CNC_0004

MAKE: Workbench - A-axis - Assembly

Preliminary Considerations:

Thoughts:

The A-axis may only be for filament winding. Therefore the loading might be quite small.

Perhaps a NEMA 24 motor, as on the very small Parker Hannifin linear slide, in conjunction with one of the two 5:1 planetary reducers might do. Probably too week and too fast.

Perhaps 2 of the Japan Servo Co. Ltd. motors, each with a timing belt drive might do.

Initial Perceived Requirements:

Minimum Possible Move Angle = 0.1- degree (a guess) "Start with checking the minimum possible move angle. This is the absolute limit to the accuracy of the work done on the machine." ~ from Mack3Mill document Section 4.5.2

Maximum Jog Rotation = Hundreds or thousands

Maximum Winding Rotational Speed (for torque tube) = 3rps (a guess)

Force = 13.6 (a guess) N (newton), 10 (a guess) lbf-ft (pound-force)..

Acceleration: = ?

Unit:	Force; [F]	*	Angle: [u]	/	Time; [s]	=	Power [P]
English	10 lbf-ft	*	10 degrees	/	second,minute	=	ft-lbs/min; HP
		*		/		=	m-Kg/sec
metric SI	13.6 newton	*		/		=	joule
		*		/		=	Watts

Proposed Method A/ ~ 1 Motor and Driveshaft:

Probably going with two motors and moving carriage

Sketch: Currently, the sketch does not take a chuck into account.

Use cog belts to maintain rotational positioning.

Consider eliminating 3-sheave set and locating motor inline, via coupling, with X-shaft (large dia tube)

Consider replacing the X-shaft and locating a separate motor at both chucks.

Should there be chucks at one or both ends?

An example of a simple belt reduction; http://www.servotechnic.com/arrickpr23.htm

The ideal method might be to have a 3:1 gearbelt between the motor and the X-shaft and a pair of 3:1 gearbelt between the X-shaft and the 'chucks'. This will 1/ absorb the rotational shock, 2/ negate the need for 2 HOMEs, and 3/ should assure the rotational alignment of the two 'chucks'.

Proposed Method B/ ~ 2 Motors and Moving Carriage: YES GO WITH THIS

Posting placed on CNCzone September 22, 2005;

Two servomotors on a common A-axis??

The requirement is for an A-axis that is 13 ft. long (or 25 ft) and it must be driven from both ends.

The use of one servomotor and servodrive, plus an 13-ft X-shaft would work. However, I am wondering if this requirement might be achieved by using two servomotors and servodrives WITHOUT having to use up two of Mach3's available axis.

Would the single Mach3 be able to feed data to two servodrives, perhaps through opti-isolators? In addition, could the Error signals from the two servodrives go through and OR-gate before being passed on to Mach3?
The application is rotary, therefor no Limits should be required. In addition, would a single Home at one end of the axis do the job? Is a home even required?

The 2 existing Japan servos Ebay 7538066615 might be appropriate for this application. The have a reduction of 12.5:1 and 371 RPM (6.2 rps)

Reply; by ger21; Just try using the step and direction from a single axis into both drives. if there is enough current, it will work.

By me; Yes it should work Two servodrives ~ one for each servomotor.

Concern: What holds the two motors in azimuth alignment when the power is off and therefore at the start of operation? Every axis, including both ends of the A-axis may require a HOME so that all axii will be aligned at the start of a job. Or, just let them align themselves by removing excessive twist at the start.

Concern: The two motors will probably never have exactly matched poles. Does this mean that one motor will be doing most of the work. Or, would the homing align the poles of both motors?? Why won't they have exactly matched poles?

Concern: Would a high tension on the cable, used in producing the torque-tube and spar, put too strong a lateral force on the THK blocks and tracks?? The carriage could be 'tied' to the Unistrut table.

Yes this is looking good. Add it to wiring diagram.

Concern: Does the electrical system brake the motors to minimize over-travel or must the motors have brakes?

See the calculations for the CNC 0018 little Japan Servo gearmotors below.

Another advantage is that the remote end can be on a carriage that slides on the X-axis tracks and separate 2, 3 or 4 blocks and be locked in position on the X-axis by locking a pinion on the gear track or by clamping onto the Unistrut. Two power wires and four control wires will go between this motor and its Gecko servodrive.

Brace: Resist the tension between the two ends of the A-axis or fix the position of the travelling carriage by a 'flexible bar behind the carriage. It attaches to the carriage and to the Unistrut.

_______________________

THK Load Calculations:

From page A-219. P = (M_c / 2) * 0.0931 = 0.039 kN-m = 29 lbf-ft.

Could be 2 * 29 X 2 X (12"/10.5") =133 lbs maximum static force the clamp should help, as long as it does not put a load on the blocks and track.

Notes:

Pictures of possible means of laying Torque tube.

http://www.ndt.aeat.co.uk/noticeboards/mms15/Images/FilamentWinding_process%20Owen%20Corning.jpg

www.advancedcerametrics.com/ grooved.html

There must be no twisting by the lineshaft, therefor the motor and encoder can be mounted at the end of the table.

Components:

Motor:

Calculations:

Motor:

CNC 0018 Two little Japan Servo gearmotors might be OK. The following is copied from this web page.

The output speed of the 12.5:1 reducer is 371 or 344 rpm and a torque of 0.53 N.m [74.99 oz in]. This is 0.0258 hp., per axis end.

A/ For a maximum A-axis of 3 rps (180 rpm) the final reduction must be 344/180 = 1.9:1.

74.99 * 1.9 = 142.5 oz-in = 0.74 lb-ft. Times 2 motors = 1.48 lb-ft. This is very likely too little for the A-axis.

B/ For a maximum A-axis of 1.5 rps (90 rpm) the final reduction must be 344/90 = 3.8:1. And this will result in a total torque of 2.96 lb-ft. This MIGHT be OK for the A-axis.

C/ could consider a greater ratio on the belt drive. This slower speed may be OK for the spar but it may be too slow for the torque tube. Perhaps a two-speed at both ends of the c-axis will allow for higher speed winding of the torque tube.

CNC 0016 Tamagawa TRE Servomotor, 300W, 50VDC, 7.5A, Maximum speed at 50VDC is 3000RPM

For a maximum A-axis of 3 rps (180 rpm) the total reduction must be less than (3000/180 = 1.9:1). Say 15:1

300W / 735 = 0.408 HP. Torque = HP/RPM x 10⁶ = (0.408 / 180) x 10⁶= 2266oz-in (142 lb-in) This may be too much for the A-axis, however both the ratio and the motor speed can be reduced to give less power and consume a lower amperage.

If the Tamagawa motor cannot be made to work, a NEMA 23 will be too light. Check out a NEMA 32 to see if it might be strong enough.

Cog Belts and Sheaves (2 sets req'd):

Calculations:

For Use with Japan Motor/reducer:

Timing Belts:

For ref; The belt on the linear slide 404Xr 200mm [CNC 0014] from the motor to the screw is 1/8.5" [3mm] and the width is 9/16" [15mm]. The motor will be a NEMA 23. The Japan motor looks close to NEMA 23, however it has a 12.5:1 reduction.

Calculation base on above sentence; 0.035 hp * (5 / 8.5) * (1" / 9/16") * 12.5 ratio = 0.45 hp. I.e. design for .45 HP at 371 rpm. This appears to be too high.

______________________________

HTD TIMING BELT DRIVES, 5mm pitch, 9mm width, aluminum pulleys, 72 groove and 34 groove

Motor/reducer output power: The output speed of the 12.5:1 reducer is 371 or 344 rpm and a torque of 0.53 N.m [74.99 oz in]. This is 0.0258 hp per drive.

Using a Service factor of 1.5 and a Speed-up (greater than 3.5:1) factor of 0.4 the maximum allowable Application horse power is 0.0285 * 1.9 = 0.049 hp. (from Boston cat.)

The horsepower rating of the 30-groove pulley (2.4:1 ratio) at 300 rpm is 0.204 hp and at 500 rpm is 0.249.

The horsepower rating of the 18-groove pulley (4:1 ratio) at 300 rpm is 0.108 hp and at 500 rpm is 0.150

It appears that the belt drive could handle motors that are 3 times stronger than the Japan servomotors.

The length through the bore on the small pulleys is less than the shaft length on the reducer. Good.

The stock bores may not match the shaft diameter on the reducer. Bad.

Boston Gear: I have the hard copy catalog.

Small pulley: HTD, 5mm pitch, 9mm width, aluminum pulleys, 18 groove. Pitch dia. = .677" [16.94mm]

Small pulley: HTD, 5mm pitch, 9mm width, aluminum pulleys, 30 groove. Pitch dia. = 1.128" [28.65mm]

Large pulley: HTD, 5mm pitch, 9mm width, aluminum pulleys, 72 groove. Pitch dia. = 2.707" [68.76mm]

Belt: HDT, 5mm pitch, 9mm width, xxx groove.

For center distance see: Boston catalog page 120.

http://staging.smartcats.com/bost_root/web/products/shaft/timing.html#

http://staging.smartcats.com/bost_root/web/pdf/product_sections/bearing_pp_142_156.pdf

Problem: The bore in the large pulley is only 3/8"

sdp-si: https://sdp-si.com/eStore/ I have the hard copy catalog - See section 2.

Small pulley: HTD, 5mm pitch, 9mm width, aluminum pulleys, 30 groove. https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=59087&GroupID=217

Large pulley: HTD, 5mm pitch, 9mm width, aluminum pulleys, 72 groove. https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=59093&GroupID=217

Belt: HDT, 5mm pitch, 9mm width, 338 groove. Typical sample. https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=6800&GroupID=342

Optibelt also makes HDT 5M Series. I have the hard copy catalog.

Option: HDT is about 20% more expensive than GT2

Large pulley: GT2, 5mm pitch, 15mm width, aluminum pulleys, 72 groove. https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=61618&GroupID=217

_________ I am intending to use the HTD above, not the series below. __________

Morse catalog, Section H.

1/5" [5mm?] (XL) Pitch -or- 3/8" (L) Pitch

XL with 28 or 30 grooves for the driver is light, but.....

XL with 60 or 72 grooves for the driven

Belt XL 3/8" wide is too light.

There must be a L driver sheave, by some other manufacturer, that is closer to the 1" long output shaft on the reducer. One that has a clamp attachment.

Chuck:

For attachment to A-axis plates at one or both ends.

Craftsman

Concern: It (or they) will add mass and inertial to the rotation of the A-axis, which will effect acceleration and deceleration. Perhaps the Chuck could be removable.

Lineshaft Bearings:

Cable and Tensioner:

The cable that is stretched between the 2 'chucks' on the C-axis.

Home and Travel Limit Sensors:
Consider using Parker Daedal units. This will give standardization on all three linear axes. Might also consider one of the units of the baby linear slide for A-axis home and or Limits.

Perhaps the A-axis requires an absolute encoder.

Cable Carrier:

Could have small cable carrier for the floating A-axis motor going to the right (in opposite direction from the X-axis one). Or just use flexible metal conduit but shield the control wires from the power wires.

Purchased Items that MIGHT be used:

Gearcase - Planetary - 5:1 ratio ~ Item # CNC_0019 This is for NEMA 23 and will therefore be too light ~ Unless, perhaps one was used at each end of the lineshaft. However the planetary gearboxes will not negate the need for the cog belts and sheaves.

Servomotor c/w Encoder ~ Item # CNC_0017 The three Electrocrafts

Servomotor c/w Encoder ~ Item # CNC_0016: This is the Tamagawa. The maximum speed is 3,000 rpm less actual voltage etc.

Outside Sites on Rotary Table:

http://www.newmarksystems.com/rotary-stage-rt2.html Have hard copy.

This may be too elaborate for what is needed. It appears that it will not take an encoder. Worm gear is not efficient.

http://franke-gmbh.de/en/06_download/06_01_kataloge/pdf/franke_positioning_systems_en.pdf

Consider 'homemade' using Boston worm and gear. See page 73 in catalog.

http://www.techno-isel.com/CNC_Routers/Accessories8.htm

line Products, 4" Rotary Table, P/N 3700 ~ http://www.sherline.com/3700cncpg.htm. The mount accepts a #23 frame size stepper motor for CNC control and this may not accept a servo motor.

3" Probably too small. http://www.newmarksystems.com/rotary-stage-rt3.html

Shaft Mounted Gear Reducer:

http://www.allproducts.com/manufacture98/gearbox/product1.html. INGECO - Industrial Gear Corporation. ¨ RATINGS - 0.25 KW TO 30 KW , ¨ RATIO - 5:1, 13:1,15:1 AND 20:1

http://homepages.picknowl.com.au/scottt/This%20is%20a%20reduction%20gearbox.html

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Last Revised: Monday, June 8, 2007