ฝัง
- เผยแพร่เมื่อ 10 มิ.ย. 2024
- Finishing up the Electronics Enclosure for my Grizzly G0704 CNC conversion.
This DIY CNC conversion has been a fun and educational experience so far.
Using a Mesa 7I76E controller card and LinuxCNC the conversion is nearly complete.
Important Note... Don't power on a servo motor system without the motors connected. Mine uses stepper motors and it's OK for my build.
Another Note/Update: At 10:57 in the video I talk about a set of terminal blocks for the Alarm outputs and the need for pull-up resistors. I recently discovered the the alarm outputs may be configurable ON SOME DRIVERS, in the driver's configuration software to change the polarity of the alarm output from negative to positive. It's not mentioned in the driver's documentation, but it seems to be an option in the software. If so, the pull-up resistors (and those terminal blocks) would not be necessary. On my stepper drivers the alarm output is an opto-isolator with a NPN photo-transistor output. Since the Mesa card GPIO has input resistance of about 20K Ohms to field power
ground, the emitter can be connected directly to the GPIO pin. I'll be removing the pull-up resistors and the related terminal blocks. Not sure how I missed that during the build.
Fan/Cooling Update: With summer arriving, temperatures in the garage are climbing. With greater that 90°F ambient temperature, the stepper drives are hot to the touch. Maybe ~120°-125°F. Just to be safe I upgraded the fans to 80mm x 80mm x 25mm (from the 15mm version) and replaced the foam filter with a wire mesh one. The foam dust filter seemed to block about half of the air flow. Now the incoming to outgoing air temperature differential is about 5°F, and the drives feel much cooler.
In the video I talk about running the steppers on lower than rated voltage. I was experimenting with the effect of different (lower) voltages on the steppers. Stepper motors should be run at their rated voltage. If you want to reduce their power and lower their operating temperature because the motors are oversized for example, do it by reducing the current setting on the stepper motor driver. Not by lowering the voltage.
The DC-DC Step Down (Buck) Converter Power Module to power the volt/amp meters is designed around the LM2596HVS IC/chip. The module I'm using is rated for up to 53VDC input. The grounds of all the stepper power supplies and all the Volt/Amp meters are tied together. The positive lines are kept separate. One Power supply, the 48VDC Z-Axis, power, all three Volt/Amp meters.
The Screw Starter is an Ullman Devices DE-1, though they make other models.
The white connectors are Molex brand, for14-20 AWG wire. Model - Latch Lock, MLX, 2.13mm D.
Part numbers vary depending on the number of pins. I mistakenly said Amphenol connectors in the video. Habit from my aircraft maintenance days.
Chapters:
0:00 Intro
0:14 Epson Label Printer and Software
1:00 Labeling the 24VDC Terminal Blocks
1:38 Exterior Overview
2:09 A Look Inside / Volt and Amp Meters
3:24 Backplane Design Goal / Removing Power Supplies
4:58 Stepper Driver Power Connector Key
5:48 Removing the Backplane
6:59 Installing a few Wire Duct Covers
8:10 System Overview
14:53 Reinstall the Backplane / Screw Starter
17:08 Power On
20:10 Power Off
![[TH] VCT Masters Shanghai Playoffs - Grand Finals // GEN vs TH](http://i.ytimg.com/vi/HL-hhLrtctw/mqdefault.jpg)
Wow.... my head is spinning. Nice job!😊
That controller box is a work of art. Well done!
Thanks!
That has to be the best use of cabinet space I've seen on a control box. I have easy access to all of my components but then again, my case is probably twice the size. Great fore thought on placing the electronics, especially the power supplies.
Thanks. I'm thinking of doing a video on what worked out well and what I'd do different... there's always some things that could use a bit of change once one has the benefit of hindsight.
Nice design, very clean. Great looking project, thank you.
Your welcome. Hope it helps some others with their builds.
Very impressive
Nice job, thanks for sharing! A concern I see is the estop shuts power to the stepper motor power supplies, my z axis would fall down perhaps onto the work in that case. Thanks again for sharing your videos.
Excellent point about the Z-axis falling without power to the motor. It's good for others to see your comment and keep in mind that it could be an issue for their build.
My Z-axis doesn't move when power is removed from the mill, so it's not an issue for me.
As for my e-stop approach, I use the "pause" function most of the time to stop the mill if I see some issue. I don't use the e-stop unless something major has gone wrong.
There are several approaches to e-stop functionality. I set it where the pause function is the way I'll stop the mill most of the time. In my setup, the e-stop is for when I want to stop-everything-right-now. Like there's fire coming out of the controller, or an axis has crashed and I want to kill all power everywhere. If a stepper driver, or power supply is smoking, I want to be able to shut everything off instantly.
Others may choose to take a different approach to E-Stop implementation. Or need to, for reasons like a falling Z-axis.
On the falling Z-axis... If my Z-axis tended to fall when I removed power, I'd probably make a normally-engaged brake of some kind to stop the Z-axis from moving. Maybe something like... spring tension keeps the brake engaged, and when power is applied a solenoid disengages the brake.
Thanks for commenting!
I watched the complete series. Great job (also the videos)! You should have way more views. One question; I wonder about the sizing of the power supplies. You use a separate PS for each motor. I was surprised about the low readings on the displays (max 2 amp I guess). Do you think the peak power is much higher? What is the rating of these power supplies and motors? And did you ever considered a shared PS? Again, thank you for taking the time to create this quality content.
Thanks!
I don't think the peak current is much higher. The steppers aren't really being driven very hard. The power supplies are variable, up to 48VDC (they actually go to about 50VDC) and 10 amps. The NEMA 34 driver is up to 8.5 amps and up to 110VDC or 80VAC (more on this in a minute). The NEMA 24 drivers are up to 7 amps and 24-50VDC.
Having multiple power supplies brings the luxury of having a backup available should one fail since one 10A unit will easily run two stepper drivers. That said if I were to do it over I'd use stepper drivers that will accept AC volts like the NEMA 34 driver (CL86Y). That way I could power the steppers with a step down toroidal transformer in a separate enclosure, opening up space in, and simplifying, the main enclosure. Would probably have to de-tune (lower the peak amps) the CL86Y for the smaller steppers.
Since posting the videos, I've also upgraded the cooling fans and replaced the E-Stop connector with a better one.
Thank you for the info
Thank you for taking your valuable time to share with us.
Your welcome
Hello. Can you make the electrical project available?
The screw starter is the tool I've always wanted but never knew existed.
Thanks for that.
Your cab is super neat, how are the internal case temps at extended running ?
I like to keep my hybrid stepper drivers cool.
Your welcome. There's a little more info in the description on the screw starter.
I've had some that don't work as well. This one has pretty stout springs so it hold the screws well.
As for the internal case temps., I have no idea at the moment. The mill hasn't run more than 30 minutes yet.
Judging by the amps being drawn by the system so far though, I don't expect it to be a problem. I've got about 0.5 amps from X and Y, plus ~1 amp from Z. So about two amps total at an average of 40 volts makes for 80 Watts. Even if that was just an 80 watt heater element, which it's not, the two fans would be plenty to exhaust the heat. I think. 🤔 Think of those two case fans blowing on a 100 watt light bulb, which is essentially a 100 watt heater.
Just ran the mill for most of the day today in an 85°F garage. At the end of the day the exhaust air temperature was 102°F; so a temperature delta of 17°F. Not too bad at all.
Now that summer is arriving and the temperatures in my garage are rising, I'm getting a better look at the temperatures and cooling capability of the fans. See the description for an update. Basically I upgraded the fans to 80mm x 80mm x 25mm and replaced the foam filter with a wire mesh one.
Do you happen to have the 3d print files or where to find them for some of the build? Anything would help!! Great work!
I'll try to get to it sometime this year. I'm swamped with things to do at the moment.
What is the model number and brand of those quick connectors between your base and the door?
The white connectors are Molex brand, for14-20 AWG wire. Model - Latch Lock, MLX, 2.13mm D.
Part numbers vary depending on the number of pins.
I mistakenly said Amphenol connectors in the video. Habit from my aircraft maintenance days.
Is it necessary for the power supply to the motor drivers to be switched via contactor? Wouldn't the alarm input to the mesa card already tell the drivers to stop?
That's correct. The alarm input would should/would stop the drivers. Shutting off the power supplies VIA the contactor is redundant and sort of a sledge hammer approach. I did it as a backup in case there's an unforeseen problem in the Mesa card alarm circuit, like a faulty relay or loose wire etc.