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I'm pretty new to machining, so please forgive me if my questions have
already been re-hashed ad nauseam. I have a Rong Fu Geared Head
Mill/Drill from Enco. So far I've only made one part!

(nothing about machining until the
very end)

At any rate, I've discovered that I really can't stand using the dials
and I want to reduce the backlash of the machine. I've also started
working on converting the machine to CNC. So, here's my questions:

1) I have roughly .015" backlash in my X and Y travels. I've heard talk
about "double-nutting" in order to reduce backlash. Has anyone done this
to one of the little Mill/Drills? Any advice on how to go about doing it?
I've considered going to ball screws but my understanding is that ball
screws make it so that the machine can not be used for manual milling -
is that correct?

2) Judging by others' comments, it appears that one of the biggest
disadvantages to the little Mill/Drills is that you lose your position
when you move the head up and down. Has anyone done anything to address
this?

3) I don't expect to have the machine converted to CNC anytime in the
near future, in the meantime I'd really like a DRO for at least the X and
Y axis.

The least expensive method (once you factor in the cost of the
PC/Monitor..etc) and the quickest to get setup seems to be to use
digimatic scales (the ones that are kind of like digital calipers without
the caliper part) with SPC output to an external 3-axis readout. WTtool
sells the readout for $249 and the individual scales are available for
roughly $200 for three, so call it $500 once I make the
brackets/shipping..etc. The disadvantage to this is, as far as I know, I
can't get the SPC outputs into a PC.

I'm planning on using servo motors (already have two) with Gecko drives
for my CNC upgrade. The servo motors have encoders attached so in a sense
the external DRO would be redundant. So, I *could* get the X/Y motors
hooked up (which has a lot of other advantages, but will be very
expensive because all of a suddenly I will have my credit card out and
will be calling Gecko for drives, and getting a power supply
and...and..and..) and use the encoders on the motors with one of the free
DRO software utilities. One disadvantage to this is the servo encoders
will have to compensate for backlash which may or may not be a problem. I
assume it isn't a huge problem because it appears to be common practice.

The other method would be to build my own rotary-to-linear encoder system
which certainly has appeal and could have better resolution than either
of the two previous methods. However I don't know that it is necessary...

So, bottom line, is there an advantage to having two DRO systems on a
single mill? If I put on a digimatic scale system will I end up junking
it once I get my CNC stuff completed?

Thanks!

--C.S.

I'm pretty new to machining, so please forgive me if my questions have
already been re-hashed ad nauseam. I have a Rong Fu Geared Head
Mill/Drill from Enco. So far I've only made one part!

(nothing about machining until the
very end)

Err. That should have been:



--C.S.

In a message dated 10/21/2002 9:02:26 PM Mountain Daylight Time,
cs@... writes:

Is Model Engineers Workshop a magazine?

Yes it is and I like it the best of all, but it is only aimed at making tools
etc for the workshop, no models or club stuff. It is available in the US
thru:
wiseowl@...
There are some back issues available, but it took me over two years to get
all of them and went all over the world to do so.

In a message dated 10/21/2002 9:02:26 PM Mountain Daylight Time,
cs@... writes:

I guess I could buy
longer center drills but that doesn't really 'solve' the problem.

The option that I took was to buy screw machine drills, they are much shorter
and will work except when the hole has to be really deep. The 1/2 inch bit
is about 3.9 OAL, the number and letter drills are shorter than the 1/2 is.
I bought all three sets in one box. Saves a lot of Z axis cranking.
bill
CCED

2) Judging by others' comments, it appears that one of the biggest
disadvantages to the little Mill/Drills is that you lose your position
when you move the head up and down. Has anyone done anything to address
this?

Two suggestions

1/ Try to plan your work so you don't have to move the head. Measure up
your various tools eg your R8 collet chuck, drill chuck etc so you know in
advance how much room you need to change from one to another. Then when
starting a job you can set the head just far enough above the work to
extract one tool holder and replace it with another.

2/ Have a look in Model Engineers Workshop there have been a numbe of
articles on this. Quite a good suggestion was to bolt a laser pointer on the
mill head (Horizontal plane) and aim it at a wall some distance away. Draw a
vertical line on the wall. If the mill head is rotated when it is raised or
lowered then you can get it back into alignment by moving the head until the
laser spot is on the line again.

Alan Matheson

2) Judging by others' comments, it appears that one of the biggest
disadvantages to the little Mill/Drills is that you lose your position
when you move the head up and down. Has anyone done anything to address
this?

Two suggestions

1/ Try to plan your work so you don't have to move the head. Measure up
your various tools eg your R8 collet chuck, drill chuck etc so you know in
advance how much room you need to change from one to another. Then when
starting a job you can set the head just far enough above the work to
extract one tool holder and replace it with another.

Yeah, I've tried that.. Mostly my problem has been in drilling/taping
1/2"+ holes where if I have the head high enough to get my drill bit out
of the chuck, it is too high for my center drill. I guess I could buy
longer center drills but that doesn't really 'solve' the problem.

2/ Have a look in Model Engineers Workshop there have been a numbe of
articles on this. Quite a good suggestion was to bolt a laser pointer on the
mill head (Horizontal plane) and aim it at a wall some distance away. Draw a
vertical line on the wall. If the mill head is rotated when it is raised or
lowered then you can get it back into alignment by moving the head until the
laser spot is on the line again.

Now that is a very interesting and novel solution. I think I like that!
Is Model Engineers Workshop a magazine?

--C.S.

On Mon, 21 Oct 2002, C.S.Mo wrote:

At any rate, I've discovered that I really can't stand using the dials

I find them functional but annoying.

3) I don't expect to have the machine converted to CNC anytime in the
near future, in the meantime I'd really like a DRO for at least the X and
Y axis.
The least expensive method (once you factor in the cost of the
PC/Monitor..etc) and the quickest to get setup seems to be to use
digimatic scales (the ones that are kind of like digital calipers without
the caliper part) with SPC output to an external 3-axis readout. WTtool
sells the readout for $249 and the individual scales are available for
roughly $200 for three, so call it $500 once I make the

You can probably get the scales for a bit cheaper but not a lot. Search
for "JTS machinery" on ebay.

brackets/shipping..etc. The disadvantage to this is, as far as I know, I
can't get the SPC outputs into a PC.

It's possible to do this but you will probably have to build the device
yourself. I think it's been done before but I can't remember where
off hand. Anyway I don't think the SPC output is fast enough (50
samples/sec.) to use for machine control. It's fine for a DRO but that's
probably about it.

I'm planning on using servo motors (already have two) with Gecko drives
for my CNC upgrade. The servo motors have encoders attached so in a sense
the external DRO would be redundant. So, I *could* get the X/Y motors
hooked up (which has a lot of other advantages, but will be very
expensive because all of a suddenly I will have my credit card out and
will be calling Gecko for drives, and getting a power supply
and...and..and..) and use the encoders on the motors with one of the free
DRO software utilities. One disadvantage to this is the servo encoders
will have to compensate for backlash which may or may not be a problem. I
assume it isn't a huge problem because it appears to be common practice.

If the encoders are attached to the motors they won't help with backlash
at all. The encoders need to reflect movement of the *table* and not the
motors. The advantage to servos is that the control system will turn the
motors until the table gets to where it's supposed to be, whether it's X
revolutions or X + a little more because of backlash. Where as steppers
just turn a set amount and assume the table got to where it's supposed to
be.

The other method would be to build my own rotary-to-linear encoder system
which certainly has appeal and could have better resolution than either
of the two previous methods. However I don't know that it is necessary...

This might be harder than you think. I investigated this for awhile but
decided it wasn't really worth the effort. Even if you do get a system
that can read to 0.0001" is it really going to be accurate? At that level
all kinds of things start to become an issue; flex in various places like
the column and table, play in the bearings of the encoder mechanism, even
thermal expansion.

So, bottom line, is there an advantage to having two DRO systems on a
single mill?

Depends on how long you want to run with just the DRO. If it's going to
be awhile before you switch to CNC then it might be worth the effort.

If I put on a digimatic scale system will I end up junking
it once I get my CNC stuff completed?

When you switch to CNC you will most likely be able to sell the DRO setup
for not much loss.

C|

Hi C.S.,

Firstly I have a concern about your band saw and mill stands.
Although your welds look very good, you still should consider adding
braces to the legs! As you raise and lower your saw head you're
going to cause metal fatigue in those joints. This is especially
going to be a problem if you convert your mill to CNC. Given that
the inertia of the table will be repeatedly torquing your stand. All
you need to do is throw in some 45-degree braces or the like.

As for questions about the Rong Fu mill, there is a Yahoo group
that specifically covers this mill.

Go here:

That's what I know! Now let's talk about what I don't know. I
also have a Rong Fu mill drill ( RF31 ). Parts created zero and my
CNC conversion knowledge is minimal. So, I'm sort of in the same
boat as your self. I just started collecting tooling as I just got
the mill a few weeks ago. But as far as indexing the head, I plan to
do something along the lines of a laser from the head to the base
rather than the popular head to the wall method. Problem with the
later is I plan on building a stand with casters. I'm thinking of
some kind of microscopic sensor of some kind. But haven't drawn any
plans yet. Take a look at a program under development called Mach 1
formerly known as Maser5.

Go here:

And here:

I'm not certain, but think Mach 1 will read your rotary optical
encoders and give the readouts on your computer monitor. This in
addition to acting as a software based controller for G code
interpretation and motion control.

Well that's about all I can think of for now. I hope you continue to
enjoy your new shop!

All the best,
James


--- In CAD_CAM_EDM_DRO@y..., C.S. Mo <cs@v...> wrote:

I'm pretty new to machining, so please forgive me if my questions

have

already been re-hashed ad nauseam. I have a Rong Fu Geared Head
Mill/Drill from Enco. So far I've only made one part!

(nothing about machining until

the

very end)

At any rate, I've discovered that I really can't stand using the

dials

and I want to reduce the backlash of the machine. I've also started
working on converting the machine to CNC. So, here's my questions:

1) I have roughly .015" backlash in my X and Y travels. I've heard

talk

about "double-nutting" in order to reduce backlash. Has anyone done

this

to one of the little Mill/Drills? Any advice on how to go about

doing it?

I've considered going to ball screws but my understanding is that

ball

screws make it so that the machine can not be used for manual

milling -

is that correct?

2) Judging by others' comments, it appears that one of the biggest
disadvantages to the little Mill/Drills is that you lose your

position

when you move the head up and down. Has anyone done anything to

address

this?

3) I don't expect to have the machine converted to CNC anytime in

the

near future, in the meantime I'd really like a DRO for at least the

X and

Y axis.

The least expensive method (once you factor in the cost of the
PC/Monitor..etc) and the quickest to get setup seems to be to use
digimatic scales (the ones that are kind of like digital calipers

without

the caliper part) with SPC output to an external 3-axis readout.

WTtool

sells the readout for $249 and the individual scales are available

for

roughly $200 for three, so call it $500 once I make the
brackets/shipping..etc. The disadvantage to this is, as far as I

know, I

can't get the SPC outputs into a PC.

I'm planning on using servo motors (already have two) with Gecko

drives

for my CNC upgrade. The servo motors have encoders attached so in a

sense

the external DRO would be redundant. So, I *could* get the X/Y

motors

hooked up (which has a lot of other advantages, but will be very
expensive because all of a suddenly I will have my credit card out

and

will be calling Gecko for drives, and getting a power supply
and...and..and..) and use the encoders on the motors with one of

the free

DRO software utilities. One disadvantage to this is the servo

encoders

will have to compensate for backlash which may or may not be a

problem. I

assume it isn't a huge problem because it appears to be common

practice.

The other method would be to build my own rotary-to-linear encoder

system

which certainly has appeal and could have better resolution than

either

of the two previous methods. However I don't know that it is

necessary...

So, bottom line, is there an advantage to having two DRO systems on

a

single mill? If I put on a digimatic scale system will I end up

junking

it once I get my CNC stuff completed?

Thanks!

--C.S.

--- In CAD_CAM_EDM_DRO@y..., "quazga" <quazga@y...> wrote:

Hi C.S.,

, I plan to

do something along the lines of a laser from the head to the base
rather than the popular head to the wall method. Problem with the
later is I plan on building a stand with casters. I'm thinking of
some kind of microscopic sensor of some kind. But haven't drawn

any
A couple of years ago, before being donated a full sized mill, I
posted a circuit on metalwebnews about how to build a head position
sensor with a dual element photoresistor and a laser pointer. It
proved to be accurate to about +- .002 of head deflection on a mill
drill. Contact me off list and I will try to dig up my old circuit
and some pix of the unit.

Hi C.S.,

Firstly I have a concern about your band saw and mill stands.
Although your welds look very good, you still should consider adding
braces to the legs! As you raise and lower your saw head you're

The bandsaw stand is boxed so I wouldn't worry about that. The mill stand
is 2x2 1/4" wall square steel tube - you could park a truck on it....

----

To bring back a question that has been recently discussed with Ballscrews
but not Acme rod..

I have roughly .015" backlash in my X and Y travels. I've heard talk
about "double-nutting" in order to reduce backlash. Has anyone done this
to one of the little Mill/Drills? Any advice on how to go about doing it?
I've considered going to ball screws but my understanding is that ball
screws make it so that the machine can not be used for manual milling -
is that correct?

--C.S.

The caveat on using a ballscrew feed in a manual mill is
because the ballscrew provides virtually no friction,
compared to an acme screw feed. You'd want a small prony
brake, or some kind of damper to keep the table from moving
when you took your hand off the crank. Best bet is to
couple the ballscrews to either a servo or stepper (in that
order of preference) as they would effectively hold
position at the end of each move, assuming that they are
controlled by a CNC system.

RayHex

----------

From: C.S. Mo <cs@...>

To bring back a question that has been recently discussed

with Ballscrews

but not Acme rod..

I have roughly .015" backlash in my X and Y travels. I've

heard talk

about "double-nutting" in order to reduce backlash. Has

anyone done this

to one of the little Mill/Drills? Any advice on how to go

about doing it?

I've considered going to ball screws but my

understanding is that ball

screws make it so that the machine can not be used for

manual milling -

is that correct?

What is a "prony brake"? I have a pair of servo motors but they do not
seem to provide any resistance with the power off. I want to be able to
use the machine for manual machining as well as CNC...

--C.S.

CS,
There are many references on the web:


RichD

"C.S. Mo" wrote:

The Chevalier CNC I used for several years had a manual mode in which
servos were fully disconnected, and no pronies, etc. ALL mills will
occasionally send the table flying if table locks are not employed. The
only time I ever had this happen, it was on a plain screw horizontal
Cincinnati.




At 08:22 PM 10/30/02 -0600, you wrote:

The caveat on using a ballscrew feed in a manual mill is
because the ballscrew provides virtually no friction,
compared to an acme screw feed. You'd want a small prony
brake, or some kind of damper to keep the table from moving
when you took your hand off the crank. Best bet is to
couple the ballscrews to either a servo or stepper (in that
order of preference) as they would effectively hold
position at the end of each move, assuming that they are
controlled by a CNC system.

RayHex

----------

From: C.S. Mo <cs@...>

To bring back a question that has been recently discussed

with Ballscrews

but not Acme rod..

I have roughly .015" backlash in my X and Y travels. I've

heard talk

about "double-nutting" in order to reduce backlash. Has

anyone done this

to one of the little Mill/Drills? Any advice on how to go

about doing it?

I've considered going to ball screws but my

understanding is that ball

screws make it so that the machine can not be used for

manual milling -

is that correct?

Addresses:
FAQ:
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I've red somewhere about self-breaking ballscrews which is a combination
with a normal screw, will try to get more info.
Alex