Yes!  Thank you. 

> On Jul 22, 2020, at 11:07 PM, John Dammeyer <jo...@autoartisans.com> wrote:
> 
> 
>> -----Original Message-----
>> From: Thaddeus Waldner [mailto:thadw...@gmail.com]
>> Sent: July-22-20 8:43 PM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with 
>> Bostomatic BD18-2 to linuxcnc
>> 
>> Start with a 226 oz in
>> 
>> / 16 = 14.125 lb in
>> 
>> 5 threads per inch is the same as a belt pulley with a circumference of 0.2
>> inches
>> 
>> since our unit is in lb in, we need to go from a pulley with diameter of
>> Pi, to diameter of .2
>> 
>> thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force
>> 
>> divide that by your mass of 200lb and you get
>> 
>> 1.109 g
>> 
>> 1g = roughly 32in/s^2 so
>> 
>> 35.69 in/s^2
>> 
>> This is close to your ballpark guess of 40
>> 
>> Did I make a mistake anywhere?
>> 
> 
> 1 G is 32 ft/sec^2 or 384 in/sec^2 and that's where it falls apart.  Based on 
> real life the acceleration value is out by a factor of about 100.
> 
> And I don't understand why
> " since our unit is in lb in, we need to go from a pulley with diameter of  
> Pi, to diameter of .2"
> 
> It could well be that Jon Elson's explanation of linear force is incorrect.  
> 
> John
> 
> 
>> 
>> 
>>> On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson <
>>> nicklas.karlsso...@gmail.com> wrote:
>>> 
>>> On Wed, 22 Jul 2020 11:29:36 -0700
>>> Chris Albertson <albertson.ch...@gmail.com> wrote:
>>> 
>>>> I don't see any relation between max acceleration and max speed.
>>>> Acceleration is determined by (1) the mass of the table and (2) the
>>>> torque the motor can produce while speed is determined by the max RPM
>>>> of the motor.
>>> 
>>> Mostly agree though as torque usually depend mostly on current there will
>>> be a resistive voltage drop at higher torque which will reduce speed at
>>> higher torque, speed reduction is usually small. For example series
>>> connected DC motors and induction motors made for direct will reduce speed
>>> so there are exceptions but do not expect these are used as servo motors
>>> anyway.
>>> 
>>> Change gear ratio and use motor with same power different speed may change
>>> acceleration due to rotor inertia.
>>> 
>>>> It is very easy to buy a tiny motor with low torque that spins very
>>>> fast.  Or you can find powerful but slow motors.   Multiplying the
>>>> speed by three to find acceleration, if it works is just a
>>>> coincidence.  The factor could be 0.5 or 10.
>>> 
>>> High torque motors usually need a gear box or will become heavy. This is
>>> because flux and current is multiplied to get force while there is choice
>>> between current or flux in electric motor air gap, there is an optimal
>>> choice then either air gap area or diameter need to be increased. Magnetic
>>> materials will saturate then flux get high enough while conductor losses
>>> increase with current.
>>> 
>>>> There are two whys to go.  A mechanical engineer would start with a
>>>> requirement for a certain speed and a certain acceleration.  His boss
>>>> would give him those goals and then he would select a motor and drive.
>>>>  The other way used by most amateurs is to just buy a motor that
>>>> "seems right" and then test it to see what speed and a certain
>>>> acceleration you can get from it.
>>> 
>>> Not sure the boss will ask mechanical engineer about speed and a certain
>>> acceleration and then give these as a goal to the engineer. It is common
>>> boss read economics and contract but then it come to technical details odd
>>> things may happen.
>>> 
>>> 
>>> Nicklas SB Karlsson
>>> 
>>> 
>>> _______________________________________________
>>> Emc-users mailing list
>>> Emc-users@lists.sourceforge.net
>>> https://lists.sourceforge.net/lists/listinfo/emc-users
>>> 
>> 
>> _______________________________________________
>> Emc-users mailing list
>> Emc-users@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/emc-users
> 
> 
> 
> _______________________________________________
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users


_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Reply via email to