Author Topic: Transmission for table feed (Read 11539 times)

scout800 · « **on:** November 23, 2014, 10:09:41 PM »

Hello Gentlemen, I'm trying to build a transmission for a table feed on my small mill. I have the basic rough design in my head , I have this gear motor that I want to use the problem is it only turns 9 rpm with no load. I understand gear ratios so may bee i can overcome this . My question is what would be a good max rpm to end with? I plan on using a speed controller to turn rpms down from max. I will also incorporate a neutral and reverse in trans might be easier than reversing current since I have to have a neutral any way. Am I going about this wrong? Should I scrap the idea and do it another way? I was just trying to use what I have. Below are pics of gear motor and the end of my mill table. Any input would be helpful thanx in advance

Dave.

Lew_Merrick_PE · « **Reply #1 on:** November 24, 2014, 11:49:34 AM »

Hi Dave,

We will need more information if we are going to properly confuse the issue. Where are you located? The answer may depend upon where you are located. What is the pitch of the leadscrew you are driving? There are probably other questions that have escaped what's left of my mind.

Let's assume you have a .100 inch/rev. leadscrew. Further, let us assume that you may wish to run a roughing cut with a 4-flute cutter at 2500 rpm that works out to .005 inch/flute. That says that you need, in the cut at least, 2500 X 4 X .005 = 50 in/min cutting speed (mind you, these "numbers" were pulled out of quality thin air). More to the point, you want to "rapid" from "stop to stop" in (say) 30 seconds. If your "stop to stop" travel is (say) 20 inches then you will want to drive it at 20 / .100 / .5 = 100 rpm.

If I am not mistaken, the motor you have can accept either a PWM or SCR type speed controller. This is not my field, but there used to be relatively inexpensive (SCR) speed controllers that gave you (from memory, mind you) 20% to 150% of rated (rpm) speed for such motors. You would then have to ratio gearing from there.

Does this help?

BillTodd · « **Reply #2 on:** November 24, 2014, 12:33:09 PM »

just happen to have a bridgeport powerfeed in for repair, it has a range from 15-875 mm/min (1/2 - 34 inches/min), plus rapid motion

Its motor must be the better part of 1/2hp (375w), your 1/15hp (50w) may limit your maximum speed somewhat!

Bill

bertie_bassett · « **Reply #3 on:** November 24, 2014, 04:20:57 PM »

how fast do you currently turn the handles when machining? that should give you a reasonable number for max working rpm of the feed shaft.
can the gearing in that box be altered or are you thinking of adding external gears to increase the speed? if you go external, then a set of tumblers would give you forward, reverse and a neutral in the middle.

scout800 · « **Reply #4 on:** November 24, 2014, 09:16:29 PM »

Thank you Gentlemen for taking the time to steer me straight. Lew, I'm not sure of the tpi on the lead screw , however you are right it is .100 per revolution. My table has 16 inches travel stop to stop, total of 160 revolutions. I was allready thinking of 10:1 gear ratio but may bee I should up that to 15 or 20 to one so that i can achieve the speeds I need.
Bill you may be right I didn't realize the feed motor on the bridge port at work had that much power. I did some checking today and I do most of my machining at 80 rpm but that screw is .200 per rev. so I think that would be the same as 160 rpm on mine with no load of course.
Bertie, I really haven't machined any thing yet . I plan to use external gear box, was thinking of something like the reverse, neutral, and forward like they do with the feed screw on my lathe . Not sure what tumblers are but would like to know , where would i find pics of those?
Forgive my ignorance please, you guys are a great help to me I appreciate your valuable time and wisdom.
Thanx Dave.

awemawson · « **Reply #5 on:** November 25, 2014, 04:21:51 AM »

Tumbler reverse is described nicely here:

http://www.lathes.co.uk/latheparts/page16.html

BillTodd · « **Reply #6 on:** November 25, 2014, 06:20:59 AM »

I thought you might like to look inside a couple of commercial units:

This one is an Align (pretty much the same as the Servo Units)

The DC motor is 110v @ ~3A max it uses a electrical reverse and a simple dog clutch

BillTodd · « **Reply #7 on:** November 25, 2014, 06:26:23 AM »

This one is a Bridgeport:

The motor plate is knackered but judging from size it looks to be about 1/2hp.

Inside is a bevel gear and a dog clutch. The clutch is engaged by a spring on the shaft. it is held off by the lever (with the bent axle!) and spring (left). The operating rod (centre vertical) has a cam that releases the lever.

Reverse is electrical.

BillTodd · « **Reply #8 on:** November 25, 2014, 06:31:43 AM »

And this is one I made for my Drill/Mill :

The thing started life as a bed lift mechanism.

The dog-clutch is engaged with a solenoid. Reverse is electronic. Power is limited to about 75w, No rapid. (my mill has roller nuts, so there is very little friction on the X axis lead-screw)

John Hill · « **Reply #9 on:** November 25, 2014, 02:03:02 PM »

Slow and steady is more useful than rapid, rapid is good but not essential if you can easily disengage the motor from the feed screw just use the handles for positioning.

scout800 · « **Reply #10 on:** November 25, 2014, 07:22:34 PM »

Andrew , that is what i thought tumblers were thank you for the pic. Bill, you have been more than help full nice pics , and again thank you for your time it really helps me. John you are right, most of the speeds i use are slow any way. I think mid to slow speed is better than no speed, I was thinking last night it's only a 16 inch table stop to stop. How often would I be machining stop to stop ? Probably not very often , more like 4 to 8 inches at the most. I am used to using the 48 inch table at work and I use the rapid a lot. I guess I was comparing apples to oranges and probably shouldn't have. Any way I will continue on with the project and i will post picks and keep you posted. Thanx again Gentlemen.
Dave.

BillTodd · « **Reply #11 on:** November 28, 2014, 06:24:37 AM »

here's another idea you might concider...

how about an automatic clutch so all that is required to operate it is a simple switch?

The video show an anti reversing mechanism

Two-way anti-reverse transmission 1b:

by connecting the leadscrew to the green shaft, the handle to the red shaft and power feed to the blue ring (currently fixed) any motion of the blue ring will drive the green shaft but motion of the red shaft will not try to drive the blue ring.

scout800 · « **Reply #12 on:** November 30, 2014, 09:37:08 PM »

Hi Bill, wow that video is really cool . The things people think up amaze me, that's awesome. However , I saw some where where somebody was using a planetary gear set to speed up an end mill. So I thought this might work, so I went to Harbor Freight and bought a 1\2 inch air drill for a whopping $24.99, took it home and dismantled it. It turns out it has double planetary gear set, with an 18:1 ratio. I'm going to try and use it. If I make a simple spring loaded in/out cog like in the bridgeport drive , I'll locate it between the chuck and the drive motor. I'll then make a bearing support for the other end (sort of a pillow block if you will) then mount it all to a plate that mounts to my table. The drive motor says you can reverse it by switching two wires , so i will wire in a on/off/on toggle switch for directions through a variable speed. I'm sure when that time comes I will need some assistance. What do you Gentlemen think? Is there anything I'm missing ? Any input is helpful . Thanx for the interest.
Dave.

scout800 · « **Reply #13 on:** December 06, 2014, 09:10:46 PM »

Hello , This is my first build log so bear with me please. I had some time to go out in the shop today to start on my transmission project. If you remember I decided to use a 1/2 drill planetary set to speed up motor rpm. After I took it apart I cut the end of drill case with the band saw and put in lathe to square the end, with this screwed into the planetary end of the drill it supports the rear ring gear. Then I machined the air vein rotor to accept a new press on bearing and pressed it on. This will be the end that gets the coupler for the lead screw. Next will be the supports to mount the assembly to a plate that the motor will be mounted too. I'll keep you posted thanx for looking.
Dave.

BaronJ · « **Reply #14 on:** December 24, 2014, 12:40:33 PM »

Hi Dave,

I used a car wiper motor for my mill table feed. I used a tumbler mechanism to reverse the drive direction and a variable voltage power supply to get variable feed rates.

scout800 · « **Reply #15 on:** December 24, 2014, 09:08:49 PM »

Nice idea Baron, are you running that on a variable to 12 volts or going higher with the voltage? I havent been able to get out in the shop for the last few weeks to continue my build, hopefully i'll be able to get out there over the holidays i'll keep you posted . Thanx for the interest in my build, happy Holidays every one .

Dave.

BaronJ · « **Reply #16 on:** December 25, 2014, 12:27:22 AM »

Hi Dave,

This is actually the second version that I built, the first being a little slow because the gears were too large. This one also has the motor and output shaft on the opposite side.

In use I find that anywhere between 6 and 18 volts covers the range of speeds that are most useful. I can bump up the voltage to 30, but this is really only a medium traverse speed, about 5 meters a minute.

If you want more details let me know.

scout800 · « **Reply #17 on:** December 25, 2014, 12:00:41 PM »

Nice work Baron! This is actually turning into a nice thread I think, and hopefully help full to others. My question is , is there a way to regulate 110 v house current down to make something like that work or would you need some sort of other power supply? I think your idea using the wiper motor is an excellent idea, they have plenty of torque and I think it's a worm gear drive isn't it? Thanx for posting, any more info, on this would be great.
Dave.

BaronJ · « **Reply #18 on:** December 25, 2014, 12:53:59 PM »

Hello Dave,

First Christmas Greetings to all.

I did a build log on another forum for both versions of the mill table drive using two different salvaged wiper motors. Both came from the local scrap yard for next to nothing, also both wiper motors had dual speed motors giving a fast and slow speed. As you can see from the pictures they are handed and one also has an output shaft that is only about two thirds the length of the other. Both wiper motors have an M8 nut securing the motion arm onto a splined taper at one end of the drive shaft. The other end goes through the "Mazak" bell housing supported by a sintered bronze sleeve bearing to a plastic or fibre worm wheel that is driven by the worm machined onto the shaft of the motor armature. The worm wheel is prevented from floating by the plate that carries the switches for stopping the motor when it has done one revolution. The float control mechanism on the armature is slightly different on both motors. One has a thrust ball at the worm end of the shaft and the other has a washer at the armature end of the worm that bears on a short sleeve bearing. On both wiper motors the commutator end bearing is a plain sleeve with an oil wick surrounding it. Both wiper motors run in the same direction for the same voltage polarity. Whilst these wiper motors will run in either direction, they are intended to run in one direction only. This fact was the reason for choosing to use a tumbler mechanism for reversing the direction of table travel in addition the tumbler allowed the table to be disconnected so that the right hand, hand wheel could be used to set the table position manually.

With regard to the power supply: I have not yet got around to replacing my variable voltage power supply with a speed controller. I did find a very nice low voltage transformer that will provide 24 volts at 2 amps in the scrap yard, but have to design a power FET controller to use with it. Something like a 555 to produce a PWM signal to a power FET is the sort of thing that I have in mind.

I'll post some pictures and come back with further info.

BaronJ · « **Reply #19 on:** December 25, 2014, 01:12:15 PM »

Hi Dave,

The first two pictures are general shots of the drive taken whilst testing and making the tumbler lever. The next two pictures are from underneath showing the indent mechanism to provide positive positions for the tumbler. There is a strong spring (not shown) used to press the long boiler rivet head into the indent, placed over the rivet shaft. The bottom picture was taken whilst testing that it actually worked to drive the mill table as desired.

scout800 · « **Reply #20 on:** December 26, 2014, 10:06:57 AM »

Thanx Baron, you have a finely honed imagination. That is a nice quality to have , and fortunately that quality seems to be in abundance on this site and makes it rather interesting. Unfortunately that quality seems to be dwindling out in the world, oh well at least we have a place we can go to supplement our qualities. Thanx for sharing I appreciate it.

Dave.

Mike Bondarczuk · « **Reply #21 on:** January 28, 2015, 04:42:37 PM »

Hi Baron,
Just found this thread and have been looking for an x axis motor drive for my old Chester 626 mill as the new commercial units do not fit the short shaft fitted.
Would you be able to indicate where your build log is sited so that I can find it and have a look to see how I can also use a windscreen wiper motor as a drive unit.
Many thanks in advance,
Mike

BaronJ · « **Reply #22 on:** January 29, 2015, 09:04:36 AM »

Hello Mike, Guys,

This is where the build log is :-
<http://www.homemodelenginemachinist.com/showthread.php?t=23130>

I think I did another one somewhere. If I can track it down I'll post that one as well.

News:

Author Topic: Transmission for table feed (Read 11539 times)