DIY Laser/XY Gantry

Background

RussleH and 'RepRap' Matt (talk) took a look at the work is of the IMP Pick and Place at Ciseco

Locking a magnetic tape linear encoders, simlar to used on the PnP
This can give very high accuracy position feed back and at high speed

http://www.machine-dro.co.uk/digital-readout-systems/magnetic-tape-linear-encoders.html?p=1

Specifications

Size:

• Minimum working area 600mm x 900mm

Speed:

• 1000m/s for scan (X axis)
• 500mm/s for Y axis

Precision:

• 0.01mm

Type of Gantry

Possible driver systems

• Fixed motor and looped belt to carriage
• Carriage mounted motor and fixed belt
• fixed motor driving a leadscrew
• fixed motor driving a ballscrew

Most lower cost laser cutters use belt drives.

Most larger machines use ball screws. Here are notes on the two ideas:

Belt Drive

Advantages

• Low cost
• Standard
• Motors can be smaller (less inertia)
• Most low cost and DIY lasers use this method

Disadvantages

• Precision will get worse (belt wear)
• Not repeatable precision (belts will stretch if moving fast)

Belt Drive costs

• XY gantry for DIY laser is available here for $950 (=£590). The cutting size/ working area is 900mm x 600mm. This comes with 2 x 5A motors.

http://www.lightobject.com/XLE-900600-XY-Stages-complete-kit-for-DIY-CO2-Laser-2-yrs-warranty-P762.aspx

Ball Screws

More information on ball screws can be found here:

• http://www.cnczone.com/forums/linear_rotary_motion/8813-ballscrew_basics.html

• http://www.nskamericas.com/cps/rde/xbcr/na_en/Ball_Screw_Tutorial.pdf

Advantages

• High precision
• Repeatable precision for its whole lifetime
• Used in commercial designs
• Unusual and interesting - not been done for table top lasers before.

Disadvantages

• Need to build this with high precision
• No DIY design available
• Higher cost
• Larger motors required (more inertia)

Ball Screw costs

These prices have come from Zapp Automation (http://www.zappautomation.co.uk/en/). This is not necessarily the lowest cost.

Parts required include:

Ball screw 25mm diameter, 25mm Pitch:

• 2 x 600mm @£6/100mm = £72
• 1 x 900mm @£6/100mm = £54

End mounts:

• 3 x floating 25mm diameter @£30 = £90
• 3 x fixed 25mm diameter @£60 = £180

Ball Nuts:

• 3 x R25-25A2-FSED @£75 = £225

• 3 x Motor couplers @£10 = £30

Ground bar

• 1 x 1m length @£1.20/100mm = £12
• 1 x linear bearings = £4

Total cost = £667

Notes: Supplier of ball screws and parts:

• http://www.misumi-europe.com/index.aspx?lang=EN&fn=sub11_3.aspx&mu=06&css=L2&ref=

• http://stores.ebay.com/linearmotionbearings/

Type of Motor

Motors for each of the above could be one of the following

• DC motor
• stepper motor
• brushless servo motor