Exercise 1. Answer the questions.

1. What equipment does the company Haas Automation Inc. produce? 2. What is the power of motors in the lathes offered by the company? 3. What tooling can be supplied with the lathes? 4. What are the prices of the machine-tools? 5. What operations are done with a part if there is only one lathe? 6. In which way can productivity be raised using two machines?

Exercise 2. Form all possible derivatives from the following words:

a product, operation, short, possible, quickly.

Exercise 3. Give synonyms to the following words from the text:

to offer, small, to boost, expensive, to perform, productivity.

7. Harmonic Goes Linear

a drive	привід	rotation	обертання
accuracy	точність	missing	відсутній
to cause	викликати	a pulley	шків
a screw	гвинт	to fold	згортати, складати
a gearhead	зубчастий редуктор	to wind	крутитися, обертатися
a brake	тормоз	CEO (a chief executive officer)	генеральний директор
maintenance	обслуговування	tension	напруга
lubrication	змазка	backlash	мертвий хід
to transmit	передавати	play	люфт
to fit	поміщати	stroke	хід
a spline	зубчасте колесо	a bearing	підшипник
an assembly	вузол	thrust	тяга
rigid	жорсткий	revolution	оберт
to be engaged	бути задіяним	pitch ratio	шагове відношення

A linear drive that brings the advantages of harmonic drives to linear motion can achieve high accuracy in long lengths that cause problems in screw-type drives, and it also works without gearheads or brakes, according to a manufacturer that has introduced one.

The manufacturer, Animatics Corp. of Santa Clara, Calif., says the design has fewer parts, requires less maintenance, and never needs lubrication.

To understand how it works, first consider the workings of a conventional harmonic drive. It consists of three pieces. The first is a wave generator, an elliptical steel disk that usually transmits power from a motor or servo. It fits inside a flex spline, a steel cup with gear teeth on the outside of its thin walls that deform to take on the wave generator’s elliptical shape. This elliptical assembly fits inside a rigid, toothed circular spline so that 30 percent of the teeth are engaged at all times.

So far, it sounds like just another collection of gears. But the flex spline has fewer teeth than the circular spline. This means that every time the flex spline makes a full rotation forward, the circular spline moves backward by the number of gears equal to the missing teeth. So if the flex spline has 200 teeth and the circular spline 202 teeth, then it would move backward two teeth for every rotation, a 100:1 reduction ratio in only a few inches of space.

So how does this apply to linear drives? Most conventional linear drives combine a motor and gearhead with pulleys to pull a linear stage back and forth. Animatics’ harmonic linear drive uses a recirculating belt that folds back upon itself as it winds over several pulleys with different diameters. The different diameters of the pulleys work like the mismatched gear teeth in a harmonic drive to force the belt to travel at different rates in different areas.

“By adding a few $5 pulleys, we’ve eliminated a $300 to $500 gearhead,” Animatics CEO Robert Bigler said. He also noted that since the belt is always in tension, it comes to a complete stop without backlash. “Gearheads have to have some play, because if you try to preload them, you’ll have problems with the bearings,” he added.

Bigler claims that the harmonic linear drive performs about as well as highly accurate but more expensive ball screw drives, especially in medium to long lengths where screws begin to vibrate.

The new drives come in standard stroke lengths of 100 to 3,200 millimeters and equivalent pitch ratios of 2.5 mm per revolution to 12.5 mm per revolution. The company’s HLD60 model generates up to 450 newtons of thrust with an average moment loading of up to 150 newton-meters.

Дата добавления: 2015-10-30