This is a peristaltic pump individual project that i was required to do in my first year at Imperial College. It tested various aspects of the design aspect of engineering including making solidworks CAD models, bearing size selection, design to manufacture and idea development.

I was provided with the what was required of the pump and i had to go and develop the idea whilst working along tight design restrictions. By design restrictions i mean the dimensions of the peristaltic pump (does not include the transmission drive system) were provided to me and all i had to do is create a solidworks model. Later on in the course i was given further instructions on the drive system of the pump. I was to design a transmission system (with appropriate gears), intermediate shaft, bearings (able to withstand design loads) and a housing for the gear box.

The pump was to be:

  1. Driven at 180 r.p.m
  2. Able to transfer enough water equivalent to a situation when the peristaltic pump was to be driven by hand would require a force of 10N to a handle of 150mm
  3. Provided a range of a.c motors which would deliver the necessary force as No. 2
  4. keep in mind during the design process that 200 units of the pump were to be produced

CALCULATIONS

N.B 180 rpm= 30 rev/sec

ω=6∏ rad/sec

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Torque= F.r= 10N x 150mm = 1.5 Nm

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N.B 1300 was the 240v a.c motor provided

Starting torque need to start the pump so that it does not stall= 1.5Nm/speed ratio =0.208Nm

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Gear selection

Criteria for bearings were:

  1. Low Price
  2. Durability
  3. Compact design
  4. Easily assembled into housing

where ω1/ω2= speed ratio and N(a)-(b) are the number of teeth on the gears. (i.e total of 4 gears used). I would only make sense to choose two pairs of identical gears i.e N(a)=N(c) e.t.c. refer to assembly drawings below of unsure.

I choose an arbitrary number of teeth to work with so i can calculate the number of teeth on the other pair of gears

Using two pairs of identical gears means the expression to calculate teeth number reduces to give the number of teeth on the second pair of gears:

Now i had to choose a suitable modulus of the gears (N.B all the gears will have to have the same MODULUS to MESH) to calculate the modulus look into a gear catalogue. Gears of small modulus is usually cheap but too small will give minute teeth and strength   of gears is compromised and too big will be expensive and have big teeth and therefore a bigger gearbox design (wasting money) but will hold large design loads (not really an issue here as load is not large).

I choose a 1.5 modulus gears.

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Gears A and B

Gears A and B

Maximum Force on gears = Max Torque/ Pitch Circle Diameter (PCD)

N.B Starting Torque = 0.208Nm and Torque Pump needs is 1.5Nm. It is important to get your head around this concept as what force a gear experiences will be determined here. The gear which is nearest to the Peristaltic Pump , the device that requires the torque of 1.5Nm to push the water. Therefore max force this gear will experience is 1.5/PCD.

Remember the gear connected to the pump is the 54 teeth on because u eventually downgrade the r.p.m from the standard motor (1300) to 180.  Look at the assembly drawings below to see what i am talking about.

Rendered Image

Rendered Image

Rendered Image

Assembly Drawing

Pump Assembly Drawing

Pump Assembly Drawing

DETAILED PART DRAWING

DETAILED BOTTOM HOUSING DRAWING

DETAILED BOTTOM HOUSING DRAWING

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DOWNLOAD RENDERED IMAGES

DOWNLOAD SOLIDWORKS E-DRAWINGS (PUMP)

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