Difference between revisions of "User:DrRob"

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(Adding instructions for making the belt anchors)
(Step 1 of moving the belt anchors to their own page)
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== Belt anchors ==
 
== Belt anchors ==
  
<gallery>
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I designed and made my own [[/Belt anchors|belt anchors]] using parts and tools that I had readily available.
File:drrob-belt-anchor-below.png|Belt anchor viewed from below
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File:drrob-belt-anchor-above.png|Belt anchor viewed from above
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</gallery>
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=== Parts list ===
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Per belt anchor, so x4 for each ShapeOko:
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* 3x M5 x 8mm bolts
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* 3x M5 washers
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* 1x M5 nut
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* ~50mm length of aluminium right-angle section, sides ~10-12mm
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* 1/4" x 3/4" x 2-1/2" steel strip with two holes, supplied with the ShapeOko kit
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=== Tools required ===
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* Drill
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* 4.5mm drill bit
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* 5mm drill bit
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* 5mm thread tap
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* hacksaw or jigsaw to cut the aluminium
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=== How to make them ===
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# Cut two ~25mm lengths of aluminium right-angle section
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#* Actually the top piece doesn't need to be right-angle section - you can use a flat strip of a similar width instead
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# Hold one piece against the steel strip as shown in diagram 1 below, so that the tops are flush, and mark the position of the hole with a pencil
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# Centre-punch the centre of the hole
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# Drill through with a 5mm drill bit
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# Now take the other piece of right-angle section, and centre punch roughly in the centre of the left-most third, and the right-most third, and shown in diagram 2 below
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# Clamp the two sections together as shown in diagram 3 below
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# Drill through the unclamped side with a 4.5mm bit
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# Tap the 4.5mm hole to 5mm
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# Remove the clamp
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# Drill out the hole in the top piece ONLY to 5mm, removing the thread
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# Put the sections back together, and screw in one of the bolts to clamp them back together
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# Repeat for the other side, as shown in Diagram 4
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# Using a 5mm bolt, nut and washer, fit the bottom section to the steel strip
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# Place the end of the belt across the top, between the two threaded holes, then loop it back on itself, teeth to teeth.
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# Put the other section on top, and screw two bolts through into the lower section.  Don't do it up tight yet.
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# Using the loop of belt as a handle, pull the belt tight, using your precisely calibrated muscles to pull with 6lbs of tension, and while holding that tension, tighten the two bolts to clamp the belt in place.
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#* Obviously you only need to apply the tension while doing the second side of each belt.
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<gallery>
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File:Drrob-belt-anchor-step-mark-punch-drill.png|Diagram 1
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File:Drrob-belt-anchor-step-punch.png|Diagram 2
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File:Drrob-belt-anchor-step-clamp-drill-and-tap.png|Diagram 3
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File:Drrob-belt-anchor-step-drill-and-tap.png|Diagram 4
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</gallery>
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Revision as of 15:30, 27 March 2012

DrRob is located just outside Cambridge in the UK, and has just completed the "Hello World" of ShapeOko [insert touchdown dance].

Ordering parts in the UK

These are the best prices I've found in the UK for ordering the parts other than the main kit:

The Seeeduino and the stepper drivers have arrived. I can't believe how tiny the stepper drivers are! I may need to borrow a smaller pair of hands to wire them up.

The Tap & Die set and the Rotary tool have arrived. The little button that locks the spindle on the rotary tool while you tighten the collet feels very flimsy, but otherwise looks ok. It's quite a bit bigger than my Dremel.

The steppers are on order (special order from Technobots, but worth it for £8.26 cheaper each than at proto-pic.co.uk) and I'm in the queue for the main kit of parts. I have a few days off from work in a couple of weeks, so crossing my fingers that everything will be here by then.

20th Feb: the steppers and heatsinks for the stepper drivers arrived today.

PSU

I've bought a secondhand 7.2A 24V PSU from Ebay. It was removed from some equipment, and needs mounting in a case so that no-one gets electrocuted:

26th Feb: The case I've made isn't going to win any design awards, but it does the job.

The underside of the PSU is an aluminium plate, which is connected to the main heatsink which is the back plate. I've left a space underneath it in the case, so if it gets hot during use I can put a fan in there to circulate air.

Stepper driver board

I've designed and built a Stripboard stepper driver carrier board.

Construction

The lead screw passing through the delrin nut isn't at all square. I've allowed for that by drilling out the holes in the motor plate to 7mm (I had to drill them anyway as I have one of the original delrin nuts with the 6mm bolts).

The M3 x 10mm bolts for attaching the NEMA 17 stepper motors were a tiny bit too long. I cut a mm or two off the end with a dremel and cutting disc.

I made some belt anchors, each from a couple of 25mm sections of right-angle aluminium, drilled and tapped. I looped the belt back on itself, teeth to teeth, to give two flat sides to clamp against.

It took quite a bit of experimentation to work out the correct value for Grbl's $7 setting (step port invert mask), which turned out to be 200, with all the steppers wired normally.

Don't make the mistake I made and let your ShapeOko write with a Sharpie pen onto paper resting on your desk. My desk has a tattoo now.

Belt anchors

I designed and made my own belt anchors using parts and tools that I had readily available.