Opinions about different motor assemblies, ballscrews, and bearings

[bandtank]

There are three things I'd like to ask the forum to give me some advice about since I'm having trouble making up my mind.

1) Motors and drivers: I changed my plan from my other thread to go ahead and buy new steppers, but I'm still not sold on the idea of buying a driver as none of them really seem robust to me. I design stuff like that for a living and the designs really bother me, especially the fact that there is no USB interface on something like the Gecko 540. However, I'll weigh the pros and cons of designing my own, even though I'm positive I could make a better one, as time is an issue. Assuming I buy a motor/driver setup, would anyone recommend the HobbyCNC Pro kit instead of a Gecko and accompanying drives? I found a post on these forums a while ago showing that the Gecko ends up being a better deal than it initially seems since you have to 'add' more parts to the HobbyCNC kits to make them function correctly, but I can't find it again. Any thoughts on this?

1a) If I were to buy something like a Gecko 540 (I only really need a 3 axis machine, but it seems like such a good deal anyway), does it support running a motor on all 4 ports even if 2 of them could be configured as X-axis (for dual X-axis drive)? Is that even possible to configure in Mach3? Or would I have to run two motors in parallel on a single driver?

2) I have tentatively decided to use ballscrews instead of acme threaded rods. I found a thread where someone was asking about buying from linearmotionbearings2008 on ebay and people seemed to react positively. Is there anything else I should know about this or would buying something like this work as-is? I have a local place that will machine the ends to work with end blocks, so that shouldn't be an issue.

3) I don't really want to use linear motion carriages or whatever they are called. I'd rather use linear bearings, something like this if it seems reasonable. Any comments?

Thanks in advance for any help or advice.

[ger21]

1) the reason there's no USB on a G540 is because you can't drive a stepper motor through a USB connection. Step and direction signals must come from a parallel port or from an external motion controller.

Gecko vs HobbyCNC. HobbyCNC offers decent performance, especially for the price. Gecko's offer many more features, and depending on which model you choose, is usually capable of double the performance of a HobbyCNC.

And with a G540, you can run 4 motors with two of them slaved in software (Mach3).

2) Should work fine. As long as it's mounted properly.

3) Many people use them just fine. Not sure what you're comparing them to, though.

[bandtank]

Originally Posted by ger21 1) the reason there's no USB on a G540 is because you can't drive a stepper motor through a USB connection. Step and direction signals must come from a parallel port or from an external motion controller. Gecko vs HobbyCNC. HobbyCNC offers decent performance, especially for the price. Gecko's offer many more features, and depending on which model you choose, is usually capable of double the performance of a HobbyCNC. And with a G540, you can run 4 motors with two of them slaved in software (Mach3). 2) Should work fine. As long as it's mounted properly. 3) Many people use them just fine. Not sure what you're comparing them to, though.

Thanks for your reply.

What I meant in part 1) is that the Gecko doesn't have an onboard microcontroller to convert USB frames to step/direction. It's really just a bunch of logical toggling and PWM in terms of what needs to be sent to each motor controller. This sort of thing is extremely cheap and easy to do. Considering the price of this equipment, it's just annoying to me that it isn't implemented especially since LPT was phased out a long time ago as a legacy standard.

Gecko vs. HobbyCNC. Ok, that's exactly what I wanted to know. I think I'm going to go with a Gecko then. I know the question "which motors should I use?" is very open ended, but how should I go about narrowing the criteria I will use to select one? I see a lot of people using 380oz. in. motors (at least I think that's the torque they specify), but how did they settle on that number and where do you buy them? Also, in response to being able to slave two motors in software...perfect. That's what I was hoping.


2) What do you mean? I'm assuming there must be something tricky about it, or maybe you were just saying that they'll work fine as long as I buy the proper parts to mount them.

3) I guess I didn't ask the question very well. What I meant to say was something like - do you think linear bearings are better than the multiple skate bearing linear carriages that a lot of the prepacked kits seem to include? It seems as though linear bearings can be a lot more accurate, tolerate some slop while remaining true, and are more expensive. Is that a fair summary and if so do you recommend using them if the budget allows it? Or is there a better choice?

[ger21]

What I meant in part 1) is that the Gecko doesn't have an onboard microcontroller to convert USB frames to step/direction. It's really just a bunch of logical toggling and PWM in terms of what needs to be sent to each motor controller. This sort of thing is extremely cheap and easy to do. Considering the price of this equipment, it's just annoying to me that it isn't implemented especially since LPT was phased out a long time ago as a legacy standard.

No, it's not easy to do. Afaik, there are no stepper drives with this feature available. But, there are USB options for use with Mach3. One is the ncPod, but development stopped on it a few years ago. http://ncpod.oemtech.com/
There is a Mach3 plugin for it, that seemed to be mostly finished, but most of the early adopters of it have abandoned it in favor of the Smoothstepper. www.warp9td.com

There are a lot of Smoothstepper users, but it's been in development for a few years and there are still a few Mach3 features not yet implemented. But for the most part, it works very well.

Another option is http://www.usbcnc.com/
Comes with their control software and hardware motion controller.

And one other by a member here. http://rc.cis.si/projects/cnc_motion/

All of these will work with the G540, or any step and direction drives.

2) Yes.

3)

From worst to best: (imo)

1) Skate bearings on angle or pipe.
2) Carriages from www.cncrouterparts.com
3) DualV wheels and track
4) Linear bearings on round rails (Your choice)
5) Linear bearings on profile rails http://www.automation4less.com/linear.htm

There are many variations of 1-3 as well.

[bandtank]

Originally Posted by ger21 No, it's not easy to do. Afaik, there are no stepper drives with this feature available. But, there are USB options for use with Mach3. One is the ncPod, but development stopped on it a few years ago. http://ncpod.oemtech.com/ There is a Mach3 plugin for it, that seemed to be mostly finished, but most of the early adopters of it have abandoned it in favor of the Smoothstepper. www.warp9td.com There are a lot of Smoothstepper users, but it's been in development for a few years and there are still a few Mach3 features not yet implemented. But for the most part, it works very well. Another option is http://www.usbcnc.com/ Comes with their control software and hardware motion controller. And one other by a member here. http://rc.cis.si/projects/cnc_motion/ All of these will work with the G540, or any step and direction drives.

From a hardware perspective, it is rather cheap to implement USB functionality. I see no reason why an experienced engineer couldn't have done this by now in a pre-existing, proven solution like the Gecko 540. I design and write firmware for embedded hardware as my job and porting code from a legacy I/O port into something like an IEEE library is straight forward. No reason to beat this point to death though as it's not included and that's that. I'm just baffled by this because of how cool and developed this hobby is. I was definitely surprised to see an LPT port. I'll probably just 'man up' and stick with the Gecko 540 as it does everything I could hope for and is a good price.

Originally Posted by ger21 2) Yes.

Cool, that's what I was hoping you'd say.

Originally Posted by ger21 3) From worst to best: (imo) 1) Skate bearings on angle or pipe. 2) Carriages from www.cncrouterparts.com 3) DualV wheels and track 4) Linear bearings on round rails (Your choice) 5) Linear bearings on profile rails http://www.automation4less.com/linear.htm There are many variations of 1-3 as well.

Very helpful! I assumed a list sort of like this but I had no idea how to order it and I definitely didn't realize there were so many options. Thanks!

[ger21]

Originally Posted by bandtank From a hardware perspective, it is rather cheap to implement USB functionality.

The difficulty is integrating it with software that was never designed to support it. Without writing new software from the ground up, it gets a lot trickier. That's why the two Mach3 USB options are not yet finished, and the other two use their own software, written to work with their hardware.

[bandtank]

Originally Posted by ger21 The difficulty is integrating it with software that was never designed to support it. Without writing new software from the ground up, it gets a lot trickier. That's why the two Mach3 USB options are not yet finished, and the other two use their own software, written to work with their hardware.

For $175, whoever is developing Mach3 should be able to do it.

[ger21]

Originally Posted by bandtank For $175, whoever is developing Mach3 should be able to do it.

The original developer worked 16 hour days, 7 days a week over several years to get Mach3 near where it is today. He then retired, and handed it over to the current developer. Still a one man show. And a bargain at $175. Look around, anything comparable to Mach3 will set you back well over several thousand dollars.

[rowbare]

Originally Posted by bandtank From a hardware perspective, it is rather cheap to implement USB functionality. I see no reason why an experienced engineer couldn't have done this by now in a pre-existing, proven solution like the Gecko 540.

A complication is that USB is not specified for real time applications. Any interface must somehow work around that.

Regarding the eBay ballscrews, I don't know if you noticed that the seller also offers them machined with bearing blocks.

[bandtank]

Originally Posted by rowbare A complication is that USB is not specified for real time applications. Any interface must somehow work around that. Regarding the eBay ballscrews, I don't know if you noticed that the seller also offers them machined with bearing blocks.

It looks like he only offers them machined on one side though. I couldn't find any that are machined on both ends and I was under the impression that both ends needed it. Am I wrong about that?

[ger21]

The auction you linked to says it comes with both ends machined and includes two end blocks, one for each end.

[bandtank]

Originally Posted by ger21 The auction you linked to says it comes with both ends machined and includes two end blocks, one for each end.

I see that now. The verbiage is still a little bit confusing though as he says to ask about machining the ends further down in the auction. Maybe I'll just send him a message to be completely sure. Thanks for pointing that out.