Reply with QuoteThat is the smallest Mag-Drill I've ever seen, who makes it? All that I've ever used required a chain hoist to move them around!
Widgit
Once the first rail was installed we started working on the second rail, we used a large piece of 4” angle iron and fixed the 2 bearing blocks to it, then rode it up and down to get the rails parallel. Once the rails are parallel each hole is drilled and tapped one at a time, then a cap screw is installed and the next hole is punched, rail removed, hole drilled, hole tapped, rail put back in place, cap screw fastened then repeat for the next 30 holes. Once all of the holes were drilled, we repeated the leveling process with the jacking screws.
That is the smallest Mag-Drill I've ever seen, who makes it? All that I've ever used required a chain hoist to move them around!
Widgit
www.widgitmaster.com
It's not what you take away, it's what you are left with that counts!
Widgit you should be able to build a mag drill!
This is going to be a monster machine. Can't wait to see how it goes!
Originally Posted by widgitmaster
It's a Jancy Magforce, picked it up rebuilt on Kijiji. Used it SO MUCH on this project. It's heavy but your still able to muscle it into place with one arm and flip the magnet on with the other, once on it's not going anywhere. The bottom of the 6x6 frame has like 60 access holes so that we could install nuts on all of the X-rail cap screw bolts, wanted to it better clamping then just the 3/16 wall tube.
Here it is, cutters are not too expensive either.
Jancy Magforce Portable Magnetic-Base Drill, 120V, 10.2 Amp Motor, 1-5/8" Diameter x 2" Depth Capacity: Amazon.com: Industrial & Scientific
I used this one for my build.
BLUEROCK ® Tools Model BRM-35A Typhoon Magnetic Drill Roto-Broach: Amazon.com: Industrial & Scientific
It worked okay for all the holes I needed. The jack screw idea is a good one. Are you going to pot the rails with epoxy once straight and flat?
Thanks for the link! slimneill+
www.widgitmaster.com
It's not what you take away, it's what you are left with that counts!
Yeah, we are about 80% complete the build now, just need to order a spindle and run all the wiring, get all the electronics working and build the working table. (hopefully by X-mas we will have the wiring done) These pics were taken back in May. We have been at the build for over a year now. The Gantry we built is significantly larger then the CAD pics at the start of this thread.
We had to reverse engineer a lot of the machine to make all of the part fit, this was good and bad, good because we already had parts at our disposal and they were cheap and because that was one less thing that needed to be researched and ordered. But also bad because you end up with parts that are too big, or too small and you need to make them work. The X-ball screw was this way, the ball screw mounting bearings were ~11 feet apart, the table frame we were building off of was only 10’ long, so we needed to improvise, we built 3 shelves from ¾” plate, 2 for either end of the ball screw to mount to and one to mount the X-motor to so that pulley for the motor and ball screw were inline. The motor shelf was also slotted to allow it to be moved to tension the belt once installed.
Once the X-rails were installed focus went to the bottom of the gantry aka the cart which will fix the ball screw to the gantry and support the Gantry’s vertical posts. The cart will support a lot of weight so it was important that it was rigid to minimize deflection. We ended up making it from 2”x4”-¼” wall tube. The X-bearings were mounted to a ½” steel plate on either side of the machine, and then the cart was mounted to the plates. These pictures show it clamped to the ½” plate below.
Anti-twist –Rack & Pinion
We didn’t want to use rack and pinion to drive the X axis, you lose precision and resolution that way. We didn’t want dual x-motor drives, they are a tuning nightmare. We didn’t have the money for dual 9’ ball screws. We wanted a single motor to drive the X and a single ball screw to do it. Now there is a lot of debate about the gantry twisting and rotating on the X axis if cutting on the edge of the table with a large side load, the gantry and consequently the linear bearings will rotate and bind and your accuracy will be reduced the farther from center you get. Well we came up with an anti-twist set up that has eliminated any twist of the gantry that we can physically apply to the machine.
It was an insane amount of work to design and fabricate and make sure it wouldn’t interfere with anything else in the build, we ended up installing a passive rack and pinion setup on the X just to prevent rotation. But we think what we came up with eliminates any of the Cons to using a single drive for a long X table machine.
The basic concept is that you have two sets of racks mounted on either side of the table with pinion gears which ride on the fixed racks as the gantry cart travels up and down the X direction. The important part is to use a stiff bar to connect and fix the two pinion gears together in rotation. So that both pinions are locked together and rotate in unison.
If you come across a case where the gantry is trying to bind up on one side and twist the whole gantry one pinion gear will attempt to travel less while the other travels more (travel = pinion gear rotation in the rack), but because pinion gears are locked together with a large diameter stiff shaft, any relative motion between pinion gears will cause the shaft to try and flex. The shaft’s torsion resistance will make it act like a torsion bar spring and the shaft will transfer force back to the cart in the opposite manner it was created, correcting any cart rotation instantly. It’s basically the same concept as a torsion bar suspension on a car except instead of opposing vertical motion we are opposing rotation.
We used a 1” solid steel drive shaft from McMaster Carr, based on the max torque from the motor and ball screw, the shaft would only flex half a degree over its entire length in the worst case scenario. We fixed the steel shaft securely to the gantry cart using 4 sets of mounted cast iron ball bearings also from McMaster Carr. Then machined some 1”x3” tube and mounted them to the underside of the cart and the bearings under that, using shims to line the racks up perfectly with the racks that we had already mounted on the inside of the 6x6 tube frame.
When it’s all assembled the X ball screw is very close to touching the pinion shaft. It’s all contained underneath the gantry cart and will never be visible. It was a huge pain to install and set up but it could make a huge difference in keeping the table square during side loading. Only time will tell if it was even necessary.
Sorry that took so long to explain.
here are pics to explain the process...
I'd wondered about the gantry and single screw.
That solution is a neat approach similar in concept to the opposing wire over pulleys ("make your gantry rock solid" thread)
I'll be watching the build with interest.
Thanks Pippin88, we saw the pulley cable solution, we thought this would be more heavy duty and robust.
The last step was to mount the ball-screw to the gantry cart. To do this we used a 0.5" steel plate, tapped it and mounted it to 2 of the bearing tubes. The bolted the ball-screw to the plate. X was now complete.
Gantry upright mounting plates
We needed to make sure that this gantry could be adjusted for alignment once fully assembled if we didn’t get it perfect right away. We didn’t want to weld everything for 2 reasons: 1- No ability to correct for warp changes over time. 2-Because this thing the gantry will be over 1000 lbs when fully assembled there is no way to manually lift it or adjust it in fine increments like you could do with smaller machines. Plus we need to be able to put it together without 10 guys, a fork truck or overhead cranes.
We decided to use two ¾” plates machined smooth, with jacking screws to manually adjust for misalignment once all complete. The bottom plate is mounted rigidly to the gantry cart. The top plate has built in slots so allow for up to ½” adjustment if we find ourselves way out to lunch.
The plate you see here with blueing in is fixed to the cart. The top plate is meant to slide on top then be clamped down tight. Because the gantry uprights are at the back of the cart we needed to be able to get to all 6 bolts so the bolts in the bottom thread upwards into the top plate and the bottom fixed plate is slotted. You can see this in pics 3 and 4.
Upper Gantry Fabrication
The Gantry is built up of 5”x5” -1/4” wall steel tube. It was going to be 4” tube but we wanted to ball screw and motor to be completely enclosed to keep the dust out and they were both over 4” diameter. We went with ¼” wall because we knew we were going to be mounting the linear rails to it and didn’t want to drill access holes in the back side to allow for nuts to be installed, access holes would just weaken it. We didn’t know exactly what we would be using as a Z or spindle at the time, but we knew it was going to be several hundred pounds, we had a few ideas but wanted to be safe and be cable of carrying anything we mounted on it.
It started with a 24 foot length of 5x5 and cut it to the correct length using horizontal band saw then milled the ends square and flat. The tube actually turned out to be straighter then we hoped. We didn’t want to take the chance of welding it up and it twisting or warping because then the rails wouldn’t have a flat surface to rest on. So we built the ball screw mounting plates which would be installed inside the gantry. The started off as ¾” steel plate and thick angle iron cut down to look like brackets. The motor is also mounted on the ballscrew mounting plate with slots in the plate to allow the motor to tension the belt.
There are 3” holes at both ends of the gantry to allow for the running of the wires inside the frame instead of on the outside. Vertical pieces were machines the fit and square.
When it was all assembled (pre weld) it was very close to being perfectly flat. The last pic has a 12’ straight edge resting on the surface where the rails will eventually be mounted. There is virtually no rocking, maybe out 20 thou over the entire length.
Last edited by slimneill; 12-13-2013 at 10:15 AM.
holy hell.....
this is a monster machine!
How much Z clearance/movement are you going to have?
The z will is capable of 16" of travel. But we didn't want to have the gantry way up there for the 5% chance we need to cut something 16 inches high. With 3" of plywood on top of the table base there will be 12" of clearance between the bottom of the gantry and the table top.
So 12" of z trave normally, 15" if the table top is reduced.
Nice, so if you add a 4th axis you could swing 15inches in theory.
That is the plan. Already have ideas for the 4th axis. We want to build a 12x6 snooker table and carve the legs out with the machine.
Once we had the ball screw mounts all assembled we put in the other vertical pieces and clamped it all together to prevent as much distortion as possible. We used wood in the center to prevent it from bowing in and clamped it solid is every possible direction we could.
Y-Rail drilling holes
We started by centering one rail on the 5x5 and punching the first hole through the hole in the rail. On the opposite side we put two clamps on it to fix the rails end center on the tube. This way when we move the rail out of the way to drill and tap the hole and put it back into place it’s the exact same spot. We continued this cycle, mark the hole, drill the hole, tap the hole, reassemble the rail with all previous cap screws and then punch the next hole, remove all cap screw, move the rail out of the way, drill …. Until we were done the entire rail. When we were done all of the holes were fairly accurate and collinear which would allow us to adjust the rails easier when they were to be mounted permanently.
Once the first rail was mounted we did the same as on the X, used a piece of steel plate with 2 bearing blocks offset from one another the planned distance. Rolled that up and down the two rails to get the second rail parallel to the first one and repeated the same cycle of marking the hole, drilling, tapping, assembling, marking, un-assembling and so on until it was all drilled straight.
(In the last pic you can see the ball screw installed)
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