Finally bought some steppers and drivers for my X2 Mill

[Jwest7788]

Figured I would start a thread. This is intended to be a mid-long term project, as I am a total novice and intend to learn all of this CNC stuff from scratch.

Ordered some Steppers and drivers to get me started converting my X2 mini mill. Will be using the ACME rods for now, plan to upgrade to ballscrews down the road a bit. (Kinda expensive, aren't they? haha)

Will update when they show up with some project pics.

JW

 

[kylemp]

If you need some help let me know.

 

[Alexander]

I used the acme screws on my cnc conversion and it is just great. The addition of ballscrews is not necessary. Ball screws have a few disadvantages and the only advantages are reduced backlash and improved efficiency in motion transmission.

 

[kylemp]

I've never heard of any disadvantages for ballscrews, what are you referring to specifically?

I agree that the are not necessary for the conversion but the ability to climb mill is nice and not require any backlash compensation is a big plus. Mach 3 and probably all the other controllers will have compensation functions but they might not work that well in certain instances.. Think of milling a helical pocket or thread milling.

You can alway do it later though, and I would think scraping in the ways on your machine would be slightly higher priority initially (if you haven't already done it).

I don't know if I would go the ultra expensive route right away myself if doing the screw conversion, just go for the cheap Chinese rolled screws for the first iteration and if your still having issues later you could go to nsk or something later (pricey).

 

[Alexander]

The biggest disadvsntage of ballscrews in a cnc conversion is the acme feed screw is self locking and the ball screw will transmit cutting forces back into the stepper drivetrain while cutting. Example while running a facemill across the x axis the y axis will want to move due to the sideways cutting force from the facemill.

 

[Alexander]

This problem is made worse because most ballscrews have greatly increased lead when compaired to the same size acme screws.

 

[Jwest7788]

If you need some help let me know.

Thank you, Will do!

The biggest disadvsntage of ballscrews in a cnc conversion is the acme feed screw is self locking and the ball screw will transmit cutting forces back into the stepper drivetrain while cutting. Example while running a facemill across the x axis the y axis will want to move due to the sideways cutting force from the facemill.

What stops ball screws from "unwinding" themselves in these situations? Holding force of the stepper?

My current plan is to dish out for a Z-axis ball screw, to try to take some strain off of the stepper, as the head is heavy. Looking into a counter balance, or I've come across air spring kits of this mill online to help also.

I've ordered a bunch of little parts I'll need get the x and y setup. Thrust bearings, preload washers, couplings, etc. Plan to copy an few off the shelf conversion kit that gave enough pics and installation insturctions that it was easy to copy. I do plan to use the existing leadscrews for X and Y. (They're metric, but I should be able to figure out the conversion to imperial inside of mach3, right?) (This is the other reason I like the idea of a conversion, Not very good at thinking in metric for this stuff just yet, lol)

These came yesterday:

(Not really the perfect setup, but should work)
425oz/in steppers. I think a little bit overkill for my mill, but the price jump was manageable with these Chinese parts.
Just waiting on a parallel port for an old PC I have, a cheap PC monitor, and a generic PC power cable, and I'll have the "brains" of the operation figured, and ready for testing.


I like the idea of getting my CNC skills to the point that thread milling would be an option, but for now am focused on getting up and running, then milling a slot like @Alexander 's new cnc. haha

JW

 

[Alexander]

Your corect the stepper holds the table from moving when you use ball screws. The holding force is what you see printed on the stepper for exaple yours will be 425oz of holding force. The torque being applied during acelleration will be higher than 425oz/in. You are corect again you can easily set up mach3 in imperial. Either unit of measurement you just input the number of pulses per unit. Nice kit there can you post the link to the vendor so i can read details on the parts.

 

[Jwest7788]

Here's the kit online:
http://www.ebay.com/itm/281867604684

Attached is the instructions from a (now defunct, out of business) manufacturer of a CNC kit I found online that I plan to copy.

JW

 

[Jwest7788]

Got windows XP Installed on an old machine. That was a blast from the past. haha

Just had to order a ps/2 mouse (green cube on the end instead of USB) as I can't get a USB mouse to work on the old machine, but can't do too much without a mouse either!

 

[kylemp]

I haven't had any success with windows 7 running Mach, so I used xp for the controller machine. Something to watch out for is if you have usb devices they can cause timing issues that will sound like a cracked bearing or something, but will be timed.. Normally I copy whatever I need onto the machine and then remove the USB drive so that I don't get the clicking it causes. Tuning the motors isn't a lot of fun in my experience but since you have measuring equipment it shouldn't be too bad.

 

[Jwest7788]

I haven't had any success with windows 7 running Mach, so I used xp for the controller machine. Something to watch out for is if you have usb devices they can cause timing issues that will sound like a cracked bearing or something, but will be timed.. Normally I copy whatever I need onto the machine and then remove the USB drive so that I don't get the clicking it causes. Tuning the motors isn't a lot of fun in my experience but since you have measuring equipment it shouldn't be too bad.

Awesome, appreciate the tip. I've been doing my best to track down the right era of hardware to avoid USB, mostly becauase it's inexpensive, but also becuase much of it I had on hand. Picked up a monitor for $5 yesterday.

Will avoid USB at all costs. Should be easy enough.

 

[kylemp]

I've only had the issue with USB drives, not other devices..

 

[Jwest7788]

I've only had the issue with USB drives, not other devices..

Makes sense. I've already got an old mouse coming, so will be playing it safe regardless.

Can always load up G-code on a floppy to avoid USB, right? (hah)

 

[PeterT]

This is kind of the issue I've read about but never really understood. Those old machines & XP OS setups must be getting hard to source by now? Are you guys saying USB is always problematic, or you have to throw more money at the problem with a different/upscale board interface, or...? I've also heard laptops = bad, regular PC = good. True? I cant think of why that would be an issue unless laptops are perpetually going sleep mode for battery consumption?

 

[kylemp]

Usb doesn't seem to be universally an issue, I run a USB mouse and keyboard on my machine with no issue but drives seem to create some polling issue that causes the problem.. Not sure if there really is a workaround for it with more money or not. I don't think that Linux has this problem if you run linuxcnc, I'll check though since we have a router running it and see how it responds.
Also, yes in regards to the laptop vs desktop in my experience. Laptops are too concerned with power consumption typically which I've had problems with in the past, but I really didn't try any more than one machine. Ideally a desktop is the way to go especially for the ability to run multiple parallel ports.
There are more options than there once was though, many more usb based controllers that seem to be able to handle the timing well enough and you can also use modbus for a lot of the other things you don't need critical timing on like a motor.

I really like this thing, the guy created a whole modbus system to hand it and it seems to work pretty well..

 

[Jwest7788]

I just installed XP on a computer that used to have windows 7 on it, and ordered a parallel card that fit on the motherboard (pcie-1)

Laptops=bad has issues I've read about (not experienced yet though):
1) good luck finding a laptop with a parallel port (parallel over USB doesn't work). I'm not confident I've ever seen one. Lol
2) laptop power savings software messes up the timing. It was something like power savings in the CPU or something.
3) most entry level laptops share ram across the gpu which has timing issues apparently?

 

[PeterT]

Don't laugh too hard at my clunky attempt at wording but here goes. A modern PC 'talking to' a modern external device via USB must involve orders of magnitude more information & transfer rate than a yesteryear PC. I'm thinking high-res printers, massively larger camera cards etc. If that's true, then what is the appeal of oldy PC & serial ports (is that what they are called?) for home CNC builds? Is it easier protocols or other CNC demands where USB is not suited? Or is it one of those, USB interfaces are available but the box just costs 1000$ type issue? Just out of interest, is there anything substantially different on how a 3d printer moves its head to a 3-axis CNC from the PC perspective? I never seem to hear much about the glue squirter crowd looking for old pc's although I'm equally naïve about those devices.

 

[kylemp]

The USB protocol is a polled system I believe, meaning when you send something on usb you don't ever have an idea of when it was received as it sits in a cue.. Parallel ports are tied direct into the bus and as such they have direct access as far as timing goes.. That's kinda the version I understand to be true.
As far as the hot glue systems, a lot of them actually have an on board controller from what I've seen, they have something like a raspberry pi or something actually running the machine..
They also don't require the same kind of tolerance as a mill would I think, you get a couple off steps on a 3d print, no one notices.. You gouge deeper or off with an end mill, it's pretty obvious.
I honestly don't know a lot about 3d printers (by choice) so I'm mainly speculating..

 

[Jwest7788]

The USB protocol is a polled system I believe, meaning when you send something on usb you don't ever have an idea of when it was received as it sits in a cue.. Parallel ports are tied direct into the bus and as such they have direct access as far as timing goes.. That's kinda the version I understand to be true.
As far as the hot glue systems, a lot of them actually have an on board controller from what I've seen, they have something like a raspberry pi or something actually running the machine..
They also don't require the same kind of tolerance as a mill would I think, you get a couple off steps on a 3d print, no one notices.. You gouge deeper or off with an end mill, it's pretty obvious.
I honestly don't know a lot about 3d printers (by choice) so I'm mainly speculating..

You're spot on with the USB issue. USB sends information in packets, which isn't real time.

We had some issues at work with live streaming audio over a USB mic due to the software needing actual live audio, packets were no go.
I could be wrong, but I think it's possible to determine the packet timing and rebuild the live data, which is kinda how USB mics work, and would probably be how those cheap USB drive boards for cnc work too.

Also, doesn't Mach3 require a parellel port specifically? This is likely why the cnc crowd is hunting old machines, the 3D printers probably have newer software solutions without the requirement..


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