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| scout800:
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:
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:
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:
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:
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. |
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