Author Topic: 3D printing, an aid to pattern making?  (Read 617 times)

Offline Alyn Foundry

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3D printing, an aid to pattern making?
« on: June 30, 2020, 03:53:15 PM »
I have questions, many, about the topic title above.

Knowing that many members here use this technology for a lot of different things, can " decent " patterns be reproduced using this method?

By decent I'm referring to external finish. Would the printed parts need " fettling " with filler to get the smooth surface finish that's required?

How about a flywheel pattern? It would have to be in two halves for ease of moulding.

Core boxes, smooth on the inside for easy sand core removal?

My boys discovered the finished cylinder and end covers for my Brayton " Readymotor " yesterday evening but my work stopped when confronted with the daunting task of making a 2 foot/600 mm long 2,1/2" diameter core box for the air receiver column.

Your feedback would be greatly appreciated on this subject, cheers Graham. :thinking:


Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #1 on: June 30, 2020, 04:18:01 PM »
A lot will depend on the printer, those at the cheaper end will not have as smooth a finish as those costing more but it is common to improve the surface, sometimes with chemicals or their vapours to smooth the surface or as you say good of sanding and filler.

The casting medium will also affect finish, a coarse sand is less likely to show the layers than a fine petrobond for example, just like it would show grain in rough wooden patterns

Two halves or multiple part patterns are not a problem

Box surface swill be similar to pattern surfaces

Your corebox could be printed as several shorter sections and then joined together as that is quite a large item for a lot of printers to produce.

take a look at Myfordboy's site for an idea of what he can produce casting at home from his own prints from various printers. He has a lot of videos too.

https://myfordboy.blogspot.com/p/the-essex-hot-air-engine.html

t=71s

This was printed and cast for someone I suggested to use him as she needed a pattern as well as the casting

t=58s
« Last Edit: June 30, 2020, 04:55:50 PM by Jasonb »

Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #2 on: June 30, 2020, 05:43:09 PM »
The other thing to consider is what is your or the boys CAD drawing ability as your print will only be as good as the shape you tell it to print. You would need something like this though at 2 1/2" dia don't know why you can't ram some sand into a bit of plastic rain water pipe unless it is not a plain cylindrical void.


Offline Alyn Foundry

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Re: 3D printing, an aid to pattern making?
« Reply #3 on: June 30, 2020, 05:46:28 PM »
Thanks Jason.

Obviously I'm pretty well versed in the " art " of moulding, casting and traditional pattern making but this area is totally alien to me.

Liked the " matrix " forming of the flywheel rim.   :ThumbsUp:

So the use of " high build " primer might help with final surface finish?

Cheers Graham.

Offline Alyn Foundry

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Re: 3D printing, an aid to pattern making?
« Reply #4 on: June 30, 2020, 05:55:37 PM »
Our posts crossed Jason.

We've never looked at CAD probably because I'm a little, nay a lot IT illiterate. I prefer the " old school " approach having had a good mentoring in my childhood. My grandpa was a Shipwright  and taught me every aspect of woodworking, in fact I still use his trusty Stanley Bedrock plane whenever the need arises.

Cheers Graham.

Offline Alyn Foundry

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Re: 3D printing, an aid to pattern making?
« Reply #5 on: June 30, 2020, 06:17:46 PM »
Thanks for the corebox rendition Jason, interesting.

This engine bed will be done at a " professional " Iron founders, I'm not sure a piece of plastic drainpipe would be acceptable? However the core does need a 3,1/4" flange at the bottom end to create a recess for the air receiver cover plate.

I take it that the " shrinkage allowance " ( 1/8" per foot linear, Iron ) is put into the basic drawing program at the start?

How would one go about doing the " lazy S " spokes out of interest?

Cheers Graham.

Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #6 on: June 30, 2020, 06:38:16 PM »
I expected you could skip the bits in the middle of the videos but they do show the printing and final surface finish.

Yes a few coats of a high build filler/primer should do. I suppose the output of the cheaper printers can be compared to sawn or turned wood which would need sanding and filling before you could pull a decent mould off it.

You can handle the shrinkage in one of two ways, either include it as you draw the item or draw it to finished size and then use the "scale" function which can be any +/- percentage that you want and even possible to set differently for length and width. Draft and machining allowance can be quickly added by some programmes eg click the surface and then add say 3mm allowance others you need to include for that at drawing stage

When drawing a flywheel with curved spokes you draw a section of the spoke at one end or either end if you also want it ti taper and then a line which is the path trough the middle of the spoke. The CAD will then "extrude" the drawn cross section along that path. You would generally draw one spoke and then use a "circular pattern" to repeat around a ctr point as many times as you needed. Fillets can then be added where spoke meets hub and rim. Will see whatI can sketch out.

Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #7 on: June 30, 2020, 06:54:44 PM »
I just quickly altered my drawing for the Muncaster flywheel from curved to S shape to give an idea, photo names will give an idea of whats going on

Offline Alyn Foundry

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Re: 3D printing, an aid to pattern making?
« Reply #8 on: June 30, 2020, 07:03:27 PM »
WOW

Simply amazing Jason. I wish we could build them as quick eh?

Would you be interested in a " commission " ?   ;)

Cheers Graham.

Offline Alyn Foundry

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Re: 3D printing, an aid to pattern making?
« Reply #9 on: June 30, 2020, 07:07:29 PM »
 ;)

Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #10 on: June 30, 2020, 07:08:32 PM »
Give me some sizes

Offline Alyn Foundry

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Re: 3D printing, an aid to pattern making?
« Reply #11 on: June 30, 2020, 08:05:39 PM »
Probably tomorrow Jason.

But just in case folks thought I was jesting....

The cylinder was too large to bore accurately with my lathe so I resorted to my trusty Buma cylinder boring machine that I had made to work for single cylinder motor cycle engines.

Cheers Graham.

Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #12 on: June 30, 2020, 08:30:38 PM »
That's big!

Quite a few flywheels being printed in this thread by Pat J

http://www.classicsteamengineering.com/threads/3d-printed-engine-patterns-by-admin.1301/

Offline Jasonb

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Re: 3D printing, an aid to pattern making?
« Reply #13 on: July 02, 2020, 11:14:30 AM »
Maybe a picture of the preliminary flywheel pattern will get a few more comments from those with 3D printers or casting experience, if not try saying the flywheel is for your vacuum cleaner which should get the posts flowing :LittleDevil:


Offline steamer

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Re: 3D printing, an aid to pattern making?
« Reply #14 on: July 02, 2020, 12:12:01 PM »
Maybe a picture of the preliminary flywheel pattern will get a few more comments from those with 3D printers or casting experience, if not try saying the flywheel is for your vacuum cleaner which should get the posts flowing :LittleDevil:



sorry guys....not much time these days with my daughter....in any case.   Absolutely What Jason said!....especially at the scale youre building.   A little high build will work, but the finish can be improved by the printer programming, and watching my son do it, it's an art in and of itself.   

Being able to scale the print for shrinkage is very convenient.   Printing a pattern with a fixed parting line is quite doable, and you can also print in the alignment features.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!