Messages

51

General Mach Discussion / Re: Only X-axis motor is working

« on: April 01, 2018, 12:59:52 AM »

Right now I have the windings in series. So should I put them in parallel for a better performance?

(still trying to figure out why they even have an 8 wire model.

52

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 06:23:51 PM »

I shall than you, then, for what could be considered a compliment.

I have a dry sense of humor, myself, so no worries.

What I had read, and gathered, is that microstepping would have less torque than full stepping, hence the thoughts on adding gear reduction.
The trade-off being that gear reduction would add in a component of inaccuracy or slop when shifting directions. This is something I do not want to introduce, especially when I migrate from the CNC build to adding CNC capabilities to my home mill and lathe. I had considered other methods to insure the accuracy of the direction change in that project, though. I imagine that, once it's calculated, I could add the necessary correction to the G-code generation and/or the Mach3 profile. But that's a way down the line so I won't focus on it yet.

My next step is to determine which setting on my drivers will yield the best results. And determine which stepper motors I want to invest in.

I wanted to go to a NEMA 34 with dual shaft (dual shaft for my X-axis only needed) but there's a decent set of NEMA 23 with a reported over 400 oz/in rating
It's a few dollars more I can get 1600 oz/in in a NEMA 34.

When I say "a few dollars more" I mean it's almost twice the price.

My CNC mill will only be a 24" X 48" (or 650cm X 1300cm for the Aussie)

53

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 05:00:34 PM »

First posting on steppers: 18/March
This posting on steppers: 31/March
The learning curve has been steep but effective?

Cheers
Roger

I'm not sure if this was sarcasm or praise.
Most of the time has been spent trying to get the stupid bad cable diagnosed. Now that that is over with I am free to tune.

The extra vibration at certain speeds sounds like resonance.

Mass i.e. a load should alter that but sometimes you have to work round it.

Steps per rev is usually fixed and written on the motor - generally 200 or 1.8deg per step, do you mean you set micro steps to 400??

I think you might be right about the resonance. I have everything mounted to 1/4" plastic sheets right now so any vibration is enhanced in sound. Watching the zip tie I have on the motor shaft helps me see if there's more vibration or less depending on the configuration.

Yes, the motors have the steps per rev on them and yes it's 1.8 deg per step. The drivers, however, have the capability to microstep (apparently) and when I set the drivers to microstep I seem to have a better result in the accuracy of maintaining step. If I set the driver to 200 steps then I seem to lose staps. If I set it to 800 steps then I seem to have a better accuracy.

If I end up using the most accurate settings then I'm going to have to have some serious gear reduction in the final build. 

54

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 03:51:55 PM »

This morning I changed the stepper driver configuration to 400 steps per revolution and it seems smoother. I ran my test g-code and the stepper returned to zero after the test. This is the first time it's done that.

I do still get extra "vibration" at a lower speed but it appears to hold steps so that's a plus.

There are other configurations I can pursue on the driver so I'll probably play around a little more.

I still need to get some new steppers with more strength when I do the actual build so I don't know that I need to worry about these 8 wire motors too much. I figure if I can make them work perfect then a four wire motor would probably be childs play.

55

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 01:53:20 PM »

That's how I started.
The weird thing is that every (good)  configuration yields similar results. Low speeds are choppy and there are missed steps when running a g-code.

56

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 03:11:24 AM »

When drive A is half the price of drive B, you may find that Drive A is VERY popular.
But when Drive A is half the price of drive B, I ask myself WHY is it so much cheaper?
Generalities ...

Cheers
Roger

True. And there were cheaper drivers.

I'm not giving up on the drivers til I test them with a 4 wire stepper.

57

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 02:28:20 AM »

Does your driver include 'anti-resonance'? Without this, you can sometimes get quite poor performance.

Cheers
Roger

Don't know, I will have to look into that.
I'm using a VERY popular driver. I can't imagine it being that popular if it's built like crud.

58

General Mach Discussion / Re: Only X-axis motor is working

« on: March 31, 2018, 01:35:06 AM »

Hi,
the highest power/torque will be achieved with a parallel combination. It will also be the combination which gets hottest fastest.

The trick to wiring them in parallel is to ensure that the two windings of the pair are co-phase. You either have to measure it by feeding a signal into one
coil and monitor the phase of the voltage induced in the second.

The diagram you posted suggests that you have enough information to do it by trial and error if the groupings of the four windings into two phases can be believed.

Wire the two phases in what you think is co-phase and try it. The swap the one winding in one phase only and try it, if its better then that phase has now got co-phase windings,
if not they were co-phase in the previous wiring condition. Now do the same excerise with the other motor phase.

Once you've got it correct don't keep fiddling with it. It will just keep introducing more diagnostic variables when you are actually trying to eliminate them.

Craig

Once I get it right, I'm done fiddling. LOL

I know which coils pair. I'm not worried about that. I verified it earlier as well.

To find the polarity of the paired coils, I excited one of the coils to see the step. I kept trying different combinations of polarities and coils until it did NOT step from the known step.
Once I had that pair set with the proper polarity I was able to do the same with the other set of coils.

When I was done I compared to the diagram I posted and they match. Basically, I double checked them.

Now I have them wired in parallel and just need to find a way to make them step clean.

59

General Mach Discussion / Re: Only X-axis motor is working

« on: March 30, 2018, 11:49:24 PM »

I need to find a different way to figure out the coils.

I suppose there are only a few different configurations that are possible.

I've tried in parallel. I've tried in series. Some were more fruitful than others. Some danced on my glass coffee table. Quite loudly, I might add.

I'm still not getting a smooth acceleration.

Yes, It might be the power supply. I understand that. It's just bugging me that it "shouldn't" be the power supply as this power supply went with these motors and worked great.

60

General Mach Discussion / Re: Only X-axis motor is working

« on: March 30, 2018, 08:25:36 PM »

I just found this sheet that appears to match my motors.
I need to translate it from German (I think) but the color combination looks the same.

http://www.robotikhardware.de/download/23lmc30415.pdf