Millright Mega V 3-Axis conversion

[perry]

I'm starting to convert my Mega V to Masso. This is going to be a slow-motion process because the machine is at my office and I'm only there 2-3 days per week due to the coronavirus pandemic. While there, I only have short bits of time to work on it, usually while I'm waiting for other stuff (file copies, film scans, etc) to finish up unattended.

So here is the machine in its (almost complete) enclosure:

Mine is the 19"x19" Mega V - the small one. This machine has rack and pinion X and Y axes, and lead screw Z-axis. It comes with the dewalt router, but I'll eventually switch that over to a spindle, which I already have. Unfortunately, the spindle can't fit on the Z-axis plate they provide, because it's too tall and hits the Z motor. So I've designed a new Z-plate with an integrated tramming plate, and that will give me the needed clearance. Once I'm up and running I plan to cut that from aluminum and get it installed. That'll be phase 2 of this project.

I will be re-using the stepper motor drivers from the Mega V controller, but little else.

The power supply is pretty bulky, so I bought a DIN-rail mounted 48V 480W PSU to replace it. The wiring of the Mega V is a bit of a mess. Many of the connectors are soldered kind of sloppily, and none of the cabling is shielded. The motors are hardwired, so I 3D printed some caps for the motors and will be snipping the cables and installing 4-pin aviation connectors on them. I'm replacing the hardwired cables with shielded 18/4 cable.

The homing switches are currently mechanical switches with terrible wiring (unshielded, unsheathed even). These will be replaced with optical switches connected with shielded twisted pair cable.

Last night I got the Masso powered on and the software installed.

I'm using a 24V PSU for the Masso. I also have a 12V PSU I could use. Since the Masso just passes the 24V through to its power outputs, I'd need to reduce that voltage for 12V cooling fans for the enclosure. Am I better off powering 12V stuff directly from its own psu, and using the relay board to turn them on and off , or should I just use the 12V PSU for the masso and tap the power from its power outputs? Similarly, my homing switches require 5V (I have a DIN 5V PSU that I could use for that). It seems cleaner to me to use a separate 5V PSU to power those. In both cases, I want them powered on when the masso powers up.

 

[cncnutz]

Hi perry

If you are going to use the Masso TTl relay module I would stick with the 24 volt power supply as the relays are 24 volt.

Since you only want to run a fan on 12 volts have you considered a 24 to 12 volt regulator to drop the voltage or a 24 volt fan? I'm assuming you are using a computer style fan so those can be got in both 12 and 24 volt formats.

With regards the 5 volt sensors you could also look at a voltage regulator to knock 24 volts down to 5v especially as they are low power devices or look at different sensors. Most proximity sensors are 10 to 30 volt working and could run direct off the 24 volt supply. Sorry I'm not trying to redesign your machine but the cost of going to all 24 volt components would be far less than buying 1 Din Rail PSU and you end up with a simpler, cleaner, less confusing install. If you use a separate 5 volt power supply make sure you tie the -ve rail of the PSU's together or the Masso inputs will not see the signal.

I would recommend installing a DIN rail mounted DC power distribution in the cabinet and power everything from there. Don't run fans off the Masso auxiliary power terminals as they are designed only for low power devices like proximity sensors but even then I would power them from the distribution instead and avoid using the auxiliary power on Masso at all. Just my personal opinion.

Looking good so far. Hope you get more time to work on it.

Cheers Peter

 

[perry]

Thanks. I already have 5, 12, 24 and 48V DIN rail PSUs (some purchased for this project, some leftover from others), so it's not so much about the cost, but it will add some complexity to the wiring for sure. Same with fans. We build our own workstations at the office so I've got buckets of 12v 80mm and 120mm cooling fans. Getting 24V fans for this might make sense though. Then I'd just be looking at three PSUs - 48V for the stepper drivers, 24V for the Masso, fans and Relay module, 5v for the homing switches.

I have more DIN rail mounted terminal blocks, with jumpers, arriving tomorrow. So basically a simple PDU. Once that's in place I'll lay out the wiring and see how much of a mess I've really made.

Looking good so far. Hope you get more time to work on it.

Thanks. That's been both a blessing and a curse. A blessing because I've been able to think things through more thoroughly than if I just slapped it together, and a curse because I've been able to think things through more thoroughly than if I just slapped it together. I have changed my mind a few too many times at this point but I'm pretty happy with where I am now on this.

 

[perry]

Starting to get the thing wired up. I'm waiting until the power switch and larger estop that I ordered arrive tomorrow. I'll be using an AC panel-mount switch to turn the whole box on and off. I went back and forth on having one small PSU there to power a master power relay, but in the end decided that I'd rather just power the whole thing on and off from the front panel.

Getting the driver-to-sidewall connectors set up:

And installed in the box:

The low voltage access panel on the bottom is for the video, USB and pendant cabling. It just seemed easier to use something like this than to put in panel-mount connectors and make cables for all that stuff.

Once I have the AC power all set up, I'll start moving the stepper drivers in one at a time and wiring them up and testing them.

 

[perry]

Got a bit more work done on the control box this afternoon.

The AC power switch I bought is now installed, connected and working properly. This is the master switch for the control box:

The e-stop isn't connected just yet. I'm doing this sequentially, without connecting up the Masso just yet.

Inside you can see the wiring. Trying desperately to keep it neat. There isn't really enough room to put cable channels in there and still leave room for good airflow, so lots of zip ties I guess...

Per the advice I got in another forum post, I'm putting a StepperOnline DM542T driver on my X axis. The Y axis on the Mega V uses one driver for both motors. You can see what they did on the DIP switches, because the current setting is double what it was on the X axis (since, two motors). I set the DIPs to match the old X-axis driver settings, which have the same pulse/rev settings as the Y, but half the current draw of the single-Y driver. The StepperOnline driver is pretty close, but not exact in terms of the current, so hopefully that will be ok for the X axis. I doubt it's going to matter much, the difference is .14A RMS and .19A peak (both lower on the DM542T).

And, powered on:

All three PSUs are working properly, and are wired into a DC power block on the same DIN rail as the stepper drivers, along with the fuse for the Masso. The Relays will go on the lower rail, and the Masso at the bottom. I've started to wire up the driver-to-sidewall cabling, and once the Masso is installed tomorrow, I'll start getting the control cabling wired up. I'm doing all this in the office and not in the basement shop, so I'll be testing with a single motor I've removed from the machine, one at a time to make sure it's going. So far so good though!

 

[perry]

Got a bit more work in on this today:

Power switch lights up now, and the e-stop and pendant are working as well.

And on the inside, I replaced the zip-tied wiring with proper cable channels. Much nicer in there now. They're a bit taller than I'd like but I think they shouldn't impede airflow into the power supplies, which was my main concern.

Next up: Wiring up the motors from the Masso to the drivers. Not sure I'll get to that today, though.

 

[perry]

And, one of the motors wired up and doing what it's supposed to.

 

[perry]

A bit more done today. All the motor caps are on:

and all the patch cables from the motors to the control box are built and tested:

And I even had time to get all the motors back onto the machine:

The internal wiring in the enclosure will go through a channel that hasn't been installed yet. Still need to do the homing switches, the door switch and a couple spare wires for the relays (use TBD, but one will likely be for the lights inside the enclosure). I decided to forego the 5V optical switches I bought ($9 for a 5-pack, so no big deal), and I ordered some good Omron proximity sensors. I think I'm going to mount the Y sensor(s) on the yellow front plates of the unit, the X on a post in the t-slot on top of the gantry, and the Z where the original one was, but I'll need to figure out some kind of mount for it, since it's behind the Z-plate in kind of an odd spot.

Slowly coming together. I hope by next week to have the control box downstairs and mounted on the wall, so I can start finally using this thing.

 

[perry]

Some more progress today:

The control box is now on the wall next to the router enclosure

Motors and the new proximity sensors are wired up.

On Friday, I'll get the proximity sensors mounted on the machine. I need to drill some holes in the angle bracket I'm using for mounts, and figure out exactly how I'm going to mount the Z homing switch, but they're all tested and working, so it's really just a matter of getting them into place. A bit of tidying up on the wiring inside the enclosure and I can start configuring the Masso for my motors and doing some tests. Fingers crossed I'll be cutting something on Friday but more likely it'll be next week.

 

[perry]

Everything is connected up now.

Omron proximity sensors installed (hopefully the way I'm doing this isn't an issue. Theoretically the X or Y axes could crash into the sensors. I could theoretically mount them on the sides, facing in, but it would require a fair bit more work to set up. Right now I have soft limits set up so as long as I'm homed I'm good).

Had to get creative with the Z axis because the sensor is farther out than the bracket Millright supplies for the mechanical trigger on their stock switches (eg: a bolt). T-nut to the rescue!

And... homing works:



Lastly, does this seem weird to any of you? This is a basement room with 16" thick concrete ceilings and concrete floors. it's silent in the room. The sound you hear is ONLY the sound of the steppers in idle mode. There is no motion, and there are no fans going anywhere. Yet they sound like they're fan cooled or something! I tried each one individually and they all do it but all four combined makes it much louder.

 

[cncnutz]

Hi Perry,

I'm fairly certain that the drives use chopper circuits to create the required wave forms needed to hold and move the motors. An oscilloscope will tell you what is going on for sure.

Even more disturbing is when they start talking to you late at night. When doing fine engraving late at night with the spindle barely making a noise I would hear talking and kept thinking I had left the radio on, only I didn't have a radio. Stepper motors can make strange noises.

You are in the final stages when they start singing to you.

Cheers Peter

 

[perry]

We have a 16mm/35mm film cleaning machine from the 1970s. There's a whole thing in the manual letting you know that the singing sound from the stepper motors inside is perfectly normal and to not be alarmed by it! New tech at the time, I guess...

I'm familiar with the sounds they make while running (and kind of like them - there are some pretty elaborate musical compositions on youtube people have put together with multiple steppers). but I've never heard a set of them so loud when not doing anything. I've confirmed with at least one other Mega V owner that his are noisy as well. It just seemed weird to me, but if they work correctly I guess that's just the way they are.

 

[perry]

First cuts!

just a test in some scrap HDPE. Much calibration to do, I m sure.