Shoptask, Ballscrews, and CNC (long)
Posted by
beer@s...
on 2000-02-07 12:30:19 UTC
Well, I may be preaching to the converted here, but my Shoptask is now
finally CNC'd and I'm SURE that I've died and gone to heaven !
It's been a long and very interesting road, and many thanks go out to
all the people who've helped, including many on this list. Special
thanks go out to Dan Mauch, who many of you know, and Chuck McGhee, who
you may not.
~~~~~ the following is going to sound like an ad, but so what. There's
enough crooks and sheisters around that when good people come along,
they should be mentioned ~~~~
Chuck manufactures a ball screw retro-fit for Shoptasks. You supply
him with relevant brackets and fixtures from your Shoptask ( which he
machines for you ) and he returns to you a set of ballscrews with
double-ball nuts ready to bolt on. The ONLY tools required are a set
of allen keys and there is NO machining required.
This last item is an important one, as it's very hard to use your own
machine to modify fundamental parts of your machine and even harder to
do it precisely enough.
The feel of the ball screws is unbelieveable. Sitting loose on the
bench and turning the cranks, if felt like a round shaft turning in a
very nice pillow block. It did NOT feel like a thread. If I didn't see
the gear at the end shaft moving in and out, I wouldn't have believed
that there was a thread there at all.
The proof's in the pudding though - on the machine, not on the bench,
and here's the result.
After carefully following Chuck's installation instructions, the
backlash on my X axis is as close to zero as I can possibly measure.
With a .0001" dial gauge on it, I CANNOT wiggle/move the crank a small
enough amount to not move the needle. It's just as simple as that. X
lash is zero.
Y lash is currently non-zero, but damned small. ( It's under.001", how
far under is hard to measure.) I attribute the non-zeroness to one or
two things.
1. The design of the Shoptask's mounting bracket. I think a slightly
better designed bracket allowing the use of roller thrust bearings ( as
on the X axis ) instead of the supplied needle thrust bearings MAY make
for a better design.
Chuck disagrees with me and so maybe ..
2. There may still be a bit of work to be done on the gibs.
Non-flatness in the gib itself will add some lash, as will incorrectly
adjusted gibs ( the table can rack in either case ). I may work on this
some more.
However, I'm SO HAPPY with the parts I'm turning out right now that
trying to "improve" this little thing is WAY down at the bottom of the
list.
Chuck does all this work on Shoptasks ! He's got two, both highly
modified, and turns out the most amazing pieces. Just seeing what
can be done with exactly the same machine as sits in my shop has been
heartening.
And he sure seems to like this CNC thing, as he's got steppers on almost
everything ! X-Y-Z, sure, CNC rotary table, sure, but he's got a
ballscrew/stepper drive on his tailstock and another on his compound
and a few more I can't even remember.
http://206.19.206.56/cgresearch.htm
or
http://www.ktmarketing.com/CNC.html
~~~ end of ad ~~~
Summary Points:
---------------
1. This conversion has fundamentally changed the way I do things now.
I'm still coming to grips with the implications. Parts I would not even
have ATTEMPTED to create manually I now EXPECT to be able to produce.
2. A fundamental ( there's that word again ) limitation of these
smaller machines is their lack of rigidity. CNC actually goes a long
way towards correcting that. I still can't take a .250" cut, but
taking 25 .010" cuts is no longer a boring deal nor an arduous task.
Let the machine do the work, do it quickly and do it as precisely as I
ever could, or even more so.
Facemilling a bunch of those 8" x 12" riser blocks is not going to be
delayed as one more boring repetitive task. Bolt it up and let it go.
Boring deep holes .001" at a time to minimize cutter deflection and then
having it stopped at a precise point to make a FLAT shoulder is now
easy, precise and a LOT cheaper than buying custom reamers or custom
counterbores.
3. I'm going to stock up on high quality 1/4" and/or 3/8" endmills.
There's a lot less need to have one of every size, methinks.
Other Comments:
---------------
Thanks again to DanM, who's been a big source of help and inspiration.
Last Word of Advice:
--------------------
When you disassemble your X and Y axis, you'll want to clean everything
up. This is a good idea. Accidentally throwing out your thrust
bearings when you do so is not !
There is nothing more frustrating than having this VERY cool set of
ballscrews just waiting to be bolted on and the VERY FIRST PART you need
to do so is GONE .. JUST FREAKIN' GONE !
Ever tried to find metric thrust bearings on a Saturday morning ?
Wednesday afternoon and thirty bucks later ...
Alan
--
Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta
finally CNC'd and I'm SURE that I've died and gone to heaven !
It's been a long and very interesting road, and many thanks go out to
all the people who've helped, including many on this list. Special
thanks go out to Dan Mauch, who many of you know, and Chuck McGhee, who
you may not.
~~~~~ the following is going to sound like an ad, but so what. There's
enough crooks and sheisters around that when good people come along,
they should be mentioned ~~~~
Chuck manufactures a ball screw retro-fit for Shoptasks. You supply
him with relevant brackets and fixtures from your Shoptask ( which he
machines for you ) and he returns to you a set of ballscrews with
double-ball nuts ready to bolt on. The ONLY tools required are a set
of allen keys and there is NO machining required.
This last item is an important one, as it's very hard to use your own
machine to modify fundamental parts of your machine and even harder to
do it precisely enough.
The feel of the ball screws is unbelieveable. Sitting loose on the
bench and turning the cranks, if felt like a round shaft turning in a
very nice pillow block. It did NOT feel like a thread. If I didn't see
the gear at the end shaft moving in and out, I wouldn't have believed
that there was a thread there at all.
The proof's in the pudding though - on the machine, not on the bench,
and here's the result.
After carefully following Chuck's installation instructions, the
backlash on my X axis is as close to zero as I can possibly measure.
With a .0001" dial gauge on it, I CANNOT wiggle/move the crank a small
enough amount to not move the needle. It's just as simple as that. X
lash is zero.
Y lash is currently non-zero, but damned small. ( It's under.001", how
far under is hard to measure.) I attribute the non-zeroness to one or
two things.
1. The design of the Shoptask's mounting bracket. I think a slightly
better designed bracket allowing the use of roller thrust bearings ( as
on the X axis ) instead of the supplied needle thrust bearings MAY make
for a better design.
Chuck disagrees with me and so maybe ..
2. There may still be a bit of work to be done on the gibs.
Non-flatness in the gib itself will add some lash, as will incorrectly
adjusted gibs ( the table can rack in either case ). I may work on this
some more.
However, I'm SO HAPPY with the parts I'm turning out right now that
trying to "improve" this little thing is WAY down at the bottom of the
list.
Chuck does all this work on Shoptasks ! He's got two, both highly
modified, and turns out the most amazing pieces. Just seeing what
can be done with exactly the same machine as sits in my shop has been
heartening.
And he sure seems to like this CNC thing, as he's got steppers on almost
everything ! X-Y-Z, sure, CNC rotary table, sure, but he's got a
ballscrew/stepper drive on his tailstock and another on his compound
and a few more I can't even remember.
http://206.19.206.56/cgresearch.htm
or
http://www.ktmarketing.com/CNC.html
~~~ end of ad ~~~
Summary Points:
---------------
1. This conversion has fundamentally changed the way I do things now.
I'm still coming to grips with the implications. Parts I would not even
have ATTEMPTED to create manually I now EXPECT to be able to produce.
2. A fundamental ( there's that word again ) limitation of these
smaller machines is their lack of rigidity. CNC actually goes a long
way towards correcting that. I still can't take a .250" cut, but
taking 25 .010" cuts is no longer a boring deal nor an arduous task.
Let the machine do the work, do it quickly and do it as precisely as I
ever could, or even more so.
Facemilling a bunch of those 8" x 12" riser blocks is not going to be
delayed as one more boring repetitive task. Bolt it up and let it go.
Boring deep holes .001" at a time to minimize cutter deflection and then
having it stopped at a precise point to make a FLAT shoulder is now
easy, precise and a LOT cheaper than buying custom reamers or custom
counterbores.
3. I'm going to stock up on high quality 1/4" and/or 3/8" endmills.
There's a lot less need to have one of every size, methinks.
Other Comments:
---------------
Thanks again to DanM, who's been a big source of help and inspiration.
Last Word of Advice:
--------------------
When you disassemble your X and Y axis, you'll want to clean everything
up. This is a good idea. Accidentally throwing out your thrust
bearings when you do so is not !
There is nothing more frustrating than having this VERY cool set of
ballscrews just waiting to be bolted on and the VERY FIRST PART you need
to do so is GONE .. JUST FREAKIN' GONE !
Ever tried to find metric thrust bearings on a Saturday morning ?
Wednesday afternoon and thirty bucks later ...
Alan
--
Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta