Week 7:- Base Unit Design Challenges 1
1. Base unit is a unit where all the units are assembled on that Plate EX. ( Pin unit,Clamp unit, Rest unit etc. )
Typical parts are :-
* Base plate * Weld Bars * Pedestal * Floor plate * Channels * Floor box.
2. Points need to consider while designing Base units,
* Working height
* Base plate consideration.
* Eye bolt holes.
* space consideration
3. Dumb unit is the complex unit design due to space constrains there is less space available & Have to adjust all the parts in available space. IT consist of dump cylinder to perform the operation of clamping & Unclamping car panel.
* Dump units are used when we can not use normal units like clamp unit, pin unit etc. Due to some space constraints. The designed parts should be small in size but can do their functions effectively.
* It contains the dump cylinder which will be the heavier part in all the unit, The riser & blade should have enough strength to bear the load of the cylinder & all the unit as well. The riser & blade thickness should be more in this type of unts.
* The parts should be designed by considering the open condition of the unit. In the open condition of the unit the parts should not fall to another unit.
* We can use any cylinder in this case which suits our requirements. In the below image of the dump unit Both clamp cylinder & hinge cylinders are used.
5. Slide unit are positioning units which are used to position the fixtures, weld gun, units, robots into position for further operations
6. Points needs to consider while designing the Slide unit.
1) LM guide ways are preffered over hardened guide ways due to least co-eficient of friction
2) Slide unit essentially consist of LM guides, Linear cylinder ,front & rear stoppers, front & rear shock absorber, two proximity switches/reed switches for sensing the two end position, bellows or protection cover for rails.
3) Center trunnion/rear clevis mounted cylinders are ideally used for slide unit application as this allows for some float to take up mis-alignment.
4) Reverse stroke of 10mm to be considered in both forward & retracted condition.
5) Cylinder & LM guides to be validated for load & stroke.
6) LM guide rail length should be standard and should be more than the actual stroke.
7) Mechanical hard stop to be considered for both extened & retracted condition.
8) Shock absorber to be used for both extended & retracted condition to reduce impact load.
9) The two end limits to be sensed externally by a proximity switch.
10)The shock absorber should be mounted such that it is perpandicular to the pivot at mid stroke or within +/- 5degree.