Thursday, 23 May 2013

Home Made Table Power Feed for Milling Machine






Home made Table Power Feed

 After doing some work on my Home Made Mill, I found my arm was getting really tired of cranking the table back and forth, so I decided it was time to make a power feed for it. I figured I would start with the X Feed and if it worked out well, I would add one to the Z feed as well

After getting some advice from a machine forum, many had done this using inexpensive window motors. So, I picked up a few from Princess Auto and decided to go with a 24VDC one, as it seems to have more than enough torque. The unit had a 9 tooth gear on it, which comes off with a clip ring. This gear also has 9 teeth in a smaller diameter that engages with a gear type socket in the gearbox. I took the gear and welded it to a chunk of 1" rod and drilled down so the motor shaft wouldnt bottom out. I will use this gear end to "engage and disengage" the motor from the table lead screw.

On the other end I used the lathe to turn a round shaft stub, which will act as a guide into another 1" rod section that will be bolted to the table feed screw. I made a second peice with a slot cut in it to match the geard rod, which I removed some of the side. This will act as a "flexible movable chuck", which will alow the rod with the motor gear to move back and forth to engage the motor. Below are the two peices




Here is how the bits fit together


Now, had to make a plate to bolt onto the table to mount the whole assembly. Started with the end plate that mounts to the table with a hole for the lead screw. I then use a set screw to bolt the shaft clutch part to the table screw.

Next, had to make the end plate to hold the motor.

 The hole in the plate is large enough to allow the geared rod to pass and engage with the motor.

I now need to make the sides, setting the distance between the two end plates and leaving the right amount of space to allow the geared rod to be slid back and forth (to engage/disengage the power feed).

After a quick clean up (to get the rust off the steel) and a coat of tremclad, I started tapping the holes to assemble the frame.


With the frame done, it was time to make the clutch lever, which I made into a fork shape and welded on a through rod. After some adjustment and tapering the fork ends a bit, it works smooth and well.


Now, I needed to make a handle, so used some 3/8" rod, threadd one end and welded a 1" rod chunk on the other end. A bit of lathe work and the handel was done


Very pleased with the window motor, as even running 1/2 voltage (didnt have 24VDC yet so used 12VDC) I was barely able to stop the feed by holding the opposite end wheel.


While waiting for the PWM to show up, I decided to start on the control unit. Dug out a project case I have had forever and started drilling. Case works well, as it has a top and bottom shell section, and both the front and back are seperate peices. Started on the back, as the big work was getting a hole for the fan (fan was $5.00, figured why not  lol).


Decided to use molex type connectors for the motor power, as I want the wiring to be beefy and the connectors the same. Since they are square ones and I couldnt find any panel mount ones, I cut the hole so they will push through but stop at the rear tab that goes all around the connector. Made a sheet steel plate to "hold" the connectors in. Decided to use 5 Pin DIN plugs for the limit micro switches, this was I only need 1 connector for each axis set.

Since the X feed window motor is 24VDC (no idea why, but no problem) and the other two I got are 12VDC, decided to use a 24V CT transformer, and generate both 24V and 12V. I also wanted a way to secure the relays without "glue" due to possible heat and vibration (so hot glue was out  lol), so I made some sheet steel angles that will "pinch" the relays and hold them in place. Mounted all the part for the case and rear



Molex connectors stick out a lot on the back, but dont really care  lol. Also added a fuse holder as I like fuses on everything I do.



Now it was time to lay out the front panel, and even though I don't have the PWM yet, I will block out some space for it and do it later. After laying out the component placement and drilling, I used some "rub on's" for labeling (I love these) and gave it a few heavy coats of automotive clear coat.


With that dry, I stuffed all the front components (minus the PWM) and tightened it all up. Now I can start with the internal wiring.



So today I went out and mounted the control box on the mill and did a temporary routing of the cables. After testing its operation in side, decided to test it for real with the motor. Hope the motor can handle it, as while the transformer is 24V, the full wave rectified and filtered power is about 36VDC.



 Ran the unit and the motor performed well, seems to be happy with the voltage, which probably does drop under load.


 Made up a bracket to hold the adjustable limit micro switched and added a drill rod to the table with adjustable stops I lathed out.


Routed the cables and soldered it up, then made some thumb wheel adjusters for the limits. Hooked it all up and adjusted the switched and it worked perfectly.



After a bit of milling, one of the small switches croaked (guess the load was too much), so took it inside to replace it. Well, looking at the wiring ratnest I decided to revamp the unit to Rev 2. Here is the rats nest, makes it a pain to work on.


Decided I would rip out the relays and mounting hardware, and mount them on a PC board. This would cut down the wiring a lot, and make it a lot neater (plus it allows me to add max travel limit switches to kill power on both the X and Z feed.  Also redid the microswitch plate to hold the other two switches.



So, started on the PC board and discovered most of my artwork supplies are 2X size, and a lot of the stick on circles were too old and useless (wont stick). Also a lot of stuff is printed on sticky milar as all the PCB I do are normally 2X size on mylar (red and blue) and sent for photo reduction to negitives for sensitized boards. Decided I would go cheap, quick and dirty by just laying the foil pattern right on the board. Was a pain trimming the big pads I had (only ones that still stuck), but finally got it done. Since I had double sided material I made the board double sidded and used pads and wire to make plate through holes.

Finally finished and dumped it in the etchant. After a while the coper was vanishing right before my eyes, always love this part.



Once done I stuffed up the board and crossed my fingers the layout was right (usually use Design Spark to do the schematic and then the foil pattern to error check, but after upgrading to ver 5 I couldnt get it to work and the idiots at there site wont respond to my6 help requests. I guess you get what you pay for, this was free).


 After checking power and wiring up the unit it worked great. I then installed the PWM that finally came today and it worked great. Case is a lot cleaner looking and cant wait to get the unit back on the mill and try out the speed control.



Feed works great, so I decided to clean up things a bit and put a guard plate over the limit switch assembly

More to come

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