Machining & Bonding ACRYLIC 2

[SyncroTec]

I am designing a spool valve using acrylic for the manifold
housing. There are also fluid pathways grooved in the acrylic that are somewhat complex. So the manifold housing is made from sections.

1)I need suggestions on a bonding process that can be done easily with out special equipment and cheaply? I have heard that some companies who specialize in acrylic use diffusion bonding, some use a special solvent. I have heard that MEK works, but not sure on how well it will complete seal.

2) The fluid pathway after machining needs to be smooth and free of particles. Anyone know of a chemical to polish the pathways or a method to do this? Some of the pathways are internal so flame or friction polishing is out of the question.

3) What are the limitations if the acrylic is not annealed after machining?

 

[MikeHalloran]

1. Easy, cheap, ... not possible. Diffusion bonding works, but does distort the parts, especially threads.

You'll need a different solvent for each brand/type of acrylic, and the acrylic suppliers can't be very helpful. When you find the right combination, it works great.

2. Use sharp tools (that are _never_ used for anything else) and slow feeds in the finish cut. The traditional coolant for machining is kerosene. Some soluble oils will work okay, some will craze the acrylic, some will interfere with bonding.

3. If the acrylic is not annealed before and after machining, you will _never_ get a good part. To anneal it properly, you will need to buy a computer controlled oven, use a very long (days) annealing cycle, and build a polarimeter so you can tell when it's sufficiently annealed.

I.e., if you don't farm it out, you are looking at several years of trial and error development.



Mike Halloran
Pembroke Pines, FL, USA

 

[DAVIDSTECKER]

To polish the inside passages you might contact Extrude Hone in Irwin, PA.
It is an abrasive slurrie that is past back and forth through the passages under pressure.
The information I have about them is from 1991 out of Fastener Technology International magizine.

 

[Philrock]

It's my understanding that acrylic can be very simply solvent welded with acetone. Just flood one of the surfaces with acetone then put the parts in contact. Welding happens in seconds, so there is virtually no time to adjust position once the parts are in contact. Excess acetone will evaporate quickly if exposed to open air. Excess acetone trapped in internal passages could be a problem - perhaps you could blow it out with air a few seconds after welding.

 

[Timelord]

Syncrotec,

I have used a lot of acrylic because it is a very good high voltage insulator and easy to work with. MEK will work for solvent welds, but methylene cloride is the best solvent for acrylic. We never annealed it, the benefits were not noticable. To make good solvent welds, you need flush fitting joints and we used to shim the joint open with a small (.005-.010) shim and flow the solvent into the joint wiht a syringe. With the small crack, the solvent wicks into the joint easily. Pull the shims when the solvent has filled the joint and let the sides come together. If the weld is optically clear you have a good joint. To develop nearly full strength takes a couple of days for the solvent to difuse out of the joint.

Timelord