Milling Table Stepper Motor

[cfellows]

Thanks, to all, for the input.

GRBL is of interest because it's free. The GRBL shield is $75 shipped and that includes 2.5 amp stepper drivers, probably enough for my 3 amp rated steppers.

Mach3 is $175. That still leaves me with the needs for stepper drivers. The Gecko G540 would be a great choice but it costs nearly $300. I could round that out with Mach3 Mill Wizard for another $75 and now I've got a pretty serious CNC setup.

But one solution is $75 and the other is well over $500. I don't have an identified need for CNC, I just think it would be neat to have.

Here is a video of a setup with a mill very similar to mine, using GRBL and the GRBL shield. Looks pretty compelling to me.

[ame]http://www.youtube.com/watch?v=mHmDhi2u2BE[/ame]

Chuck

 

[cfellows]

I do have Alibre. Just updated to the latest release a month or two ago. It outputs STL, Step, and IGES files among others.

I just downloaded freemill which is incorporated in the Visual CAD/Visual CAM product. Visual Cad and Visual CAM will only run in demo mode, but the freemill seems to work with no limits. Freemill will accept STL, Step, and/or IGES files so now I'm good from CAD through CAM.

Chuck

 

[dman]

http://www.ecklersoft.com/

^^ did you check out RT STEPPER? ^^ $80 for a dongle and free software based on linux cnc yet runs under windows isn't bad.

also if you have 6 or 8 wire motors you can build lini steppers. not as cheap but not nearly what mach costs either.

http://www.piclist.com/techref/io/stepper/linistep/index.htm

but if that's not right for your motors or you want to go cheaper there are chinese chips for about $10 that can supply what you need. i'm thinking this is what i'll use for my lathe. though the arduino system looks intersting. i think i can make use of sub routines and other things.

 

[dnalot]

I have been using Mach-3 or its forerunner for about 14 years and have been using Visualmill for the same amount of time. I am using visualmill V5 expert now, so a bit outdated. I think you will find the "freemill" very satisfactory and fairly easy to use. Soon you will want to add a forth axis and thats when you will need to get your wallet out.

Love you posts, keep them coming.

Mark T

 

[cfellows]

Thanks, Mark.

Dman, I did have a brief look ecklersoft.com. Might have another look at it but I don't want to get too far out in the weeds.

I probably need to focus on the stepper drivers at this point. I'm a little concerned that the 2.5 amps from the GRBL shield might not be enough, and would ideally like to find something would easily supply up to 3.5 amps. My Nema 23 motors (370 oz in) are rated at 3 amps and if they aren't strong enough, I also have a NEMA 34, 1600 oz in stepper rated at 3.5 amps. I could buy a second one for another $100 or so, including shipping so both X & Y axes are covered. I think one of the smaller, NEMA 23 would be sufficient for the Z Axis.

I'll have another look at some of the Chinese 3 axis controllers. I've read mixed reviews on them but they are inexpensive.

More later...

Chuck

 

[RonGinger]

All stepper drivers are not created equal. I recently helped a fellow with a Zen Router. He had one of the Chinese 3 axis board, with the TB65?? chip. It moved the machine, but poorly and slow. I replaced it with the new PMDX-340 box and the machine now moves nearly 4 times faster, with no missed steps and very smoothly. Both drivers are set for 3 amps. There is more to moving a motor than just the current rating.

I know you said you were doing this project just for fun, and that you didnt see any particular benefit to CNC. When you get a system running well you will wonder how you ever made models without CNC. You are putting a lot of effort into this, why use the cheapest parts and risk building a system that works so poorly you wont find it useful?

 

[dman]

Thanks, Mark.

Dman, I did have a brief look ecklersoft.com. Might have another look at it but I don't want to get too far out in the weeds.

I probably need to focus on the stepper drivers at this point. I'm a little concerned that the 2.5 amps from the GRBL shield might not be enough, and would ideally like to find something would easily supply up to 3.5 amps. My Nema 23 motors (370 oz in) are rated at 3 amps and if they aren't strong enough, I also have a NEMA 34, 1600 oz in stepper rated at 3.5 amps. I could buy a second one for another $100 or so, including shipping so both X & Y axes are covered. I think one of the smaller, NEMA 23 would be sufficient for the Z Axis.

I'll have another look at some of the Chinese 3 axis controllers. I've read mixed reviews on them but they are inexpensive.

More later...

Chuck

it's free to download the software and do simulations. you only have to pay for the dongle and the prices is cheaper than i remember. about $66 if you don't buy it with the case.

i think the nema23 motors are fine. the motors and gearing will change the resolution. the resolution you can achieve is gonna be high. higher resolution will effect the speeds possible based on bandwidth from the dongle, be it a grbl, smooth stepper, or rt stepper or whatever. but you will not likely have a shortage. the travel is small enough that you might not miss extra speed. i also think the nema34 motor may be speed limited because of inductance. but the high torque may make them viable with different gearing. they might be quieter but need finer microstepping to get a good resolution.

motor selection can be pretty broad on a mini mill. but i used this spread sheet, i can't remember the source and can't find the original but here is a saved version with my requirements plugged in.

if you can find the full motor specs you can play around with the settings to try to find the best pulley ratios. unfortunately it doesn't have a box for gear ratio so you have to change the screw pitch and if your anal, change the screw length to emulate inertia. on a small machine this range can be wide but on a bp you can imagine it's hard to find something adequate and it's not worth the money to go with servo drives. i'd buy a broken enclosed machine at that point.

View attachment steppers.xls

 

[cfellows]

All stepper drivers are not created equal. I recently helped a fellow with a Zen Router. He had one of the Chinese 3 axis board, with the TB65?? chip. It moved the machine, but poorly and slow. I replaced it with the new PMDX-340 box and the machine now moves nearly 4 times faster, with no missed steps and very smoothly. Both drivers are set for 3 amps. There is more to moving a motor than just the current rating.

I know you said you were doing this project just for fun, and that you didnt see any particular benefit to CNC. When you get a system running well you will wonder how you ever made models without CNC. You are putting a lot of effort into this, why use the cheapest parts and risk building a system that works so poorly you wont find it useful?

I don't disagree with you, Ron. For me at least, it just comes down to choices. The more I spend on the CNC setup, the less I have to spend on other things. And unfortunately, I do want lots of other things!

However, I also hate wasting money on things that don't work right. The PMDX-340 is a very desirable unit, especially with the built in power supply and all running on regular house current, but the price is pretty steep. The Gecko G540 is looking mighty attractive me right now. I could use it with the GRBL software or with Mach 3 if I decide to go that route. And I would have the comfort of knowing it's pretty likely to perform exactly the way I think it's going to.

Chuck

 

[cfellows]

I've started a new thread on this conversion over in the CNC section.

Chuck