Re: Re: Engraving and engine turning

-----Original Message-----
From: Bertho Boman <boman@...>
To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
Date: Saturday, July 31, 1999 8:51 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Engraving and engine turning

>From: Bertho Boman <boman@...>
>
>Hello Peter,
>
>I understand that backlash is not good and pre-load will in many cases fix

it.

>
>What I do not understand is why pre-load "up" versus removing the return

spring in the quill handle and let the weight of the

>quill pre-load it self "down" or even adding weights if needed. Also being

pre-loaded "down", the cutter can never catch and

>dig deeper.

Hi Berto
Because the return spring is on the pinion shaft it is not acting directly
on the quill, therefor any backlash between the pinion and the quill is
uncontrolled, if you preloaded the quill downover, it would be hanging on
the back of the pinion tooth, no matter how far you drove it with your
stepper motor, the quill is not driven down you would therefor have the
backlash in the upward direction which would cause problems, I much prefer
to have the quill preloaded up, it has been this way for a couple of
years now without any problems.

Peter Smith

>
>I have a related question but I will start a separate thread from the

engraving on that one.

>
>Best Regards,
>Bertho
>
>Peter Smith wrote:
>
>> From: "Peter Smith" <peter@...>
>>
>> -----Original Message-----
>> From: Bertho Boman <boman@...>
>> To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
>> Date: Saturday, July 31, 1999 7:25 PM
>> Subject: Re: [CAD_CAM_EDM_DRO] Re: Engraving and engine turning
>>
>> >From: Bertho Boman <boman@...>
>>
>> Bertho
>> If you have backlash on the quill, and it is not preloaded, when taking

a

>> deep or heavy cut, the action of the cutter will take over and pull the
>> cutter into the job by the amount of backlash that you have, not very

good

>> if you want a nice flat surface, hence the preload to keep the cutter up,
>> and the quill pulled against the pinion and worm drive.
>>
>> Peter Smith
>> >
>> >There are fancy "constant force" springs available but the simple/ crude
>> solution is to use rather long springs. That way the
>> >percent elongation is not large and the force is rather constant. With

the

>> spring system there will not be any significant mass
>> >added to accelerate and deaccelerate. I realize that this might not be
>> important in some systems but it is always interesting
>> >to compare options.
>> >
>> >It also surprised me a little that you are using it as a method of
>> pre-load. I thought the idea of weights and pulleys or
>> >springs is to reduce the load on the motor and make the load similar in
>> both directions. Thereafter the system's PID constants
>> >can be optimized and will be optimum moving both up and down.
>> >
>> >Bertho Boman
>> >========================================
>> >
>> >Peter Smith wrote: <peter@...>
>> >
>> >> Ian/Peter
>> >> I have been using the wire rope, pulleys, and weights ploy, for a

couple

>> of
>> >> years on my mill, it started as a quick fix to the backlash problem,

but

>> I
>> >> must admit it works very well, maintaining a constant load on the

quill,

>> >> instead of as with a spring the further the quill goes down the

tighter

>> the
>> >> spring gets the greater the load on the motor, but my god it does look
>> ugly.
>> >> The countrbalance is about 3lbs heavier than the quill, but as the Z
>> stepper
>> >> is at a ratio of 20 / 1 it does'nt seem to mind the preload.
>> >> I might get around to doing one of Dans permanent fixes, but I
>> suspect
>> >> that the quality of the rack and pinion on my far eastern mill might

not

>> >> allow such a proper cure. ( why upset something thats working ok)
>> >
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>Welcome to CAD_CAM_EDM_DRO@...,an unmodulated list for the

discussion of shop built systems in the above catagories.

>To Unsubscribe, read archives, change to or from digest.
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