Monday, December 31, 2007

PICKIT2 Clone

Just received a PICKIT2 equivalent from the courier service few minutes ago. Works on first plug in... uses Microchip standard software (PICKIT2 and MPLAB) without any other software or driver... real value for money for those developing with PIC...
Had a double AA carrying case next to me... nibbed a small rectangle for the mini USB connector and fixed a double-sided tape to the back... voila... an instant casing for the programmer/debugger... protecting it from short circuit as well as handling abuse...

While I try to find time for the millions of hobby I have, I wish a VERY HAPPY AND SAFE NEW YEAR to all...

A very productive weekend...

Managed to accomplish a lot this weekend... Went for grocery shopping, took the kid to the park, had some nasi lemak, and, of course, worked on the hobby...

Finally got the time and peacefulness of mind to make the mount for the high speed water cooled spindle. Milled out of 0.5in 6061 aluminum, it worked like a charm. The riser was from the old proxxon riser, so I only had to make the horizontal piece. I also took the time to replace the water pump to a bigger unit with about 3m max head pressure... no problem so far...

Photo showing the spindle on the sherline... apart from the color, it is a nice match... no problem for the z-axis stepper to move it up and down...
The spindle bottom view. I mounted the magnets as per previous installment... tested and worked fine... may explore closed loop spindle speed control later...
The enclosure and the water cooling tank at the bottom... after about 2 hours of cutting with reasonable load, the water temperature rose about 5 deg celcius... nothing to worry about...
The first piece totally milled using the high speed spindle... from the center hole to the middle and end slots to the drilled holes... What is it... a new riser for the sherline to replace the old ones... so far so happy with the results...

Thursday, December 27, 2007

Quick update on PWM-to-analog for Mach3

I was using the schematic from here to make my PWM-to-10V converter. After changing the PWM frequency from the default 5Hz to something around 200Hz, I was able to somehow control the VFD input. Still got some issues but currently using a workaround.

  1. Converter not giving full 10V at maximum frequency. At full speed, the converter only provides around 8.5V thus limiting my top speed to around 20000rpm. Workaround: Set maximum operating frequency on VFD to around 30000rpm thus at 8.5V, I was achieving 24000rpm.
  2. Frequency control not linear. I notice that the accuracy of the PWM control is around 5%. This is within my acceptable 'error rate' :-)
I believe the problem really lies in Mach3 configuration somehow. Will continue to search for optimum solution.

Also found out that the aquarium water pump I have does not have enough pressure to push the water up the tube (about 2.5 feet vertical) when tube is empty. Need to get a bigger pump soon...

Wednesday, December 26, 2007

VFD in Driver Casing

Had some free time over the holidays so I decided to give a go to locate the VFD into the current driver casing. Initial test shows that the VFD isn't as noisy so there is no false step on the stepper when the VFD is operating. Photos show the results...

This is how my front cover looks like. The VFD is under control of Mach3 (except for the spindle speed. Still awaiting suitable optocoupler for PWM-to-10V conversion).
The internals. The VFD is mounted on the drive bays using a bent 4mm acrylic.
The rear plate. Separate socket for the VFD power input and additional socket for the VFD 3-phase output. VFD connectors on top whereas the stepper connectors at the bottom.
Photo of my breakout board. The two relays to control the VFD forward and reverse switches under Mach3 command.

Next to do is the PWM-to-10V converter. There's a spare parallel port pin available for that function. The first converter I made had two problems: unable to hit 10V at maximum output and fluctuating voltage during intermediate pwm. Probably the optocoupler I have isn't suited for the intended purpose. Back to component sourcing...

Wednesday, December 19, 2007

Final version of the cooling system

Got some free time last night so I managed to tryout the new setup for the cooling system. It's basically the same approach. Main difference is the size of the container, all the interconnect tubes are plastics and the cooling fins resting horizontal on top of the container. The 6-liters cooling water should be able to absorb significant heat should the heatfins fail to dissipate it efficiently.
Wanted to stick the inverter for the high speed spindle into the driver casing... waiting for suitable free time... also need to acquire some connectors for the mains power and the spindle 3-phase wires... later on that...

Monday, December 17, 2007

Been a busy weekend...

Managed to find time to work on the hobby during the busy weekend...

The stepper drivers repacked into a new casing. More space, easier for maintenance and upgrade. A full height PC casing makes modding very easy...

Broke the cover of the old meters but mounted it anyway...

Current contraception for the cooling system to check for flowrate, pressure drop, etc. Basically an aquarium pump passing through a CPU cooler heatfins... Yellowish green came from the car radiator coolant... So far so good, able to take the heat of a stalled 800W spindle... Most likely not the final setup... not happy with a few things...

Wednesday, December 12, 2007

New toy... Water Cooled High Speed Spindle

Picked up this spindle yesterday. Should be able to handle my milling requirement... overkill for the Sherline but can be used later should I decide to replace the Sherline. Need to make the mounting as well as the water circulation system...

Spindle Spec: 800W, 150V max, 400Hz max, 24000rpm
Inverter Spec: 1.5kW, frequency upto 1.5kHz, voltage upto 400V (3-phase)

Thursday, December 6, 2007

Accomodating noisy Sherline spindle...

For the past 1 week, my system was acting funny. Whenever the Sherline spindle is on, my steppers would step by itself. Changing to different spindles (Proxxon/Dremel/Router) doesn't replicate the problem. I presume something is wrong with the Sherline or my electronics somehow became more sensitive to noise.

After several trial to fix the electronics (rearranging the wires, putting a noise filter) and the spindle (checking for worn-out brushes), I gave up. Details here at Yahoo group

After digging further and several internet searches later, I decided to make myself a low-pass filter to be fitted at the input (step/dir/enable) of my stepper driver - PICStep. This site triggered me to do it and I used the values given there (1k0 resistor, 1n0 capacitor, ~150kHz cutoff). It worked like a charm from the first power up. Not a single step on the steppers either when the spindle is running or start/stop switching. Everything back to normal now... Photo of the contraception with schematic shown below.

Monday, December 3, 2007

Engraver infinite hands...

Every engraver know that sometime it is really PITA to get the material to be engraved to be 100% flat. I was helping a friend to set up his Sherline CNC last Saturday and and, as luck set in, I noticed he was repairing a top end engraver unit (probably a Roland machine). The material to be engraved was placed flat on the machine without any clamp whatsoever... Upon my enquiry, I was 'introduced' to the adhesive plate the unit had. It is basically a foam like piece of rubber/plastic that was kinda sticky (think of Post-It note). The best part is that it is reuseable if taken care correctly... Quickly acquire some for myself, comes in sheet about 2mm thick and 200mm x 125mm rectangle.

Shown below, the adhesive foam on an engraving jig for my Sherline. I mounted it on a piece of 4mm acrylic coupled with basic ruler made from normal engraving plate.

The same jig in its' storage box... the small piece on the right is the balance from the original piece... anyone read Japanese?