Making a concrete mold, am I on the right track?

[djarboe]

I want to make a mold to pour concrete pieces for a garden border. I want to put a pattern on the face of the pieces. Of course, my CarveWright came to mind for the face portion of the mold.

Consequently, the carving needs to be "inverse". I just gave it a try with a pattern, set the depth to "0", and the height to a negative value. According to the image on screen, this seemed to do the job.

Has anyone tried this? Does this seem like the right approach?

I've learned it's better to ask this forum before, rather than trust my poor judgment. Saves a little wood, time, and an lot of frustration!

[spalted]

There is an invert pattern button, just to the left of the little drill symbol. It will do it for you in one click.

You know we are going to want to see photos of your casting don't you?

[Kenm810]

Take a look at this thread of post for some ideas
First Concrete Casting ( 1 2 3 ... Last Page)

They might help a little

[djarboe]

There is an invert pattern button, just to the left of the little drill symbol. It will do it for you in one click.

You know we are going to want to see photos of your casting don't you?

Excellent observation. Hmm, guess I should check out all those buttons.
Thanks for the tip! Will post the results, and any suggestions after my trials.

THANKS!

[djarboe]

Take a look at this thread of post for some ideas
First Concrete Casting ( 1 2 3 ... Last Page)

They might help a little

This was actually a lot of help. While my project will produce blocks only about 1.5" thick, the conversation about some sort of mold release for the concrete was quite useful.

THANKS!

[Icutone2]

Please show your work. I have been contemplation this for some time.
Thanks
Lee

[rjustice]

Depending on how big, and deep, it would probably work quite well to carve your shape in delrin. This material machines very well, has a little flexability, and is somewhat slippery, which may eliminate the need for mold release. It can be found in different thicknesses and sizes at McMaster Carr, or US Plastics. Corian may also work well too, although i think the Delrin is a little more slippery. You will need to put a couple strips of tape on the bottom to give the belts, and the tracking wheel something to grip too as well.

Hope this helps, And i would love to see how it comes out as well...


Happy Carving,

Ron

[TerryT]

I started to make some molds with a thermoform machine I built. Seemed to work well except the plastic sheets I was using were too thick and didn't form very well. I still plan to get some thinner material and try again.

[Metalhead781]

I'm actually going to be making some concrete molds. I have a lot of experience as a mold technician and pattern maker for a company that produced aluminum processing equipment. We made molds all day every day to be cast with fireproof concrete. We used mainly foam for the molds since they were only used once generally however some were used several times. The expanded polystyrene sheets you can find at home improvement stores worked great for small molds (considering at times the liners for the equipment took tons of material) . I would suggest making your pattern on thin sheet of this then cutting a "frame" and using some light duty adhesive and insulation washers to hold the mold to a piece of ply. The best and most inexpensive release agent we used was veg. shortening or crisco. We used it by the 5gal box normally reserved for commercial bakeries. A foam mold for blocks like you describe may get up to five or six casts before you'd have to redo it. Just wipe out the mold, a little more crisco and recast.

I didn't bother looking into the other thread so i don't know if this info is in there as well however this is what my experience gives me.

Good luck
MH

[rjustice]

I'm actually going to be making some concrete molds. I have a lot of experience as a mold technician and pattern maker for a company that produced aluminum processing equipment. We made molds all day every day to be cast with fireproof concrete. We used mainly foam for the molds since they were only used once generally however some were used several times. The expanded polystyrene sheets you can find at home improvement stores worked great for small molds (considering at times the liners for the equipment took tons of material) . I would suggest making your pattern on thin sheet of this then cutting a "frame" and using some light duty adhesive and insulation washers to hold the mold to a piece of ply. The best and most inexpensive release agent we used was veg. shortening or crisco. We used it by the 5gal box normally reserved for commercial bakeries. A foam mold for blocks like you describe may get up to five or six casts before you'd have to redo it. Just wipe out the mold, a little more crisco and recast.

I didn't bother looking into the other thread so i don't know if this info is in there as well however this is what my experience gives me.

Good luck
MH

MH,
My background is in the plastic injection mold making business, quite different background than yours, so I have limited knowledge on how the concrete will want to stick to different surfaces. I have built wood forms for sidewalks, steps, and things like that, I was always taught to spray the wood with kerosene, or diesel feul (no smoking during that stage ) and the forms come off easily.

I have pondered the thought of good, long lasting forms, for smaller items, and based on machining up prototype parts at work, i found that the Delrin (which is a plastic resin called Acetal) machines very nicely. It doesnt ball up on the cutter, and leaves a rather shiny slippery surface. I havent tried the release properties of Delrin with concrete, but have with other resins. In your experience, do you think it would want to adhere to something like this, or release easily???.. I have wanted to try this but have never took the time. (actually Lori, my wife has wanted me to try this ) If you were making dozens or hundreds of an item, I am thinking this could be the ticket to keep from having to make several foam forms... Since you have experience with the concrete forming i would love to know your thoughts?

Thanks!

Ron

.... As Iron sharpens Iron, so one Man sharpens another!