Supporting > Additive Machining

3D printing a conrod pattern

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A7er:
I have 3D printed a conrod pattern with my resin printer and the baseplate it will be fixed to with my Ender3. I used the Ender3 for the plate because I am unsure about getting a really flat plate from the resin printer. I will fill the layer lines on the plate and then glue the conrod to it using the raised bosses to locate the conrod. I can then make a frame around the plate for the sand mould, either resin bound or sodium silicate bound. Maybe try both. I still have to work out the best way of getting the molten aluminium into the mould. The conrod is 89mm long and has a 6mm dia hole in each end. Sorry, no rule for scale! The picture with two plates shows an earlier attempt at mounting a different conrod.

BillTodd:
Looking good :NotWorthy:

If they were required to be really straight , itd be possible to add a  coupl of sacrificial fillets on the back to balance the effect of the pocket on the front ( shrinkage of the thicker outer section bends the part upward -  I have had the same effect on a part just printed)

If you need something flat, then minimising the cross-section is vital, even if that means printing it upright.

Alyn Foundry:
Hi A7er.

Is that a pattern half or the whole conrod? With a little thought and registering you can use it to create both halves during moulding.

Place your runner as close as you can to the big end to reduce shrinkage.

 :cheers:  Graham.

A7er:
Hi Graham.
It is just one half. The conrod pattern is dead centre of the base plate. The base plate will define the size of the flask. Make one side using epoxy resin/sand mix and when it has set remove the flask and hopefully the mould should pull away from the pattern. Reassemble and repeat to get the other side. Glue the two moulds together, one half will have a simple sprue/gateing system and then sit the whole thing in a greensand filled flask in case of spillage. That's the plan, which went a little wrong when after I had glued the conrod to the base with epoxy glue, filled any gaps and sprayed it, the next day the conrod had distorted on the base. It must have been a reaction to the paint. I managed to remove the conrod and straighten it with a little heat. I glued it back on the base, but didn't paint it. It hasn't distorted so I feel ready to make a flask and try a casting. I am printing out a modified version of the conrod that is both halves that have been hollowed with a wall thickness of 1mm. If the print has worked (I will check it in a moment) I can then fill the void with an epoxy putty which should make it as strong as a part printed with PLA.

Alyn Foundry:
Sounds like you’ve got a plan.   :ThumbsUp:

Having always used Greensand moulding here don’t forget to throughly vent the mould. And use a good “ head “ on the sprue to prevent a sink.

Have you allowed for shrinkage in the pattern itself? Aluminium has a shrinkage of 3/16” per Foot, linear.

 :cheers: Graham.

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