CNC Letters and Totem Signs
We were asked by a local sign company to help manufacture the totem sign plus a number of Aluminium composite letters.
THE PROCESS FOR EXTERNAL LETTERS
Quite a simple one we were supplied A CAD File (Computer Aided Design) from the sign company we checked over the file to make sure it was ok for CNC machining once we checked the file we had to work out and organize the material for the letters this was done by nesting all the same colours of letters into separate 10×5 sheets to get the best yield once the nesting was done we saved the main CAD file and exported it to A.I so we could program the tool paths (the code that tells the CNC Router what to do) the letters here in this case we doubled up with a white background and a blue face both made from Aluminium composite material.
Aluminium composite (a material with a plastic core sandwiched with thin aluminium skin typical .3mm thick each side comes in various pre painted colours very common in the sign trade as it pretty cheap easy to machine and has various finishes).
Now that we have the CAD file ready for machining we import this file into our CAM software so we can start to programing the CNC machines. We use Artcam for our CNC routers as it's a very good and a powerful software package.
How do you Create tool paths for cutting these letters
First of you need to set the model size in the Artcam software this is typically the size of the material you are going to cutting or it can be the size of your CNC machine bed, for this it is just the material size we used 10×5 sheets which is 3 x 1.5m
Once you enter the material size you import your file after the file is uploaded make sure you maximize your material by nesting the letters nothing worse than wasting material, now your letters are organized for best yield from the material you need to set their position within the sheet and within CNC router bed his is done by setting your datum points (a point where the CNC reads all the measurements from) you normally have 2 datums one on the software and one on the CNC machine bed, with us we set the datums from the bottom right corner of the sheet and the same on the CNC router.
Now we have the letters nested, set in the correct position for machining the next stage is to apply the tool paths this is very simply, you simply select what you want to cut, click the profile tab within this drop down menu you have various commands like cut position –inside line or outside line, cut direction– clock wise anti clock wise, speed of cut, spindle Rpm, lead ins etc, you simply select what commands you need and then apply them to your selection, after you create this command this is known as your tool path.
You have your tool path created now so next thing to do is send that code to the CNC router for cutting this is a simply process all you do in our system is save the tool path into a specific folder in the machine spooler. Once the tool path is saved you are finally ready to start cutting the sheet, go to the CNC router controls on the machine, load your material onto the machine bed secure the material via the vacuum system make sure the hold down is good so material does not move when being cut, select your program check the cutting tool is sharp and not chipped if all of this is fine hit start and let the CNC router cut away. After the CNC Router is finished turn of the vacuum hold down and dust extractor then remove the cut letters, clean down the machine bed if needed then repeat the process for the next sheet.
Thats the basic of CNC cut letters now with this job we needed to glue the 2 sets of letters together again a pretty simply process just sand down the back layer so the glue has something to stick to, glue and press the letters together allow to cure and they are ready.
For the letters fixtures we simply used large sign locators again glued onto the back of the backing letter, the local sign company who these letters where for want to do their own layout so that saved us a bit of time not having the do the paper layouts.
THE TOTEM LIGH BOXES
We also had to clad a large steel frame with white and blue folded composite panels the overall size was 10m in height with 4 sides and 2 inlayed light boxes.
PROCESS FOR THIS
We were given the outside measurements of the existing steel frame all we had to do here was create a number of folded panel to go over the steel work pretty simply we made up the panel design in composer and transferred this to the CNC router for cutting and folding all the panels where the same size just in various colours white and blue, we machined each panel and fabricated it so it would fit onto the steel work the local sign company applied the final graphics and done the fitting, really quite a simply totem wrap.
THE LIGHT BOXES
The light boxes where just not as straight forward the main problem was we had to add a halo light that would go around the perimeter of each light box, each light box was inlayed with white acrylic and covered in yellow trans vinyl so they would illuminate. We made the folded fascia box and inlayed them with 5mm opal acrylic we also made a back box to hold the electrics which fitted nice and neatly inside the front box after some discussion with the local sign firm we thought it best to make a frame to space these folded panels of the main totem this also gave us room to add leds onto the back of the back box this in turn gave us a really nice halo around the entire light box just a quick and simple way of creating this halo light any other way was just tricky anyway turned out great and it was a nice job to do