Excitech CNC Modifications Thread...

[Eclipze]

Interested to find out what modifications people have made to their machines.
Both necessary modifications and optional modifications.

I've finally got the time to get the CNC up and running for my requirements, and it's turned out to be a bigger job than expected. I'II post up some of my mods...

[Eclipze]

SHM0609 with 1.5kW HSD Spindle.
Increasing the Z-axis travel.

I had a look at the travel on the Z axis and was a little surprised to find I could lower the collet to the table surface, "before" the travel ran out. I worked out the axis could lower another 20mm (if the table wasn't there ). Given the smallest tool bit I have is ~20mm, the spindle is set ~40mm too low.

The maximum travel the Z carriage can move is ~160mm. The most I could move it was 134mm before the collet nut was touching the table. If I had a small tool bit loaded, then it's really only 114mm of travel. Which is rather pathetic given the actual 160mm travel available.

I removed the spindle mounting plate and machined new bolt holes for the spindle 40mm higher. The result is I now have a spindle that moves from 16mm above the table to 176mm above the table. Perfect result, as with my smallest tool bit loaded I can still machine to the table. I still need to face mill the table to get it level, so I'II end up with a few millimeters more room

The distance between the table and the bottom of the gantry is ~124mm. So now I can load a tool bit 50mm long and still get full clearance under the gantry.

I considered having multiple position bolt holes, but it seemed a pain to align the spindle plate once, and I wan't to thread lock the bolts. So ditched the multiple position option.

Summary:
Before... 0 to 134mm travel. Usable range, 114mm
After... 16 to 176mm travel. Usable range, 156mm (36% improvement).

[Eclipze]

SHM0609
Earth Wiring... Australia 240VAC.

They've wired up the earth for the stepper transformers, 24VDC power supply and the VFD, but did not wire it to the socket for the 240VAC.

I measured 108VAC with the multimeter between chassis and transformer ground. Pretty annoyed that they skimped on this wire, as it's pretty dangerous.

If you touch any metal, whether it's the chassis or even the plug on the DSP controller... and you get a zap or it attracts your attention, be careful. Check your earth wire is connected at the IEC plug at the rear of the machine.

I've re-wired mine... safety first.

[Eclipze]

SHG0609
DSP to Mach3 Conversion...

I found I didn't like the DSP controller. Once you have used something like Mach3, the DSP seems like a toy with limited scope. I decided to design my own (electronics is my thing).

Has full opto-isolation to protect the PC.

Runs a small micro that provides a watchdog function. The CNC is only active if Mach3 sends the watchdog signal, so glitches on the parallel port while the computer is booting doesn't make the CNC move. Also, if the emergency stop switch is hit the power is cut, which the watchdog detects as it's happening and reports to Mach3 - which halts all movement before the caps discharge more than a few volts.

Has ports for coolant and zero tool, as well as spindle control. The Spindle control I've done a little differently though. I wanted to control the spindle via the gcode. So a simple "S6000" command changes the spindle speed to 5000rpm as the gcode runs. This is very handy when having tool changes, but also when using the same tool for different types of cuts/feedrates. Most importantly, for different materials. Mach3 sends out a PWM signal, whereby the duty is proportional to the speed. You can of course filter this signal and put the result into the VFD speed control input. I chose to run it through a micro so I could accurately filter and adjust (translate) the levels for accuracy/stability. The VFD also has an analog output, which is proportional to the spindles current speed. I measure that with the micro and convert it to a pulse per revolution frequency output, which Mach3 reads. It shows the spindle RPM on the PC screen.... just because I'm too lazy to walk over to the machine and read the VFD display hahaa.... Not quite, it also gives me the option to up/down override the spindle speed while the gcode is running, and see what speed I'm changing too. The interface for the VFD actually resides right at the VFD, so the analog signals aren't strung out through all the other electrics picking up electrical noise.

One pet hate of the DSP cable was that it poked straight out the front. I put a vertical socket, so I can later put a lid across the front of the control box to stop material showering in there at some point.

So far I've got it all connected up and running, except for the limit switches. I want to fit hardware limit switches on each axis, rather than just have them on one end or use soft limits. No sure how I'm going to approach that mod yet.

Once everything is done, I'II get around to neatening up the wiring

[Eclipze]

SHM0609
4th Axis Stepper Driver

Added a Gecko Drive G203V to the system, so I can later run a 4th axis. The G203V's handle up to 80V, which is great for this machine as it's running at 76VDC. Ignore the 50V labels on the wiring. It's actually 50VAC from the transformers and they have used the same labels everywhere (noobs hahaa...).

I've used some doubled sided thermal transfer pads to bond it to the control box, which will help dissipate the heat. Also put some bolts in place to make sure it doesn't come loose with all the vibrations.

When I spoke to Excitech earlier about added a 4th axis, they said the DSP currently doesn't handle a 4th axis. You can of course disable one axis to run the 4th for limited functionality, but not all 4 at once. They said they were working on new firmware that could handle a 4th axis, but not ETA. That was ~mid-2009 I discussed that with them. As I'm using Mach3 instead of the DSP, 4th axis is no problem.

[Eclipze]

VFD
Brake Resistors

I've installed some brake resistors in line with the manuals specifications for the VFD. Two 220R 150W wired in parallel, 1.5kW HSD VFD. The purpose of them is to slow the spindle quicker once turned off.

I'm actually a little confused on this one. After installing them, there was no change. So I went through a lot of the VFD settings. I've reduced the ramp up/down times which has made a big difference, but I'm unsure if the brake resistors have made a contribution. I went through so many settings, I can't remember what exactly I've tried - just went around in circles. The manual seems to explain how to change the settings, but not specifically what the settings do! Gets more complicated because some settings are only in effect given other settings have certain levels/options. Plan to have another go at it, connecting/disconnecting the brake resistors to see if they make a difference or not.

Can anyone shed some light on the settings for improving deceleration?

[Eclipze]

SHM0609
Zero Tool, using Mach3

Using the Mach3 mod that Greolt made...
http://www.cnczone.com/forums/showthread.php?t=36099

A small disc of FR4 copper clad fibreglass (aka single sided PCB material) and I have a zero tool. Works perfectly. I have an additional alligator clip connected to ground, so I can clip it to the tool bit so it has a good ground reference. But I suspect it isn't needed for this machine like it is my other CNC.

[mecanicu]

wow man you did alot of usefull things on you cnc...i"m interested in changing the dsp to pc..because i wanna add a 4th axis on my shm2030a cnc pls tell me the exact step's you did..i have posted on excitech routers thread/4th axis on exitech pls read my thread.

tx mecanicu

[Eclipze]

Originally Posted by mecanicu wow man you did alot of usefull things on you cnc...i"m interested in changing the dsp to pc..because i wanna add a 4th axis on my shm2030a cnc pls tell me the exact step's you did..i have posted on excitech routers thread/4th axis on exitech pls read my thread. tx mecanicu

You need a different interface board, as the current one is specific to the DSP handset. The interface board will connect to the PC's parallel port instead of the DSP. It will directly control the step and direction of the stepper motors, as well as read the home switches etc... Best to get one that has opto isolation to limit the possibility for damage to the PC port. Also make sure to get an interface board that will run at the same voltage, in my case the DSP board used a 24VDC supply. You will also need PC software to drive the CNC, where you load the GCODE and run it. The popular low cost choice is Mach3 www.machsupport.com

I do think you are wise moving away from using the DSP if you want to add a 4th axis, as the DSP is quite a limited controller. There is little information available and the firmware is in the hands of the China suppliers, who are quite evidently only interested in new sales, not support.

[mecanicu]

tx four you'r replay.....but pls tell me exctly a controller model that can support 24v and 4 axis that can be used on a excitech machine..

Best Regards

[Eclipze]

Originally Posted by mecanicu tx four you'r replay.....but pls tell me exctly a controller model that can support 24v and 4 axis that can be used on a excitech machine..

...I can't help you, as I've never looked for one. I designed my own.

[mecanicu]

Originally Posted by Eclipze ...I can't help you, as I've never looked for one. I designed my own.

if you ar thinking on selling the board or the schematic's i'm interested...