Brushless Makita mod

(Griff Carpenter) #1

Would appreciate some engineering help…

I’m thinking one of these, with one of these

The PS is rated 12-18 volts, should work ok with the router. I wonder, is it feasible to use it to power the SO3 as well. I forget, is the SO3 24 volts?


(William Adams) #2

Some folks have been discussing this on the Unofficial Shapeoko group on Facebook.

(Stephen Gullage) #3

interesting that it comes with a 1/4" and 3/8" collet instead of the usual 1/4" and 1/8"

(Griff Carpenter) #4

Thanks Will but I do not have a Facebook account.

(Vince) #5

@Griff. I’ll be making a post on here when I get the ac to dc adapter :wink:

The regular rt701c pulls a max 6.5 amps. Now I couldn’t find any real numbers about the brushless one but they say it’s more efficient. I opted to go for a cheaper 5 amp power supply to see if it would push it ok. edit I might need more watts, we’ll see

The 3/8s collet was a nice surprise

(Phil Thien) #6

6.5a @ 120v. So watts = ~780. Now with an 18v/5a power supply, you will generate a maximum of 90-watts.

(Griff Carpenter) #7

So the Mean Well I’m looking at is 15-18 volts at 23.2 amps for 348-418 watts.

Edit. Interesting discussion here on “Max Watts Out” for power tools.

(Stephen Gullage) #8

From the router manual: “If the tool is operated continuously at low speed for a long time, the motor will get overloaded, resulting in tool malfunction”

Additional info: On this page, they did a real world test, with a roughly 5 second per foot feet rate, the 5Ah battery lasted about 31 minutes. (380 feet at 5 seconds/foot). So that means the motor is pulling about 10A at 18v, or 180watts. That would mean it’s roughly a 1/4 HP motor. (180W/746W/HP).

Both of these facts seem to indicate to me that 1) you’re going to need a big power supply to power it (at least 12A to accommodate a 85% eff, probably 15A to be safe), and 2) you run the risk of burning out the motor by running it for a long time, and 3) it’s seriously under powered for a CNC machine.

(Phil Thien) #9

The power supply should be able to handle the power required by the tool during cutting, and I’d want to avoid running the power supply at full rated output for long periods of time.

For my use (smaller bits cutting acrylic) I’ll bet you I wouldn’t need more than 200-watts.

(Griff Carpenter) #10

The PS is rated at 23.2 amps @90% efficiency so it seems sufficient to my non EE eyes.

Oh well, I just discovered the 350/15 volt is obsolete, no longer available. The 350 range now is 12v, 24v, 36v…

(Vince) #11

Reading that fully charged 18v packs are around 20v I decided to try a 24v power supply that can be adjusted to 21, 15amp continous rated. $20, be here on Thursday.

Hopefully nothing catches fire :rofl:

(Stephen Gullage) #12

The mantra of the mad DIY’er

(Griff Carpenter) #13

Hope that chinesium ps doesn’t burn your shop down! Probably ok for proof of concept though.

(Vince) #14

I really wanted to buy the 0-30volt 20 amp bench power supply but you got it, this should be ok for proof of concept.

Im going to take apart an rt701c to check bearing compatibility. There is a specialty bearing house by us, would love a high performance ceramic option

(mikep) #15

Not far behind “Hold my beer!”

(Vince) #16

Good news. This should be no problem

Decided to test out the 90 watt power supply and it turns on leds and briefly starts the brushless motor for about 3 seconds before the adapter trips.

With more juice we should be in business. Add a nice box for the PS with fan and amp meter to see load

Hopefully with everything working out this could shape up to be a nice relatively low cost spindle upgrade.

(AS to positive)

(William Adams) #17

Surprised so much of the innards are in a plastic housing — wonder if that’s done to make assembly easier?

(Vince) #19

Lower bearing is the same but upper bearings are very different. This is an rt701c with over a 1.5 years of high rpm use and aluminum abuse. Look at the commutator wear :hushed:

(William Adams) #20

Looking at that photo, it does raise a concern — if so much of the RT0701 is empty space dedicate to cooling air flow, will the brushless motor be likely to overheat?

(Vince) #21

The brushless plastic housing is 30% thicker in the thinnest areas and I feel like the upper bearing support is better as well. It also has a more consistent air gap around motor and plastic case. Also noticed all hardware is bigger.

Hopefully the brushless will create much less heat because its more efficient. Really depends on what kind of amps it will be pulling. Not worried though, the big shapeoko spindle mount is a great heatsink!

On a side note both my corded bearings have measurable axial endplay… definitely going to look into higher quality replacements and establish a service interval

Edit 90 watts is enough to run no load at speed 1.5 :rofl: