Open source CNC Plasma cutter, a general idea and a lot of info.

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05 Mar 2019 21:02 #127824 by tommylight

jmr wrote:
Tommy: once You get some sleep please tell me if you have seen one of these in any machines:


Thanks


No, but sure looks like the internal coil of very slim motor with no metal core. Interesting, i wonder what is the efficiency of such things?

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05 Mar 2019 21:47 #127832 by jmr

tommylight wrote:

jmr wrote:
Tommy: once You get some sleep please tell me if you have seen one of these in any machines:


Thanks


No, but sure looks like the internal coil of very slim motor with no metal core. Interesting, i wonder what is the efficiency of such things?

I found some general info: https://www.motioncontroltips.com/faq-servo-pancake-motors-work/
There was also article in some old technical newspaper (1960~?) that was readable online. When searching for pancake motor I got a lot of confusing info, so maybe this term is not very specific. On aliexpress it was even related to ordinary permanent magnet DC motor. Today there are the AC motors of similar kind, but reversed - the neodymium magnets are on the rotor. Those can be found in electric Toyotas, its just a few kilos for ~40kW of power. Not sure about efficiency, but i may have seen a number around 80%
It's not that I would ever want to pay for a new one, but they can be found in piles of other thrash in the scrapyard, with just the brush holders broken off. Look out for them:woohoo:
I may be able to send you one if there is enough of them so you could try it in some monster.
Unfortunately I still don't know where to use them best, but they should be good for a laser or plasma. I will try to take some photos, I believe some of them were made in France, I have also Polish copies (licensed or pirated, not sure which way...). Inner and outer connections on the rotor were electron beam welded. 1kW or 1.5kW with forced cooling is around 26cm in diameter and ~8cm in height plus shaft. Smaller shaft is on the back to connect the tach or encoder. Acceleration is crazy, torque possibly too. I need to solder another servo driver with some heavy fets and big PSU.

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06 Mar 2019 15:05 #127891 by andypugh
[quote="tommylight" post=127824
No, but sure looks like the internal coil of very slim motor with no metal core. Interesting, i wonder what is the efficiency of such things?[/quote]

To be very specific it looks like the rotor of the Lynch motor.

en.wikipedia.org/wiki/Lynch_motor
The following user(s) said Thank You: tommylight

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08 Mar 2019 01:24 #128054 by tommylight
Checked that last night, interesting, especially the nearly 90% efficiency ! It uses brushes, lots of them. No more brushes, if i can help it. :)

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08 Mar 2019 11:58 #128076 by Leon82
it appears they made them at one point, brushless also, but are discontinued
www.robotcombat.com/store_etek.html

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09 Mar 2019 08:34 #128139 by pl7i92
what from the tread theme do you mean by open source
All here is open and the thc component can get modified to all the available plasmas

the Thing is most on Budget and USE
we got 2 Running in Education School 4 on build they are running for 2hr a Year with the same part in all Schools
so costs are considering low at 700USD completig with Rack and cutter

and i got a Thankfull helping person that runs 3 Plasmas in a 6day 8hr Timespace
that build the Oversize 2,5x1,5meter workarea Plasmas at a cost of 5000Euros

so there is mutch space in between and also UP and on
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10 Mar 2019 00:28 #128188 by tommylight
Open source, or open info that should include some other stuff that i did not have time to do yet, but getting closer.
Plan is to make some low cost machines that can do good work, not just hobby or fiddling with them all the time.
We know the software is working and very reliable, so making something reliable on the hardware side should make a nice machine.

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10 Mar 2019 17:40 #128258 by pl7i92
on the plasma side it is all about the GROUND and the THC

my Helper people got 4Plasmas in use cutting in 8hr shifts on VERY VERY low costs

if you got a good Hardware must not be expensive it needs to fit your need

For instant a Hypertherm 125 CNC at 2850USD
is not that efecctiv if you mashine got M542 Drivers

and a servo Mashine with 1KW Servos will not be good with a 25A Plasma

And at least the Budget is to blame for most
this feeds to the Maker Side how is able to build a 3meter Table

Small business will use Mashine Builder and Hobbyists will try there best
as infos here ARE realy perfect

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14 Mar 2019 08:32 #128565 by jmr
Reliability is important. How much trouble does the cutting dust cause? When I first thought about it, I saw bellows in my mind. Then I saw some more photos and it seems linear rail/carriage with build in wipers is "good enough". Is that really good enough? How much lubrication is needed?
I saw some in factory working in glass dust, running dry and getting some abuse, that was not very reliable but it worked for quite long time getting more and more play.
Should I make some shield above and around the torch to protect the rail from piercing products?
There are claims of belt drive being a good way. I know it can be used as a rack, this way teeth can be facing the bottom and would not collect the dust deposit, however it means the motor has to be mobile too which means more mass to accelerate. I found some T type (with the notches) belt with steel reinforcement, looped and probably long enough the whole rail. I can run the return side through the "tunnel" on the back of the beam, but what about the front? Should I worry about the dust? I plan to use the water table.

All of this "openness" means it's quite easy to upgrade if you start right. This is why the first few post of this topic have so much value, they are based on a lot of experience. A machine with shitty 40A plasma will cut faster and more precise than you can trace the material for manual cutting unless you fail seriously. Problems that pop up during build can be addressed earlier if they are expected. This is why I am not so sure about the dust issue, but hey, drawer slides do work well.

I put some pancake photos here:
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The smaller one is 300W with resolver on some kind of test stand connected to 400W DC motor with coils instead of stator magnets. the CEM model M19 is quite comparable to Axem MC19S - I found crazy priced spares here: inverterdrive.com/group/Armature-Discs/P...ring-Brush-Set-AXEM/
The oldest polish one is from 1971. I think the original patent is US3090880A from 1950s. I have some extra brushes and rotors, they show very little wear. As the articles state, there is little arcing and wear on the brushes - I believe the bearing failure is similarly possible as brush failure. Dismantling requires demagnetizing of the magnets - there are two wire loops with ends hidden under one plate. Maybe one day I will check the field strength with gaussmeter and attempt to change the noisy bearings in the worst of them and see if I can put it back together and remagnetize. Theres four of them, I will try to get them running. I think I could swap a good one for a decent straight plasma torch:P

@Tommylight: How often do You meet a bad bearing in an AC drive? I saw its quite possible to replace them with lots of caution and ducktape, and Andy even managed to turn the shaft and not end with hairy cylinder of swarf.
Thanks!

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14 Mar 2019 16:22 #128593 by pl7i92
if you run your cutter 8hr shift
and no waterbassin
you will get in trouble
the water also is not safe to be inside
you need for more then 40meter CUT per day inside a room
a Airflow system

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