We recently brought a drill press and as we have got a limited budget so that one was found from a scrapyard and later repainted. The mechanical parts was in perfect working condition but this thing lacks alot for power. Needs a wakeup call everytime we turn on the switch and might fell a sleep drilling holes larger than 10mm.
Besides that this thing is damn heavy and obviously need a socket so the mobility of this tool arround the workspace is zero.
In this instructable we are going to address all these problems and do our best to bring this beast to life again.
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Step 1: The Idea
Currently the drill is powered by a bulky induction motor, transmitting the power through a pair of pullies that allows to spin the chuck at various speed and torque.
The idea here is to rip off the older power house and replace with a much more powerful brushless hub motor from an old hoverboard. The reason being the face that this thing has got plenty of torque and these days you can easily find one for cheap as well.
Now these motors are outrunner brushless motor and they can produce a huge amount of torque. So instead of messing up with gears and pullies we have decided to drive the chuck directly with the hub attached to the main shaft and the stator enclosed within. This will not only reduce the amount of work and the probablity of getting this drill ruined but if we can implement the whole idea sucessfully, the efficiency of this whole powerhouse is going to be preety good, so let hopr for the best.
Now before we rip it a part, time to modify the motor.
Step 2: Motor Modification
The motor from the hoverboard is a permanent magnet outrunner brushless motor. The outer casing is the hub containing all the magnets and its the rotor. Inside we have got the stator wrapped with enammled copper wire. Now as we undo the six allen screws provided on the motor casing and seperated the rotor and stator time to take the hall sensors apart as we will later use a sensorless speed controller.
Now to mount the stator we need to remove the shaft and the holder from the centre of the stator. So we drilled holes at each end of the trigonal holder and cut off the supports. Later we filed the edges to make a good clearance between the stator and the shaft adapter thats going to hold the rotor.
Step 3: Stator Holder
To drive the chuck directly we need to mount the stator arround the main shaft. The ideal place for that is the bearing holder but we have got very limited clearance if we are going to use the three holes that were pre drilled inside the stator.
So we are going to use a 6mm thick metal plate with a dia of 125mm to act as the holder for the stator. So the plate will be mounted on top of the bearing holder and later we are going to mount the stator on top of the metal plate.
Step 4: Modifing the Rotor
Now to drive the drill chuck we need to mount the rotor on top of the main shaft. So instead of making a customized adapter what we decided to do is to modify the main shaft pully to act as a holder for the rotor. So we cut down the top half of the pully and later we flush cut the top of the adapter so help the rotor sit as close to the centre as possible.
Next we drilled a 40mm hole exactly in the cente of the the rotor, removing the ball bearing along with its assembly. To make sure that this hole is exact in the centre we did made final cuts on the lathe machine as there is very limited clearance between the rotor and the stator.
Next we glued the rotor to the the shaft adapter and drilled six holes for mounting both of them together. Next the rotor holes were enlarged to 5mm and we tapped the threads inside the shaft adapter.
Step 5: Paint Time
As to the point everything seems to go flawless so we made sure they look flawless too, time for the paint job and matt black it is.
Step 6: Solving the Twist
Well like all the crazy project ideas we got, there is always a problem waiting right in the middle of the project, so there are two of them.
Once we dry fitted everything, the first problem we faced is rotor getting stucked to the stator as the machining of both the parts we not upto the marks so we messed with the 0.5 mm clearance. We made every possible effort to get this thing solved but for the time being the only solution that can help us get through is to grind the rotor!!! yes you have heard it right and yes its crazy. But believe its almost impossible to get it solved otherwise as we dont own a lathe at this moment and the lather workers in our area are going to further ruin this whole unit. So we did carefully grinded the sides of the rotor and eventually fixed the problem.
The next problem is with the speed controller. The one we initially decided to go with is a cheap Chinese one thats avliable to drive hoverboard motor. Ratted at 10 cells and 350 watts of power initially sounds like good enough but this crap ESC just wasnt able to get the juice out of the hub motor and made us doubt the power of this huge motor.
So we switched the ESC with a more powerful RC Car ESC ratted at 150A and 6 cells lipo. Originally the motor is made for 10 cells which is nearly 42v and provided a decent speed so with the car ESC operating the motor at 6 cells (25.2v) the drilling speed will not be sufficient. So we rewired the hub motor. This is a 27 pole stator with three phase running across the motor. Each phase consists of three sets and each set consist of three poles. Now it takes more amount of time for current to travel all three sets as they are connected in series and thus the speed of rotation is very low. So to increase the speed of the motor what we are going to do is to connect all three sets in parallel andd we are going to do that with all three phase.
Step 7: Motor Assembly
With the stator rewired and the paint dried we started assembling the motor. First we mounted the stator holder on top of the bearing holder. next the stator is mounted on the stator holder while making sure that its as centred as possible.
Next we coupled the rotor to the shafte adapter using six allen screws. The rotor along with the shafty adapter is then slided onto the shaft and we tightened the mounting nut in place. Thankfully this time we got the rotor spining perfectly arroun the stator without touching it.
Now time to deliver power to the motor.
Step 8: Batteries, ESC and Servo Tester
To power the brushless motor we are going to use an RC car speed controller rated for 150A and 6 cells(25.2v). Now as we have ripped off alot of weight so we took a step ahead and decided to go with the cordless setup by uisng onboard lithium pollymer batteries. Each battery is a three cell (11.1v) and thus we have to connect both of them in series.
Now to drive the ESC manually and controll the speed of the motor we are going to use a servo tester thats goin to provide the required PWM controller to the ESC and help us controll the speed of the chuck accurately and yes without messing up with the mehanical pullies or any gear.
Step 9: Mounting the Batteries,ESC and the Servo Tester
Next we mounted the batteries inside the drill press housing thats now empty. The speed controller is mounted over the top plate that we have just cut out of plastic sheet to hold everything temporarily.
To controll the speed of the chuck the servo tester is mounted on the left side of the housing where the on/off switch was mounted previously. Now with the ESC connected to the motor and the batteries attached we are ready to test this thing out.
Step 10: End Results
To test the drill press we charged the batteries and started testing. Previously the drillpress was unable to start spining as we turn the switch one, but this time all we need to do is to turn the know to a particular speed and the chuck starts to spin.
Compared to the previous setup which is corded induction motor so we are bound to stay close to the socket but with the current setup we can operate cordlessly and with aconsiderableweight loss we can now move the drill press arround our workspace as per our convinience of working.
The previous setup was unable to drill hole above 10mm in metal sheets but with the new powerhouse we first drilled hole upto 20mm using a step bit without any problem. Next we hooked up hole saw with 36mm dia and later moved to a 40mm dia holesaw and the drill press seems to handle both of them without any problem.
With the RC Car ESC this hoverboard motor performed like an unstopabble beast. Besided that with the direct drive mechanism not only the noice levels are low but the reliablity of the whole mechanism has been increased significantly. We have worked with the drill press for our upcoming project to drill a bunch of holes in metal tubing and sheets and this thing can hold upto an hour of drilling time which is more than enough for us.
Not to mention that with the new setup we can control the speed of rotation accurately and without messing up with the belt and pullies as with the previous setup.
Besides that there are some improvments that we have planned to make such as the top enclosure, as the spinning rotor is close to the head during the drilling process, so we are waiting for our 3D printer for that to get done. Besided we will also make a dedicated battery pack which can provide us further extended operating time and also added with a BMS unit so that we wont drain the battery packs.
Guys I hope you like this project.
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