Instructions

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CNC ROTARY INDEXER

P/N 8700

SHERLINE

PRODUCTS

INCORPORATED 1974

SHERLINE PRODUCTS INC. • 3235 Executive Ridge • Vista • California 92081-8527 • FAX: (760) 727-7857 • Toll Free Order Line: (800) 541-0735

Local, International and Tech. Assistance: (760) 727-5857 • Internet: www.sherline.com • E-mail: sherline@sherline.com

4/22/09 Page 1 of 18

Installing and Using

The Sherline CNC Rotary Table and Controller

By Bryan Mumford and Joe Martin

Introduction

Bryan Mumford and I are very proud of this product. It

has taken Sherline twice the investment in both time and

money compared to what we originally planned for this

project. This project would have been a lot easier if we

built the $4000 product that we are competing with. We

have taken a very expensive product that has only been

available to very successful professional businesses and

produced a self-contained unit that not only has the features

of the expensive units, it is also simpler to use and very

affordable. In fact, it is so inexpensive, home hobbyists can

now afford to own and use this equipment. It should also be

noted that we didn’t copy anyone to accomplish this feat.

My only disappointment was that I was unable to ﬁnd a

way to adapt our existing rotary tables to a CNC unit. It

just couldn’t be done in a cost-effective manner because

of the mechanical parts that couldn’t be interchanged due

to the way the rotary table is manufactured.

Even though the computer is small, it is a very complex

device that both computes and drives the stepper motor in

microsteps. Like all electronic devices, the easier it is to

operate, the harder it is to design and program. We believe

the instructions are easy to read and shouldn’t give you any

problems, but if they do, please notify us at Sherline, and

we will attempt to improve them. We want our instructions

to be the best in the business. The most important rule is

to always work safely and accurately.

Power of the Motor

The stepper motor is rated at over 100 oz-in of torque,

with the highest power being achieved at low RPM. The

maximum speed of 50°/sec provides high speed but very

little power. To use that setting for positioning, the system

must be completely free from drag. We recommend using a

maximum speed of 40°/sec as a positioning speed to avoid

stalling the stepper motor. When cutting, slow speed should

be used to take advantage of the motor’s power.

Positioning Accuracy

The ﬁrst thing to understand about the rotary table is the

accuracy that can be obtained in real terms. The stepper

motor takes 400 steps to make exactly one revolution. This

motor drives the worm, which needs to make 72 revolutions

to make the rotary table turn exactly one revolution. This

means that it takes 28,800 steps (400 x 72) to drive the

rotary table one complete revolution. Take this number and

divide by the number of degrees in a circle (360°) and we

end up with 80 steps for each degree or 0.0125

° (or 0.75

minutes) for each step. The built-in computer will calculate

to the closest position. This means the ﬁnal position will be

within ± ½ step. This turns out to be a very small amount,

because the sine of this angle is only 0.0001091. This will

amount to 0.109

" (2.77 mm) rise in 1000 (83- 4 or 25.4 m)

when compared to a ﬂat plane. This is just .00022" (.0055

mm) at the edge of the table.

Mechanical Accuracy

The gear that turns electronic signals into a real movement

has been hobbed directly into the table, which means the

teeth have been generated on a machine that cuts the teeth

with a cutter similar to a worm as the part is turning. This

eliminates any error associated with cutting each tooth

individually. As anyone associated with the machine trades

realizes, “nothing is perfect”. This is also the case for this

product; however, I seriously doubt if anyone buying it could

measure the mechanical indexing error of the worm and

gear. The electronic system has no error in its calculations,

but it does round off as previously explained.

The Importance of Reading the Instructions

It is impossible to make a product this complex “idiot proof”.

The best rule I’ve ever come up with when dealing with

any type of CNC equipment is this: “You have to know

what the unit will do after you push the button BEFORE

you push the button.” This can only be accomplished by

reading the instructions and “playing with the rotary table”

at the same time until you thoroughly understand how the

features of this unit work. It isn’t necessary to understand

the interfacing options to safely operate the CNC rotary

table. Don’t mount this unit on a mill that has a cutter in the

spindle until you truly understand how to control it.

CAUTION: The power cord

receptical in the control box is

easily damaged. Plug and unplug

the power connector with care!

Summary of content (18 pages)

PAGE 1
CAUTION: The power cord receptical in the control box is easily damaged. Plug and unplug the power connector with care! SHERLINE PRODUCTS INCORPORATED 1974 CNC ROTARY INDEXER P/N 8700 Installing and Using The Sherline CNC Rotary Table and Controller By Bryan Mumford and Joe Martin Introduction Bryan Mumford and I are very proud of this product. It has taken Sherline twice the investment in both time and money compared to what we originally planned for this project.
PAGE 2
Precautions When Turning On the Unit • As with any piece of electronic equipment, make sure the power is off before plugging the stepper motor connecting cord into the control unit. • If a part has been aligned on the table and the power is switched off; the part should be realigned after turning the unit back on before continuing. Electrical “spikes” can cause the motor to move a few steps when turning it on.
PAGE 3
in each movement. The units are degrees per second. Whenever the table moves, it starts at the SLOW feed rate and ramps up to the FAST setting. If you set the FAST rate the same as the SLOW rate, the rate of motion will be constant during the move. The table does not have much power at the fastest settings, so very fast settings should only be used for positioning, not for cutting operations. Experience will teach you what speeds are appropriate for your own work.
PAGE 4
When the number of divisions you want is displayed, press [ENTER]. For example, suppose you typed “030” for the number of divisions. After you hit the [ENTER] key, the LCD screen will display: have much power and should only be used for positioning the table quickly, not for cutting operations. • The controller uses “ramping” to accelerate and decelerate during each movement. You can enter the minimum and maximum speeds used to suit your work.
PAGE 5
To use the Degrees Mode, press the [ENTER] key. The LCD screen will then display: the current position is 340 degrees (360 degrees minus 20 degrees). PANIC STOP—Any time the table is moving you can stop it immediately by hitting the [STOP] (Jog) key. This will stop all motion and put you into the JOG mode. You to lose your place in the program you were running and will have to start over. Degrees: 000.000 Enter a number You can now enter the number of degrees you wish to travel at each movement.
PAGE 6
The “1:1” means you’re working on program one, block number one. The ﬁrst movement in this example will move the table 90 degrees clockwise. To change this amount, type the number keys. You can press [NXT] to move the cursor to the right or [PRV] to move the cursor to the left. Insert and Delete When entering a program you may make a mistake, or you may wish to modify a program after it has been entered. You can INSERT and DELETE program blocks to correct or modify an existing program.
PAGE 7
zero for the number of divisions in the Division Mode, or zero for the number of degrees in the Degrees Mode. During continuous motion, the table will start moving at the SLOW speed setting, ramp up to the FAST speed setting, and keep turning until you stop it with the [STOP] key. When the table goes into Continuous Motion, the LCD screen will display something similar to: only be entered after a “Begin Loop” has been entered. It is acceptable to have a “Pause” command entered in the loop program.
PAGE 8
The controller can be operated from a remote switch. This will allow you to keep the controller in a more “friendly” environment and have a more durable switch used for starting a programmed sequence. To incorporate this feature, connect the remote trigger switch that is normally open to the SENSE INPUT and GROUND wires of the included 8-pin connector cord. (NOTE: The ﬁrst time a program is run, it must be initiated by hitting the [NXT] button on the keyboard.
PAGE 9
It would be difﬁcult to describe the many combinations that could be generated using this method, so I’ll give you a general “overview” of the rules and leave the rest up to your imagination. Two Linear controllers could be linked to produce any number of sequences for simple but useful movements. For example, one controller could drive the mill table X-axis, and the other could drill with the Z-axis. 1.) The Master controller that initiates the sequence may be in any motion mode.
PAGE 10
have come a long way at becoming a good machinist. You will ﬁnd erasers aren’t much good and no one has come up with a good “putting on” tool when it comes to metal parts. Complex parts are very difﬁcult to make. When you are making one off “one-of-a-kind” parts, don’t worry about how long it takes. Spend your time planning and checking so you don’t have to start over. backlash has to be considered in a different way if an “off balance” ﬁxture is mounted.
PAGE 11
are doing a hole layout, you very seldom can work with the angles and dimensions on your drawing because of the cutter diameter. FIGURE 6—Cutter machining outside of part. FIGURE 9—Offsetting the rotary table to cut segments. of this nature, but to accurately make a precision part of this type is what a rotary table is all about. In most cases, I will leave you to your own common sense as to the depth of cuts and how much to leave from roughing and ﬁnish cuts.
PAGE 12
and the table rotated in a clockwise direction. It is quicker to cut the ﬁrst half of all four segments, then move the Y offset and complete the segments. If you are going to try something like this for a ﬁrst project, check your entire plan out with .001” cuts and be positive you are correct before making cuts that could scrap your part. (See Figure 11.) FIGURE 11—Completing the spokes of a wheel. FIGURE 10—Drawing and calculations for cutter paths.
PAGE 13
would be a 24-pitch gear would have 24 teeth with a pitch diameter of 1" The OD of this gear would be equal to the pitch diameter to the number of teeth you wish to cut plus 2. To calculate this diameter all you have to do is divide the amount of teeth you wish to cut by the pitch of the gear. 26 divided by the pitch 24 and you get 1.0833, which will be the OD of a 24-tooth (24T) gear with a 24 pitch (P) in inches.
PAGE 14
A Note on Mounting the Right Angle Attachment On the side of the worm housing (see exploded view on page 16) are four holes, which are used to mount the optional right angle attachment, P/N 3701. They go all the way through the part. In order to keep dirt and chips from entering the worm housing, set screws have been installed in the holes. Before the right angle attachment can be mounted, these set screws must be removed. Be sure to reinstall them when the right angle attachment is removed.
PAGE 15
The Sherline CNC rotary table controller was designed by Bryan Mumford at Mumford Micro Systems in conjunction with Sherline Products, Inc. Thanks to John Wettroth for advice and suggestions. Sherline Replacement Parts Orders: (800) 541-0735 Technical Assistance, Mechanical: (760) 727-5857 Technical Assistance, Programming (Bryan Mumford): (805) 687-5116) Bryan Mumford, Mumford Micro Systems 3933 Antone Road, Santa Barbara, CA 93110 Phone: (805) 687-5116 Fax: (805) 687-4905 bryan@bmumford.com http://www.
PAGE 16
PART NO. REQ. 10930 30560 35580 37090 37100 37110 37121 37131 37122 37123 37124 37150 37160 37170 37200 37210 37220 40050 2 4 2 1 1 1 (1) (1) 1 1 1 1 1 1 2 1 1 1 DESCRIPTION PART NO. REQ. 3/8” Bearing 10-32 T-nut Hold-down clamp Chuck adapter Rotary table base Rotary table top CNC rotary table worm housing (Not sold sep.) CNC rotary table worm shaft (Not sold sep.
PAGE 17
(Copy this page and use it for future program records) Program Sheet BLOCK MOVE FEED BLOCK PAUSE -17- MOVE FEED PAUSE
PAGE 18
NOTE: Though this drawing is labeled as P/N 37511, that is the part number for the plate only. To order the complete accessory including hold-down screws and T-nuts, order P/N 8710.