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max axis speed
« on: October 23, 2013, 03:23:03 AM »
I am starting to test my homebuilt machine (demo only as yet) and have two new (to me) Vexta 5 phase drivers to match 23 size 5 phase steppers and 10:1 planetaries.
The new drivers are 230v ac input and capable of rated 1.4 amp per phase, so MUCH better than the baby 24v dc driver I had been using.
With the old driver I could achieve 300mm/min with great stability with slippage ocurring around 400mm/min.
The new drivers are stable at 1500mm/min, the maximum speed I can configure in the version of Mach3 I am using. I would like to try faster if only to find the 'ceiling'.

My question 'is Mach3 limited to 1500mm/min or is it the demo version I am using?'
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Offline Hood

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Re: max axis speed
« Reply #1 on: October 23, 2013, 03:28:28 AM »
I am not sure if the kernel is now limited to 25KHz in demo or not. If not increase the kernel a bit and that will allow greater rapids. Be aware however that the higher the kernel the more chance you have of your computer causing problems such as crashes or lock ups, so only have the kernel set to what you need rather than bumping it way up to 100KHz.
Hood
Re: max axis speed
« Reply #2 on: October 23, 2013, 03:51:35 AM »
Thanks for your reply. I have tried upping the pulse rate when doing pulse engine tests. My computer starts going cranky around 65k.
I think the demo version is limited to 25k under use conditions but will try tweaking!
Academic excerise in any event, motor overheating is going to defeat me long before I reach limiting speed.

Early days testing these new drivers but it apears that they heat up more around 800mm/min than 1500mm/min. Seems strange to me.
Have not yet developed a decent test scheme to track results of each variable but suspect I will back off from rated current to stay kool
and set rapids to suit.

Is there some sweet spot that I should be aiming for?
My wife left with my best friend...
     and I miss him!

Offline Hood

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Re: max axis speed
« Reply #3 on: October 23, 2013, 05:02:18 AM »
Its all trial and error as far as steppers are concerned.
Hood
Re: max axis speed
« Reply #4 on: October 23, 2013, 05:37:03 AM »
Set pulser to 45k (didnt realise I had to restart Mach3 to achieve it!) and sure enough the max configurable axis speeds increase. As it turns out I was close to max at 1500mm/min, still works at 2000 but stalls ocasionally at 2200. Could try tweaking pulse durations but am happy that I have established a speed limit. My machine only has 200x200x200 travels in any event and rapids of the order of 2000 seem more than adequate. Suffice it to say I am delighted with the extra go the new drivers offer. Must now look for a third one for Z axis...and pay for it...ho-hum.

Motor heating issue is more of a concern. With driver set to deliver rated current time to excessive motor heat at 500mm/min is shorter than at 1000mm/min. It seems that motror heating is worst in the region 400-700mm/min. Why this should be so I dont know.

I will bring my scope and current probe home from work this weekend and try to make some useful measurements.
My wife left with my best friend...
     and I miss him!