Re: [CAD_CAM_EDM_DRO] Re: Treadmill motors as Servos

Hi John,

I would aim a bit higher than 80 IPM. 80IPM is rather low for wood. I
would go for something like 150IPM. With ballscrews you could probably
go to twice that.

At 150IPM the screw will be doing 150 * 10 = 1500RPM.
At 35kHz (Mach3's middle kernel speed setting) with a 200 CPR encoder
the motor will do 35000/(200 * 4) = 43.75 RPS = 2626RPM
The ideal reduction ratio would be 2625/1500 = 1.75:1.

Your screws are quite small diameter so you will be very close to the
critical speed where they start to whip. Go here
<http://www.nookindustries.com/ball/BallCalculators.cfm> and look at the
inch ball critical speed calculator. It looks like your 32" axis will
probably have to be run a bit slower to keep under the critical speed.

Les


John Hansford wrote:

> Hi Les,
>
> I'm not sure HOW to calculate it on this machine I'm making.
> I'm not after great speed...80 IPM would be plenty good.
> It's only about half done. That's why I got interested
> in using servos before I made all the brackets & hardware.
>
> It uses 1/2-10 acme for a screw. I want it to cut 3/4" thick MDF
> shapes. It'll have a cutting area of 28" x 32".
>
> I'll rig it it to use a router or an R8 spindle, so the speeds
> will vary between 1000 to 30,000 rpm. The reason for that is the
> spindle is quieter and generates much less airborn dust. It's
> an experimental thing to try out before welding up a good single
> purpose production machine.
>
> John
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Leslie Newell <lesnewell@...>
> wrote:
>
>> Those pulleys are a lot cheaper than I can get them here in the UK.
>> Shaftloc or other taper fittings are good. Apart from being a pain to
>> make, traditional keyways have a tendency to come loose and wear. One
>> machine I repaired a while back had a key that had worn nearly round.
>> The keyway was a horrible mess as well.
>>
>> Have you actually calculated the reduction ratio you need? My mill
>> worked out 4:1 but your machine may be different. What type of machine
>> have you got and what materials are you cutting? What is the maximum
>> rapid speed you want? Also what is your ballscrew pitch?
>>
>> Les
>>
>>
>> kz1927 wrote:
>>
>>> Hi Les,
>>>
>>> Your consideration and experience is Greatly simplifying what
>>> could be an expensive and frustrating, trial & error experience
>>> for me.
>>>
>>> I am as grateful as a person can be.
>>>
>>> I'll go with the surpluscenter encoders...they're proven to work
>>> on your setup. Plus I'll have a few spare motors for (something)?
>>>
>>> I'm looking at these pulleys
>>>
>>> http://www.sdp-si.com/estore/CoverPg/Shaftloc/HTD5_Pulley.htm
>>>
>>> I'd get a 20 and an 80 for 4:1 reduction.
>>> I think I've got that right.
>>>
>>> John
>>>
>>>
>>>
>
>
>
>
>
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