modifying imodela for a brushless motor.

Post questions, share ideas and techniques relating to the iModela
chevy6600
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modifying imodela for a brushless motor.

Post by chevy6600 » Sat Mar 10, 2012 12:26 pm

Hi joules, i thought i would start a new thread for my Hot Rod imodela motor as out of all my mod's and intended mod`s the motor mod is the one i am most excited on doing :mrgreen: so to start off i thought i would `wet your appetite ` as it were with a couple of pics.
brushless motor.jpg
size:2226, rpm:1250kv, 12v, max amp:8amp, weight:35gr, shaft:3mm
brushless motor.jpg (4.68 KiB) Viewed 9968 times
For the power supply i have got an old 12v computer power supply converted as a stand alone unit that makes available the 3.3v , 5v , and 12v (i`m always keen on these mod's :D ) this should be more than capable of supplying the amps needed as the motor spec indicates a max of 8amps.

For the brushless controller i have this as per pic.
controler.jpg
cont. current:18amp, volt range: 5.6v to 16.8v, weight:21gr
controler.jpg (8.15 KiB) Viewed 9968 times
I have made my own signal generator and speed control to feed the brushless controller (pic in due course).

and i found a cheap supplier for the gears. Here is a few of them.
Attachments
gears.jpg

Joules
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Location: Yorkshire

Re: modifying imodela for a brushless motor.

Post by Joules » Sat Mar 10, 2012 3:38 pm

:lol: your motors too small (I can't find a ROFL smiley) I have played with brushless motors also on my MDX-3. I always got annoyed with speed controllers in that you had to arm them first before you could use them. Now however, the use of Arduino's and Basic Atom controllers it so much simpler. Did some hunting for you on the net, you fly model helicopters ? Same here, and micro rc aircraft.

I have been watching development of the Parkzone/Eflite brushless motors, they are tiny and I would guess more in keeping with the iModela's capabilities. That said you carry on, I am more than intrigued to see what you come up with.

I take it you are going to ignore the iModela motor feedback issue (adaptive machining). I have some fast accurate current sensors I use with Arduino's that I would use to feed back (artificially load) the iModela's motor circuit, that way the adaptive machining still works... :lol: then again with the "Horse Power" you have in mind full speed is the only speed.

chevy6600
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Posts: 237
Joined: Thu Dec 29, 2011 11:29 pm
Location: uk. midlands

Re: modifying imodela for a brushless motor.

Post by chevy6600 » Sat Mar 10, 2012 5:20 pm

Hi joules, i`m just having a break from my project and doing a bit of pondering, read your post, i thought you might find my post amusing, good to see that you`re also a fellow R/C flyer, do i understand correctly that you have dabbled with Arduino's etc. then?, never thought of googling for `usernames` for people, i`ll do the same for you when i have more time in due course if you don`t mind, you may of picked up that i have dabbled programing pic controllers then but at the mo i`m trying a simpler root. I`m interested on how you got on with your mod using brushless motor ?. My reasoning with the motor is that the brushless motor being slower rpm but gaining with the power will be geared to give me something like 20,000 spindle rpm. I still intend to have auto sensing. I first thought that the imoderla was doing some clever motor control as it is bound to have some king of controller chip on board (have not looked) kind of rpm monitoring from the motor back emf or picking up a pulse train from the motor supply then adjusting current but i have found out they did not bother with all that, they just supply the motor with 3v, the spindle speed is read by an infrared sensor attached to a small pcb board at the back of the spindle housing and if it picks up that there is a drop in spindle speed it drops the feed rate, if the spindle false below 3,000rpm the program shuts down and informs you that there is a fault and the motor is stopped, well now i`m wondering if there is a max. spindle speed the software will read before it causes a shut down, my plans to reach 20,000rpm may be foiled by the software, if this is the case i will have to write my gcode to have a stationary spindle as i have tried this and the imodela software will still run but it thinks that the spindle is stationary but unknown to the software i`ll have this brushless motor running....though it would be great to have my motor interacting with the software. I have not bothered to post any of these questions to roland as i reckon that they will not be too pleased in what i`m doing ....i`d better carry on with my project, catch you soon.

Joules
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Location: Yorkshire

Re: modifying imodela for a brushless motor.

Post by Joules » Sat Mar 10, 2012 5:44 pm

Hmmm, interesting to learn it may all be done optically. You could consider breaking out the optic sensor and pick up off the brushless motor shaft, that might work.

:lol: my brushless motor work was years before Arduino ever appeared on the scene, it never went anywhere other than a relay to switch in a servo tester that controlled the speed control once it had been armed. I never was happy with the setup as you couldn't be sure the spindle was off till power got removed. I currently run the MDX-3 with a small Maxxon dc motor direct drive.

You have got me thinking again about trying a mod on it as we have all the "new" technology to make a better job this time round. The MDX-3 just quit when the spindle motor current got too high. Vibration was its biggest problem as it used an O ring running on an alloy flywheel for drive. Once you got dust on the O ring it ran like a dirt bike on a ploughed field, didn't contribute to surface finish. :shock:

chevy6600
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Joined: Thu Dec 29, 2011 11:29 pm
Location: uk. midlands

Re: modifying imodela for a brushless motor.

Post by chevy6600 » Tue Mar 13, 2012 7:30 pm

Hi all, i have an update with the parts i have made for the brushless conversion. I had to machine the gear bores as the gears were running out off centre so that is why you can see that the gears have a brass bush, they were cheap moulded gears and had a .25mm run out, i guess you only get what you pay for :| . As you can see there are 6 gears that give me a wide speed range, the largest and smallest has a ratio of 1.8:1gearing up the motor speed gives me a spindle speed of 24,500rpm running on full 12v. Pairing the gears gives me the ratios 1.8:1, 1.53:1, 1.16:1, they are interchangeable from motor and spindle so if swopped also give me .55:1, .65:1, .85:1. If i use just 2 pairs of gears i do not even have to move the motor and i can get 4 ratios so that is probably what i shall do to keep it quick change.
The brass `top hat` is to make the motor shaft 4mm the same as the spindle size. The ally parts are the gear to shaft locks.
The motor is also controlled variably and will also run from my 5v supply which will halve (roughly) the speed and power if so wished. If your wondering if the motor is too powerful the power can be throttled back, if the variable speed is used to slow down the motor the power is also diminished considerably but due to one of the gear ratios can still have a spindle speed of my choosing, so at these first tests the motor is a perfect match as i can have the speed and power from as little or as much to suit any circumstance......hmm i wonder if cutting ally is a possibility! ;)
The black motor bracket is made of sheet steel and the clear plastic part is a dust shield that covers the spindle from the motor and the elements. My camera battery has run out and i`ll tidy a couple of things up so i`ll post again with some pics of the assembled assembly in due coarse.
Attachments
gears.jpg

chevy6600
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Posts: 237
Joined: Thu Dec 29, 2011 11:29 pm
Location: uk. midlands

Re: modifying imodela for a brushless motor.

Post by chevy6600 » Wed Mar 14, 2012 7:30 pm

Hi all, here are a few more pic`s of the completed imodela. The motor is practically the same size as the original but due the gears is mounted a few mm further out. The motor has proper ball bearings so is ideal for long running spells, i have test run it cutting softwood at similar speeds as the original motor and the motor never even got luke warm so if engraving or using small dia cutters i can not see the motor start to get warm at all which means the motor is not going to have it`s power degrade by heat draining the magnets, and also due to brushless motors not having any brushes which is one reason why they are 85%+ efficient compared to the original expected 50 to 55 % i am expecting the motor to last a long time. I contemplated putting the electronics inside the imodela control box as there is ample room but i am trying not to drill, machine, alter things more than i need (it`s nice to be able to back-step if needed), my control box is clipped on and the wires are run through existing gaps.
The way the controller works is: power supply switched on, the motor controller automatically arms with a couple of pips and only if the dial is in the off position (safety). It can be left like this for as long as needed without fear of the spindle running, the spindle speed can then be selected and start running by turning the same knob and if turned back to the off it does not need to be re armed it stays ready for use. I could of used the old 3v motor supply to switch on/off the motor but in the past i wanted to have the motor switched off when i wanted, so now i have full control while testing the `x` `y` axis without a running motor.
I still am able to have the spindle speed readout work even up to my 24,700rpm so i`m glad of that , and as the imodela governs the feed rate from the spindle speed and not the motor i have also still got the auto cutting functioning correctly, which is great :D . When a job is started the `imodela controller` program arms itself and it is at this time i switch on my motor, i have about 5 seconds to do this or the program stops and informs me that there is a problem with the motor (well it is`nt there any more is it :lol: ) from this point on it sees that the spindle is moving (from my motor) and thinks all is well and takes the current spindle speed as a base setting so if it sees it drop from this it then lowers the feed rate as normal, the difference here is the base spindle speed can be of my choosing, by me setting the speed within the first 5sec arming period.
As the brushless controller is from R/C parts trade and ready made i can even program it to have breaking, soft start, soft slow down, change the timing of the motor, cut-off voltage, governor.
Attachments
front view.jpg
front view of `Hot Rod` motor mod.
side view.jpg
side view of attached motor control.
back view.jpg
back of imodela showing my attached motor control

chevy6600
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Posts: 237
Joined: Thu Dec 29, 2011 11:29 pm
Location: uk. midlands

Re: modifying imodela for a brushless motor.

Post by chevy6600 » Wed Mar 14, 2012 7:38 pm

here is a close up of the gears and a better view of the `Hot Rod` motor. I`ll come back with some results in due course but initialy it looks very promising. :mrgreen:
Attachments
close up view.jpg

chevy6600
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Posts: 237
Joined: Thu Dec 29, 2011 11:29 pm
Location: uk. midlands

Re: modifying imodela for a brushless motor.

Post by chevy6600 » Thu Mar 22, 2012 8:30 pm

Hi all, well i have been doing a bit of experimenting with a couple of cutters, after my initial trial with a 2 flute slot mill, i thought a carbide burr would be ideal as it requires high speeds and has very little chips due to the high number of teeth and although the finish is second to non i had a problem with the occasional `digging in`, at various points, i believe the harmonics of the noise the machine makes caused the burr to vibrate just enough for the burr to dig down a micron or two and as all the burr-face-teeth took a bite they all pulled the burr down into the ally, as far as i can judge about 0.1mm it would then carry on perfectly, the burr was setup with full length sticking out of the spindle 25mm (give or take), 0.5mm depth-cut and a cut of 0.1mm using full speed feed rate (the only speed available using the `control` program), i also tried only cutting a depth-cut of 0.1mm and a cut of 0.2mm but i could still get the occasional `swirl` in the ally plate. I have put this result down to the fact that the table is not sturdy enough on the `Y` axis runners as this is the most flexible part of the machine at the moment.
I have not used the most ideal setting ie. short cutter length in spindle, slow feed speed, as i wanted a more true to life situation. The next cutter i tried is a 2 flute 3mm dia carbide slot mill, i will add that it is a used one, that i have used to bore out a spindle-bore in my 4mm spindle i have also made (used a grade 8 bolt) i used this used cutter as this will give a more true to life result as any cnc work being done is going to take several hours and will get blunt in a short time and i wanted to find out what a cutter would be like half way through a job, well as you can see from the photo`s the finish pretty much looks as though it has been ground, there are no steps or gouge marks and i believe that i would be happy to walk away from the machine knowing that it was not under duress. As you can see from the photo the step you can see is 0.2 mm which is the depth i was taking and i was taking a cut of 0.3mm with a full feed rate ( again, hobsons choice), the cutter was a bit shorter so is mounted 22 out of the spindle.
You may be able to make out the first cut i made at the back side, you can see that i had `surface cut` in a circular pattern, this was done with a new but same size cutter and i was taking 0.3mm depth and 2mm wide at full speed and had no problems, but as the cutter would not stay that sharp for too long, the setting could not be relied to not give problems for too long as the cutter would start to get blunt at some stage.
I have not finished yet so i be back when i have some more info.
Attachments
ally plate top.jpg
ally plate top2.jpg
ally plate side.jpg

Minestorm
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Joined: Mon Nov 07, 2011 11:04 pm

Re: modifying imodela for a brushless motor.

Post by Minestorm » Mon Apr 09, 2012 1:23 pm

I notice TechSoft have the spare motors now (along with other spares).

£7 for 2 which is good value.

chevy6600
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Posts: 237
Joined: Thu Dec 29, 2011 11:29 pm
Location: uk. midlands

Re: modifying imodela for a brushless motor.

Post by chevy6600 » Sun Apr 15, 2012 12:29 am

Hi all, i am beginning to see the benefit of my mods now, i have ground up a 10mm 4flute mill cutter to have a 4mm shaft to suite my 4mm spindle so i thought you might like to see how it worked out cutting balsa wood, i have put a link to the youtube video if you fancy having a look.
For those of you who are curious on the imodela cutting capabilities i have done some more testing. I have just bodged together a pattern to use for cutting it is not anything in particular but just something to demonstrate the capabilities.

To start off i have used rolands modela player 4 to use as a bench mark and using their settings with a milling cutter size 2.1mm 2 flute with the suggested speeds and feed rates as per the program, material setup as styrenefoam to give the standard imodela settings the `benefit of the doubt` . I did not bother with the surfacing and only did the pocketing and outer perimeter milling which due to the programs way of working had to be done in one go but had to have a roughing and a finishing operations.

The next test was using 3rd party software using the same 2.1mm cutter, same styrenefoam material but i have done a surfacing, an inner pocketing and then an outer operation, so the difference between these 2 tests boils down to the modela player 4 and 3rd party improved tool paths and cutting methods plus the additional surface mill operation.

the 3rd test i have used my 10mm 4 flute special milling cutter to do the surfacing then a 4mm 2 flute milling cutter to do the pocketing and outer milling operation but setup to cut balsa wood, the depth, feed rates are what i felt the machine could handle easily.

As you can see from the chart the time to machine the same item was reduced from 8.34 hours down to 18.4 min.
imodela cutting info.pdf
(133.14 KiB) Downloaded 1209 times
As it is always better to see these things in action i have put together a video :mrgreen:
The youtube video shows hogging out surfacing operation using my special 10mm 4 flute cutter.

http://www.youtube.com/watch?v=4_eKaKSxW6E

P.S. i did at first use my 10mm to hogg out the whole thing in balsa wood with a depth of 5mm ....it took 7min to do the whole lot!! but the cutter was under strain and making noises so although it had done it i cannot say it was good for the machine. The tests as per the chart were done easily and could be pushed further if the truth be known.....i thought that you might like to see it being pushed :mrgreen: so here is the link
http://youtu.be/NF2nHEKGZsE
as it is not working at it`s best you can only watch it by using this link....it is not out for all to see.

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