[justCNCit]

So

Just finished building this but am dismayed to find that the speed of the steppers doesn't even come close to being able to feed the router at the speed it has to go in order not to burn bits right out and the work.

Plus when taking deep cuts at minimum speed the router just stalls out.

Ive considered building a gear/pulley to gear down the speed but this is completely incompatible with this CNC machine.

Does anyone know of a router able to cut at a lower speed with some torque or do I have to upgrade to ballscrews/servos.

If so this CNC can plug itself up the ass after all this work.

[dertsap]

are you close to a princess auto , they have a small variable speed plunge router that has 1/4" and 5/16 collets , its onlt 38 bucks , ive got one for general woodworking and it works ok , or you could look at getting a craftsman

[dertsap]

oops !!


after looking closer at your pic , i guess you do have princess close by

what drivers and motor sizes are you using ?

[justCNCit]

sorry the pictures so fuzzy, the motors are 400 oz in Xylotex with their 4 axis drive box.

Fastest cutting speeds available with this machine is 30 IPM.

[cnczoner]

Perhaps you can get some type of speed controller in there -- depending on the type of motor in your router.

[justCNCit]

It has speed control, its just that it chops the AC current down so that it has little power at the lower RPM's. This has caused it to stall when entering a cut at 30 inches per minute.

I've been told it takes at least 100 inches per minute at the available feedrate in order to reach the right cutting speed. That is impossible without servos on this machine.

Since the steppers work fine at 30 IPM and that speed is fine for me, and many people run machines with steppers and routers, how do they get away with not burning out the work/cutters.

[ger21]

Using 1/2-10 5 start and a hobbyCNC board at 36V, people get 200+ipm with motors similar to those that you have.

[justCNCit]

I will certainly look into that.

[Mike Stevenson]

I don't want to blow my motors

justCNCit,

I think you should listen to ger21. He knows what he's talking about.

[dertsap]

i don t know what kind of resolution you would like but i ran my other system with 3/4-6 acme screws using 400oz motors and it worked great and fairly quick

[justCNCit]

Resolution doesn't much matter so long as it makes the machine work. I've given it some thought over the last few days and figure maybe it has to be done.

Have to source the screws/nuts and the drive board for it though, and at the same time have to work on a tool that tuned in the rails.

[rgoldner]

I believe you are seeing mid band resonance (if you try to tune the motors to higher velocity they don't work well). You need inertial dampers on the motors. Using a Xylotex driver you should be able to double the motor speeds with dampers. A better way to fix the problem is by using Gecko drivers (they are bring out a 4 axis low cost system very soon). Geckos have electronic mid band resonance correction built in.

[justCNCit]

Man, I don't know anymore. Invested all this time and cash into running 10 TPI screws with the Xylotex setup.

Kinda worked fine, of course my machine is very roughly setup and the bearings rub when it moves. That is, the thrust bearings primarily when the screws turn tend to rub, but the rails themselves are in such rough shape that sometimes when running at peak (30 IPM) we hit a spot on the rail and the motors just lose the step.

Realizing also that at 10 TPI there is alot of torque going to waste and theoretically hitting the correct torque curve these motors should be able to push the router reasonably enough through material.

Lacking input from more people running wood routers, I am leaning in Ger's direction and thinking of changing the screws.

I hate relying on math, because without engineering background there are many variables that could go wrong.

I built this machine the first time knowing some things were probably wrong in order to establish what needed fixing for the second time to make it work properly.

[dertsap]

don t let yourself get concerned , it looks like you more or less have all the right stuff , its probably just a matter of tweaking here and there and you should be rocking , if you look at joe's build for an example , i believe he used the hobbycnc board and 280oz motors with 1/2"-10 tpi and he's getting some good speed out of it ,correct me if i'm wrong but i think he's getting 200 ipm

[ger21]

, if you look at joe's build for an example , i believe he used the hobbycnc board and 280oz motors with 1/2"-10 tpi and he's getting some good speed out of it ,correct me if i'm wrong but i think he's getting 200 ipm

That's using 1/2-8 2 start I think. Most people building his 2006 machine switched from 1/2-10 to 1/2-8 2 start and doubled or tripled their top speeds.

With his new 4x4 machines, most are using 1/2-10 5 start and are getting close to 300ipm, but you may need Geckos to get that speed.

The Xylotex is known to suffer from resonance issues. If you want to keep using it, even with new screws, you need to make some dampers to get rid of the resonance. You'll need double shaft steppers though.

[justCNCit]

Seems to me avoiding dumb vibration dampers & change to Gecko wouldn't only solve the resonance issue but bump up motor efficiency somehow.

[ger21]

Yes, going with Gecko's would be the preferred route to take.

[justCNCit]

I was looking at Gecko drives, they are rated for 7 amps, and are $110 each, so that's about $440 + brokerage for new drives. Plus I'd have to learn how to configure them down to 2.5 amps?

But I guess the voltage is also controllable? where can I find the info I need to put this setup together. The screws aren't that big a deal I know where to get them. But the drives are alot more money for me and I am unsure how to proceed.

All I know is the project is stalled till this issue is fixed.

[ger21]

In the next few weeks, for a limited time, Gecko will be offering 3.5amp 50V drives for $29. The regular price will be $61 after a two week period. I think those would be a better choice. Look for the "Cheap Drives" thread for more info.

[dertsap]

I was looking at Gecko drives, they are rated for 7 amps, and are $110 each, so that's about $440 + brokerage for new drives. .

i didn t pay any broker fees , they sent them thru the mail , got them pretty quickly as well
you can t go wrong with them drivers , i used a stepperworld board before buying the geckos , the difference made me sick , i was happy with the fet3 until i found out how bad off it really was in compare to some better quality drivers
plus the freedom to add larger motors at any given time is priceless