Help needed building a expandable frame for moulds

[SMaund]

Hello all, I have been trying to design a frame that is expandable. It will be used as a mould to make resin sheets.

It needs to start at the size of 30cm x 10cm up to 3M x 1M and able to stop anywhere in between Height or Length.

The design I have included has a routered straight cuts in the longer sides of the frame, so that the two shorter lengths can slide along it. Although this will not allow me to adjust the Height.

The design isn’t flat like it is pictured, I’m not able to draw things in third dimension.

Please let me know if you know a way of doing this, or if I need to give more information, thank you.

 

[Sporky McGuffin]

You could maybe do something like the Trend Varijig:

 

[Keith 66]

^^^^^ First class idea, Place on a sheet of melamine faced chipboard or plywood (or plate glass if you can find a bit big enough) You will need to apply a release agent either wax polish or blue pva release agent (Not the same as pva Glue!)
Radiuses on inside corners if required can be done with plasticine or you can buy wax corner fillet already made in various sizes from grp suppliers. You can also use brown packing tape to protect what you dont want resin to stick to.

 

[Sporky McGuffin]

I've had an apostrophe!

Make a set of side beams out of melamine faced chipboard (stealing that bit from Keith 66), maybe at 50cm, 1m, 2m, and 3m lengths. In the "top" of one end of each drill a vertical hole, then you can use four of these (similar exist on other colours at different prices) to hold the whole thing together:

https://www.axminstertools.com/ujk-technology-universal-fence-clamps-pair-502711
Thus you get smooth internal faces and infinite adjustability. Maybe add a squaring bit on the outside of each beam so that the clamps inherently pull the jig into square - if you're cunning about the shape of that bit then pretty much any clamp could work.

If that doesn't make sense I could do a little 3D drawing in Rhino later.

 

[Adam W.]

I've had an apostrophe!

Did it hurt ?

 

[Droogs]

I would epoxy the varijig set up to the bottom of boards and then once the size is set seal the corner etc with bathroom silicone, adjustable, reusable and easily cleanable

 

[Sporky McGuffin]

Did it hurt ?

Only when I lathe.

 

[SMaund]

I've had an apostrophe!

Make a set of side beams out of melamine faced chipboard (stealing that bit from Keith 66), maybe at 50cm, 1m, 2m, and 3m lengths. In the "top" of one end of each drill a vertical hole, then you can use four of these (similar exist on other colours at different prices) to hold the whole thing together:

https://www.axminstertools.com/ujk-technology-universal-fence-clamps-pair-502711
Thus you get smooth internal faces and infinite adjustability. Maybe add a squaring bit on the outside of each beam so that the clamps inherently pull the jig into square - if you're cunning about the shape of that bit then pretty much any clamp could work.

If that doesn't make sense I could do a little 3D drawing in Rhino later.

Thank you very much for your feedback, a drawing of your idea would help greatly.

 

[SMaund]

Thank you all for your feedback

 

[Inspector]

I see a flaw in your desire to have a one size jig for all. How to clamp all the sides tight to the base sheet when you are in the size ranges where the reach of your clamp jaws end? Two sides can always be along the edge of the base sheet but what to do when you want to hold the other two sides that are not near the maximum limit of the sheet? If you screw them down your base sheet ends up riddled with holes that will mess up the finished product. The only possible way I could see it beginning to work is if the base is sheet steel (on a welded frame to keep it flat) is painted with a tough paint and the size bars have a lot of magnets in them like these. https://www.leevalley.com/en-ca/shop/tools/jigs-guides-and-fixtures/56000-mag-jig-magnetic-clamps. They would end up costing more than multiple jigs in the sizes needed most often or sacrificial made and scrapped as needed.

Pete

 

[Sporky McGuffin]

I see a flaw in your desire to have a one size jig for all. How to clamp all the sides tight to the base sheet when you are in the size ranges where the reach of your clamp jaws end?

I was wondering if you'd have to seal the jig to the base plate anyway, at which point you could just clamp each beam to the base where it crosses it at an edge to hold it in place.

I didn't get around to doing a sketch yesterday, but I think I can illustrate this easily enough when I do.

 

[murphy]

I see a flaw in your desire to have a one size jig for all. How to clamp all the sides tight to the base sheet when you are in the size ranges where the reach of your clamp jaws end? Two sides can always be along the edge of the base sheet but what to do when you want to hold the other two sides that are not near the maximum limit of the sheet? If you screw them down your base sheet ends up riddled with holes that will mess up the finished product. The only possible way I could see it beginning to work is if the base is sheet steel (on a welded frame to keep it flat) is painted with a tough paint and the size bars have a lot of magnets in them like these. https://www.leevalley.com/en-ca/shop/tools/jigs-guides-and-fixtures/56000-mag-jig-magnetic-clamps. They would end up costing more than multiple jigs in the sizes needed most often or sacrificial made and scrapped as needed.

Pete

Does anyone know where to get these magnets in the UK, or feather boards with the same magnets

 

[Yojevol]

There known as Magswitch. Just google that. They make a variety of accessories to go with them but not cheap.
Brian

 

[murphy]

There known as Magswitch. Just google that. They make a variety of accessories to go with them but not cheap.
Brian

Thank's Brian, yes I found them on Amazon, which seems to be the only UK seller, and you are correct they are expensive

 

[Sporky McGuffin]

I've got a couple of the featherboards but they were bought on sale. They're really, really good, but I can't deny they're expensive.

 

[Yojevol]

Summarising the advise so far this is my take for an economical solution:-

There would be a fixed rail along the long edge and movable rails as shown. Use G-clamps wherever possible and a UJK style clamp at the inaccessible point. My contribution is to use weights to keep the rails flat on the table which would have to be strong enough to minimise distortion.
Screws in lieu of the weights may be possible if old screw holes could be filled and sanded off.
Another suggestion is to have various lengths of rail available to minimise the surplus ends sticking out from the table.
Brian

 

[SMaund]

Summarising the advise so far this is my take for an economical solution:-
View attachment 124741
There would be a fixed rail along the long edge and movable rails as shown. Use G-clamps wherever possible and a UJK style clamp at the inaccessible point. My contribution is to use weights to keep the rails flat on the table which would have to be strong enough to minimise distortion.
Screws in lieu of the weights may be possible if old screw holes could be filled and sanded off.
Another suggestion is to have various lengths of rail available to minimise the surplus ends sticking out from the table.
Brian

Thank you very much Brian, that looks like it would do the job perfectly

 

[Sporky McGuffin]

I like the fixed rail idea! Otherwise that's very much like I'd imagined - here are my sketches:

Individual beam:

The whole shebang (minus base plate):

 

[baldkev]

What resin are you planning to use? And what thickness?
If its for thin sheet in epoxy, make the biggest size, pour your sheet and cut the sizes you need..... probably easiest

 

[SMaund]

I like the fixed rail idea! Otherwise that's very much like I'd imagined - here are my sketches:

Individual beam:

View attachment 124754

The whole shebang (minus base plate):

View attachment 124755

Thank you, I like the square edges and would make for easy clamping, I think I will implement that, thank you for taking your time to do this