OK, I have been looking all over these forums and there are all sorts of answers to this question. So here is what I am building and I really could use some feedback. I am building a Primo, parts are printing now. Thank you Ryan. I am using Stainless extruded 1" OD .065 wall (I think), polished tube. I am using the standard dewalt trim router. I would like a work surface that is 24" x 24" with about 5" to 6" Z axis. I would like to cut and route all sorts of wood and aluminum. Help me out is this reasonable? Do I need the stands for the X and Y axis to stop the deflection? If I eventually change the spindle to something that is more dedicated for this sort of stuff, and I getting into trouble for this size?
Come one, come all; give me your thoughts.
Thank you in advance.
–BA
Given the usual lengths of endmills do you really think you’ll need that much Z travel? Sometimes easier to bring the work to the bit than the bit to the work.
If it isn’t perfect, it isn’t hard to change it, so I wouldn’t worry about it too much yet.
Wood is pretty forgiving. It tends to let you get away with a lot by just turning the bit faster, and making smaller chips/dust. Aluminum is a bit harder, because it can gum up on itself, and you really need to get the cut metal away from the bit. When you don’t have your Al settings just right, then you need a lot of load to cut with a gummy bit, or plow through already cut chips. That’s why a smaller machine is recommended for Al, especially when you’re starting.
24"x24" is a good starting size, especially if you have no CAM experience. I think you’ll get some great wood projects in, and even dip a toe in aluminum. But a 6" Z has me worried. The deflection in the gantry, and the Z axis is going to be sticking pretty far out to reach the work. Double the distance the Z is reaching, and it will quardruple the flex. If the bit bites a big bite, then all your carefully selected speeds and depth of cut won’t matter.
The “standard” advice is to go with as small a Z as you can handle, and the minimum for the primo is 81mm, or just over 3 inches. That’s enough to carve the side of a 2x4, and do any sheet work you can think of. If that’s not enough, you can build a table with a 3" drop section in it, and just place thicker workpieces in the cavity.
But honestly, don’t worry too much about it. It is your machine and you can do what you want with it. The primo is very new, and we don’t know how a 6" Z will react to aluminum (although I suspect you’ll have a rough time).
As Jeff said, the more the Z travels from its home position the more leverage applied as you’re cutting. Of course a lot depends on your needs, you can tolerate more flex if you’re making a sign than a part that must fit an assembly exactly. The important thing? Have fun!
Ryan recently added a blurb about the Z height on the calculator page. I recently highlighted the part about the Z. So don’t feel bad if this info seems hard to find.
I’m making my Primo 24"x24"x4". It’s very very similar to the size I had for my Burly. After a few changes and trying to add a vac attachment, I think my final Burly size was 23"x22"x~4". I add 3 stacks of 3/4" mdf to my spoilboard when I’m cutting anything less than 1/2". This brings the spoilboard up to the bit to reduce how far down the Z travels for the cuts.