Re: Low cost Servo Controller

David,
A manual Bridgeport is worth more as a manual than it is after spending a
lot of money converting it to CNC. Instead, find a Bridgeport BOSS 3, 4 or
5. they sell for around $2500.00 and have the ballscrews, stepper motors and
power supplies already in place. Usually they have a logic board problem and
that is not a problem if you are converting to a PC control.
You could sell your manual for enough to get 2 of the boss machines.
Darrell

----- Original Message -----
From: David Howland <dhowland@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Wednesday, September 15, 1999 10:11 AM
Subject: RE: [CAD_CAM_EDM_DRO] Low cost Servo Controller


> From: David Howland <dhowland@...>
>
> Dan your post answers a lot of questions for me. First of all, the quotes
I've got on ballscrews came in the $800 range. This made me question if the
total expense was worth it. From the McMaster-Carr catalog, Bridgeport
Ballscrew kits are in fact $742.86, however, as you suggust, the components
are less and might be applied to whatever makes since. I have a limited
amount of room in my totally manual shop, however, I do have enough room for
a smaller mini-mill and as you are doing, perhaps converting a smaller new
addition to the shop and leaving the Bridgeport to it's 90 degree turns will
enhance what I can accomplish without exceeding more than $5,000 in total
additional cost. What do you suppose I might be able to do with $5,000 for
a mini-mill conversion including all the software to drawing a part on the
screen and cutting it out of 6061 on the mill? Some of the mini mills don't
look very strong. Something with a little heft to it?
>
> At that point, how bad was EMC to convert? What do you like about Dan 's
controller?
>
> David Howland
>
> -----Original Message-----
> From: Dan Falck [SMTP:dfalck@...]
> Sent: Tuesday, September 14, 1999 6:10 PM
> To: CAD_CAM_EDM_DRO@onelist.com
> Subject: RE: [CAD_CAM_EDM_DRO] Low cost Servo Controller
>
> From: Dan Falck <dfalck@...>
>
> Dave,
>
> I thought that running with acme screws just plain sucked. The program
> that I was running at the time- Dancam had backlash compensation, but my
> stepper system at the time was underpowered and consequently lost steps
and
> ran too slow. I did program like it was a manual mill, but losing steps
> made it impossible. One time, I was milling out a pocket in a piece of
> cold rolled steel, taking 1/8" deep passes at a time. The machine lost
> steps every pass and I didn't relize it- when it was done, the pocket was
> out of shape and the end mill was chipped up. The next day, I called
> Rockford Ballscrew and ordered a pair of 5/8" ballnuts and ballscrews.
> They cost $275 ( rolled thread and double preload nuts). It was a
> decision that I haven't regretted. I can set the preload for less than
> .001" backlash by tightening up the knurled nuts. Everything is much
> smoother now and the system is more reliable. Later on, I added a more
> powerful stepper driver system.
> Over a year ago, I bought Maxnc Deluxe to run the system. It seemed to
run
> okay. It's simple to setup and runs a lot of G-codes. It has backlash
> compensation as does every other PC cnc program out ther. But, when I
was
> running some production parts, I would occasionally ruin a part with some
> missed steps ( a bunch of missed steps at a time). It seemed really odd.
> The error always seemed to come up at the same point in the cycle ( this
> was a fixture with 7 islands loaded with plastic parts). Soon after that,
> I loaded EMC onto the machine and never got that error running the same
> parts. So, I don't know if some software can contribute to lost steps,
but
> it sure seemed that way to me.
>
>
> Dave, right now I am retrofitting a new mill- a little RF-45 bedmill. It
> will have ballscrews on it. The Acme screws are going in the scrap bin.
> McMaster Carr sells a lot of different ballscrews and ballnuts for general
> industrial work. These certainly aren't for toolroom applications, but
> will work fine for most stuff. Currently, I have in the shop ballscrews
> and ballnuts 3/4" dia. that are going in the machine. They sold for $30
> each. The ballscrews go for $1.64 per inch. This is very reasonable.
> Saturday, I made a yoke for the X-axis that holds two ballnuts and adjusts
> for preload. Ballscrews aren't that hard to install and they aren't that
> expensive anymore.
>
> Software: I am a convert to EMC. There is much more potential to it
than
> with any Windows/Dos software. Fred is writing new code for it every day
> and he's getting paid for it! That's the best value for our tax dollars
> that I've seen. Go back to the beginning of the Archives on our list to
> see all the reasons for me liking it.
>
> Current shop setup:
>
> Mill/drill
> 470 oz-in steppers
> 5-6 amp half step drives
> 15 amp 24 volt power supply (36 volts with no load)
> 5/8" ballscrews
> EMC running the machine
>
> Sherline for light engraving
> 65 oz-in stepper Y axis
> 110 oz-in stepper X axis
> 100 oz-in stepper Z axis
> 2.5 amp half step drives
> 24 volt power supply from DEC printer
> regular Sherline leadscrews
> Maxnc running the machine
>
> Index Knee mill ( baby knee mill)
> Acme screws
> human running hand wheels and sweating profusely- Hmm, this needs to be
> retrofitted!
>
> Next machine in shop (within two weeks):
> Rong Fu RF-45 mini bedmill
> some sort of hybrid servo system from Dan Mauch
> 3/4" ballscrews
> EMC running the machine
>
> That's all I can type for the night. Time to make some more parts.
>
> Dan
>
>
> At 03:01 PM 9/14/1999 , you wrote:
> >From: David Howland <dhowland@...>
> >
> >Dan (Falck), It seems as though you have a fair amount of experience in
> the area I am exploring. Others may also have this kind of experience as
> well. You have run CNC without ballscrews. You said you tried this and
> upgraded to ballscrews after running without them for a few months. Aside
> from the cutter sucking the table out of position, as it can in manual
> milling, was a major part of the NO FUN aspect of working with the
> backlash, the fact that you had to program in a manner to adjust for it.
> That is, before changing directions, add steps to the program just to deal
> with the backlash? Was that less fun than what you had to do to keep the
> cutters from sucking the work into themselves? Your third experience of
> loosing steps I suppose meant that you had to reduce the feed rates to
> reduce the torque required from the stepper motors? Did you experience
the
> steppers loosing steps because of fast table moves, such as Home, jog or
> power supply overloads?
> >
> >If you had more speed and no lost steps, in your case, how important and
> how expensive is the ballscrew? Was the aspect of the cutter sucking into
> the work a major or a minor issue in the attention required to work around
> that problem?
> >
> >When Fred got EMC up for steppers, did you bring up EMC for your shop?
If
> not, what operating system do you run and what software and hardware do
you
> run in your shop? When you move into servo systems, what cost effective
> options sound good to you? What does it take to make that transistion?
> >
> >Thanks for your help.
> >
> >David Howland
> >
> >
> >
>
>
>
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> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
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> To Unsubscribe, read archives, change to or from digest.
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