Background:
The Belt is modeled to move with constant velocity. We want it to index.
An Indexing Belt is one where, in one machine cycle:
1.There is an Index-Period: The belt moves to a position during one phase of the machine cycle.
2.There is a Dwell-Period: The belt stops at that position for the remainder of the machine cycle.
We must change the motion-values that we give to the kinematic-chains.
We connect new Function-Blocks to the input-connector of the Motion-Dimension FB to give a different motion to the Belt.
Step 15.6: Video of Pattern
Indexing Belt
Function-Blocks for a Constant Velocity Belt
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Function-Blocks for a Constant-Velocity Belt These are the Function-Blocks to model the Constant Velocity Belt. The MMA motion value is the independent variable at the input of the separate X & Y Motion FBs. It does not matter how fast or slow the MMA, for each MMA value at the input to the Motion FBs, there is one output that connects to the X and Y Slider axes. |
Function-Blocks for an Indexing Belt
We want to index the Belts 12 times. The input to the X-axis and Y-axis Motion FB must Index by 30 degrees We want the belt to index along the path, and stop at fixed positions during the dwell. To do this, replace the motion that is given to the input-connectors of the Motion FBs •We replace the steady motion, provided by the MMA... •...with an Index motion linked to a Motion FB Note: the MMA must still be at the input-connector to the Indexing Motion FB |
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This is an example 'Indexing Motion'. Segment 1: X-axis : 0 - 180º | Y-axis : 0º - 30º Segment 2: Y-axis (Dwell Segment) : X-axis : 180º - 360º.| Y-axis =30º| The image shows the position and acceleration graphs. |
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Question: Spot the problem? Answer: The output from the indexing motion changes from 0 – 30º in one machine cycle. Thus, the belt and pocket move in one machine cycle (0 – 360 of the MMA), again and again. We need to do index the Belt 12 times (12×) in one machine cycle (0 – 360 of the MMA).
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To index the Belt 12 times... To index the belt motion twelve times (12×) in one machine cycle (0 – 360 of the MMA): 1.Connect the Linear-Motion FB to a Gearing FB 2.Edit the Gearing FB and enter Gearing-Ratio=12 Now, the motion-values at the output from the Gearing FB and input to the Motion FB are from 12×(0 ... 360) = (0 ... 4320º) as the MMA changes from 0 to 360. |
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The Graph to the left shows the output from the Motion FB as a function of the input, to the Motion FB: 0 – 4320º Note: To see the input to the Motion FB, (0 to 4320), connect a wire from the Gearing FB as the X-axis of the Graph FB Question: Spot the Problem? Answer: The output from the Motion FB does one index to 30º each 0 - 360 at its input, but resets to 0º, and does this motion again and again, 12×. |
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We will use the Accumulate Output radio-button in the Motion FB dialog-box. 1.Edit the Motion FB again 2.Click Output Option : Accumulate Output. |
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This graph now shows: •Y-axis: output from Motion FB, is from 0º to 360º. •X-axis: input to the Motion FB (or the output from the Gearing FB) is from 0º to 4320º. The output (Y-axis) from the Motion FB increases from 0 – 30º for the first 180º of the of the, and stays at 30º between 180 – 360º. Then the output (Y-axis)t increases to 60º for from 360º to 540º There are 12 indexes in one cycle of the MMA. Each index increases the position of the output by 30º. This is the motion that we want for the pocket and chain-link The pocket and chain-link will move 12 times, in one cycle of the MMA. |
