Dicing with Delrin - A Repair Job.

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Pete W.:

--- Quote from: awemawson on November 17, 2016, 09:06:01 AM ---Excellent work Pete - coming along nicely ... Why do they have the letter 'A' impressed into them :scratch:

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Hi there, Andrew,

Thank you for your encouragement.

The blanks (aka 'dominos') started at a nominal 1" width but the saw wobbled so I milled a good long edge on each one. The drilling template features were arranged in relation to what would have been a centre line and I aligned the template with the good edge of the dominos. This resulted in the drilled dominos being asymmetrical but only by a smidgeon. It doesn't show very well in the photos but the tongue on the end of the component is slightly nearer to one edge than to the other, so there is actually a 'front' face and a 'rear' face. So I decided to mark the 'front' face - it really ought to have been an 'F' rather than an 'A' but the 'A' sits in the corner of the box of stamps so it was easier to pull out of the box than the 'F'. :D :D :D

Well, you did ask! :lol: :ddb: :lol: :ddb: :lol: :ddb:

When I've profiled the remaining three pieces and drilled & tapped the grub-screw holes (and selected the best pair of mounts), I'll post a photo of the complete loupe - hopefully that will make things clearer.

Pete W.:

--- Quote from: Joules on November 17, 2016, 11:39:44 AM ---Just out of interest, Delrin has a melting point of 175 ℃ it would be feasible to make an alloy mould use a slug of delrin in a tube and a bottle jack (close fitting piston). Heat the mould and tube to 175 ℃, digital thermometer to keep an eye on temperature, then squeeze the delrin slug into the mould. Bit like the guys making Delrin nuts for lead screws, might not be worth the effort for a one off, but maybe worth gaining the knowledge especially if you are likely to have repeat work or multiple components.
I just offer this thought as I am in the process of making a mould to shoot some delrin components for a client :thumbup: Not using a bottle jack I might add :lol:

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Hi there, Joules, thank you for your post.

In weighing up my approach to this job, I figured that I had more likelihood of success hewing from solid than by getting set up with moulding. I just didn't think the work of making the mould plus making and perfecting a moulding machine would be cost effective. I only need a pair of mounts but decided to push forward with five blanks (aka 'dominos') because when I cut the strip of Delrin off the side of the 250 mm x 250 mm piece I bought from eBay and cut that into arbitrarily size blanks, five was the number I got!
Your moulding project sounds very interesting - please do start a thread and share with us how you approach it and what results you achieve. :nrocks:

Joules:
:( Can't show the actual part or mould, but will try to make up a widget and demonstrate the technique..... Might end up being this Christmas break project. Nice work by the way Pete, meant to say that in the earlier post.

Pete W.:

--- Quote from: Joules on November 17, 2016, 01:31:51 PM --- :( Can't show the actual part or mould (NDA) but will try to make up a widget and demonstrate the technique..... Might end up being this Christmas break project. Nice work by the way Pete, meant to say that in the earlier post.

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Hi there, again, Joules,

Thank you for your post and for your kind comment.

When making a mould for a Delrin part, do you have to allow for shrinkage? If so, how much? I remember that the Davall Gear company used to say, proudly, in their catalogue that they compensated for shrinkage when making the moulds for their small plastic gears. :smart: :smart: :smart:

I thought of another reason for my not choosing the moulding approach for my project - the method I'm using uses facilities I already have and that I've had for some time. If I'd gone with the injection moulding machine plus mould approach, I would have needed another shed!! :D :) :D :) :D :)

DMIOM:

--- Quote from: awemawson on November 17, 2016, 09:06:01 AM --- Excellent work Pete - coming along nicely ... Why do they have the letter 'A' impressed into them :scratch:
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:smart:
given Pete is working on what might be classed as a scientific instrument, it was totally logical: 'A' for the Anterior face (and if the reverse had needed marking, it would have been 'P' for Posterior)

Dave :coffee:

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