Changes 20110829

This improvement iteration is for conversion of 2 banks of 4 x pickup heads from DVD to pneumatic

Every so often a DVD drive head will not come up fully, resulting in problems.  Considered upping from 5 to 6 volts (as from hints from observations its the stepper itself slipping),  but as I've found some very usable pneumatic parts.. well..

The PIC18F4610 interface board firmware will be updated to reflect driving the new heads

The Excel GCODE generator not need changing as it is above firmware that will interpret the commands (have be careful that new heads go down / up in same timeframe as existing (hopefully faster)

The Mach3 VB dialogs will be updated to allow testing the pneumatics

Donor pneumatics as purchased (multiple sets purchased as need 8 sets for 8 heads)

The pneumatic actuator we will be reusing:

The specific disassembled parts:


Additional springs:

New head assembly:

Implementation Observations:

Needed to balance:

- Down speed for pickup: As with the DVD drive heads, if down too fast on pickup , can bounce components out of peeled tape

- Down pressure, don't want to punch into parts

- Up stroke speed, as fast as possible please

- Up stroke start - not too abrupt

- Up stroke stop - not too abrupt

Ran new heads with no extra springs initially:

- tuned air supply to 0.3Mpa as any higher and too much downward force on components (according to my finger..)

- Air speed controls wide open both up and down strokes

- at 0.3Mpa no need to slow downwards stroke (initially occasional parts bounced by impact.. dropped air supply pressure down to 0.3Mpa)

- upwards stroke is way too slow

Added compression spring to cushion upward stroke, and extension spring to full cylinder action:

- air supply up to 0.4Mpa, tested by my finger

- downward stroke much slower, downward speed control is still wide open

- upward stroke starts abruptly but ends well with compression spring

Hardware changes:

Have on hand the following parts:

8 x  Head extension springs: Century Spring Corp C-1 1/8" x 1. 1/2" x 0.015

4 x Head compression spring: Century Spring Corp C-582 3/16 x 1 3/8 x .016

- Cut down to 4 x 12mm lengths

2 x (used) Festo MZH-3-0,4-LED Pneumatic 24v valves on a manifold

16 x (used) SMC AS1000 airspeed regulators

8 x (used) Festo ESA-6-20-PK-3 or ESAA-6-20-P-A Micro one way cylinders

- 3mm shafts, 20mm stroke

8 x (used) Micro linear slides & associated hardware (as it came assembled with the above cylinders)

- Bracket (alloy)

- - Preparation: Cut off support arms from either side

- - 2mm hole & M2 bolt for top of extension spring, 45mm up, 5mm in from linear bearing edge

- slider (plastic)

- - Preparation:

- - - File top of stop from 5mm to 6mm down from top edge

- - - File bottom of stop so is 8mm top to bottom

- - - File leading edges can fit pickup tube

- - - 2mm hole & M2 bolt on bottom for other end of extension spring

Miscellaneous pneumatic fittings & hose

2 x optoisolated 4 way Mosfet driver PCB (DIY'd)

Fabricate new parts:

- Fabricate 8 x New 40 x 40 (trimmedto 40 x 25) aluminium L profile head brackets

- Cut 8 new 5/32 brass pickup tubes 90mm

Assembly per head:

- Hot glue pickup tube to linear slide assembly

- Bolt linear slide assembly to bracket

- Bolt bracket to gantry & align vertically

- Cable tie vacuum solenoid valves from previous heads to new bracket & connect hose to pickup tube

- Fit pickup industrial syringe tube to pickup tube (18ga)

Pneumatic air switching assembly per bank:

Connect Festo Solenoid valve manifold 4 x outputs, each to 2 x SMC air speed controllers (one for down speed & one for up)

Mount above on a base board

Connect per head (run hose), output from above manifold assembly to each heads pneumatic cylinder

Mount new 4 x Mosfet switching PCB & connect to above manifold & connect to PIC interface PCB


Connect air supply -> demistor/regulator -> above manifold air input

PIC18F4610 Interface PCB changes

- After this change:

  • RC0-3 -> 4 x Mosfet driver PCB -> 4 x pneumatic valves for Left 4 heads
  • RC4-7 -> 4 x Mosfet driver PCB -> 4 x pneumatic valves for Right 4 heads
  • RD0-3 -> 4 x Mosfet driver PCB -> 4 x vacuum valves for Left 4 heads
  • RD4-7 -> 4 x Mosfet driver PCB -> 4 x vacuum valves for Right4 heads

- Firmware updated so that any Z axis movement command (as per current via B0/B1) for heads 4-7 as well as acting per currently (controlling DVD head stepper control PCB via RC0-3 7 RC4-7)  it will also:

- - if DIR is for down (+ve increment), switches on above mosfet channel (RA0-3)

- - if Dir is up, switches the Mosfet channel off

Software changes

Mach 3 main vb dialog has up / down buttons added for each head


Finally a front surface mirror has arrived (from Scotland, gotta love tehe interweb) so that has been fitted to the up facing USB camera