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Did you use a center punch and center drill on those holes?
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Hi gang; I'm a long-time lurker on the forum and have been learning oodles over the past 2 years. I began construction of my cnc about a year ago, but only recently found the space (in my Dad's garage!) to attempt completing the build.
I will be making a modified Solsylva belt-driven cnc within a completely enclosed box to control dust propagation. The CNC frame itself will be welded steel and have a table area of 48" x 30". Since I have to operate in a section of the third car garage, I am trying to make everything as compact as feasable.
I have already built the hobbycnc controller and will be using the 305oz-in steppers. The majority of the gantry parts have also already been cut out and drilled on a POS Harbor Freight drill press. I used a caliper, center punch, and Dykem to locate the holes, but I think slop in those crappy bearings are going to be the limiting factor in regards to the accuracy of the placement. Hoping to get .001" - .003" accuracy over the length of the table when the machine is complete.
I'll start of with a few pics:
1) Here a draft of the overall design concept. The box sides will be hinged to allow accomodation of oversized pieces.
2) My Dad in the process of helping me put together the "box". Completion of the box will be the next step in the build.
3) All the gantry parts drilled and ready to go. Will begin assembly after the housing box is completed.
4) The results of my Dykem layout and crappy Harbor Freight drill-press.
Last edited by sonicwonder2000; 06-03-2009 at 08:36 PM. Reason: spelhing
Did you use a center punch and center drill on those holes?
Yep. Center punch, and a 1/16" pilot hole and then stepped drill sizes to the final size.Originally Posted by Hirudin
I finished up most of the box today by adding gussets to stabalize the whole thing. It is VERY stiff! I can sit my 180Lbs butt on the table and jump up and down with no perceptable flex. The table top (mdf) sits flat, but the table frame is not completely flat. Rather than screwing the mdf on, I will need to use some gap filling glue (silicone?) to ensure that the table top sits nicely. Just for the record, I HATE this polyurethane "gorilla glue"; the stuff foams and gets everywhere! Hope a bit of paint will make it all look better ...
Pics:
1) A detail of the framing.
2) The mdf layed on.
3,4) An example of the gap
5) Table flat
Lest anyone think I've been slacking, I've actually been hard at work on this machine; made some progess, had some setbacks, and learned LOTS of lessons ...
1) GAS PIPE sucks for rails! This stuff is just not straight. I sanded mine smooth, and my neighbor even asked if it was stainless steel because it looks so purdy. Even though it looks straight to the naked eye, there are minute twists and variations in the surface. I was hoping to get .001" accuracy per foot over the length of the table but I now feel even .01" per foot might be pushing it. If I had a lathe, I would turn it down, but lacking the resources and funds I will live with what I've got.
2) When modeling with CAD, make sure you model nuts and account for their clearances. I have had a ***** of a time grinding parts down to make them fit. A dremel has definately been my best friend on this proj so far.
I'm gonna try to bring this thread up to date with what I've completed thus far.
Pics up next ...
Last edited by sonicwonder2000; 07-02-2009 at 12:34 AM.
First up - the gantry beam. This consists of an aluminum channel with gas pipe rails which are drilled and tapped and bolted on atop a 1"x1/2"x1/8" c-channel. I started off using "shelf standards" for the rail supports. This stuff is basically stamped sheet metal and as crooked as a politician's smile. I switched it out for the 1x1/2" aluminum extrusion which was very straight. The differences in clearance required me to futz with the rest of the machine so everything would fit correctly. A painstaking take-apart, grind, fit, take-apart, drill, fit, grind process ensued that took a few days to complete.
PICS:
1) A rendering of the parts which have been completed so far.
2) The gantry beam laid flat.
3) The gantry beam end view.
Last edited by sonicwonder2000; 07-01-2009 at 08:27 PM.
Next up, the gantry side plates. These go on either end of the gantry beam and have bearings that ride on the x-rails (which have yet to be constructed). The idlers are made with pvc piping per David's instructions. The construction of these plates went off without a hitch.
PICS:
1,2) Side plate (stepper side). This will eventually carry the y-stepper motor which will drive the z-car via a belt. Note the "figure 8 cutout" - it was meant to be circular to house a bearing but i made a small boo-boo
3,4,5) Side plate (belt-tensioning side).
Last edited by sonicwonder2000; 07-01-2009 at 08:28 PM.
Now is when things started getting REALLY hairy. Construction of the gantry z-rails. Again, I started off using shelving standards, only to discover that it was not straight. I replaced it with 1x1/2x1/8" c-channel extrusion and that created some real problems with placement. Everything in the z-car is VERY tightly placed, and this change seemed to ripple out, redimensioning all the nuts, holes, and clearances in the carriage.
I rebuilt the entire z-rail system only to discover it was still twisted a small amount (1/64" or so). Come to discover it was my gas pipe rails that were buggering me up all along... Oh well - 1/1000" is pretty much out the window now
PICS:
1,2,3) Z-rail. The spindle will eventually mount to the bottom plate.
4) The belt retaining/tensioning mechanism. Although this looks big, the whole thing is pretty small. Those screws are 1/2" #8 machine screws.
Next up the z-carriage. The entire assembly will ride along the gantry beam providing z and y axis movement. As mentioned above, the clearances here are excruciatingly tight. I had to grind off almost every nut to make everything fit correctly.
PICS:
1) Z-car front. Z-bearings are mounted here and pulled in to the z-rails via 1/4" threaded tensioning rods (not shown here)
2) Z-car back. Houses the y-bearings which are pulled to the rails via tensioning rods. If you look at the bottom angle, you will note that it had to be mangled to allow for the shorter clearance of the new aluminum extrusion rail supports.
3,4) You can see how close the bearings rotate to the nuts. They had to be ground down to prevent rubbing on the bearings and causing binding.
Last edited by sonicwonder2000; 07-01-2009 at 08:30 PM.
And now the whole z-car assembled (minus the drive mechanism). This took a week of tweaking to get all the clearances working without binding. VERY frustrating, but (hopefully) working now.
PICS:
1,2) The z-car with z-rails and tension members in place.
3) Top tensioning member. Note how close they are to the z-rails. The z-bearing bolts and nuts had to be ground down to allow the bearings to sit slightly lower and create clearance.
4) Bottom tensioning member. Tight again!
The z limits of travel will be defined by where the belt clamps begins to impinge on the pulleys. I will need to put some sort of mechanical stop here as well as limit switches.
PICS:
1) Bottom travel limit.
2) Top travel limit.
More updates to come soon!
Wow, sonic, you've been busy! That is certainly going to be one stout carriage! I can't believe you got all that stuff in there - the fit was tight enough in the basic design!
I do have a couple of comments, looking at the pictures - I would get some nylock nuts and use them everywhere. After my table started running, any bolt that had jam nuts would eventually loosen. This was even after I used Locktite (the blue removable one.)
It looks like you've got aluminum pulleys. So do I, but I've had to order some steel ones that go on the steppers - they would work loose, especially on the Z axis, which has to lift the carriage and the router. The steppers have a flat on them, and the set screws were in line with them, but they still worked loose. As soon as they slip you've lost steps, which ruins the work. Trying to tighten them, when there is only 1.5 to 2 threads to hold on to, just doesn't cut it. And yes, this after using the Locktite stuff. I hate set screws. I am going to try the steel pulleys, and if that doesn't do it, I am going to look at pinning the pulley to the stepper shaft.
Although the black pipe might seem rough, since the gantry is rested at four points it evidently gets evened out a bit as it travels. I know the pipe was much straighter than when I started tightening the mounting nuts. Getting them firmly attached without distorting the pipe took me quite a while. Much is made up for by making a constant Z pass with an endmill across your sacrifice board - whatever variation there is in Z as X and Y changes is somewhat compensated by this. I thought about getting some better rod, but that costs lots of dinero, but we can always upgrade to that if need be later.
Anywho, looks like you're doing a great job on your table, and I hope it works like a swiss watch for you!
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