Hey all - working on building my frame. I’m brand new at this so any feedback would be appreciated.
I’m limited to a single wall of my garage, and I don’t have the luxury of depth required for the traditional stands if I’m going to park a car in it when the CNC isn’t in use. That being said, I’m going for a hinged, wall-mounted frame and I just want to make sure I’m not crazy. The basic idea is here (admittedly not to scale or in CAD or anything fancy):
The boards are 2x4s. Orange are motors, purple are hinges, red are screws (circles go deep, lines are pocket-hole screws), blue is the wasteboard/cutting area (3/4" mdf? 1/2" mdf?), green are adjustable (stick out more or less) brackets to support the work-piece until it can be secured to the wasteboard (or if the cut doesn’t go too low). I know I’d need some flip out supports that will give the angle I need from the hinges. Any pro tips on this design before I go ahead and get materials?
I’ve seen a LOT about unistrut (and I admittedly don’t know what that is, how much it’ll cost, or how to secure things to it - all of which I do understand about a 2x4!) - so I’m open to suggestions. Also, should I put the motor bar as close to the hinges as possible?
Looks good, I have a hinged frame too with 4 heavy duty door hinges. The reason was to test different tilt angles (8° too less, 20° too much) when in use and to make it flat when not needed.
If you have width, go for a 12 ft motor distance. Better accuracy in the low corners. You might want to consider a thin ‘frame’ around the sheet to be able to cut to the corners without the sled tipping.
I might be able to do 12’ - my understanding though is that I’d have to get a different chain set, right? What’s the inaccuracy zone with a 10’ setup? Is it just inaccurate to in the bottom corners 1’x1’ area? or is it a large portion of the bottom corners? Also, how much of an inaccuracy are we looking at? If it’s 1/16th or better, I think I can live with that for a while.
How wide does the frame need to be to cut near the edge? 6" buffer to keep the sled from tipping or more like 12"? Also, if you cut materials of different widths, that frame will need to be adjustable to the width of the material, right?
Yes, longer chains needed. If you got your set recently, you might already have the longer chains.
A very rough estimate of problematic areas on the sheet is this. The white is ok, the more it goes into the blue, the errors get bigger.
There is a great excel-sheet in the Forum where you can enter you sled weight and the dimensions of your frame to see the forces, just need to find it… 3mm and more errors in the corners. It however also depends on how good you can calibrate, but getting the frame right is the best way to start.
just a few inches so the sled still has support, and yes, would need to be same thickness of the material you are cutting
Ok. Thanks for the visual. I think I’ll put a 12’ board across if it’ll fit, and then just mount it at 10’ for now if the chains are too small. I ordered my kit this week from EastBaySource so I’m not sure if that has the longer chains or not, but I’ll check when I get it. It seems like they need to be 13’ long for a 12’ setup - is that right?
I’ve seen the spreadsheet, but I honestly don’t know what to make of the force values. What value is “good” or “bad”? I saw some chatter about the force being related to the tensioning you need to give to the slack chain (e.g., a 8 lb force meaning you can use up to an 8 lb weight for tension or something like that), but beyond that, I’m not sure how to interpret the values there. It’s safe to say - I’m no engineer, but I’m teachable. A layman’s interpretation of the force values, what’s too high and what’s too low, and what happens as you go higher or lower than safe values would be nice to help me understand the machine better.
I’d go with a 2x6 for the beam holding the motors and make sure it sits out far enough to keep your chains parallel to the work surface, which will depend on your sled ring height, which will be dictated by the weights and router selection/ z axis setup on the sled.
Thanks for the input. I’m fairly sure I’ll use the Rigid R22002, two bricks from Home Depot, and the default z-axis that comes with the EastBaySource kit (which I understand isn’t optimal, but better than manual!). Planning on cutting 3/4" plywood. I’m making my sled out of 3/4" melamine (heard that helps reduce friction), so I should probably add some scrap 2x4 underneath the 2x6 to get it to sit out far enough yeah (since the sled ring will be further out than that.
Thanks for all of the thoughts as I work toward getting this all set up. I’m excited to start building - Open to more input/suggestions!
Another question:
Since the weight of the sled is primarily at the bottom, can I avoid adding a frame at the top?
If I add a frame to prevent the sled from tipping when near the edges, that should only apply to the 2 sides and maybe the bottom (depending on the angle of the frame). I’m envisioning a set of removable frames of different widths that can get added onto the base frame depending on the thickness of the material being cut - it would be fairly easy to do if gravity and chain tension keep the sled on the piece near the top and at the bottom. Anyone know if the sled tips off the top or bottom near the edge or if it’s just the sides?
It depends on where your sled center of gravity is and when it tips. If you are cutting with 1/8" bit, which are shorter than the 1/4" bits, the router is closer to the base and it may be less likely to tip than if using a 1/4" bit and is further out from the surface. If the ring is too low, it will tip off the bottom, if too high, it will tip off the top, so it will depend. I don’t have a frame around the cutting area and mine tips off the bottom, but not within 1/4" of top. I don’t run to the sides all the way. It won’t tip off the edges of exposed material in the middle of the cut area, but it is easy to frame stuff in the middle of the work space. You will have to try it and see what works. It could get heavy if you put a lot of framing on it and want to lift it up on the hinges. Also, you might consider putting in a stop or way to ensure your system slope is consistent when you cut so the sled movement and calibration is consistent from setup to setup.
Thank you @Orob. Below is a modified design (more to scale-ish) with a 12-ft board setup (2x6) a shorter frame (since it didn’t affect the numbers in the spreadsheet too negatively) to save space. I’ve included the output from the excel sheet to get feedback on whether or not this will work. I’m hoping to be able to use the whole 4x8 sheet with some degree of accuracy - we’ll see how calibration and setup goes!
Blue = wasteboard, Red = screws, Yellow = stop to hold angle, Purple = Hinge, Green = adjustable hardware to support the piece until mounted to wasteboard, Orange = motors.
Please contribute any feedback you might have for this design! I’m hoping to go buy it all tomorrow or Friday!
EDIT: It looks like I’m hinging the motor beam to the wall, but I’m not - that beam is secured to the 2x4s underneath it (which are secured to another 2x4, which is hinged to the wall).
you need more space at the bottom. 1" will expand when hinged out, but you need at least 12" to move router to bottom, otherwise bricks will hit the floor.
increase the height of the motor bar as well 30" is better than 23". Most projects are cut in the middle. make sled weight around 26-27 lbs , the defaut is around 23 lbs, not 20 lbs like the spreadsheet says
@Metalmaslow thanks for the suggestions. The distance from the bottom isn’t from the ground. This rig will be hanging about 2 ft off the ground in the garage, so I shouldn’t have issues bottoming out.
Totally didn’t think about the sled weight changing so I’ll up it to 30” motor to workpiece distance
Final sketch of the set-up before I build. Any last-minute revisions? I have the space, so I went ahead and raised the motors to 36" (have the space to go higher, but is there any measurable benefit?)
Make sure the beam with the motors can not flex. Not even a little bit. I had to mod my 2x4 3 times to get the flex out and ‘sandwiched’ scrap wood to it (not pretty). Perhaps bringing the outer two hinges closer to the motors would prevent a flexing?
You could also use hard insulation foam sheets. I use OSB, probably not the best for the bit-life. I have the sheets nailed to the frame with a nail-gun and plastic nails, so no tool gets killed. I mix my own wood-filler out of sawdust and wood glue, so the spoil-board gets a bit of sanding and can stay ‘forever’.
Edit: I get my OSB for free from a marble factory. It is waste packing material for them
what kind of hinges did you wind up using? looks like you used cement screws to attach a 2x4 to the wall and then you used regular butt hinges to connect to that?
