Re: MaxNC modifications

On the Ah-Ha software there can be a problem. I had one customer that had my
2 amp drivers and ran into a problem with lost steps. We finally figured out
that there is a timimng set up in the ah-ha set menu. We increased the time
and the prblem went away.
Dan
-----Original Message-----
From: Tim Goldstein <timg@...>
To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
Date: Tuesday, June 15, 1999 8:00 PM
Subject: Re: [CAD_CAM_EDM_DRO] MaxNC modifications

>From: "Tim Goldstein" <timg@...>
>
>Jon,
>
>I am sure you said, but what are you using for a controller? How many amps
>are you running to the motors and at what voltage? What is the volt & amp
>rating of your motors? What is the max feed rate you are trying to achieve?
>
>I think you can safely assume your lost steps are not due to the software

at

>this point. From my playing with a number of software products I have

pretty

>well come to the conclusion that if you are having lost steps it is not the
>software that is usually at fault. Do you have lost steps even at very slow
>feeds or are the lost steps most common at fast rates? The torque curve on

a

>stepper falls off very rapidly with increasing RPM, so if you try to go too
>quickly you can easily get to the point of having too little torque to get
>the job done even with very large motors (actually, lager motors tend to
>drop off in torque faster than small ones and turn less RPMs). You can also
>have a problem if you have a very slow acceleration rate and your motor

hits

>a harmonic in the ramp up. Often if you increase the acceleration you can
>get past the troublesome RPM without losing a step.
>
>A problem I had that drove me crazy was phantom steps. It seems that RF off
>the drive circuitry was inducing a signal into the step wiring on one of my
>axis. It was manifesting as lost steps when it really was unwanted steps. I
>ended up curing this by shielding the wires in a wrap of aluminum foil and
>grounding it at one end. Maybe you could also use ferrite filters?? (can

one

>of you electronic gurus help explain if this would be a useful method? Jon,
>Mo, ?)
>
>I am sure with the help of people on the list we can figure out why you are
>losing steps and get it fixed.
>
>
>Tim
>[Denver, CO]
>
>
>> -----Original Message-----
>> From: Jon Anderson [mailto:janders@...]
>> Sent: Tuesday, June 15, 1999 7:10 PM
>> To: CAD_CAM_EDM_DRO@onelist.com
>> Subject: Re: [CAD_CAM_EDM_DRO] MaxNC modifications
>>
>>
>> From: Jon Anderson <janders@...>
>>
>> Andrew Werby wrote:
>>
>> > [What is the advantage to using Aha software on the MaxNC, over
>> using their
>> > supplied software?]
>>
>> Stock setup way too wimpy and slow. While I'm sort of playing around
>> with my MAX,
>> I do use it in my business, and my dad uses it a lot (learning CNC in
>> his 70's!)
>> for some commercial work he does. We needed more performance. Tried the
>> step/direction
>> version with Cyberpak drivers and MAE motors and found we were losing
>> steps. Bought
>> the PacSci motors (from Bill Griffin, used, he has no more...), still
>> losing steps.
>> Bought Compumotor drivers (brand new, obs stock) from a motion control
>> outfit in
>> Florida (can dig up the name and URL), still losing steps.
>> Tried Ah-ha software both to try and cure lost steps, and for a better
>> interface, better
>> handling of radius comp, and the ability to search directories for files
>> and not have
>> to dump out of the program just to look up a filename. Still losing
>> steps btw, and have not
>> had time to dig deeper.
>>
>> > [Were these easy to mount, or did you need to machine new
>> mounting plates?
>>
>> Plates use existing holes in MAXNC. Motor attaches to standoffs to
>> accommodate
>> helical couplers.
>>
>> > [Where did these come from? Are they what Aha recommends?]
>>
>> Ah-ha was the last item purchased, I'm sure they'd prefer we had bought
>> their whole
>> setup. Maybe we should have...
>>
>> > motor mount plates with preloaded ball bearings to
>> > handle thrust loads,
>> > [Were these something you purchased or built from scratch? ]
>>
>> Fabricated the plates and the shaft. Leadscrew attaches to the shaft
>> same as stock on the MAX.
>> Screw side has hex for wrench, other side has 5/16 nylock nut to adjust
>> play in bearings.
>>
>> >
>> > BS&A ActiveCam nuts and 16 pitch screws,
>> > [Are these ball-screws, or is this an anti-backlash modification to
>> > standard screws?]
>>
>> Acme screws, and an attempt to cure backlash. Mostly successful. Nut
>> screws into 1/4" AL
>> plate that in turn is screwed to saddle. These nuts are available in
>> V-thread, so you
>> could fit them to the stock screws EXCEPT that they mount outside the
>> saddle so screws
>> must be extended or you lose travel.
>>
>> > [Do you think they would fit a stock zero-backlash nut?]
>>
>> (referring to the Thomson econo ball screws) No, probably not. If one
>> wanted to play with
>> ball sizes, one could probably get down to little or no backlash. For
>> the size machine you
>> are thinking about, you will want the larger 5/8 screws that Dan
>> mentioned. The small screws
>> over long lengths can whip at higher rpm, and buckle under compression.
>> They would be fairly easy to adapt to the MAXNC and could be fitted to a
>> Sherline if one had
>> access to a full size mill for the modifications. Would be very tight
>> however. These little
>> ballscrews might also work well to CNC a smaller lathe. The sample I got
>> is useless for any
>> CNC testing as it's too short, but I'm going to purchase a longer screw
>> and two nuts to play
>> with.
>>
>> Control systems? Heck, wish I knew. Still having minor lost step
>> problems. Wish I had a local
>> expert that could come over and tell me what I've done wrong...
>> For econo linear bearings in a router application, personally I think
>> I'd look around for some
>> surplus Thomson ball bushings and fully supported rails.
>>
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