CNC Lathe Servo Spindle Upgrade

[JimDawson]

OK the motor is bolted into place.

Had to cut a notch out of the corner of the motor mount to clear the Z axis servo


Had to build new gussets and drill & tap a few new holes.
And the motor mounted on the base , ready to install


Too heavy for my poor old back to lift (about 130 lbs), but that's what they make forklifts for.

Just enough clearance to get it in there


And the wiring started. That's a beast of a power cable.

 

[rwm]

I'm wondering why I don't use MIC-6 plate more often for structural stuff?
Robert

 

[JimDawson]

I'm wondering why I don't use MIC-6 plate more often for structural stuff?
Robert

$$$$ maybe?

I got a 4'x8'x1'' sheet for basically free, and another half sheet of 3/4'' for almost free. It gets used for special projects. I wouldn't want to have to buy it today, MIC-6 has always been a bit expensive, and aluminum prices have doubled (or more) in the last 6 months. It sure does machine nice.

 

[rwm]

I need a piece 1 x 4'. I am seeing MIC6 for less than large pieces of 6061? Yes, prices are way up.
Robert

 

[JimDawson]

OK, I got it running today, the lathe can make parts again.

Took awhile to get the parameters set up, a bit more complicated than your average VFD, the manual is 709 pages, but well documented and very readable. The setup software made things much easier. The drive does have a keypad and LED display for manual entry, but the whole thing is about 1.5 inches square, not exactly user friendly.

While the lathe will run now, and work exactly like it did before the upgrade, we still don't have a C axis (spindle indexing). I need to do some programming to implement the C axis functionality. I'll post a video of that in action when I get it done.

In the mean time, here is a video of the first time I tried to jog the spindle. Not much to see, but at least it turns under computer control.

 

[JimDawson]

For those of you who don't know, our CNC lathe is a Hardinge Conquest 42 with live tooling so is capable of both turning and limited milling and cross drilling functionality. It has been upgraded with all new controls/motors and my CNC software.

We were finally able to shut the lathe down long enough to install and debug the new software with the C axis code. I spent about a week writing the code that I thought would work, loaded it up, and after a couple of days debugging got it working....... Sort of. All it had at this point was spindle indexing, which is what I needed for the current parts design. So at this point it would switch between normal turning and C axis mode under G code control. In normal spindle mode the spindle was operated the same as would be operated with a VFD for speed control, and the C axis indexing mode the spindle would be moved some number of encoder pulses to position like any axis would be controlled in position mode.

Then I redesigned a part and realized that I could cut 2 minutes machining time off of that part by eliminating one operation if I had full C axis interpolation. We make thousands of those parts, so 2 minutes is huge. This required operating the spindle in a completely different control mode under all conditions. I had been controlling the spindle like you would when using a VFD rather than a servo motor, well, because I was using a VFD to run the spindle before the motor upgrade. The servo drive was perfectly happy to operate in that mode so I just continued to use it. This involves sending a +/- 10V analog command voltage out to the drive, where in this case, +10V = +3000 (CW rotation) RPM, -10V = -3000 (CCW rotation) RPM, and 0V = 0 RPM. The voltage command is linear and programmable from the controller in very small voltage increments, (volts/RPM) * the desired RPM. Very simple, and the drive takes care of the speed control, same as turning the speed pot on the VFD.

So back to the drawing board, and completely re-think the spindle operation mode. And do this while not screwing up constant surface speed, rigid tapping, thread milling, and single point threading which has been working flawlessly up until now.

Constant surface speed is where you give the machine (from the G code) a surface speed that you want to cut at, and it varies the spindle RPM based on the current diameter of the part, and updated about every 10ms. So as you are turning, the part diameter is getting smaller with each pass, so the spindle RPM is adjusted on the fly by an amount to maintain the programmed surface speed. The G code also has an upper and lower speed range to work in, without that, if the tool tip was at 0 diameter, like for a facing cut, the RPM required to maintain a constant surface speed would be infinity, maybe a bit fast for the spindle.

This of course required a complete and rather complex re-write of all the spindle operating code in both the controller software as well as the CNC program software, the math involved is a bit more complex as well as having additional servo parameters and variables to deal with. Then in addition modify the CNC program code to understand C axis interpolation and output the correct controller code to make it do what the G code tells it to do. I managed to pull this off and get it all working in two days. Of course anytime you make any software changes, you fix one thing and break 3 other things. Always makes programming a challenge. When writing code for an office application the worst that can happen is the program crashes or you get bad data out, but for real time machine control, things can go catastrophically wrong in a hurry. You can actually break expensive things, a lot more care in programming is required, and always keep your hand on the E-stop button when testing.

At the same time I was crazy enough to add 10 tools to the turret (in software) so we can run dual tool holders in some of the turret stations. So for instance tool 4 could be a drill and tool 14 could be a tap. Both would be in turret position 4 with different offsets. This code seemed to work correctly out of the gate. But I haven't really used it yet, so still needs to be proved out.

I fixed the last known bug last night and fired the machine up again making some needed parts. I still have not proved out all of C axis functionality, but not using it for the currently running parts, and the other needed functions seem to be working OK.

Overall I think this was a success, but time will tell how many unknown bugs are hiding in there just waiting to bite me at the worst possible moment. I'll post a video of the C axis in action when we run some parts that actually use it.

On another note, we are looking at another Hardinge CNC lathe, 7 axis, with Y axis, live tooling, and a sub-spindle. Another upgrade project

 

[vtcnc]

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)?

While I too am jumping up and down, it isn't because I share the same sentiment. JIT turns out means having having the right amount of inventory in all elements of the supply chain.

If you read the original ( and I mean original ) documents on JIT out of Toyota, Honda, Canon and others...here is what you will never read: JIT or Just-In-Time = Zero Inventory.

The same western MBA/consultant mistake was made when they "mastered" JIT and moved on to "Zero Defects". They gutted quality departments - because "quality is built into the product" so we don't need no stinkin' quality department.

In my time learning about JIT from some credible sources, one of things I was told was that JIT means having the right amount of inventory in the right place from the beginning of the supply chain to the very end. The unfortunate mistake most copycats of Toyota and Japanese Management made was that they thought this stuff was cookie cutter and could be applied in isolation with no consequences up and downstream from the point of implementation.

In almost every application of JIT that I have been involved in, I sufficiently warn the higher ups and especially spend an inordinate amount of time with the CFO explaining that when implemented, a JIT philosophy will lead to greater overall inventory. EDIT: (because they are already running too low due to misunderstanding their capacity and demand.) However, your turns will increase, you will produce more product cash cycles tend to be faster. One has to ask if this is what they want to happen prior to a "proper" installation of JIT techniques in your supply chain.

Yes, complete and total misunderstanding over decades, plus negligence and mishandling of supply chains have made the post pandemic recovery far worse than it needed to be. But to say that JIT is the cause is not necessarily true - it is people who manage systems, not ideas.

 

[extropic]

<snip But to say that JIT is the cause is not necessarily true - it is people who manage systems, not ideas.

I wasn't talking about a concept (idea). I was talking about real world. People implement all systems. It seems to me they often don't do it very well.
Take the case of the local ACE Hardware, many items are stocked in very low quantities. The bean counters can define, ad infinitum, the cost of goods in inventory. What they have no idea of is the cost of sales lost because they don't have the goods on the shelf or because the customer is motivated to shop on the web after numerous shortfalls at the store. They are chocking themselves to death.

 

[vtcnc]

I wasn't talking about a concept (idea). I was talking about real world. People implement all systems. It seems to me they often don't do it very well.
Take the case of the local ACE Hardware, many items are stocked in very low quantities. The bean counters can define, ad infinitum, the cost of goods in inventory. What they have no idea of is the cost of sales lost because they don't have the goods on the shelf or because the customer is motivated to shop on the web after numerous shortfalls at the store. They are chocking themselves to death.

Yeah, I think we are saying the same thing!

 

[JimDawson]

I wasn't talking about a concept (idea). I was talking about real world. People implement all systems. It seems to me they often don't do it very well.
Take the case of the local ACE Hardware, many items are stocked in very low quantities. The bean counters can define, ad infinitum, the cost of goods in inventory. What they have no idea of is the cost of sales lost because they don't have the goods on the shelf or because the customer is motivated to shop on the web after numerous shortfalls at the store. They are chocking themselves to death.

I had an experience with this very thing yesterday. My roommate went went to Walmart to buy an on sale TV, and pick up 25ft of RG6 coax and a splitter. No stock on the RG6, OK, over to Fred-Meyer (a large west coast chain with a good electronics department), no luck there either. So I ordered from Amazon, I'll have it here today and free shipping. It wasn't worth driving all over town to find the hardware. I really do try to support the local vendors, but they need to have the stock on hand.