New Casting Pattern Evolving --- Angle Plate. Metrology version and Fixturing Version

I have been having some fun designing an angle plate with the intention of making it in two versions in cast iron. Both will have the same curving handle, but the fixturing version will have thicker base and face plates and the metrology version will have still robust but thinner base and face plates. The base plates of both will be heavier for functional and aesthetic reasons than the face plates. The fixturing version will easily accomodate a 5/8" tee-slot and whatever holes, tapped and plain, as one might want. The metrology version intended to be scraped to 20 to 40 PPI.

The patterns and corebox will be filament printed in PLA.

I've been drawing them in Onshape and will provide a few screenshots here. But to really see them nicely rendered and in a format that allows rotation, magnification, section viewing, measurement, etc., it will be best to view them in Onshape by clicking on the link. Note: there are several tabs across the bottom of the page. "Ass'd Insert Base in Angle Copy 1" is probably the place to start.

https://cad.onshape.com/documents/3...renderMode=0&uiState=637aeb8c68307e0562de63ac

The metrology version weighs 17 pounds as calculated by Onshape. It usually calculates casting weights within an ounce or two.



There is still some cleanup work to do like chamfering the edges and I will need to make a corebox so that the lettering can be rendered with an epoxy-bound core. Here is an image of the corebox beginnings.


Another angle:


Here is a drawing (I've got a lot yet to learn about rendering drawings in Onshape.)



Since nothing has been committed to pattern making yet, the plans can be easily altered and I welcome suggestions for improvements.

Denis

 

Excuse my ignorance, what is an angle plate used for?

 

Looks nice Denis. Do you machine the bigger 'L' part square/true and leave the inner two faces and handle/brace as cast?

 

Generally used in machining, fabricating, and mechanical applications, they are used to verify a square condition or to hold work at 90 degrees. Like other precision equipment such as surface plates and other metrology instruments they are produced in varying levels of accuracy and utility. From good to insanely precise. High precision ones are often kept in a padded box and handled like fragile treasure. Unsurprisingly and much to his credit Denis is producing one for more robust mechanical use and one for measurement purposes.
That’s all I know about it. I’ll watch and learn from here.

Pete

 

Pete pretty much covered it as to use. Additional foundry-related issues that affect the usability of the angle plates is the quality of the iron from which they are made. The iron should be very uniform in hardness and, especially for metrology plates be quite soft as that makes scraping them easier. Wear resistance is not a very important factor as they are handled carefully to avoid making dings (which can be stoned off) on the precision surfaces. And, yes, I would definitely keep mine in a custom wood box to protect it from bumps and bruises and rust. In use, it is a common practice to handle reference metrology tools with insulating gloves or rags to avoid distortion due to local heating from body contact. Sometimes users even put aluminum foil on their chest and abdomen to reduce radiant heat distortion.

Fixturing angle plates can be made to tolerances that match the machinist’s needs. Heavy coarse work can be done with milled faces. Next come precision ground faces if warranted. And, generally, the most precise ones are hand scraped against precision master plates (usually granite) and squareness is checked against precision master cylinders or using other techniques. One cool thing about squares, whether a basic carpenter’s square or a precision square, is that they are self-checking if simple proper testing techniques are used.

Side note: 3 flat surface plates can be used as a self-checking trio to generate a 3 reference flats of accuracy limited only by the patience and skill of the maker as worked out by Whitworth in 1840 when the evolving steam/mechanical age was evolving and high precision standards became essential.



Denis

 

We used to make something similar in shape. We cast it with the corner down...v shaped..to avoid machining the ends. The only drawback to that is you would have to core under the handle but would be able to draw the letters on top side without a core.

 

Thanks for the idea of coring under the strut, Billy. I had not considered that. And, yes, I could do it that way. For now, I think I will try it as shown. I am toying with making a silicate or epoxy bound mold for both the primary mold and the core. I think I might make a rather thin-walled primary mold which I would embed in green sand to reinforce it. 3-D printing might easily allow making a fairly form-fitting box in which to form the silicate mold thus conserving bound sand. like I said, nothing in concrete, but thinking along those lines. The hoped-for repair part for my resin printer should come tomorrow. I'll use that for the core box due to resin's finer resolution.

Denis.

 

We totally eliminated all cores here now so any type of handle or protrusion like that has to be mechanically retracted inside the pattern before the mold drawn. Kind of cool but sometimes a pain in the butt. I kind of miss those old days...with all the core boxes..and all the chaplets...and all of the formaldehyde and oil cores smoking up the atmosphere...yeah...just thinking about it gives me a headache.LOL

 

I decided to make a mold of this half-sized angle plate in epoxy-bound sand. I printed core boxes and made half of the mold last night.

Here are Onshape images of the flask with half of the pattern inside (sorry, I do not have actual photos of the flasks):


You can see the pattern drew cleanly and the epoxy mold is bullet-proof. I used 5% 1:5 type epoxy and I probably can use 3% on the drag of the mold. You can see I made divots in the mold to register the drag and there is a blind riser also. Since this will be cast in iron, I added 5 % coal to the sand too. The pattern, riser, and flask were all printed.


Once I get my replacement resin printer and can make the logo portion of the core box, I will insert the core and get this cast. I am very anxious to give it a whirl. I plan to embed the epoxy mold in a bigger green sand mold intending that the green sand reinforce the thin epoxy mold. That is a new method for me.

Denis

 

Today I molded the drag portion of this epoxy-bound mold. Yesterday I tried molding it with only 3% binding epoxy but that proved to provide a core that could be OK for many circumstances, but was not strong enough for this pattern. So, I again used 5% epoxy and that provided excellent strength.

I also used vaseline as a release agent for the bound sand and found it worked extremely well. There was no adhesion of sand to the pattern this time and, though the pattern was still pretty tightly engaged in the sand, it did release more easily than it did with wax.



My resin printer is to arrive Wednesday, So I hope to make a core box Thursday and cast this little angle plate with a real core within a week.

I think I will use maybe 2 degrees of draft on patterns for future small complex epoxy-bound sand molds. That might make release just a little easier. I think green sand must "give" a little to release a pattern. Epoxy is rock solid so it offers no such accommodation.

Note to self: Never buy a printer from 3DPintersOnline Store. They may have the cheapest prices, but you'll pay in wait time and poor responsiveness. They charged my card immediately on getting my order but waited a full week to get my order to UPS. When I complained about their epic slowness, they tried to blame UPS holiday slowness. But that was clearly not the case. UPS is tracking exactly as expected. I pointed this out to the rep at 3D---no response. I should have known better than to order from them in the first place.

Denis

 

You are doing something wrong using 5% epoxy resin also there is a risk of getting blowholes with that much resin. I use 1.5% for very thin cores and have never had one break. Removing the cores from the core box is very easy provided a light dusting of talc is used.

 

That makes me wonder if, for this purpose, are all epoxies created equal? I think likely not and if not, what should one look for when selecting an epoxy?

 

I suppose all epoxies are not created equal, but I am using a reputable 5:1 epoxy---West System. So, I doubt the resin is at fault. It is possible for the small quatities I am using that i did not get ideal distribution of the epoxy on the sand grains. But the distribution was pretty good.

That said, not all "cores" are created equal either. What I am making is a fairly complex mold with lots of tight corners and there is the triangular shape in the center that is "trapped" by the pattern so that it has no wiggle room. I have made cores in the past that had very simple topography and had good luck in the 2% epoxy range.

http://forums.thehomefoundry.org/in...epoxy-and-maybe-polyester-to-make-cores.1924/

But those cores had tons of draft and were very simple. The current pattern has thin deep sections with a lot of surface area and none too much draft at best. I think that i sthe major factor here.

So, going forward, I will pay closer attention to mixing sand and epoxy. And I will try dusting with talc---I did dust for the current molds with graphite which I have usually found to be a better release agent than talc. I will also change my pattern design to include more draft. I am anxious to pour the current mold. My SLA printer came today. So, I should be able to print the core box and pour it in the next week. One possible interfering factor in that schedule is a pretty intense cold spell with temps well below freezing will hit my region in a very few days.

Denis

 

I'd be tempted to offer to buy one from you, but at 11" x 6.75", it's too big for my mini mill.

Roger

 

Thanks for the epoxy core links Denis, I have a need for something like this on a project.

 

Roger, I am planning to print this in full-size and half-size versions. I can not guarantee that this will become a reality. But, I am pushing forward to get the project done. My new AnyCubic SLA printer is printing its test print as I key this message. Waiting for the printer has held me up for two weeks...

This is what my core should look like.


This is the latest and I think final drawing of the pattern with core print.


Thecore is .1" deeper than the core print so there should be a .1" recess for lettering in the handle.

I think the half-size models will be "cute" and potentially useful. The proportions of the drawing above are intended for measurement, not heavy fixturing. I will make a version that has heavier faces that I think will better for fixturing. No reason the lighter one could not be used for appropriate jobs though. Both will be in full and half-sized models.

Price??? Dunno yet.

Denis

 

Cool. I'll stay subscribed to this thread and follow along, then.
And I'd want one for fixturing, please.

FWIW, the Chinese Sieg X2 bed is 3-5/8" wide, so if you kept the 4" width, but half-sized the other two dimensions, I think the size would be about perfect.

Roger

 

I have been back at work on the angle plate pattern including the core box.

Here is a short video of a completed core being removed from the box.
The sand was Green Diamond 100 mesh (6 oz) mixed with 5% sea coal and 3% XTC-3D epoxy. The mold was coated woith a thin coat of vaseline petroleum jelly as this seems to be the best release agent for epoxy cores in my shop. I cure the core with it on a seed germination mat and the whole works covered in a large bath towel. The blanket brings the assembly up to 94F and cuts cure time to 2 hours or less. The result is a very strong core with good resolution of the lettering.

The box is made up of two PLA-printed parts and one silicone rubber part. I used silicone rubber on the letters so that I did not have to worry about providing fillets on the letters. The lettering was molded from a positive constructed as a mashup of a resin print (green in color and higher resolution) and a PLA print (blue in color and convenient):

Here is the vid:

I hope the weather allows a window to try pouring the mold with core soon.

Denis

 

I took the core out to the barn and did some mold packing.

The core fit nicely . However, the sand decided to teach me a lesson about fillets. The broken out area recurred on a couple or three attempts. Though at first it looked OK visually, closer inspection showed the fillets needs some rework. OH, well...

I think the core is going to make a good impression. I am anxious to find out. The weather does not look too promising until Sunday. Though it looks like I should invert it when I make a mold I am actually going to pour.

Denis