Electroplating a Plastic Doo-da

1. Select your plastic doo-da. I stole this from a child.

2. Glue a piece of copper wire to it. Make sure it well stuck as it will be your handle from now on.I drilled a little hole and glued the wire in.

3. Clean the surface of the plastic thing with Acetone. Warning: You may need to use a less aggressive solvent on some plastics like Styrene or Acrylic. Whatever you use make sure it's a pure solvent that will evaporate without leaving anything behind.

On this head, I scrubbed with a q-tips dipped in Acetone. It's made of PVC, I think.(from this point on you will *not* touch the part to be plated)

4. As paint doesn't like sticking to PVC, I decided to use a plastic primer. This is not necessary on all plastics. The solvents in the spray paints bite into some, like the ones I mentioned above, quite well.

This needs 20 min's to dry before you coat with...5. Zinc Protect. Look at that! 90% Zinc! I did try another zinc 'cold galvanizing' spray which was just glorified decorative silver spray paint. This can is quite heavy. It dries to a very matt grey, which means very little binder. That's good for conductivity.It is important that the zinc spray overlaps from the plastic surface to the copper wire. You can see in the picture it has gone halfway down the wire. Don't forget; no touching the object.

Now clamp it standing up, somewhere warm. And leave it overnight. The solvents must all evaporate out of the paints and they need to cure before the next step. (the less solvent there is, the more the binder shrinks. Therefore the closer the zinc particles are to each other and the more conductive it is.)
That's it next day. Dry and cured.

5. The magic. Get some copper plating solution and decant a bit into a jar.(You should have you gloves and goggles on by now) You can make up your own but commercial solutions have special additives called brighteners in them and it makes a huge difference to the quality of the finish.


I got this bottle from a company in the UK called Balco.
So go a*head* and dip you painted object in...
When it comes out it looks like this! All covered in copper!I find it needs a bit of time to get a good coating. I jiggle it around in the solution for 60 sec or so. Initially it will give off some gas as little bubbles all over it surface.

This is important: What is happening is the copper in the solution is replacing the surface layer of zinc. The moving of the piece in the solution ensures that the reacted zinc is rinced off the piece allowing the copper to take its place.

6. Now your on to electroplating. This is my set up:
I had to put the vice grips on to weigh the head down because it was floating all the time. Your piece should be submerged so the bare copper wire in just in the solution.
I'm not going to go into how you do electroplating as it is another subject. There is lots of info available on the net and even in books!
Whats important is starting current. As your piece may not be 100% conductive all over you must start plating at a very low current density. That's what they call it "current density".
You can see initially I'm at 100mA. Unfortunately I don't have current control on my cheepo power supply but by voltage seems to work ok.
You'll know if you current density is OK by watching for burning at the wire in the solution. If there is brown gunk developing there drop power by half and watch...
Once you have that minimum level set you can let it plate for a minute or two. Now check it. You may see copper spreading down along the wire over the painted area. Or, on this one, it was plating all over straight away.
Once it is plating all over you can up the current!
The formula is:

Surface in Cm2*0.05= Plating current in Amps

I considered the head to be a cylinder and did a rough estimation from that.
I should note here, it is important to have adequate surface area on your copper electrodes. Twice the surface area you are plating is a good idea.
You can see here I have an electrode at either side of the tank.


Up to 1.8 Amps. I let it plate like that for 2 hours. If you can pump a bit of air through your plating mix it is a good idea. A fish tank airator works well.
I stirred the solution around every few minutes as I checked the progress. Lack of agitation can lead to streaks in the metal being deposited.
You can see the thickness of the metal deposited on the wire. Too thick is not necessary, as this is only a decorative finish.
After a bit of polishing this was the result! I could now burn out the plastic and be left with a hollow copper form.

Critical Backing Pressure

Definition: Maximum backing pressure for a steam jet or vapor vacuum pump to function normally.

This now, I think, has been the major problem with getting my Diff pump working...along with leaks.

I have constructed my pump with a deflector to pump body gap of 5/16" or 4mm.

Not the 2mm as recommended by my ever patient and helpful adviser, Mr. Hart over in the UK. (Who, to his credit, has been consistently correct with his advice over the past few years of my blundering in the world of vacuum. I have always found myself coming around to doing it the way he advised... but only after trying 'my way' first!)


Proceedures in Experimental Physics. J Strong:

The 5/16" clearance between the edge of the umbrella and the condensing wall is not critical, although an optimum exists for any specified set of pressures.

Perhaps 'optimum' should be read as 'maximum' above.


Mr. Hart recounted that he had to heat his homemade diff pump with a blowtorch to get it working the first time. As his electric heater was not doing the trick alone.

www.el-control.dk/katalog/kapitel10.pdf
Page 2:

The critical backing pressure is the highest pressure that a pump can tolerate in the backing line. If the pressure is higher than the critical pressure, the pump may stall. The critical backing pressure depends on:The pump design; the power of the heaters; and the fluid used in the vapor pump.

Now after the disappointment of my homemade diff pump not working, I have new hope of getting some results! I have a Edwards E2M5 on the way.

So the choices to get your pump going are:
-Heat it more.
-Lower backing pressure.
-Or smaller deflector to pump wall distance.

CNC mania

At this stage I have the CNC up and running. Not flawlessly mind you!
So I'd better try to catch up with myself!
After getting the supported rails mounted on the machine base, I got going on the gantry.
I put it together roughly first just to get a feel for what it would be like with the weight of the z axis. It moved very easily. A great relief!. My last machine used bronze bushes in place of bearings. They contributed a large amount of friction as far as I could feel. Though my alignments may have been off.
This is the bottom of the gantry sides. I drilled and tapped for M8 bolts.

One point to mention here is that the end you can see was finished on my trusty Aldi router table!

First I cut the Al. plate1mm or so too long. I then made a clamping jig. This consisted of two pieces of flat Al. bar 15mm*5mm or so. These were bolted to each other "squeezing" the plate in between. With a set square it is easy to fix them at 90 degrees.(good enough anyway!)
I used M6 gutter bolts to hold it together.(Low profile heads)
Now, there is a slot in the top of the router table to allow the use of an adjustable angle attachment. This slot was 6mm deep and 15mm wide. In there went the bottom of the clamping jig.
So with a few passes and adjustments, I got my nice square finish which you see above.

This is the Zaxis. The Aluminium I used was from my local friendly scrap dealer. God bless him!

Believe it or not, the12mm Alu plate I'm using came from a bird house! Now that's over engineering!
I think this axis is fairly self explanatory.
The clamp for the router is held in place with 3 M8 bolts.
In this picture I haven't put in the lead screw yet. As it stands I'm just using M8 threaded bar. I may up grade at some point.

I cut a bit of excess Al. off the to edge of the gantry. To save weight, and to make it "more workman like"!

The top hole here is 20mm and the bottom 22mm(this is to allow adjustability, more on that later). I didn't have a 22mm drill bit so I ended up using the 120 degree V router bit as a drill bit to widen the hole to 22mm! It worked a charm!

*I learned how to drill holes "properly" a few years ago. I would urge anyone to learn the real method and get them right and accurate every time. It is time consuming, especially if you have loads of holes to drill but it is worth it.*

Measure, scribe, spike point with scribe, centre punch.(double check)
Then: Clamp, align with a pointed tool in drill chuck, replace with centering drill. Drill it. Drill with pilot drill bit (3mm, or so), go ahead with the big bit. Up to 6mm/ or 8mm if your drill press is nice and ridged. Then step up gradually. There's more tricks too!

Here are some bearing blocks:

Slight Blog Departure

After a very busy last few months I'm back to my own work again. This time another project has been pushed to the top of the list due to the fact that I may have a job in a few weeks that needs it finished! So a little departure from hi-vac to CNC router. Again, I'm starting this blog in the middle of the project so I'll just drop you in there!

Quick background: This is Mark III 1/2 of "The Auto-Art Machine".
I started with an MDF one(MkI) which was way too large for my needs so I built a smaller Al. one(MkII). That had an A3 sized cutting area. Much more practical size for my needs. It did, however have some issus with 'play'! I made a few modifications to it with linear bearing on the longest axis and a few other changes. Hence the 1/2 mark. I still wasn't happy with the results.

So onward and upward to MkIII 1/2. I decided to go with 20mm rails for my X and Y axis. I bought the hardened chromed steel rail. 2m for just under 40 euro, not bad. I got it from Reliance Bearings in Dublin.(Very nice fellas, easy to deal with and helpful. 'Customer service' is a concept many companies in Ireland have yet to grasp! Not Reliance!)

But then I discovered that 20mm dia' rail will sag over my planned 800mm.(In fact, it will sag under its own weight!) So I needed to support it. I found that 1.6m of supported rail would cost 180 euro or more. So I bought 20mm square Al. bar and a 120 degree router bit, and went for it myself!
Thats the bearing that had to go on the rail. I got the bearings on Ebay 30 euro for the 4. The slot in the bottom of the bearing is 12mm but its diagram reads 10mm and standard supported rail systems have a contact of 8mm. So thats what I went for.


I used the 120 degree router bit for the shaping of the supports. I used my cheepo Aldi router table again! Using plenty of cutting oil, I did maybe 14 or 16 passes on each rail. V groove first then the sides. And got this:
I drilled them every 100mm or so to attach the rail. And I learnt that drilling case hardened steel is difficult... Untill you learn the trick! Which took me 10 bad holes. (of 16)
So here is the way I did it:

First, you will need to grind a flat. If you can get all the way through the case hardening at this point all the better. But the thing is, the case hardening was 1.5-2mm thick. This means that even if the centre of your ground area gets through, the edges did not. Very important. Next mark your centre points with a centre punch. As you are through the hardened steel in the centre it should mark just like mild steel. If not grind a bit more.

Next you will need a tile drill. Choose one with the external diameter of your thread. M6=6mm tile drill. The tip of the bit tapers down to a point so it will only be the case hardened bit which recieves the full 6mm dia., as you will only drill a little way in. The interior of the hole will be ok to continue with a 5mm, normal HSS drill bit to finish the hole. I went in about 15 mm in total. Cutting oil all the way...

Then you can get going with your tap. In theory it will never touch the hardened steel at all. I found the cone shape left by the tile drill led the tap in really well. So the last 6 holes were a dream! I broke a tap very early on, maybe hole 3 or 4, it just touched the hardened steel and snapped right off.
I counter sunk some cheese head m6 bolts and that was that.
A quick note: Aligning all the holes to be square to one another was tricky. What I did was drill and tap the first hole. Screw a nice long piece of threaded bar in and it can be used as a referance to make sure the bar is always rotated to the right angle. You could use a spirit level against the threaded bar. I eyeballed it against the pillar of the drill. That's not a good idea.

This might be a good spot to promote my new portfolio website.

www.robertclarkemodelmaking.com

Yet More Leak Testing.

Well the past few days have been filled with leak testing. It has been frustrating. Good silver solder joints going bad. Which means they were not good in the first place!
This is my blanking cap for the top of the pump barrel. Its only 6mm thick. That is the thickest I had unfortunately. I cut a groove on the lathe. As you can see it chattered a bit. Its not a big deal because it not the mating surface.

I polished the outside ring where the o-ring would press against. That all worked out well.
You see, the piece of Al. was not big enough to be a flange too, so I used this piece of acrylic as a clamp. The real problem is that the acrylic bend when you start getting near the right compression on the o-ring (20%). This, I found was deforming the cap slightly. Enough to pop the J B Welded brass adapter off.

It held long enough to do the first few tests. I am doing them at 4 Bar.


Initially I had two small leaks. So I fixed them with great enthusiasm and retested. I then found I had four leaks...


This pattern went on for two days till I finally had it sealed. So now I believe my pump is air tight. Vacuum tight? We'll see.

New Pump Interior

After the failure of my two stage chimney design I was convinced to try a single jet instead. Above is a photo of the 2" copper pipe I'm using. Its upside down here. The small holes are for the condenced oil to flow back in to the middle and the larger ones, higher up are for vapor from around the outside to whizz in to the chimney and go up.
Again this is upside down. The skirt in this case is the same diameter as the interior of my pump barrel. This is only a cap over the condensed oil not a down jet deflector.

I cut 5 nicks in the cone with an angle grinder to allow oil to flow back in to the reservoir. The cone here is another stainless steel funnel.

I don't have a pic but the deflector is also one of these funnels. I have an 8mm clearance around the circumference of the cone for the vapor to bridge before it hits the pump wall.
Fingers crossed.

Nickel Plating

I got a bit of Bright Nickel plating salts from Caswell Europe. I'm using a 'slow cooker' (which I pulled out of a skip) as my plating bath and a pure nickel electrode. This solution likes to be a bit warm in use.

I think the main things about plating successfully are: cleanliness and current control.

My power supply doesn't have current limiting so I have to use the voltage control and just watch the mA meter. Its probably gives a slower deposit or something, but I've had good results with it.
Here is one of my electrodes. I just did them for the fun, I really need to nickel plate the copper parts of the diff pump interior.

I did notice how slippy the surface became after plating. Even to run you fingernail over the surface is quite different to the feel of copper. It must become very flat and smooth at a microscopic level.