Messages

41

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 28, 2014, 06:57:52 AM »

It's the 15th day of our project. Backlash on all the 3 axes is checked. It is less than 0.01 mm. Not bad. We run a quick setup for hooking up the hydraulic spindle with our controller. The 4 core shielded cable from Khalid comes in handy once again. After checking all the stuff for the last time we shift the machine to the machine shop. A mounting plate for the machine is ready there. We decide to do the first test run on the mounting plate itself. The machine is bolted onto the mounting plate and a 3/4" 4-flute endmill tool of HSCo is mounted in the spindle. Checked the spindle rotation direction. It is rotating in the wrong direction. Switch over the supply pipes and now the direction is OK. A 50x50x20 mm pocket machining G-code is generated on Mastercam and loaded in the controller. Centered the plate, touched it with tool and all the three axes made zero. Depth of cut is set at 1 mm and we start the cut. Machining feed rate set to 200 mm per minute, spindle rpm is 300 (won't go above that). It makes a couple of cuts. So far so good. (see the video in the first post of this thread). After 3 or 4 cuts we notice an undercut on the corners. We check the structure deflection on all the slides. It's not noticeable with a dial indicator. So it must be tool deflection due to extra long adapter and conventional milling cuts we programmed. All my doubts about the machine structure not being strong enough are washed away. Must congratulate Khalid for carrying out a job perfectly.

Checked the load on the servo drives during cutting. It goes upto a max 30% on all the drives. Our guesses for the motor size have also paid off. Now the only job remaining is to mount the machine vertically (the way it was designed to be used) and do the machining which it is supposed to do. We'll do it after lunch. This was the meal I enjoyed the most on that trip .

42

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 28, 2014, 02:56:38 AM »

The second last day of the project is a Friday. We have less working hours on Fridays because of the Muslim prayers break on Friday afternoon. All the calibration and configuration of the machine was done the previous day. I do some jogging tests and adjust the max. feed and acceleration on all axes. Next thing is to test a dry run. Loaded the roadrunner and hit the cycle start. Machine finished the dry run without a hitch. Now test the system noise with the encoder index pulse signals. Uh Oh. Something's wrong again. Axes shifted almost 1mm during the program run. Ran the test again. Same results. Panic time! Checked the wiring closely. Found a loose ground connection. Fixed it. Ran the test again. This time it's only X-axis which is loosing steps. Mr. Nooruddin spent some time with the breakout board circuit and components. There was a spare channel for A axis on the BOB. Shifted the X drive I/O's to that channel and that fixed it. The machine is all ready to go and produce some chips. But we have reached the end of day. We'll have to do all the trial runs on the last day.

43

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 27, 2014, 09:53:53 PM »

Now is the time to make all the electrical connections. We used a junction box on the machine into which all the cables from motors and switches are connected. From here two 4 meter cables join it with the controller box through metallic flexible pipe. Power for all the three motors is supplied through a single 12 core shielded cable. All the three encoder signals and the proximity home switches go through a single 20 core shielded cable in a separate flexible pipe. Connected the motors one by one to the break out board and everything seems OK. Now connect all of them together and the motors start creeping motion by themselves. A quick check in Mach3 pin assignments. Switched to "Step low active" on all the three motor outputs. Creep slows down, but does not stop. Connect one motor at a time, the creep stops. Connect them all together, it starts again. Hmmm, seems like a design fault. System is catching electric noise from somewhere. Finally Mr. Nooruddin figured out that combining all the encoder cables together is causing it. Khalid brought out a nice coil of 4 core shielded cable and each encoder is re-wired separately. Motors are stable now. Calibration of all the axes and the home switches took another 15 minutes. Whole day is consumed in this exercise. 2 days still remain in the deadline. We decided to do the test machining the next day and try the vertical mount with actual simulation of our work environment on the last day.

44

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 27, 2014, 08:46:30 AM »

Machine is transferred to the CNC fitting room from the machine shop. 400 W AC servo motors from Delta are installed on all the three axes. L pitch timing belts and pulleys with 1:3 ratio. With 3000 max rpm of motors and 5 mm pitch on ball screws, we are going to get rapids of 5000 mm/min. Motor power and reduction ratio is selected from experience. We will check the actual load on drives during test runs. Two of the motors were actually dismantled from another CNC machine which we did there 3 years ago. The third motor was taken from Khalid's personal collection. This was all done to meet the deadline. Oh, and the ball screws and linear slides were also from Khalid's personal collection (he was planning to build a 3D printer with them). Any ways, we got all that assembled in the machine shop. Now it's time to do the wiring for motor power, encoders, spindle relay, home switches and emergency stops. After that motors calibration would be done. We are planning to do all that today and perform the test run the next day.

45

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 27, 2014, 03:45:50 AM »

The machine was getting reassembled after paint job when I got there. Looked very unstable at first sight. My first thought was, it's going to spit all the bolts out when they put a 3/4" endmill to the job on this one. I could lift the whole thing with my bare hands and I am not a strong person at all. Hydraulic spindle and home switches were yet to be installed. We planned to install the CNC components on it the next day when the mechanical setup would be over. Everything seems OK till now (except for the flimsiness of the machine). We are right on schedule. Three days to go for the 15 days deadline. I am seriously waiting to see the response of machine with a big tool on.

46

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 26, 2014, 09:26:15 PM »

We are well into the first week of this project and the controller electric cabinet is almost complete. I send it to the paint shop after doing all the cutting and fitting. Then another phone call from Khalid. And guess what, the plan has changed. They have scratched the idea of installing CNC on an old mill. Instead they are going to build another mill with fabricated structure, linear slides and ball screws. Khalid says that they'll do it within a week and I can go and visit them next week. My first reaction was, they will never be able to do it in the time they have allotted for it. I can stay home for some more time. The 10 hours ride to Sadiqabad is never a pleasant one with the condition of roads we have. And the summer heat of 40+ degrees was too much a deterrent. I was hopeful that monsoon rains will ease up the heat when they finish the machine in a month. But, no. They won't let up. I got the call right on time and it was 46 degrees when I reached Sadiqabad the next week.

47

Show"N"Tell ( Your Machines) / Re: CNC Portable Milling Machine in 15 Days

« on: May 26, 2014, 11:28:46 AM »

Thank you Khalid for giving me the job of story telling . OK, here it goes ...

One fine evening earlier this month I received a call from Khalid for converting a machine to CNC. They had a couple of portable milling machines at their machine shop and they wanted me to install CNC on one of them. I agreed to it without any hesitation as all his ideas have always been very unique and challenging (I love both these aspects). There was one hitch though. They wanted all that done in 15 days. The deal was that they will do all the mechanical modifications themselves and I will do the CNC stuff. I started work on the electrical panel box (there's a photo of it in Khalid's post) in Karachi while Khalid started his job in Sadiqabad. What I didn't know was that there's going to be a change of plan midway through which is going to make it more difficult (read more interesting) .

48

Mach4 General Discussion / Re: Comments about Mach4 in Demo

« on: April 25, 2014, 03:10:11 AM »

At first I didn't do it as administrator. Second time I ran it as administrator but, I guess, since a folder was already created in C:\Mach4Hobby it didn't allow to add files to it. I will try to delete that folder and install again in C:.

49

Mach4 General Discussion / Re: Comments about Mach4 in Demo

« on: April 25, 2014, 01:17:56 AM »

Couldn't install it on C: partition of my HD. I am using Windows 7 32 bit. Couldn't write files in the Mach4Hobby folder. I tried D: drive and it installed ok.

Zafar

50

Machscreen Screen Designer / Re: MachScreen releases

« on: April 08, 2014, 06:18:53 AM »

Thank you Klaus for all the marvelous work you've done so far.