I have a Genmitsu PROver 1 CNC router table, using a Dewalt 611 trim router. It does ‘ok’ cutting pine and fir and other soft material. But when I cut hard woods or acrylic or other material It loses accuracy. I attribute it to deflection from the gantry, dual wheel system, and the z-axis unit being made of 2080 extrusion with 10mm linear rods & bearings. It started out as a 300 x 400 machine, and I converted it to a 1200 x 1200 machine using their extension kit. I have designed a new Y-axis linear rail conversion, and X-axis/ gantry linear rail conversion, along with downloading the NCcnc Z-axis unit.
Before I start a complete tear down and re-man of this machine, I was wondering if it had been done by one of our members so I can bounce these ideas of somebody else with prior experience.
First off I have no experience with the Prover, but do have a 3018, and a couple home brews with Openbuilds parts, which are similar to the ProVer. I would first look at the deflection in your Z axis. That is where I’d first put my time. It would be possible to replace that if it has a lot of slop. You could make your own out of C beam available from Amazon or Makerstore usa, upper and lower plates, and either acme screw with antibacklash nut, etc. It’s a simple screw together kind of thing. If you want to go with square linear rails in lieu of wheels, you can do that as well. MGN 12 seems to fit better. MGN 15 is kind of heavy duty. I’m pretty happy with my openbuilds contraptions. I’ve been happy in the past with my X carve with extra extrusion and all the upgrades, but wanted to get away from belts.
In playing with the linear rails, the problem I see is the small holes in the blocks don’t really correspond to the dimensions in the 2020, 2040, 2080, or 4080 world. That necessitates custom plate making.
I have only a 1m, not 1.2m, gantry, and even doubled 20x80 wasn’t stiff enough. Heck, even C-beam isn’t great, but it’s a lot better than doubled 20x80.
I have interdigitated belts to reduce backlash. I do have wheels instead of linear rail and would prefer rail, but that’s not the primary source of deflection on my machine, and I’d absolutely invest in a yet stiffer gantry before investing in rails. And I’m someone who builds with linear rails now…
I bought 3 sections and eventually will convert over with ball screws. I’ve been quite happy with the regular c beam stuff, so there isn’t really any rush. It is considerably heavier and I think larger motors could be helpful. Makerspace may be the only ones selling this stuff as far as I’ve seen. I’ve heard that you can get custom extrusion made, but there is a pretty good minimum amount you need to buy to do it. I’m not sure whether that is true or not.
WOW, That’s some thick walled aluminum, about six times the wall T of my material…
The problem of 4080 C-Beam with 1204 ballscrews is that the Ballnut flange with the flange mount doesn’t fit in the 4020 center cavity. or at least the ballscrew I’ve got doesn’t. I was imagining milling/grinding down the radius sides of the ballnut and milling down the ballnut mount to fit with a 1mm clearance per, But the ballnut has plastic wiper/seal inside the ends and grinding that would not be good, besides the amount of shrapnel that would get inside, and I’m not giddy about taking apart a ballnut to see if that would work..
I’ve been pondering the idea of filing the corners off cold rolled square stock 7/16 (because I can’t find octogon shaped stock) and sliding it into the cavities on the outer ends of the beam, then sealing one end and pouring epoxy in it. That would give me a solid piece to drill and tap the 4m thread and It would deaden some vibration and aid in mounting the HGR15 rail.. I think by putting the rail on the outer ends, I can keep the leadscrew inside the cavity, and keep the side to side dims the same.
The down side would be the amount of added weight that is added to the gantry (about three kg with topped bottom rails and dual rail on the Z). But I am not an engineer…
Clearance is clearance. 1mm is a huge gap. Modifying ball nut flanges is definitely a thing; my little CNC mill has that as a feature. But yeah you really don’t want to hit the recirculation channels, and it’s not obvious to me that you could take 1.5mm off each side without hitting them.
For epoxying stock, I’d at least consider a different order of operations. First sealing one end, then pouring epoxy into the hole, then inserting the stock, then filling the remaining space if any — but I’d try to use enough epoxy that it would overflow, and have all the places I didn’t want the epoxy to go masked off, and be ready to pour off the excess.
Well, my idea was to sandwich a piece of 10 mil plastic between the end of the extrusion and the end cap on one end, clamp the extrusion so its vertical, put the stock into the cavity and slowly drizzle the epoxy onto/into the cavity until it is full almost.. And yes, masking off the rest of the world… I am messier that a three year old when it comes to glue of any kind…
I see from the posts that you are committed to changing the linear rails, and any deflection on the old 30x40 will of course be multiplied many fold on the 120x120 frame.
But the torque generated at the router mounts and gantry is much greater when cutting hardwoods and hard materials than when cutting soft materials… and that could account for a lot of the loss in accuracy.
Have you looked at what the gantry and the router mount are doing when cutting hard materials? Don’t be upset when I ask (I don’t know what you know), but are you making several shallow passes or a few deep ones? The stresses on the frame are minimized by taking several shallow passes.
Well, I know that I would expect bubbles drizzling epoxy slowly into holes and would stress about whether it would start to set before I was done. But of course your call!
I plan on using a 24hr(slow setting) hardener because of that issue, and drizzle it on one side letting it back fill Slowwwwly. Like a meditation exercise…
I haven’t tried any precise methods of measuring, But by grabbing the bit in the router(while off) and giving it about five pounds of push/pull, I can get almost 3/16 of deflection in the Y directions, and about half that in the X directions. You are right about the gantry and the Z system being the culprit. I’m of the mind that if you upgrade one axis you should go all the way, I don’t know if there is any side flex in the two Y-axis c-beams but being that I have already bought the linear rails for X and Y and am waiting on the arrival of the 200mm rails for the Z system, I am pretty committed… I’ll be sharing the step files for the conversion soon.
the bright side is the HGR15 bearing block is just shy of the 40mm end of the C-beam, so I am going to keep the linear rails on the ends..
What you have done seems to be pretty precise to me!
And 3/16" is like… 5 mm in real units of measurement! That’s huge even for wood workers like me.
I have cheap cantilever laser engraver/cutter (a single 20x20 extrusion for the Y track and a single 20x20 extrusion for the X track). Works well most of the time but it took me a long time to figure out why rectangles where coming out as trapeziums. Turns out that the V rollers were not tight on the track, so the laser would wobble away from the direction of travel. A couple of eccentric bushes (5 cents each) fixed the problem - I was surprised that the unit did not have them from factory..
Anyway you seem to have taken a sound approach to upgrading your kit. Enjoy the build.
your feedback is appreciated. Also this is the first time I have used the drawing program in Fusion, so it might be a little apprenticeship looking as I have never had a drawing lesson.
I am milling the conversion plates out of acrylic before I mill them out of Aluminum, as I have a lot of acrylic and I have to purchase the Aluminum. OR would you suggest I send the step files to ‘send_cut_send’ for an accurate product?
Modifying ball nut flanges is definitely a thing; my little CNC mill has that as a feature. But yeah you really don’t want to hit the recirculation channels, and it’s not obvious to me that you could take 1.5mm off each side without hitting them.
That’s huge even for wood workers like me.
