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Messages - joeaverage

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6431
General Mach Discussion / Re: One stepper Motor Acting Up
« on: October 05, 2017, 07:29:15 PM »
Hi,
sounds like either noise (possible) or a bad connection (probable) to the DIR terminal of your driver.

Can you connect your nominally 'bad motor' to the good driver?

Craig

6432
Hi Mick,
kool the SEM 30 series looks to be 1.2Nm in absence of fan cooling. That works out to about 192 oz.in.

Remember that a servo retains that torque right up to rated speed whereas a stepper does not. Assume a stepper
has about 1/4 of its rated torque at 1000 rpm. For a stepper to have 192 oz.in at 1000rpm means it rated torque
will be about 768 oz.in .

All you have to decide is 'if my stepper can manage 1000rpm will my axes be sufficently fast for my purposes?'
If not the you are into servo territory, steppers of ANY type are going to struggle at high speeds.

Craig

6433
General Mach Discussion / Re: A Good Source for Bit ?
« on: October 05, 2017, 05:36:20 PM »
Hi,
I use a lot of really small endmills for circuit boards and I get them from
http://stores.ebay.com/CARBIDE-PLUS?_trksid=p2047675.l2563
Great value for money and mainly Kyocera Tycom brand.

Craig

6434
Hi,
yes the parallel port continues operation along with Modbus at the same time.

Craig

6435
General Mach Discussion / Re: Gear Reduction question.
« on: October 05, 2017, 07:31:23 AM »
Hi,
2500 lb is just an informed guess. The actual stall pressure could well be more, much more.

If using half stepping the motor motion will be pretty harsh. The main reason for using microstepping is for smooth motion and the
illusory sense of increased resolution is very seductive however false it may be. You could try using 8 or 16 microstepping, the increase in smoothness
of motion may mean that its easier on the ear and may also be cooler running.

Steppers do run pretty warm, I back the current off on my motors to have them run a little cooler but they still get to 50-60 degrees C on the outside
and I imagine closer to 100 degrees inside....doesn't seem to do any harm. Whether they would stand that 24-7 as in industrial use I suspect not
but they have given me about 1000 hrs a year for several years so can't complain.

Craig

6436
General Mach Discussion / Re: Gear Reduction question.
« on: October 05, 2017, 03:00:07 AM »
Hi,
two phase steppers which are by far and away the most common move 1.8 degrees per full step, or 200 full steps per revolution.
If Mach3 or some other device pulsed the Step pin of your drive the motor would turn 1 revolution. If your stepper driver can execute half steps,
and most can, then 400 pulses are required for 1 revolution. If your drive is set to execute '8 step microsteps' then 8 x 200 =1600 pulses are
required to turn 1 revolution.

Most of us would like to believe that because we can turn an 8 microstep motor just one pulse at a time it can achieve 1/1600 th of a revolution
per pulse or 0.225 degrees per step, that is a nice fine resolution. In fact it doesn't work that way at all but nice to think that it does. Resolution is
reliably increased at half step but at quarter step it loses its reliability and accuracy. So why does everyone microstep... because steppers are smoother
when operated at 8 or 16 step microstepping.

For your application do you require very fine control? Given the gear reduction of the screw jack even 1/2 step will give you plenty of resolution.
1.8 degrees x 1/2= 0.9 degrees. 0.9degrees/6 (gear reduction)=0.15 degrees. With a pitch of 16 TPI that results in a resolution of your presshead
of 0.02 thousandths of an inch per pulse. Yeah, that's right 50 pulses for 1 thousandth of an inch...plenty good!

Steppers lose their guts when going fast, they have something like half their torque at 500 rpm. Assume you want your press to have plenty of ompf
so decide a maximum speed of your stepper is 500rpm. The maximum speed of the presshead would be 500/96=5.2 inches per minute, not really fast
but useful. Trying to work out how much ompf it got is a bit of a guess because with a large gear reduction and fine thread a large part of the input
torque it lost to friction. I would make a stab and say your 1600 oz.in will be 800 oz.in at 500 rpm and half of that lost to friction ie the actual torque
available for useful work is 400 oz.in If the diameter of the screw jack is 1 inch then the tangential force at the outer periphery of the screw is 800oz
or 50lb. With the thread mechanical advantage of (2 x PI x 1/2(radius))/ 1/16(pitch)=50.2 Therefore your presshead thrust should be in the region
of 50 x 50.5 =2513 lb. DON'T stick your finger in it! Bit of a sketchy calculation but probably close enuf for you to decide if you wish to pursue the idea.

Just goes to show what decent mechanical advantage can do.

Craig

6437
Hi Mick,
can you post some more info about your existing servos, rated torque, rated speed, frame size etc. Replacing them will require matching
specifications which can be tricky as different technologies (brushed DC vs hybrid variable reluctance) will use different figures of merit.

Craig

6438
Mach4 General Discussion / Re: Tool Height offsets ignored?
« on: October 04, 2017, 10:25:33 PM »
Hi Allen,
that is exactly the sort of thing that Mach4 makes possible. Is quite a steep learning curve to get there but
the flexibility of Mach4 outstanding.

Craig

6439
Mach4 General Discussion / Re: Tool Height offsets ignored?
« on: October 04, 2017, 09:42:13 PM »
Hi Allen,
I don't know that its related but there are two modes of operation with regard to tool numbers.
In one mode the tool number is the currently used tool  whereas in the other mode the tool number is the NEXT tool
that will be used by the current job.

Depending on the mode you may not wish an offset to be applied YET.

My understanding is that this mode 'tool number is next tool' allows the tool changer to preposition itself and save time
when changing tools, highly valuable in a production machine.

Craig

6440
General Mach Discussion / Re: Motor Tuning with 2 motors on X Axis
« on: October 04, 2017, 05:04:14 PM »
Hi,
yes the 'steps per', velocity and accel must all be the same. You can cause a motor to run in opposite direction
by swapping ONE winding OR reversing the Dir pin (active low vs active high).

Craig

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