Build Thread

Two weeks to go before the final deadline (which was revised to 8 months when we last left Sadiqabad). I get a call from customer that bed is placed on the new foundation and we can come over to finish it over. I prepare my team and leave for Sadiqabad again. 10 hours drive.

The bed is on the foundation, levelled and fastened. They are going to plaster the sides of foundation today. Masonry work won't stop us from doing light work on machine. We install the Z-axis motor with new belt and also put the X-axis motor in place.

Next day, the table is taken off the bed to install the auto-lubricating pump, it's pipes and nozzles. Mr. Nooruddin starts laying out wires for motors' encoder and power cables. Next task is to align the Y-axis screw.

Build Thread

Day 4 of our stay in Sadiqabad. Lubricating pumps is installed on the machine. Laid out its pipes and pressure nozzles. Should have been SS tubes instead of Nylon if we were not constrained by time.

Aligned the Y-axis ball screw today. Vertical alignment was out by 0.5 mm and horizontal by 1.4 mm. Fixed them all and in the end we got both the ends aligned within 0.04 mm. Next step would be to fix the ball nut to the end of table.

Build Thread

The next challenge was how to locate the position of ball nut on the table. There were two dowell holes in the nut but those where blind. Mr. Iftikhar had tried to locate them on the table but couldn't do it and he ended up giving us 3 mm loose holes which we were not sure how much misaligned they are.

We first measured the location of mounting threaded and dowell holes on the nut. Reproduced them on another plate with the help of a DRO based mill. Confirmed the dowell holes location on it by placing it on our nut. This plate acted as a template for fixing our ball nut on the table. Moved the table close to the end bearing blocks, put the dowell pins in through the template and tightened the bolts on the nut. Drill 2 more dowell holes through the template and fixed it to the table body. Sounds complicated? Yes it was. And inefficient too. We'll have to fix it later as we'll learn in the posts that follow.

In the mean time oil groves are machined onto the V-shaped ways on bottom of the planer bed. The original groves were almost cleaned up when Mr. Iftikhar overhauled the bed and grinded the v-ways on his planer.

Mr. Nooruddin is still busy with the wiring of motors, switches and other accessories.

Build Thread

8th day of our stay here. We are working 10 to 12 hours a day (week-ends included!). Khalid's team is also helping us out. Motor's wiring is almost getting there. The Z-axis motor drive is 220 V. Mr. Noorudding powered it temporarily from a wall socket and checked it's motion. The other two drives need 400 V. He has to layout some more wires for them.

Mr. Iftikhar had shipped the radial arm end support column from Gujranwala when we were in Karachi. Now I have to locate it. He says that we have to collect it from the Truck stand in the city. He seem to have misplaced the tracking number and receipt from the movers. All he has is their phone number. I contact them and then visit them. I ask them if they received a 10 ft long 500 kg machine column from Gujranwala. One of their employees recalls it and informs us that the customer has already picked it up. We go back to cusomers' premesis and find that it was lying there in their warehouse during all this time. They didn't know what it's for. We shifted it to the machine shop. It is sand blasted and painted with primer.

With all the screws and motors in place, it's time to put the guards on them. I'm not sure what's the effect of pigeon droppings on ball screw lubrication. Don't want to find out either. So better cover them up. Got some made from a local shop in Sadiqabad and a few from the fabrication shop of customer, we start putting them in place over the next few days.

Build Thread

Vertical shaft of the end-support is to be fixed to the end of radial arm. It is an unmachined cast iron surface. We strip out the paint and bolt a flat 30 mm thick plate on it. The bracket will mount on it. After mounting the shaft to it we check it's alignment. It is found 2.3 mm tilted towards the machine at the bottom end. We take off the bracket and and face its mounting surface to take out the tilt and mount it again. Had to do this exercise twice to make it aligned with the machine within 0.1 mm. Alignment in the other direction is done with a tri-square.

We mark roughly on the floor where the base of the end-support should go and then slide the shaft out. It will be installed again when we align the X and Y axes perpendicular to each other and make sure of their alignment by drilling a sqare pattern on a big surface, measuring the diagonals. The radial arm rotation is locked. We now have to figure out how to keep it locked permanently.

Build Thread

Mr. Nooruddin finally gives us the green signal that we can move all the axes with our controller. This is going to be the first test for 5.5 kW motor on Y-axis. We check all the bolts, belts, bearing blocks, lock nuts etc. and give the motor a nudge with controller. IT'S ALIVE!

Need to change the electronic gearing ratio on the drive to get the full speed. Adjusted that and ran it up to the max of 1500 rpm. There is 1:2 reduction with timing pulleys and 10 mm pitch on the ball screw. So it must be giving us 7,500 mm/min of rapids. Checked the torque on the the drive and it showed 35% torque with continuous running and 65% on start and stop. Tweaked the acceleration setting in Mach3 and ended up with a max torque of 50% on the drive. The initial calculations are paying up and behaviour of machine is predictable. So far so good with the bare table which itself is a 5 tons load. X axis motor is running on 10% of it's rated torque. Seems like we selected an extra strong motor for it. We'll check the torque on Z-axis during the drilling process.

With all the axes running we can make them perpendicular to each other. Unlock the radial arm rotation, dial and clamp a tri-square on the table and make other axis perpendicular to it within 0.005 mm in 400 mm length. Lock the radial arm again.

Build Thread

With the X and Y axes aligned with each other we need to lock the radial arm rotation. Can't disable the unlock switch altogether as unlocking is required to move the drill head on radial arm. Just the unlocking of arm rotation is to be disabled. Time to consult the original mechanical and electrical drawings of machine.

The lock happens to be on top of radial column. The locking electrical logic and the mechanism suggests that we need to disable a micro switch on the column. According to  company's safety rules we can't climb onto the machine structure or use a step ladder. A scaffolding is assembled around the column, we climb it, trace the wire number of the switch and disable it in the main wiring cabinet. Piece of cake. Took a whole day for this exercise.

Build Thread

 Piece of cake. Took a whole day for this exercise.

Hah, hah.  Piece of cake you say?   Well, compared to all the other operations....
 Nice!
But I am wondering.... If the radial arm brace is tightened into position vertically, will/do you have a lockout switch to prevent the radial arm from being raised or lowered until unlocking the brace?  Or will the brace always just float?  The machine could really rack itself if a command to raise or lower the arm were issued if the brace bracket was inadvertantly left tight.

Quote from: zafarsalam on January 24, 2013, 03:14:54 AM

Build Thread

 Piece of cake. Took a whole day for this exercise.

Hah, hah.  Piece of cake you say?   Well, compared to all the other operations....
 Nice!
But I am wondering.... If the radial arm brace is tightened into position vertically, will/do you have a lockout switch to prevent the radial arm from being raised or lowered until unlocking the brace?  Or will the brace always just float?  The machine could really rack itself if a command to raise or lower the arm were issued if the brace bracket was inadvertantly left tight.

It was an overcooked, rather burnt out, piece of cake . Beauty of this arrangement is that just the arm rotation is locked. There are different bearing surfaces which allow rotation and up/down motion of the arm. When unlock button is pressed or commanded through Mach3, only those solenoid valves turn on which supply hydraulic pressure to other locks. That's what we fished out from the drawings of machine. We had to come up with another ingeneous method to prevent the arm from going up and down when braced to the end support. Wait for that post where I'll describe it.

Build Thread

It's now time to calibrate the axes and check their repeatability. We have a couple of linear glass scales and a lathe DRO imported from China. These scales would be installed on customer's vertical lathe once we finish the calibration of this machine. X and Y axes steps per mm are calculated from the servo drives gearing ratio, timing pulleys' reduction ratio and the ball screw pitch.

Align and install the 2.5 m scale to the Y axis of machine. We get a slight difference in the readings on Mach3 and glass scales. It is because we had miscounted the number of teeth on our timing pulleys. Corrected that and ran the slide at different speeds to check the repeatability. A backlash of 0.3 mm is corrected in Mach and we get a repeatability of 0.05 mm. What a nice feeling to achieve the results after such a hard work.

X axis is calibrated similarly. Got an unusually large backlash of 0.7 mm initially. But soon caught our mistake. We hadn't locked the sliding head against the slide on radial arm. Without locking we got a scewed movement of the head which appeared as exeggerated backlash. The backlash with the locks on was 0.25 mm on X.

Z axis was a bit tricky. We didn't know about the internal gear reduction on the handwheel. What we did was put a 300 mm high block on the bed and touched it's top and then the table with a dial indicator on the quill. Noted the difference on Mach Z-axis DRO. Corrected the steps per mm value in Mach accordingly and we are back in business. Z-axis gave us a backlash of 0.6 mm. This was expected as there was a lot of gearing involved in it's movement.

Limit and home switches are also installed while this exercise is underway. End-support column and the guard cover are in the paint shop. Tomorrow we will check the repeatability on Y-axis under 2.5 tons load. Put the end-support column in place and we are finished. I'll be home well before my daughter's birthday .