CamBam
News:
 
*
Welcome, Guest. Please login or register.
Did you miss your activation email?
December 13, 2017, 14:48:21 pm


Login with username, password and session length


Pages: [1]
  Print  
Author Topic: Wax machining -- you may have already thought of this  (Read 638 times)
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« on: October 20, 2017, 19:20:10 pm »

This is just a "Hey!  Lookie what I did!" thing.

I keep some pre-cast blocks of machinable wax on-hand because infrequently, but fairly regularly, I make 'master molds' for casting silicone molds for making specialty 'dipping compounds' for pyro.

I had a mold to make that was ALL the way out to the boundaries of the pre-cast block, so there was no expedient way to clamp it to the mill.  After some cussin' and thinkin', I went out the the scrap pile, and found the worst-oxidized chunk of 1/2" aluminum plate I had that was just marginally larger than the wax block.

I cleaned-up the bottom of the plate, so it would mount securely to the mill, but left the top rugged, raw, and full of pits and oxidation.  Then I heated it until it was just hot-enough to melt the machinable wax, and just dropped the wax block on the plate.  It melted a bit, maybe using up about 0.060" of the bottom, then cooled.

It glued that block to the base-plate like it had been mechanically-fastened!  Milling the master now!

Lloyd
Logged

"Pyro for Fun and Profit for More Than Fifty Years"
driedeker
Droid
**
Offline Offline

Posts: 55


View Profile
« Reply #1 on: October 20, 2017, 20:06:56 pm »

Thats thinking outside the box
Logged
EddyCurrent
CNC Jedi
*****
Offline Offline

Posts: 3256



View Profile
« Reply #2 on: October 20, 2017, 20:16:13 pm »

When storm Ophelia passed over the other night our power went off eight times over a 24 hour period and that procedure is exactly what we do to make a candle stay upright on an old jam jar lid.
Logged
Bob La Londe
CNC Jedi
*****
Offline Offline

Posts: 3026


^ 8.5 pounds on my own hand poured bait.


View Profile WWW
« Reply #3 on: October 20, 2017, 20:38:56 pm »

This is just a "Hey!  Lookie what I did!" thing.

I keep some pre-cast blocks of machinable wax on-hand because infrequently, but fairly regularly, I make 'master molds' for casting silicone molds for making specialty 'dipping compounds' for pyro.

I had a mold to make that was ALL the way out to the boundaries of the pre-cast block, so there was no expedient way to clamp it to the mill.  After some cussin' and thinkin', I went out the the scrap pile, and found the worst-oxidized chunk of 1/2" aluminum plate I had that was just marginally larger than the wax block.

I cleaned-up the bottom of the plate, so it would mount securely to the mill, but left the top rugged, raw, and full of pits and oxidation.  Then I heated it until it was just hot-enough to melt the machinable wax, and just dropped the wax block on the plate.  It melted a bit, maybe using up about 0.060" of the bottom, then cooled.

It glued that block to the base-plate like it had been mechanically-fastened!  Milling the master now!

Lloyd

Since our discussion on rubber stamp making I started melting machining wax into a mold made of aluminum.  I can waste very little wax this way, remelt it in the same mold, and add a little if necessary from chips that blew away the last time.  Since I was going to melt the wax anyway I didn't even buy blocks.  I bought pellets which were slightly cheaper. 
Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« Reply #4 on: October 20, 2017, 20:51:38 pm »

Bob,
I blend my own from a proprietary blend I developed while I was GM of the fireworks factory.  No matter where you get it, it's 'important stuff' for a machine shop.

Lloyd
Logged

"Pyro for Fun and Profit for More Than Fifty Years"
Bubba
CNC Jedi
*****
Offline Offline

Posts: 2280



View Profile
« Reply #5 on: October 20, 2017, 22:29:12 pm »

It glued that block to the base-plate like it had been mechanically-fastened!  Milling the master now!
*********************

Great idea! Something to put in the 'memory' Wink bank for the future..
Logged

My 2
Garyhlucas
CNC Jedi
*****
Offline Offline

Posts: 1029


View Profile
« Reply #6 on: October 20, 2017, 23:23:11 pm »

We build plumbing headers and such for our waste treatment plants from HDPE. We have a Drader injectoweld gun, a hot air welder, a semi-automatic butt fusion welder, a socket fusion welder, a spin welding tool for molded tank fittings.

Now we have figured out a way to spin weld short nipples and flanged fittings using our CNC bed mill!  We mill a flat on the side of a 12 pipe. Then using an arbor to hold the pipe or fitting in the spindle we spin it, rubbing until the material melts and force them together. A perfect weld in about 10 seconds! Alignment and location is perfect too.
Logged

Gary H. Lucas

Have you read my blog?
 http://a-little-business.blogspot.com/
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« Reply #7 on: October 23, 2017, 20:39:52 pm »

You who use blocks of machinable wax might get a tickle out of this.

I had a failure with that last mold.  The silicone resin (bought from a reputable source) was out-of-date, and _I_ didn't read the date before mixing it.  It seemed to mix up OK.

But when I poured it out of the factory containers, only about 70% of it poured out!  All the 'filler solids' they'd added had settled to the bottom and congealed, making it feel like I was mixing it properly, but in fact wasn't getting the 'stuff' off the pot's bottom.  In fact, I tried after, and couldn't even spoon it out with a metal scoop!

So...I didn't have enough silicone to completely fill the mold!  DANG!  And, it didn't harden enough to be removable, thus contaminating the mold, and causing me to have to discard the whole chunk.

I re-designed it, since I had to re-do it anyway... giving leeway for tapered bits to make it easier for extraction.  And the new mold requires 9.5 POUNDS of wax in the master block.  Boy! 

The new silicone coming tomorrow had better be in date.  I sure won't miss checking both the expiry date AND the degree of settlement on the pot bottoms this time! <grin>

Lloyd
Logged

"Pyro for Fun and Profit for More Than Fifty Years"
Bob La Londe
CNC Jedi
*****
Offline Offline

Posts: 3026


^ 8.5 pounds on my own hand poured bait.


View Profile WWW
« Reply #8 on: October 23, 2017, 21:51:36 pm »

There is a cheap and cheesy way to make silicone molds in a pinch.  100% silicone caulk from your local box store, mix a little water.  Apply like paste.  There are guys using this method to make fishing tackle molds from various (sealed, greased, or with a release agent of some kind) masters.  Make sure its listed as 100% silicone caulk or sealant.  One of the keys is a uniform mixture of water through out or it will not cure.  Particularly if the cross section is large.  It does shrink some, but not as much as heat vulcanized silicone mold material. 

I personally use Smooth-On Sorta Clear which is a two part catalyst kicked silicone resin.  It has a relatively short pot life, but its fully cured in 4 hrs, and it has almost zero shrinkage during the cure.  Its kind of expensive, but it has some really good properties for me.  Its also rated as a food grade bakeable silicone.  You could make custom cookie or cupcake molds with it, and bake them in the mold. 

Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« Reply #9 on: October 23, 2017, 22:26:41 pm »

Bob,
That works (and I've used it) when doing an 'exterior application' on single-cavity mold, but doesn't work worth a darn when you've got a multi-cavity mold into which the silicone must be poured.  This is a ten-cavity mold (with DEEP cavities), and with just a little over the minimum-required wall-thickness between cavities to survive de-moulding of the dipping composition.

But thanks.  I haven't done that in about three years, and forgot about the method.

Lloyd
Logged

"Pyro for Fun and Profit for More Than Fifty Years"
Garyhlucas
CNC Jedi
*****
Offline Offline

Posts: 1029


View Profile
« Reply #10 on: October 24, 2017, 01:36:46 am »

You guys talking about wax and molding has me thinking. We make a pressure strainer with a 10 HDPE pipe body and an HDPE end cap we weld on. The cap gets sawed round from  a 4 thick slab of HDPE. Then we mill it round and cut a centered bearing hole surrounded by an offset cone shaped cavity. By time we are done Id say we have about 30% of the original material left.

So how about casting the part in an aluminum mold? Make the mold taller than the part. Fill it with the right number of pounds of HDPE scrap and maybe purge out the air with argon so the material wont oxidize. Bake it in an oven until all the material is melted and leveled out then cool it and pop it out of the mold. We have no problem with generous tapers.  What do you guys think? It gets rid of lots of the clean scrap we generate too.
Logged

Gary H. Lucas

Have you read my blog?
 http://a-little-business.blogspot.com/
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« Reply #11 on: October 24, 2017, 01:53:28 am »

I don't know, Gary.  I thought 'filled' HDPE had to be screw-melted & fed, because it wouldn't become fluid enough to mold properly otherwise. I have 'melt molded' PURE LDPE, but not filled HDPE.   And I am NOT a plastics expert, even though I managed a polystyrene injection line for a time.

There's a difference between knowing how a finished product should look in a pre-defined, pre-engineered operation, and being able to design a new operation!

Lloyd
Logged

"Pyro for Fun and Profit for More Than Fifty Years"
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« Reply #12 on: October 24, 2017, 01:56:43 am »

Um... if I might, though (again, I'm no plastics expert,   but I've actually done this one...).

SHEET HDPE is very easily pressure/vacuum molded into complex shapes.  Maybe starting with a thick-enough sheet and heating it enough would allow you to vacuum-mold such a piece with little waste.

Lloyd
Logged

"Pyro for Fun and Profit for More Than Fifty Years"
Bob La Londe
CNC Jedi
*****
Offline Offline

Posts: 3026


^ 8.5 pounds on my own hand poured bait.


View Profile WWW
« Reply #13 on: October 24, 2017, 02:51:25 am »

HDPE requires pressure depending on the exact formulation, but its my understanding it can be done with a straight piston injector at heavy hand lever pressures like you get from a Gingery type machine.
Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
lloydsp
CNC Jedi
*****
Offline Offline

Posts: 7209



View Profile
« Reply #14 on: December 06, 2017, 21:00:27 pm »

Update on wax machining.

Because my machining coolant 'contaminated' the wax to the point where it "didn't look right" and might possibly have changed its release characteristics, I decided to try pure water as the coolant.

I cleaned out my coolant system well, then filled with straight H2O.

Eh... it's not the best fluid for cutting (even) wax.  There were lots of tiny chips kind-of 'semi welded' to the cut surfaces.  That didn't happen when using my TRIM SC-520 machining coolant.

Now, the chips were not tightly-fastened to the surfaces, just "sticking in place", and a few careful minutes with an acid brush cleaned up all the problems without marring the machined surfaces.  But that didn't happen with the TRIM fluid.

I thought you'd like to know, in case you ever have an inclination to try it.

Lloyd
« Last Edit: December 06, 2017, 21:02:38 pm by lloydsp » Logged

"Pyro for Fun and Profit for More Than Fifty Years"
Pages: [1]
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines

Valid XHTML 1.0! Valid CSS! Dilber MC Theme by HarzeM
Page created in 0.164 seconds with 18 queries.

Copyright © 2008 HexRay Ltd. | Sitemap