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Help, I have 2 closed loop vexta stepper motors on a machine I have just bought. The machine has no drivers, I am looking for a 3 axis driver system, now can these closed loop steppers be run by a Bipolar or unipolar driver? or does it have to be a closed loop controller? I am not that bothered about the feedback system working as with the closed loop system, I just want to run the machine.
A closed loop stepper system consists of a stepper motor with an encoder either on the back of the motor or a linear encoder.
the closed loop would be handled by the controller not the driver.
you can use the motors as normal, you would just not connect the encoder.
Ok thts great, mechanically this thing is sweet, just I have no idea what I need to buy to get it to running on the electrics side.
This is the machine, I would like to get this running as a 3D router, any ideas on bits that are needed? Any help would be appreciated.:biggrin:
Not bad for £510... if you read off the part # on the motors or any other info we should be able to give you some clues!Quote:
Originally Posted by funkmonkey
yeh I thought it was a good buy....when I picked it up today the guy said he paid £24 at auction for it, insolvency deal....thanks a lot I thought, didnt really need to know that!
x axis - VEXTA ASM66AK-T7.2 CLOSED LOOP STEP MOTOR
Y axis - VEXTA ASM66AK-T7.2 CLOSED LOOP STEP MOTOR
z axis - VEXTA PK266-02B 2 PHASE STEPPER MOTOR WITH CLEAN DAMPER
There are quite a few optical limit switches all over it.
OK, I've added links to the data sheets to the parts above.Quote:
Originally Posted by funkmonkey
The closed loop (X, Y) motors are going to be a little tricky. They are geared 7.2:1. According to the operating manual the standard driver for these does 0.05deg/pulse, i.e. 7200 pulses/rev, which means the motor does 1000 steps/rev, some form of microstepping drive. This is great for a very accurate pick n place mechanism but far too slow for a router. You may have to look at replacing these motors, but note they are offset (motor body to shaft) due to the gearbox. Might need a new bracket making up.
The Z motor is a fairly conventional 2-phase bipolar or unipolar motor. 1.4A phase (bipolr series)
Thanks, so what I need is a new pair of motors and a 3 axis driver kit to make this work properly?
Will flog the Vexta's off on ebay I think then. What size motor roughly do you think I will need for this machine?
No worries on making bits I have a 3,000 sq ft workshop filled with machines, so I am all good.
Measure up the lead on the X & Y axis and then we can determine the motor speed and torque required for an appropriate traverse rate. Suspect 3Nm motors will do the job as the existing motors are 2.5Nm at 250revs/min in a 60mm case. A newer motor will do the same in a 34mm case so there is room to move. The existing have a flatted 8mm output shaft, but the smaller motors may have a 6 or 6,35mm shaft so some work on the couplings may be needed. Its probably not possible to use the current X&Y motors as they are not spec'd independently of the matching controller.Quote:
Originally Posted by funkmonkey
It looks like the motors are 1.2Nm holding torque so with a ratio of 7.2 that would be about 8.6Nm of holding torque, so the actual torque running would be about 4-6Nm depending on the speed /voltage.
You are right, you will need to dump the existing X and Y motors because of the gearbox, not specifically because of the max speed but also because of the 45arc minutes of backlash and that the system uses belt and pulley so that 45 arc minutes would equate to quite a bit of movement.
I would personally use a mid sized 34 frame motor if you are going to continue using the existing belts or going to a 60mm diameter (3Nm) motor if converting to ball screw.
I would also consider reducing the height of the router to make in a bit more ridged.
yeh I was going to chop a little out of the legs to get it closer to the deck to improve the stability, also the head does not move down any where near the base plate so it needs to drop down.
Thanks for the help you guys, so to recap:
Ditch the Vexta motors
Buy two new 34 frame motors
Drop the height of the x, y & z axis closer to the table
But what kit do I need to get this running? drivers, breakout etc?
Motors, Drivers, breakout board, power supply, pc and cnc contol software.
Quote:
Originally Posted by funkmonkey
Ok, so is any better than others as there seems to be a lot about?
Also the software side, we use Machine Strat, Delcam & Bobcad here. Do the drivers need specific headers in the G-code text to run?
Just Looking through a box of old motors I have here at work,
There are three with the following detail
1.8 degree step, Holding Torque 550mNm
2 VDC 2.8A
Are these any good? Noticed that you put down a torque of 3Nm so what is mNm?
Normally stepper drivers are totally dumb and only react to clock and direction.
So as long as you can get your software to generate clock and direction the driver should work fine.
Quote:
Originally Posted by funkmonkey
these drivers sound a little like me!!:dance:
3nm is 300mnm just like 300mnm is 30 ncm.
5.5Nm is a reasonable amount of holding torque and if you use the existing belt they should give you enough torque to run the machine, but you need to define what you are using it for to determine how much power you need.
Quote:
Originally Posted by funkmonkey
I want to build a router out of it, mostly for machining wood, but would like the ability to do the odd ally job too.
why, what wrong with it?
Maybe so but it’s a lot better than some of the tat I have seen floating around, thats for sure. I don’t need a massively robust machine, I own an aerospace tool room with many CNC machines, I just need this machine to help my dad who sits at a desk making 100's of wooden miniatures by hand, as his part time business. Just wanted to help him out a bit.
You wont be able to accurately do anything with ali, it will flex way too much.
reducing the height will help with the ridgidity.
I think that you could use it for routing wood and plastics but that is about it, but don’t expect too much.
You may also have a bit of hysteresis due to the belts if you try and move to quick.
cos its what I wanted to do.........
Kip, I know that is said in jest, but its getting personal. You may not agree with funkmonkey's purchase or the viability of what he wants to do, but thats no reason to cast aspersions...Quote:
Originally Posted by Kip
Irving (with my moderator hat on)
Hey I'm easy, no problem with me everyone is allowed an opinion.
My company makes tooling for casting house that manufacture turbine blades for both aero & power Gen.
To name a few,
V94, V84, V64, SGT5, GT26, GT24, GT13E, 13E2,13E3M, Tent 500, 700, 800, 1000, RB211, RB199,GEnx.............
The list is endless to be fair across many OEM's.
I'v only just noticed what machine it is !Quote:
Originally Posted by Kip
I never did check to see what it sold for, £500 ? Was it really worth that much money ?