We had to produce a number of these double sided signs for a local sign firm , the signs are fitted to a candy display which is placed into a number of shopping centers around the country .
The sign has a double face with a 70mm built up return , the sign is located onto a 3” oval stainless steel pole which is then fixed to the sweet display.
How to make this.
First of all we machined a front and a back face for the sign on one of our cnc routers the faces are machined in 6mm clear acrylic , we machined in a small recess around the inside of the both faces to help locate the signs build up , once the faces are cnc machined and the edges polished we then proceed to adding the graphics , as the graphics are on the inside of the panels so it cannot be vandalized we need to print them in reverse on clear vinyl so they stick to the acrylic once applied the print is back up in white vinyl ,
Once the print is adding to both faces we can start the building of the edge return , we use a pre coated white aluminium sheet which we cnc router to the correct size and width as to fit the perimeter exactly if this is out even ½ a millimeter it will not fit the machined recess so it very important ,we normally machine 12 strips per 8×4 sheet anyway once these are cut we start to build the edge , we cold form or hand form the edge around the profile and stick it into place as we go alone very important to keep the return 90 degrees to the bottom face if not it will not fit into the other recess on the opposite face, once we have the return built and glued into place we add the center block into the sign , the center block is just a basic holder for the stainless steel pole ,
we cnc machine a number of these blocks one for each sign , after we measure and make sure the block is in the correct position we secure it to the sign we normally use a very high quality double side tape as glue can wrinkle the printed image.
How the sign has the main return added to one face and the centre holding block in position it now time to close the sign in by adding the second face , this is the tricky bit you need to dry fit the sign first i.e don’t add any glue until it fits , we place the opposite side on top of the return a bend squeeze or alter the return until it fits into the recess on the other face once it is dry fitting ok we simple add a small amount of glue and then press the face onto the return let it sit for an hour a wipe of any over-spill leave the sign to cure overnight and that’s it job done
When cnc routering acrylic use a good sharp upwards single flute spiral tool a good operator should be fit to get a near polished edge of a cnc router with just 2 machine passes , one for roughing one for polishing .Speed and direction are very important also pay attention to your hold down method the more pressure the work piece has holding it down the better a cnc router will machine it ,cnc machines don’t like vibration this can cause the tool to vibrate which in turn leads to a poor surface and edge finish, another thing don’t be afraid to speed up the tool to many people slow down their routers as they think they will get a better finish but what I have found from over 20 years of cnc machining this is the opposite of what normally happens.
Another tip when cold forming aluminium do not over stress or over bend the aluminium as it is very hard to get it back flat again you are better under bending it always easier to bend it a bit more than trying to bend it back , take your time and bend it slowly as you go along it will stop you getting kinks in the aluminium which are very hard to get out