Author Topic: Dicing with Delrin - A Repair Job.  (Read 5016 times)

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #25 on: November 17, 2016, 12:36:31 PM »
Excellent work Pete - coming along nicely ... Why do they have the letter 'A' impressed into them  :scratch:

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. 
Best regards,

Pete W.

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Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #26 on: November 17, 2016, 12:44:56 PM »
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:


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: 
Best regards,

Pete W.

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Offline Joules

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Re: Dicing with Delrin - A Repair Job.
« Reply #27 on: November 17, 2016, 01:31:51 PM »
 :(  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.
« Last Edit: November 17, 2016, 07:13:01 PM by Joules »
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #28 on: November 17, 2016, 02:03:02 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.
 

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   :) 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline DMIOM

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Re: Dicing with Delrin - A Repair Job.
« Reply #29 on: November 17, 2016, 03:51:52 PM »
Excellent work Pete - coming along nicely ... Why do they have the letter 'A' impressed into them  :scratch:

: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:

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #30 on: November 17, 2016, 04:11:03 PM »
Why didn't I think of that?!?!   :doh:   :doh:   :doh: 
Best regards,

Pete W.

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Offline awemawson

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Re: Dicing with Delrin - A Repair Job.
« Reply #31 on: November 17, 2016, 04:47:34 PM »
... so much bullshit you should have a herd of cattle ... :lol:
Andrew Mawson
East Sussex

Offline Joules

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Re: Dicing with Delrin - A Repair Job.
« Reply #32 on: November 17, 2016, 06:33:28 PM »
Ha ha Pete, if only shrinkage was so simple...

http://www.dupont.com/content/dam/dupont/products-and-services/plastics-polymers-and-resins/thermoplastics/documents/Delrin/Delrin%20%20Acetal%20Homopolymer%20Resin%20%20Molding%20Tips.pdf

I don't tend to follow convention and enjoy the challenge of coming up with my own solutions.  I doubt the above outfit would approve of our methods, but at the end of the day we do what we have too to get the job done.  I tend not to worry over shrinkage for small parts, if I am making something precise in house I will mould then machine to size where required.  I have a small injection moulder, but it's not suitable for Delrin.

Hmmmm, for some reason I can't paste the above link as it breaks at the Copyright symbol in the URL  ???  However it works if you copy and paste it.   :doh:
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #33 on: November 19, 2016, 12:44:41 PM »
Well, I'm happy to have some more progress to report.

I've now profiled all five dominos and drilled the holes for the M2 grub-screws - they just need tapping but I intend to do that indoors and by hand.

The profiling is simple but tedious, once the saddle & vertical slide were brought into position by offering the end of the end-mill to the flank of the original mount (damaged, but not on its flank) it was just a matter of mounting each blank on the profiling fixture (see photos), traversing the cross-slide to take a small cut, turn the blank ever-so-slightly, take the next cut and so on and so on!!!  Getting and maintaining a routine was important - if the mind wanders it would be too easy to forget to de-clutch the lathe while re-positioning the work-piece and those fingers would be ever so close to that cutter!!!

Once I'd finished the profiling, I re-mounted the original mount on the fixture, swapped the end-mill for a drill chuck and the M2 tapping size drill and adjusted to align the drill with the grub-screw hole.  Swap the original mount for each of my efforts in turn and drill the holes, this time only the saddle moves, the cross-slide & vertical slide stay put.

I'm hoping to see my neighbour tomorrow to ask him if I can use his belt sander.  Profiling with the end-mill leaves a finish not a million miles from a fine knurl but before I declare that the end result I'll see how an off-cut of Delrin responds to the sander.

I set out to 'process' five blanks in case I lost any along the way.  I've currently still got five usable parts although one got bored a little over-size. 
I'll just have to be careful with the M2 tap!   :scratch:   :scratch:   :scratch: 

Right, photos:

Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline Pete49

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Re: Dicing with Delrin - A Repair Job.
« Reply #34 on: November 19, 2016, 08:58:21 PM »
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!!

And the problem is???? :beer:
Pete
oops..........oh no.........blast now I need to redo it

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #35 on: November 20, 2016, 11:14:49 AM »
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!!

And the problem is???? :beer:
Pete
 

Hi there, Pete,

Well, for one, I'm too old to start another building project, I'd rather spend my time in the workshop I've already got!   :mmr: 

It doesn't help that we're tenants rather than freeholders and, planning approval-wise, that we're in a so-called 'Area of Outstanding Natural Beauty'.
For some reason, workshops don't count as 'Natural Beauty'!!   :bang:   :bang:   :bang: 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline awemawson

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Re: Dicing with Delrin - A Repair Job.
« Reply #36 on: November 20, 2016, 11:25:42 AM »
I tell our holiday guests that we're in an 'Area of Natural Difficulty with Planning Permission' and THAT's why there are no windows in the mezzanine bedroom - planners want them still to look like cattle sheds from the outside  :bang: (yes it is an area of outstanding natural beauty but they've had down stairs windows for twenty five years and didn't when the cows were here!)
Andrew Mawson
East Sussex

Offline tom osselton

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Re: Dicing with Delrin - A Repair Job.
« Reply #37 on: November 20, 2016, 04:47:03 PM »
How about a few flat screen tv's in window casings with the cam outside? I'm thinking about doing this in the basement in the future and if your using wifi you could have different feeds.

Offline awemawson

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Re: Dicing with Delrin - A Repair Job.
« Reply #38 on: November 20, 2016, 04:54:55 PM »
I built a garage / workshop at the side of my last house that blocked off a very attractive stained glass window. I put defuse lights behind the window controlled by a light sensor that put them on in daylight and off at night  :ddb:
Andrew Mawson
East Sussex

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #39 on: November 21, 2016, 08:56:19 AM »
I built a garage / workshop at the side of my last house that blocked off a very attractive stained glass window. I put defuse lights behind the window controlled by a light sensor that put them on in daylight and off at night  :ddb:
 

How did you get to change the bulbs when they failed - or did you move out before that?!?!   :lol:   :lol:   :lol: 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #40 on: November 21, 2016, 09:01:15 AM »
I hope this project is approaching completion now!

I've fettled the five new mounts and selected the pair to incorporate in the rebuilt loupe (or is it 'loup'?).

Now to see if the owner is happy with the result.

Photos:
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline awemawson

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Re: Dicing with Delrin - A Repair Job.
« Reply #41 on: November 21, 2016, 10:05:52 AM »
I built a garage / workshop at the side of my last house that blocked off a very attractive stained glass window. I put defuse lights behind the window controlled by a light sensor that put them on in daylight and off at night  :ddb:
 

How did you get to change the bulbs when they failed - or did you move out before that?!?!   :lol:   :lol:   :lol:

House wall was one wall of 'garage' so a condition of building regulations was a fire proof barrier across the window. I just made it a sliding metal panel in channels top and bottom, so bulbs could easily be changed  :thumbup:
Andrew Mawson
East Sussex

Offline Pete W.

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Re: Dicing with Delrin - A Repair Job.
« Reply #42 on: November 25, 2016, 11:47:49 AM »
Well, I returned the repaired loupe to its owner this morning.  His initial response was favourable but I've asked that he gives me a full report when the instrument has been 'battle tested'! 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!