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Tuesday, February 28, 2017

K40 Clamping Table

Background

I have seen many versions of power and static tables, in fact I have both.
This table design, which was invented by +Scorch Works, is the simplest I have ever seen. I decided to see if I could document the design and add a few features. Then I will likely build one.
After using both the static table and the powered one I found the following:
  • The static table is hard to adjust and therefore changing out materials is a pain.
  • The powered table is a lot more expensive and seems like overkill for most of my work which is 1/8-1/4 materials. It requires power and switches, then again it does have a nice matrix of pin holes.

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For other information on the K40-S build use the  K40-S BUILD INDEX with schematics

The Origin

The original design was first posted on G+ bu +Scorch Works and deservedly garnered a lot of praise for its simplicity and innovative approach.Whereas most designs lift the target item up to the right height this design simply keeps the surface of the target at a predetermined height using a clamping bar. The top of the clamping bar is pre-adjusted such that its under-surface is at the right focal point for the laser. 
The clamp can be used without a bed. Alternately, a bed made of any kind of surface can be inserted into the clamp below the material.The thickness of the bed does not effect the focal point since it is below the target. In fact for engraving the thickness of the material does not matter either. 
Struts can be placed flat or on edge in the clamps or under the target material providing additional options for leaving a gap between the bed and the material as it is being processed.

For cutting most materials the laser should be focused 1/2  (1/2T) way through the material. Getting this setting with this design is unsolved and still an open brainstorming item.

Design

Its seemed only fair that since +Scorch Works shared this approach someone should create a set of drawings to share the build, although the design is simple enough to build without them.

Design Considerations

I set these design goals for any new design I would attempt:
  • Top adjustable reference plate with lock
    • Uses top accessible and floating 1/2-20 screws that capture and adjust the upper plate up/down
    • Loosen locking nut, adjust height then lock the nut. A one time adjustment.
  • Spring loaded clamp
    • Uses the original design
  • Easy to insert/extract from the machine [no screws]
    • The unit sits on the floor and the throat can be collapsed by releasing the locking knob and sliding the front clamp forward.
  • Easy initial install [no drilling or taping into the K40]
    • Fits between the Y gantry and rests on the floor
  • Maximize the clamping thickness 
    • The adjusting screws have substantial travel
  • Adjustable throat
    • The center shaft allows the front clamp brackets to slide forward and back with a locking knob.
  • Cutting and engraving capable
    • Haven't found a good way to lift the target above the reference plane by T/2. Thinking of an adapter that goes under the clamp and allows material to "stick up" T/2. You would need a set for each size though :(.
  • Fabrication in home shops with standard materials.
    • All the materials can be purchased at Home Depot except the threaded Nutserts (rivet nuts). Nutserts are available in many nut-bolt stores and on Amazon. 
    • Fail: the 1/4-20 shoulder bolts will need a shoulder cut in them to accommodate side mount retaining clip.
    • Aluminum from HD fabricated with pop rivets.

Faults With this Model

1. The reference angle brackets may not hold well in the middle without an additional post. I wanted to keep as much clamping surface as I could so I omitted a middle post in the inaugural design. If needed posts can be added reaching down to the floor frame. Alternately the lower clamping plate could be replaced by angle material.
2. Positioning the target T/2 upward for cutting
3. Fixed sized floors will be necessary (if floors are used).
4. Potential binding of the front bracket as it is moved rearward. If needed plastic guide wheels can be added under the adjustment screws.
5. The entire assy, might move due to vibration in K40 bed. Add rivet nuts under the back bar and attach with wing nut screws.

The Design Model

Models below using actual K40 dimensions.The gantry is not shown but the key side frame surfaces are accounted for. This is not built yet but suitable for reviewers to beat up!





Enjoy and comment
Maker Don