I have a future project in mind that involves machining 3d profiled propeller blades out of timber. I figured I’d practice the technique of machining a propeller similar to an airplane prop to work out how to do it.
I’m a little stuck as to how to finish the second side and hold onto the finished part. I am quite confident with 2 sided jobs, but the ones I have done so far are all finished with a profile toolpath and I can use tabs to hold the part on the second side, which are then hand cut to finish the job.
I downloaded an STL and am using it as my model to machine. The toolpaths will be cleaned up a lot (i.e. speeds feeds, DOC etc have not even been looked at), its just a draft of the process I’d use to do the job. The whole file is a ‘rough draft for concept’, I am still designing the future project (which is a ceiling fan)
If anyone has any input I’d greatly appreciate it, I have found a lot of 2 sided videos, documents and tutorials, but none I have found capture the best way to machine something like this.
My usual solution is to use a fixture cut for the part to fit into, then adhesive it in. (see, recently, Polyhedral Brass Dice Set and one of mine from the past A twisted little project ) Essentially, you pocket the negative of the first side to locate and support the part. I use an acrylic backerless adhesive, but many people prefer CA.
For a prop, you can also use the center hole for positioning and holding. A through hole affords a screw, and a non-through hole affords a pin, into the wasteboard.
A could say more if I could open the model. Putting images into you message makes things much easier.
Thank you! sorry I thought about putting images in but it’s hard to know the best way to show how I have it set up so far. I have thought about making a negative for the prop after machining the first side, I may spend some time modelling that now.
The operations are as follows:
1: boring operation for 4 pins - will also be machined into wasteboard
This is where I stumble a bit. I have then duplicated the adaptive and parallel path for the second setup (bottom side), but the adaptive path releases the part from the material and I can’t finish it that way
Given the alignment pins and surround, I would do the first side, then glue a piece of material to the wasteboard and machine the negative of the prop and frame, leaving a little clearance for the frame, remount, being sure to adhere the prop to the support, then machine the second side. If you don’t want it free until the end, set the bottom height for the roughing up into the part maybe 0.5mm so a skin is left. A little adhesion underneath will hold it when it is cut free. during the finishing passes.
To avoid a negative pattern support, you might want to duplicate the model and add a couple supports tying the prop to the frame to hold it all together for the second side (I use “derive” in Inventor for this so I don’t need to modify the original. I don’t recall the fusion operation) A couple light supports and a pin for the center hole may do it for you.
I thought that after you finish one side, you would make a negative of the first side to create a fixture (negative) where you would attach the milled side with place for a nut in the middle. You flip and attach the first side to the jig using masking tape and CA glue. Mill the second side but start with the center portion. When it is finished and the hole is completed, insert a bolt through and bolt to nut in fixture. Finish milling the second side ensuring your toolpaths are not touching the bolt in the middle.
I don’t quite understand - do you mean put in a boundary so that my adaptive operation doesn’t touch the central hole, only my boring operation?
Thank you guys - I think this is the route I will take, I haven’t done any work with jigs, let alone with a 3D jig…
Are there any fusion gurus who can help me creating the negative? I would usually use the ‘Split Body’ command, but it wont let me use the mesh body (the prop STL) as a splitting tool. I tried to convert the mesh body but it says it has too many triangles. If it can’t be done I’ll just model a prop and do the project with it
Really appreciate the help - I have done 2 sided, and 3D jobs, but never both at once
@enl_public your twisted project is great, it shares a lot of similarities to this in the machinine aspect