The "Cascade" - mini-cup directed jet-impingement block design (56K warn)

[Al Kaseltzer]

It might be cost effective to compromise between injection molding and machining. If the Jet tube walls are the problem, mold them as solid cylinders and then drill them out as a second step.

[satanicoo]

lol hehe looks like a very nice way around it.

[Cathar]

Originally posted by Al Kaseltzer
It might be cost effective to compromise between injection molding and machining. If the Jet tube walls are the problem, mold them as solid cylinders and then drill them out as a second step.

One of the things we did when we first make the blocks was to mill out the tubes as solid pieces, and then drill them. This actually resulted in a high percentage of the tubes snapping off from the pressure of the drilling. That, and the cost of having to use a CNC mill step after the molding means that the cost of the mold has to be amortised over a much large number of blocks (~1000) before break even is achieved.

[Since87]

If molding the nozzles is not an option, how about a molded plastic piece with brass eyelets cast in.

Possible dimensions in inches.

[Cathar]

Originally posted by Since87
If molding the nozzles is not an option, how about a molded plastic piece with brass eyelets cast in.

Possible dimensions in inches.

Take every dimension in that link and MORE than halve it, and we're getting close to where I'm at now.

[Since87]

Originally posted by Cathar
Take every dimension in that link and MORE than halve it, and we're getting close to where I'm at now.

Jeesh, no wonder it can't be molded. I'm amazed it can be machined at a reasonable cost. I had no idea how tiny those nozzles were.

[utabintarbo]

Originally posted by Cathar
Take every dimension in that link and MORE than halve it, and we're getting close to where I'm at now.

Closer?

Bob

[Cathar]

Originally posted by Since87
Jeesh, no wonder it can't be molded. I'm amazed it can be machined at a reasonable cost. I had no idea how tiny those nozzles were.

Well I did find a suitable part no. at their web-site and sent off a query for a quote.

The minimum order size is 37000 (!) and I can't get any for a sample. That's a pretty big outlay for something that I'm not sure if it would work out, and I'm not entirely certain how I would go about "molding them in" in a reliable fashion.

Maybe it's time for a another chat to the machinists...

[Since87]

Originally posted by Cathar
Well I did find a suitable part no. at their web-site and sent off a query for a quote.

The minimum order size is 37000 (!) and I can't get any for a sample. That's a pretty big outlay for something that I'm not sure if it would work out, and I'm not entirely certain how I would go about "molding them in" in a reliable fashion.

Maybe it's time for a another chat to the machinists...

Did you get a cost? I wonder if you might be running into a minimum dollar amount for them to do a production run. Maybe they have another part that is close in stock?

An alternative to casting the top around them might be ultrasonically welding them into place. (Just a thought. I don't know that ultrasonic welding is a possibility with polycarbonate.) You (actually the molder) would need a tool to slide the eyelets onto. Then the tool could be vibrated by the ultrasonic welder, and the molded piece pressed onto the eyelets.

[bigben2k]

Originally posted by Cathar
Well I did find a suitable part no. at their web-site and sent off a query for a quote.

The minimum order size is 37000 (!) and I can't get any for a sample. That's a pretty big outlay for something that I'm not sure if it would work out, and I'm not entirely certain how I would go about "molding them in" in a reliable fashion.

Maybe it's time for a another chat to the machinists...

I would think that that's the easy part! It would eliminate all this fancy CNC work.

Use the same top and simply drill out the holes. You can then either squeeze these little tubes into position, or fasten them, using a touch of an adhesive. The adhesive would only be to hold them in position, for shipping, since the waterflow would take care of it otherwise.

It's a little more hand work, but I'm sure you can figure out a way to do it in less than 2 minutes, for each block.

I guess your question is more about the alignment, isn't it?

[Cathar]

Originally posted by bigben2k
I guess your question is more about the alignment, isn't it?

Yes - alignment is rather important (extremely so). Just dropping them in by hand and hoping for the best isn't going to cut it. I suppose a "guider" piece could be made up so that the middle plate nestles into it and the tubes are pushed through and held in alignment by the guider piece would work.

Applying adhesive to 52 x 1/16" "holder" holes by hand and aligning them is a little more than 2 minutes work though...

Then again, may be possible to do a "press fit" thing. Use the guider plate, drop the tubes in, and have a top plate with pins hanging down that pushes onto the tops of the flanges and tap it with a hammer. This would naturally force the flange to flatten out and jam into the wall of the plastic tube that the pieces are sitting in, and that would solve the problem of keeping them in place and do it rather quickly. Would then have to worry about whether or not the polycarb will crack as a result of doing this though.

Yes, Since87. Bumping in a $500US minimum order size there.

[bigben2k]

You might want to look into the Weld-On products, specifically #4: it contains methylene chloride, which is used to seal cracks in polycarbonate.

Otherwise, I think you've got it.

[Since87]

Found this site.

It rates polycarbonate as "good" for "inserting". (Out of "V. Good.", "Good", "Fair", "Poor", "Not Suitable".)

A quote:

"Inserting = ultrasonic embedding of metal components like inserts into preformed holes in the moulding - provides high strength & speed, no stress build up & reduced moulding cycles."

[utabintarbo]

Molding such things in is a simple operation, the hardest part of which is hand-loading the mold with all those g-d eyelets.

Back later with a pic....

Bob

[murray13]

Consider milling the middle plate out of al. then having it annodized. With no fittings involved corrosion would be at a minimum. Plate thickness could be reduced due to better rigidity. Allignment could be done with shoulder screws (no threads except at the end). You would loose the 'cool' factor, but if it lowered manuf/assem. costs???

[bigben2k]

Yikes! I'd hate to see any kind of Alu in there, but hey, that's just me, but maybe you ought to consider a "shoulder" for the holes that hold the block together: that should help alleviate the alignment problem.

[utabintarbo]

Originally posted by utabintarbo
Molding such things in is a simple operation, the hardest part of which is hand-loading the mold with all those g-d eyelets.

Back later with a pic....

Bob

Speaking of goddam eyelets....

The pic is a little cheesy, but I think the point is discernible.:shrug:

[Cathar]

Thanks guys.

Am chasing up a "sample" size of the piece I need. Had a chat to the machinists about molding this stuff in and they were saying that doing so would be somewhat difficult due to the tiny size of the tubes.

As I described above, we talked about doing a press-fit clamp thing where the tubes are inserted into a molded middle plate. First we have a guider piece for the bottom. This is a mirror image of the bottom of the middle plate which has holes drilled into it just wider than the outer diameter of the tubes. This guides them and keeps them straight. The middle plate sits on the guider plater and keeps it supported for the later press-fit stage.

The middle plate has double drilled holes on top. One hole goes all the way through and is just wide enough for the outer diamater of the tube. The second drill hole is barely wider than the flange and goes part of the way in. The tops of the holes are also chamfered to facilitate water-flow.

The tubes are dropped into the holes and the flange nestles into it's diameter hole that's maybe 0.5mm in "shank" length. A top press-fit piece is then used on guide rails to ensure accuracy and even pressure and it has pins on it which clamped down onto the tops of the flanges. This pushes the flanges out-wards, forcing them to bite into the walls of the middle plate holes thus holding them firmly in place.

The first batch of the blocks are already under way and they'll be made with the milled approach. In the meantime I'll chase up the eyelets and see if this is a viable thing to do. Because it removes the polycarb tubes it means that the polycarb plates can be molded. Heck, if they can be molded, I may look into just doing integrated molded fittings and lose the brass barbs altogether and have polycarb straight-walled tubes coming out the top. You'd have to clamp your tubing onto it though if you were using a decent pressured pump.

utabintarbo, Since87, and bigben2k, if this works out, I owe each of you a free block.

[bigben2k]

Originally posted by Cathar
As I described above, we talked about doing a press-fit clamp thing where the tubes are inserted into a molded middle plate. First we have a guider piece for the bottom. This is a mirror image of the bottom of the middle plate which has holes drilled into it just wider than the outer diameter of the tubes. This guides them and keeps them straight. The middle plate sits on the guider plater and keeps it supported for the later press-fit stage.

The middle plate has double drilled holes on top. One hole goes all the way through and is just wide enough for the outer diamater of the tube. The second drill hole is barely wider than the flange and goes part of the way in. The tops of the holes are also chamfered to facilitate water-flow.

The tubes are dropped into the holes and the flange nestles into it's diameter hole that's maybe 0.5mm in "shank" length. A top press-fit piece is then used on guide rails to ensure accuracy and even pressure and it has pins on it which clamped down onto the tops of the flanges. This pushes the flanges out-wards, forcing them to bite into the walls of the middle plate holes thus holding them firmly in place.

The first batch of the blocks are already under way and they'll be made with the milled approach. In the meantime I'll chase up the eyelets and see if this is a viable thing to do. Because it removes the polycarb tubes it means that the polycarb plates can be molded. Heck, if they can be molded, I may look into just doing integrated molded fittings and lose the brass barbs altogether and have polycarb straight-walled tubes coming out the top. You'd have to clamp your tubing onto it though if you were using a decent pressured pump.

utabintarbo, Since87, and bigben2k, if this works out, I owe each of you a free block.

You know we're going to hold you to that

Is the reduction of the complexity of the polycarb top make molding a viable option? Or is it too early to tell?

I like the straight walled polycarb tube approach, instead of brass barbs. I think you might get requests for a single barb or groove on it, but it's really not necessary.

If it's any help, that Weld-On #4 might come in handy there, if you want to try it, as a prototype. I'd send you some, if you weren't in Oz!

[Since87]

Originally posted by Cathar
This pushes the flanges out-wards, forcing them to bite into the walls of the middle plate holes thus holding them firmly in place.

Wouldn't this create the potential for stress cracking? I did a quick search, and doing this might require annealing the piece to relieve the stresses. The annealing is very time consuming though, and appears to require fixturing similar to the mold itself. (To prevent the piece from warping?)

I'm not sure what the difficulty would be with casting the eyelets in. Maybe voids left in the piece near the eyelets, due to the poly carbonate not filling in as it flowed around?

I may look into just doing integrated molded fittings and lose the brass barbs altogether and have polycarb straight-walled tubes coming out the top.

One thing to keep in mind in designing molds is that all of the surfaces need at least 3 to 4 degrees of "draft". Meaning they need to taper so that the mold comes off the piece easily. "Straight" tubes might be problematic. And clamping tubing onto a tapered polycarbonate 'barb' might be a problem as well. The mold could be made such that it separates perpendicular to the axis of the barbs, and eliminate the need for the barb to taper, but that would leave the top piece having a 'wedged' bottom. Of course Stimpson makes much bigger eyelets too...

Can you get two different parts for that $500 minimum?

utabintarbo, Since87, and bigben2k, if this works out, I owe each of you a free block.

That is very generous of you. I'm hoping molding the parts works out.

[Cathar]

Originally posted by bigben2k
You know we're going to hold you to that

Is the reduction of the complexity of the polycarb top make molding a viable option? Or is it too early to tell?

I like the straight walled polycarb tube approach, instead of brass barbs. I think you might get requests for a single barb or groove on it, but it's really not necessary.

If it's any help, that Weld-On #4 might come in handy there, if you want to try it, as a prototype. I'd send you some, if you weren't in Oz!

No, I sincerely mean it. Hold me to it by all means.

If I'm going to bother with getting the middle plate molded, I'll just get the top plate molded as well in the same mold. The mold would have already been mostly "paid for" due to the middle plate.

Without going into exactly what each plate costs me to get them machined, we'd be looking at very significant savings on the cost to make the polycarb plates if they were molded, as opposed to machined. Enough to amortise the cost of the mold over maybe 200 blocks or so while still being able to reduce the final sale price substantially. Take off the cost of the barbs and tapping for the barbs as well, and it works out very nicely.

Getting the poly fittings "ribbed" like a barb when molding will basically double the cost of the mold, as it's a third dimension operation and requires attaching extra machinery to the mold.

I use straight copper pipe fittings on my radiators all the time, often without clamping while pushing 20PSI through the system and they don't leak. Not something that I recommend, but it shows how a straight pipe fitting can be just fine. Maybe taper the top of the fittings slightly going from 12mm to 13mm over say a 5mm length, so the hoses are easy to get on, but tighten up as you push them further down the fittings. This is basically what a barb rib does anyway and that can still be molded simply. Use 1.5mm thick walls for the fittings which gives a 10mm ID and enough strength, and a rounded base to the fittings where they meet the top of the plate for added rigidity at the stress point.

[Edit: Cross post with Since87] - Yes I'm aware of "drafting" for molds. For polycarb a 2 degree draft is sufficient.

[bigben2k]

Originally posted by Cathar
I use straight copper pipe fittings on my radiators all the time, often without clamping while pushing 20PSI through the system and they don't leak. Not something that I recommend, but it shows how a straight pipe fitting can be just fine. Maybe taper the top of the fittings slightly going from 12mm to 13mm over say a 5mm length, so the hoses are easy to get on, but tighten up as you push them further down the fittings. This is basically what a barb rib does anyway and that can still be molded simply. Use 1.5mm thick walls for the fittings which gives a 10mm ID and enough strength, and a rounded base to the fittings where they meet the top of the plate for added rigidity at the stress point.

[Edit: Cross post with Since87] - Yes I'm aware of "drafting" for molds. For polycarb a 2 degree draft is sufficient.

That 2 degree angle would be perfect!

Is there still a cheaper alternative to molding? I mean, are you sure you're not dismissing the cost, to reduce the amount of time that it would require from you to assemble the blocks?

[Cathar]

Originally posted by bigben2k
That 2 degree angle would be perfect!

Is there still a cheaper alternative to molding? I mean, are you sure you're not dismissing the cost, to reduce the amount of time that it would require from you to assemble the blocks?

Cheaper than molding eh? Like what are you suggesting?

[nicozeg]

Cathar, with that amazing precision parts your machinists can make; having to align the final assembly by eye seems a missuse of your resources. You could design some type of aligning feature on the lower face of the middle plate, that precicely match another one carved on the copper base. This could add some machinning time to your current design, but it will ensure a perfect centering of the jets every time. Once you switch to molded parts, this features comes almost for free.

[Since87]

Originally posted by nicozeg
Cathar, with that amazing precision parts your machinists can make; having to align the final assembly by eye seems a missuse of your resources. You could design some type of aligning feature on the lower face of the middle plate, that precicely match another one carved on the copper base. This could add some machinning time to your current design, but it will ensure a perfect centering of the jets every time. Once you switch to molded parts, this features comes almost for free.

I like the idea. It would be nice to have features that would keep the part from ever resting on the tubes when the block was dismantled.

It might be difficult to get a precise fit between these features. When designing molds you have to take into account how the material will shrink when it cools. However, the machining of the copper could be modified after a sample molded piece was produced, to ensure that the alignment was good.

It's often easier to mold a piece, and make the rest of the design work around the molded piece, than it is to get the molded piece to match precise dimensions.