Matchplate Trial. Simplest posssible patterns. Good learner Project

I am making another couple aluminum flask sets that require 12 pcs each set. Since the patterns lend themselves to convenient matchplate molding, and since I hope the matchplate will save me some time overall, (and since I was curious about the technique), I decided to give it a go.

Here is the first pair of side pieces for which I am making the matchplate. Both sides of the patterns are basically flat with two rectangular recesses. So, on one side I am just attaching the drafted pattern to the plate and on the other side I used Bondo to make the corresponding raised bumps which will make recesses in the casting. I simply used a square to transfer the location of the larger piece so that the bumps are correctly located.

I found that PVA made a nice parting material that prevented the Bondo from partially dissolving the lacquer I use as a finish on the pattern pieces.

Here are a few self-explanatory pics:

Here I am pressing the Bondoed pattern to the "bump" side of the plate. On the right is the bump from the other pattern piece done previously. When the Bondo got to the "leather" stage, I peeled off the squeeze-out.

Here is the PVA coated pattern pulled off the Bondo.


Here is the side opposite the bump side of the plate. I think I will just screw these pattern pieces down and fillet the join line slightly. You can see the location transfer lines drawn on the plate.


Here is some repurposed pine material planed and jointed to be assembled into flasks.


My plan is to use the mill to accurately locate holes and pins in the plate and flasks to make the cope and drag line up properly when assembled. I will make runners, risers and gates as permanent parts of the plate to save cutting time. Hopefully the runners etc will be adequate to make these simple parts cast correctly. I've already cast tem as loose patterns and their simplicity leads to easy casting.

Tomorrow I will cut the pine to proper length and screw the flasks together. I should be able to cast them soon. There will be a couple more match plates to be made as the drag height is different than the cope and cheek flasks.

I am open to suggestions as I am just trying to figger my way through this new-to-me process.

Denis

 

It looks like you’re off to a good start!

 

Looks good!

You have a cheek?

 

Yes, I drilled the plate and flask holes and put pins in the appropriate places. Then I primed it with some Evercoat High Build primer. Should be ready for a trial run tomorrow.

Yes, the pattern requires a cope, drag, and cheek arrangement. It is a prism shape and pours well pointy side down, but does not pointy side up. If I could pour it pointy-up, it would be a simple cope and drag. I have two other prism shapes that also want to be poured pointy side down too.
Using the cheek allows gating into the dependent convergence of the planes of the prism. Here is an early pour.

Here is an aluminum pattern I recently poured for an 18" prism. The yellow sand is a silicate core that is starting to fall out of its own accord (as desired).



Denis.

 

Yah, well, even the simplest project can be screwed up by the inept! Were you guys just sitting back waiting for it to dawn on me that the 4 bumps I had molded on the one side of the plate were NOT going to result in indentations in the casting? A little light went on and I tumbled to that realization. I need bumps in the sand not on the pattern!

So, I put the plate on the mill and converted those .080” high bumps to to .080 recesses. Easy enough, but still kinda embarrassing. Then I mixed up an ounce of epoxy resin and poured/painted it into the recesses where it wicked up the sides of the recesses to form nice smooth fillets. Now that’s more like it.

Denis

 

Nice work you are doing there.

 

I must say, I did wonder what the bumps were for.

 

As did I but, I figured, Denis is pretty sharp and has a lot of casting experience so I just assumed he knew what he was doing and let it go at that.

 

Nice work using the resin Denis.

 

Well, despite a potential pitfall entered but exited in time, the matchplate did its thing nicely this afternoon.

you can see I made a robust riser gate between the two flask sides. I wanted to be sure there was no shrinkage of the sides and there was not. The riser sits right under the pour basin and between the sides so it was sure to freeze last. It did feed the cast flask sides a bit. Knowing now that the plate works I’ll add the runner and splash basin to the drag side. It is sweet using a plate as the pattern pieces are pre- located, the riser is in place and “drawing” the plates is a cinch.

here are a few pics of the pin system (riser/gate block not yet in place)


Here are the castings.


I fumble fingered the cope and caused bridging at the far end of the casting. No big deal since I’ll use a table saw to remove the gate and that bridge.


Denis

 

Thanks. I like that the stuff can really work for you under the right conditions. Those milled out recesses required zero additional filleting beyond adding the resin.

Denis

 

A match plate is great to use when you can just blow and go after fiddling with patterns and feed systems by hand.

Great work!

 

Here are a couple pics showing a method for securing pattern pcs accurately located to the plate and at the same time providing a tiny fillet at the join so awss to avoid sand catching at the junction of the pattern piece and the plate. Accurate location of the pattern piece on side A (shown)
makes machining the recesses on the other side of the plate in their proper location relative to the pattern pcs pretty easy.

I used conventional epoxy glue (West 105/205) to glue the pattern pcs ontot the plate. One problem I encounter when using is epoxy glues is that they are very slippery and parts tend to want to creep as clamping pressure is applied. So, I used 1/4" ground and polished dowel pins to locate the pattern pieces on the plate. With the pins locating the parts I could clamp without having to chase the parts around the plate. By painting a modest amount of glue to the part prior to clamping, I could ensure some squeeze out. By making a swipe along the join with a paper towel it's possible to remove just the right amount of glue so that the remaining glue forms a tiny fillet as shown in the close up. Not having to futz with making a fillet at the join of the plate and pattern piece saves a good chunk of time. Plus it feels good. ;-)

I will pull the pins after the glue starts to cure for an hour or two. I did spray them with silicone release, but don't want to have to force them out after the epoxy sets up.



Denis

 

Good work.
A recommendation: use longer pins for your flask. When drawing the pattern, it keeps the mold/flask aligned with the matchplate long enough for the highest part of the pattern to clear the mold, and prevents fudging of corners The mold face won't be able to hit anything on the matchplate.

 

I hear you on the pins. These patterns are so shallow I can rock the cope off the drag using the pins as a sort of hinge. On some flasks I do have long pins and they work OK. But, I do like to use the rock method when feasible. Just a personal quirk, I guess. Once the flasks are off the plate there is no protruding sand. So reassembly of cope on drag requires no long distance quidance, only registration.

Denis

 

Now I have 3 matchplates for making flask parts. I am really liking using them and since each flask set takes 12 parts (4 each for cope, cheek, and drag) using the match plates is a real plus.

Here are a few pics:

Packed oil-bound sand molds made from repurposed pine waiting for aluminum. I'll pack a fourth and fifth tomorrow. For scale the smaller mold is 9 X 18 inches.


The three plates. Two showing the drag side and one the cope. The center plate has the pouring basdin/runner screwed into place. It is similarly positioned for each of the three plates.


A cope pulled from the plate.


I will be pouring a bunch tomorrow or Monday. Also planning a simutaneous iron melt/pour with the aluminum melting in my electroic furnace while the diesel is warming up the iron. Big day. Melting aluminum in the electric furnace is so easy, it is practical to let it cook while either melting iron or packing molds.

Denis

 

One note on rapping matchplates prior to drawing the mold off the plate: I am starting to suspect that rapping a matchplate flask to the degree that I ususally rap loose-pattern or follow-board molds may produce excessive movement of the flask relative to the somewhat heavy plate and may damage vertical surfaces on the mold. I have occasionally noted unexpected weakness of vertical surfaces on match plates pattern molds and, in thiniking about it, I believe it may be due to to much side-to-side movement of the plate and pattern relative to the sand. I'd like to hear others' observations in this regard and I will be modifying my rapping in the future. Always something!

Denis

 

I have similar experiences. I think making generous draught angles, where at all possible, is the biggest help to a clean separation, with no rapping,

Cheers Charlie

 

Today I did no rapping—-just a clean crisp lift. Very clean result. No soft edges.

I think a wood loose pattern in sand can easily move with the sand as you rap the flask so that rapping is quite gentle at the sand/pattern interface. But the plate attached to a pattern greatly increased its inertia and may result in bigger forces at the sand/pattern+board interface.

I have loose patterns that have a 1/2” diameter semi-circle of sand oriented convex upward that I learned the hard way not to rap at all side-to-side. Rapping jiggled that cove of sand enough to fracture it at its base. I can rap lightly vertically which would have compressing effect and that causes no trouble. But side-to-side cracks it at its base. Now it seems obvious as to what goes on. But rapping is such a habit, it took me a while (too long) to tumble to it.

Denis

 

To elaborate on Charlie's post: the better your pattern is - draft, fillets, finish - less rapping is required for a clean pull.