[multiplex]

I'm pretty happy with my router, it seems to consistently be able to do 80ipm. i could push it towards 95, but it has the chance to stall

but that makes me wonder, after seeing some routers on youtube - what should i expect to be able to run? i'm sure everyones setup is different, here is what i have

1/2"-5 Acme screws
425oz Nema 23 motors
1/16 microstepping

running mach3 at 45khz, and have a brand new 1.8ghz dual core computer

the new computer definitely helped to stabilize things.

i haven't tried to cut any wood at super fast speeds anyways - usually 25 - 30 ipm.

any feedback here would be great
Thanks!

[jcc3inc]

Sir,

One of the problems with acme screws is the low efficiency; it is somewhere around 20%. That means that you have only 1/5 the drive force that the motors put out. At 80 IPM or 1.333 in/sec you are running at 1333 full steps/second, not too bad. That would be 16x or 21328 pulses/sec.

I have always liked rack and pinion as a driving means. It is economical and much more efficient. Use 20 degree gearing and spring load your pinion into the rack. With some speed reduction of motor-to-pinion RPM, maybe 3:1, you should have good torque available. 20 DP gearing is readily avilable, rack can be had from www.stdsteel.com, 1/2x 1/2 x 6 ft for around $23 each in qty of (2), pinions can be had from Boston Gear or Martin Sprocket all at reasonable prices.

Regards,
Jack C.

[multiplex]

Ok yes - you have a very good point there. I forgot about the drag the lead screw creates.

Thanks!

[ger21]

Sir,

One of the problems with acme screws is the low efficiency; it is somewhere around 20%.

According to Nook, the efficiency of 1/2-10 2 start acme with a plastic nut is 57%. A little better than 20%.

[ger21]

What voltage are you running at. Voltage plays a large role in top speed. Double the voltage, you can roughly double your speed.

[microdesigns2k]

When you mentioned 'chance to stall', I assumed you meant the steppers stalling. At 80ipm, your screws are turning 6.6 revs/second. I think that is pretty good for the stepper motors. I generally don't run mine past 5 revs/second. But my motors are 300 oz-in 34 frames.

If you meant that the router is stalling, I have no idea what to expect. Mine is a 2hp vertical mill. I've never seen it slow under load.

I've read that microstepping at high speeds is less efficient at higher speeds. Perhaps you should try different step rates, including full steps. With a .200 lead, 200 full steps is still .001" resolution. Beware that the payback for this will be in strong resonance at certain speeds.

Dennis

[multiplex]

I'm running at 40 volts, which is pretty much maxing out my drivers.

all these things are good to keep in mind for the next machine. because there will always be a next machine

[zenbot]

Do you have a particularly heavy gantry that warrants the use of 450 oz./in. motors? If not you can gain a lot of speed going to lower torque 276 oz./in motors. The torque curve on 450 oz./in motors drops off at half the rpm of the 276. oz./in. Also, using gecko drives will blow your mind with their speed.

[Greolt]

I'm pretty happy with my router, it seems to consistently be able to do 80ipm. i could push it towards 95, but it has the chance to stall........................

........................i haven't tried to cut any wood at super fast speeds anyways - usually 25 - 30 ipm.

Had to laugh. I remember asking the same questions when I started this CNC stuff.

You're happily cutting at 30 ipm. I think that's what is important. Rapids don't matter that much. Unless your into "Mines bigger than yours..."

A couple of things that really do make a difference.

Get the acceleration up as fast as your machine will handle. That will affect cut times on most small jobs much more than rapids.

Second make sure you Z retract or rapid clearance or whatever your CAM software calls it is as small as practical.

Recently cut a complex Vee carve job. Took 2.5 hrs. Reduced the Z retract from 10mm to 1mm and it halved the cut time.

Greg

[ger21]

Do you have a particularly heavy gantry that warrants the use of 450 oz./in. motors? If not you can gain a lot of speed going to lower torque 276 oz./in motors. The torque curve on 450 oz./in motors drops off at half the rpm of the 276. oz./in. Also, using gecko drives will blow your mind with their speed.

Not necessarily. You can get 400-450oz motors that will still have 250oz of torque at about 1000 rpm. Look for the ones with about 6 amps rated current and 1.5V.

[ger21]

Second make sure you Z retract or rapid clearance or whatever your CAM software calls it is as small as practical.

Recently cut a complex Vee carve job. Took 2.5 hrs. Reduced the Z retract from 10mm to 1mm and it halved the cut time.

Greg

Somewhat related. Older versions of Mach3 had a slight delay when switching between G0 and G1 moves. The latest fixes this, and can also shave a fair amount of time. John Prentice posted a video (link) on the Yahoo group that demonstrated this.

[BobF]

You may also gain some speed by changing to a faster screw. 1/2 8 2 start and 1/2 10 5 start are available. These give an effective pitch of 4 and 2 turns per inch. This would increas your speed by as much as 5 times for the same motor RPM. The multi start screws are also more efficient than the single starts. You will have to do some calculations to see if you still have the required torque from the motors at a higher pitch, but many machines that started with 1/2 10 ACME are happy with 1/2 8 2 start.

[zenbot]

ger- good to know. Do you have a source for these motors?

[ger21]

Oriental Motor. I don't know the exact model number, PK 296 something I think. 400 oz, 8 wire, Nema 34, ~6 amp bipolar parallel. Keling has a similar spec motor for a little more than 1/2 the price, but don't have a torque curve for it.

[Greolt]

Somewhat related. Older versions of Mach3 had a slight delay when switching between G0 and G1 moves.

The latest fixes this, and can also shave a fair amount of time. John Prentice posted a video (link) on the Yahoo group that demonstrated this.

Gerry I searched the group for this and could not find it. Do you have a link?

Thanks, Greg