New Employee Caught Sleeping on the Job

You really can't find the staff these days.

Zeus our new employee was so tired that sleep was the only option.

Manufacturing Aluminium Prototype Parts Quickly Part 3

Carrying on from my last blog, the parts had been machined and all went really well with that.

After the parts were checked, we sent them off for polishing. This took about a week to complete as it is really labour intensive, but as you can see the results are fantastic, all in the space of two weeks! What do you think?

Manufacturing Aluminium Prototype Parts Quickly Part 2

Continuing on from my last blog in March, 'manufacturing aluminium prototype parts quickly'. The 3D printed  parts have been used as masters to make the sand casting mould and they were then sent off for heat treatment.

I printed out two master parts and gave them to the foundry, altogether we ordered 27 parts.  It's great that by only printing two parts in plastic, you can essentially use these as masters to make as many aluminium parts as needed.  We printed two because it cuts the lead time down to make the two part moulds, cutting the time almost in half.

 The part up close

So with the parts cast and heat treated, it was now down to working out how to hold the parts to machine in the detail that was needed.  After quite a bit of discussion with the machinist, we came up with this jig that would hold the casting in place whilst milling in a deep slot on the top face.

 The part post machined.

With all the parts machined, they are now off to polishing. To sum up that's 27 parts complete ready for surface finishing, all made from 2 3D printed masters.

Finite Element Analysis to re-engineer a product

JNDC were contracted to check the strength of a seat pad.
A linear static analysis was performed. Two load cases were considered as indicated in BS EN 12520:2010:
A vertical 1600N load 150mm from the centre and 100mm load from the front edge of the pad. Along with a vertical 1600N load representing a pad used in BS EN 12529:2010.

Results Case 1

Von Mises results shows a max stress of approx 68 MPa as shown in the figure below.  

When investigated further by extracting the max principal stress this was found to be 35MPa as shown below to the right. 

This is below the material limit and therefore acceptable.

Results Case 2

Von Mises results shows a max stress of approx 41 MPa as shown in the top figure.  

When investigating this further by extracting the max principal stress this was found to be 28MPa as shown in the bottom left figure. 

This is below the material limit and therefore acceptable.

Conclusions

- Seat pads to be re-engineered based on the rapid prototyped material.

- To redistribute stress concentrations, “fingers” of seat pad structure to be redesigned.  

- Stiffness of seat pad has increased in comparison with previous prototype manufactured.