shiny new servo motor. Doesn't look very big in this picture, but it's almost the same physical size as the original motor.
This thing is a Diesel truck compared to the original motor, about 4 times the maximum torque, but limited to 3000 RPM vs. the original at 6000 RPM. I have never run the spindle faster than about 2500 RPM for any operation.

And the new motor mount, we'll get this built in the next week.

That's all for now, I'll update as we progress.
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super cool! Are you going to be able to sell the old spindle motor to recoup some of the outlay?
Great stuff, as usual. Following
super cool! Are you going to be able to sell the old spindle motor to recoup some of the outlay?
No, there are a bunch of them on eBay. Not worth much because they are so reliable they just never wear out. I'll add it to my collection of Fanuc motors. Maybe it will be relegated to running my spare air compressor.
Well this project just went on hold. :( Doesn't make much sense to upgrade machines if you can't get material to run on them.

For some time now we, like everybody, have been having some supply chain issues. We can't get raw materials to build our products. We have enough parts built and raw material inventory in our in-house pipeline to cover our existing orders plus a bit more. Up until now we have been able to order material and get it within a couple weeks, now we are looking at September (maybe) before we can get the needed aluminum and stainless steel, and have been quoted triple the price or more. We have been buying about 5000 lbs/month of raw materials. So this has gone from a minor irritation to critical in the last month. So much for just-in-time manufacturing.

Fortunately, we are in a position to be able to just pull the plug for a couple months and not have it kill us, unlike many small businesses. When we shut down our costs drop to near zero, because we don't have a bank breathing down our necks for machine payments and we own the property outright. This is not going to be well received by our customers, but we hope they understand.

It's time to clean up the shop and get some maintenance done anyway. :rolleyes: Also we'll have some time to do some R&D on a new product line we have been thinking about, as well as finalizing the design of yet another product that we are working on.

Hang on to your hats folks, this may be a bumpy ride before it's over. :cautious:
Circling the drain? Is America on the lip or in free fall?

I'm jumping up an down, figuratively, in support of your sentiment about JIT.

I wonder if all MBAs are members of the (too political)?
Well, we managed to get some stainless steel to keep us going so decided to go ahead and install the new spindle motor.

Got the motor in today. That's a lot of motor.


This is impressive, the cable between the servo drive and the motor. 4 conductor, shielded
GREAT INFO and photo's!! Not to change the subject but some info from me who is into maintenance and repair.
I saw the lubrication pump in the one photo. Did you clean it too? I took a lubrication class several years ago at Trico who imports lube systems and their Lubrication Engineer recommended cleaning the reservoir, clean the filters inside and changing the oil. Also the metering units and lines checked once a year. Thanks for such a wonderful thread. Rich
Another update. We finally are able to shut the lathe down long enough to get the new spindle motor installed.

The way it was early this afternoon just after shut down.

And the new motor mount. My son whipped this up the other day. 3/4'' MIC6 aluminum plate.


And how it doesn't fit :mad: In my defense, the lathe was actually running when I took the measurements. I just totally missed this one. The good news is that I only have to nibble out the corner of the motor mount a bit and and re-drill a hole.

And an end view

I also need to relocate the base mounting bolt holes, it seems that somehow miss-measured back wall to motor mount front distance. Another minor but irritating issue. :faint:

In any case, I'll have the motor in place sometime tomorrow.

Stay tuned...............