Computer Integrated Manufacturing

Question 1
A CNC machine has one of its linear positioning axes as shown in the figure, consisting of a motor rotating a lead screw, which in turn moves a nut horizontally on which a table is mounted. The motor moves in discrete rotational steps of 50 steps per revolution. The pitch of the screw is 5 mm and the total horizontal traverse length of the table is 100 mm. What is the total number of controllable locations at which the table can be positioned on this axis?

GATE ME 2023   Manufacturing Engineering
Question 1 Explanation: 
Revolution of motor is one step =\frac{1}{50} \mathrm{rev} / \mathrm{step}
Pitch of lead screw =5 \mathrm{~mm}
movement of table
\Rightarrow 100 \mathrm{~mm}=\frac{1}{50} \times 5 \times \text { no. of steps }
or, no. of steps =1000
Question 2
Which one of the following CANNOT impart linear motion in a CNC machine?
Linear motor
Ball screw
Lead screw
Chain and sprocket
GATE ME 2022 SET-2   Manufacturing Engineering
Question 2 Explanation: 
Chain and Sprocket mechanism is not used in CNC Machines.
Linear Motors Recently linear motors are being increasingly considered for use in high performance CNC machine tools. The linear motor consists of a series of magnets attached to the machine base and a set of electrical coils potted around a steel laminate core attached to the moving slide.
The fact that there are no mechanical parts in contact means that there is no wear periodic maintenance required. Linear motors are not limited in travel like ball screws. Larger bare required to achieve high velocity, with a longer travel to prevent undue vibration.
This larger ball screw results in a higher inertia. This means a larger motor with more torque is required (introduction inertia) and the responsiveness and bandwidth of the system is reduced, resulting in poor servo performance.
Machines built with linear motors and all-digital drive systems can produce parts with higher accuracy and tighter tolerances at higher feeds and speeds. Also, they reduce significantly the non-machining time with high acceleration and deceleration rates.

Question 3
Match the additive manufacturing technique in Column I with its corresponding input material in Column II.

Additive manufacturing technique (Column I)
P. Fused deposition modelling
Q. Laminated object manufacturing
R. Selective laser sintering

Input material (Column II)
1. Photo sensitive liquid resin
2. Heat fusible powder
3. Filament of polymer
4. Sheet of thermoplastic or green compacted metal sheet
P-3, Q-4, R-2
P-1, Q-2, R-4
P-2, Q-3, R-1
P-4, Q-1, R-4
GATE ME 2022 SET-2   Manufacturing Engineering
Question 3 Explanation: 
Fused-deposition modeling consists of a computercontrolled extruder, through which a polymer filament is deposited to produce a part slice by slice.

Laminated-object manufacturing uses a laser beam or vinyl cutter to first cut the slices on paper or plastic sheets (laminations); then it applies an adhesive layer, if necessary and finally stacks the sheets to produce the part.

Selective laser sintering uses a high-powered laser beam to sinter powders or coatings on the powders in a desired pattern. Selective laser sintering has been applied to polymers, sand, ceramics, and metals.
Question 4
In a CNC machine tool, the function of an interpolator is to generate
signal for the lubrication pump during machining
error signal for tool radius compensation during machining
NC code from the part drawing during post processing
reference signal prescribing the shape of the part to be machined
GATE ME 2021 SET-2   Manufacturing Engineering
Question 4 Explanation: 
In contouring systems the machining path is usually constructed from a combination of linear and circular segments. It is only necessary to specify the coordinates of the initial and final points of each segment, and the feed rate. The operation of producing the required shape based on this information is termed interpolation and the corresponding unit is the "interpolator". The interpolator coordinates the motion along the machine axes, which are separately driven, by providing reference positions instant by instant for the position-and velocity control loops, to generate the required machining path. Typical interpolators are capable of generating linear and circular paths.
Question 5
The XY table of a NC machine tool is to move from P(1,1) to Q(51,1); all coordinates are in mm. The pitch of the NC drive leadscrew is 1 mm. If the backlash between the leadscrew and the nut is 1.8^{\circ}, then the total backlash of the table on moving from P to Q is _______mm (round off to two decimal places).
GATE ME 2021 SET-1   Manufacturing Engineering
Question 5 Explanation: 

P(1, 1) to P(51, 1) is 50 mm distance. As pitch of the leadscrew is 1 mm. It has to move 50 rotation and in each rotation, backlash is 1.8 degree. Therefore total backlash
= 1.8 x 50 degree.
In one rotation i.e. 360^{\circ} rotation - 1 mm movement take place
In 1.8 \times 50^{\circ}=\frac{1.8 \times 50}{360} \mathrm{~mm}=0.25 \mathrm{~mm}

There are 5 questions to complete.

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