View Full Version : 30 IPM is this inches per minute?
02-18-2006, 04:09 PM
I have been looking at getting plans to build a gantry routing table, but the plans says that the max speed, with the leadskrews that are suggested for the plans, is 30 IPM which I tryed to move my router 30 inches per minute and that is extreemly slow? I hope I have this wrong?
Please set me straight on this.
02-18-2006, 04:21 PM
Yes... IPM would mean just what you think.
What size table are we talking? If for a small rotozip type table 30 IPM would be ok... but for a 4'X 8' it be a (yawn) slow.
[This message has been edited by Tinkerer (edited 02-18-2006).]
02-18-2006, 04:33 PM
36"x 25" but I want one 36 x 48
any suggestions for plans for one this size
02-18-2006, 04:52 PM
Yeah, that's pretty slow, about two seconds to move one inch. I don't think the leadscrew or nut is going to overheat http://bbs.homeshopmachinist.net//smile.gif
Let's see- if the leadscrew is 10 turns per inch, and the speed is 2 seconds per inch, that's five turns per second, or 300 rpm. Maybe the speed limitation on the leadscrew is to prevent whipping of the shaft, which could occur if it's unsupported for some considerable length. That could well be a realistic max speed if the leadscrew is several feet long. Depending on the straightness of the leadscrew, it might be able to go faster without vibrating, or maybe not. I just opted out of the leadscrew approach and went to chain for my countertop saw, which has a traverse of 57 inches. The leadscrew did have too much vibration when going at the speed I wanted, escecially for the return of the carriage to home position. Instead, I'm using a motor/gearbox combo and sprocket and idler. With the ratios I have in that, one inch in two seconds is about as slow as I can make this carriage travel. A realistic maximum speed in my case is about 10 inches/second, but this is all about the gear ratio. At my fastest speed, the chain/sprocket/idler is still loafing. It sure is a lot quieter than the leadscrew and nut was. Either way, there's an exposed element, the leadscrew or the chain. I think the chain drive is going to be less troublesome because the teeth on the sprocket will tend to push foreign material through the links and thus keep the system working, whereas with a leadscrew, foreign material could end up jamming in the threads and the nut.
By the way, the chain on my system is a loop, and the bottom half of the loop runs inside a plastic tube. The exposed upper section, which has it's ends attached to the carriage, is shielded somewhat from the swarf products by the tube.
One of the problems with chain is that it will sag over long unsupported lengths, so the tension would have to be higher to keep this sag within limits. That means the chain has higher permanent tension loads on it, and the bearings for the idler and sprocket shafts will have to bear this pressure as well.
I hope some of this is useful to you.
02-18-2006, 04:52 PM
want to go faster? all it takes is more money.
More inertia to overcome means more power, larger drives, heavier ball-screws.
My cnc with 200+lb table can hit 120ipm.. but then them motors on it are about a grand each new. OF course you can buy them for a hundred each on ebay. OR more. Then the drives will set you back, and the transformer, and the controls from there on out are about the same.
02-18-2006, 04:55 PM
that's larken automation in Canada, it's a used machine.
Here's one that will do it.. $24,000
I have no clue how fast the Hitachi welding robots would go, but them red marks are the floor are the reach of the bot. About once a night one of the windows ce cpus would crash and it would go insane till it hit end stops. Meaning it could stick you with a tig or mig torch plumb through the innards.
Fast machines are dangerous, be they a fuel dragster or metal cutting machine. I watched a guy with a brush wiping milling chips, get the brush took away from him and his knuckles rapped. I laughed, a year later it happened to me. It wasn't as funny then.
[This message has been edited by David E Cofer (edited 02-18-2006).]