First CNC Project for future Astro Use :)

[MarkyD]

Well after making the 4th PCB for my dew controller and now using an Arduino Mega with a shield to mount all the regulators/MOSFETs etc I was struggling to get accuracy when drilling the holes for the components. Drilling 34 holes for an IDC connector by eye wasn't good enough and was difficult to mount the component.  I bit the bullet and got hold of a Proxxon MF70 CNC Mill.  It has only got a small bed but I already have a manual one and the accuracy of the table lead screws is very good with a nice solid cast iron base plus the size is convenient for table top use.  I'm using an Arduino Uno with a ready made CNC shield of which 4 A4988 stepper motor drivers plug straight in with grbl software on the Uno

After wiring up a test of the software (steep learning curve on G Code) using FlatCAM and bCNC - the X and Y axis homed on command but the Z axis carried on and hit the top of the pillar crushing the limit switch.  Luckily Maplins stock these switches so replaced easily.

Before connecting the Stepper I tested out the Z limit switch but the logic wasn't registering it.  A simple button code showed that the arduino was seeing the switch change state so it must be something in the grbl code.  After a lot of search and browsing the source code I found out why.  The lasted version of grbl V0.9 changed the pin for the Z limit switch.  The shield uses Pin 11 but this was swapped to Pin 12 to enable a PWM spindle control on Pin 11.  After rewriting the code I had a working z axis homing command.

So to my first CNC job was to mill out the plastic front panel for the box to house the control and PS.  Unfortunately I had the spindle to fast so it started to melt the swarf which scuffed up the surface - but the good thing about CNC is that you can stop the job and clear the melted on swarf from the bit and carry on from where you started.  Time wise it probably took a bit longer from designing in AutoCAD to creating the G Code to finishing the job but the cuts were accurate with none of the usual by hand mishaps and mis-shapen holes

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Mark

[faulksy]

very nice

[Starwiz]

Impressive   

John

[Alien 13]

I cant drill a proper hole to save my life I do make my own PCB s and even though I mark everything meticulously It ends up off and equipment panels are a nightmare.

Alan

[NickK]

The local Axminster is dangerous .. I'm not allowed in there on my own.. they have a full range of wood working gear, including manual hand tools through large machinery including the full range of proxxon. They're dinky but fully featured, solid and very expensive!

 

[Gina]

Axminster Tools in Axminster - about a dozen miles from here is a real Aladins Cave of tools of all sorts.  I have many of their tools and have been very pleased with the quality - first class goods at a good price - highly recommended   It pays to buy good quality tools.

[Vox45]

On 25/04/2016 at 20:40, MarkyD said:

So to my first CNC job was to mill out the plastic front panel for the box to house the control and PS.  Unfortunately I had the spindle to fast so it started to melt the swarf which scuffed up the surface - but the good thing about CNC is that you can stop the job and clear the melted on swarf from the bit and carry on from where you started.  Time wise it probably took a bit longer from designing in AutoCAD to creating the G Code to finishing the job but the cuts were accurate with none of the usual by hand mishaps and mis-shapen holes --

Mark

Wow that is so cool !

[Seme]

Axminster Tools looks like Hobby Craft for MEN (and Ladies)

[MarkyD]

Well the control box is built and here is my first pcb drilling project for the Arduino Mega2560 shield for my other project - the LCD Touch Screen Dew Controller.  I have yet to try Isolation routing but will need to use up my stock of photoresist PCB's first.  Drilling and then etching seems to be better at aligning the holes to the mask.

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Mark

[NickK]

Will leave this link here for anyone interested http://www.axminster.co.uk/power-tools/multitools-precision-modelling/precision-modelling-power-tools?p=2

 

I think I have found my birthday pressie.. then I can put steppers with the remaining DRV8825 I have

[Gina]

That's a nice little milling machine

[Gina]

I'm thinking of getting one of those little milling machines.  I always seem to be metal mangling by hand - I think it could be a very useful addition to my tools.  I've considered a full size milling machine in the past but discounted it on size and weight as well as cost.  I don't usually make anything bigger than this modelmakers milling machine could cope with.  3D printing has it's limitations for small, accurate and rigid parts.  I think with my interest in making clocks this could be very useful.  Converting to a CNC machine would also be on the cards having built 3D printers.

[Gina]

Dunnit   Package deal wih vice plus set of cutters and set of diamond burrs.

[MarkyD]

56 minutes ago, Gina said:

I'm thinking of getting one of those little milling machines.  I always seem to be metal mangling by hand - I think it could be a very useful addition to my tools.  I've considered a full size milling machine in the past but discounted it on size and weight as well as cost.  I don't usually make anything bigger than this modelmakers milling machine could cope with.  3D printing has it's limitations for small, accurate and rigid parts.  I think with my interest in making clocks this could be very useful.  Converting to a CNC machine would also be on the cards having built 3D printers.

It's worth getting the ready built CNC version from Axminster - They have one in stock close to you   Modifing the non cnc version seems to end up costing roughly the same and is more hassle.  It'll run on an Uno and A4988 Stepper drivers.  To save messing about I bought a driver shield from Hobby Components.  It's also worth getting a bunch of limit switches from Rapid Online as I have damaged all three axis ones whilst getting used to the G Code and movements - Maplins sell them but they are 3 times the price.  I bought a pack of 10 so I have spares.  I'm just about to start my first PCB Isolation milling task to see how it is

http://www.axminster.co.uk/proxxon-mf-70-micro-mill-cnc-507263

http://www.rapidonline.com/micro-miniature-push-button-switches-30271

http://hobbycomponents.com/shields/568-cnc-v30-arduino-compatible-shield

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Mark

[Gina]

I already have a number of appropriate parts from my now defunct Giant 3D Printer project including stepper motors, RAMPS, Arduino Meg 2560, driver modules, endstop switches, etc. so I don't expect it to cost anything like the £200+ for the CNC version.  Thanks for the suggestion though

[MarkyD]

Well that didn't go as planned.  Not paying attention and I accidently slammed the router bit into the pcb.  At 0.75mm dia it didn't stand a chance.  Hey they only cost £12 each

I carried on with the milling as an experiment to see if my setup of the autolevelling worked, which it did.  Another order to Mega Uk on its way

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Mark

[Gina]

On 06/05/2016 at 12:45, MarkyD said:

It's worth getting the ready built CNC version from Axminster - They have one in stock close to you   Modifing the non cnc version seems to end up costing roughly the same and is more hassle.  It'll run on an Uno and A4988 Stepper drivers.  To save messing about I bought a driver shield from Hobby Components.  It's also worth getting a bunch of limit switches from Rapid Online as I have damaged all three axis ones whilst getting used to the G Code and movements - Maplins sell them but they are 3 times the price.  I bought a pack of 10 so I have spares.  I'm just about to start my first PCB Isolation milling task to see how it is

http://www.axminster.co.uk/proxxon-mf-70-micro-mill-cnc-507263

http://www.rapidonline.com/micro-miniature-push-button-switches-30271

http://hobbycomponents.com/shields/568-cnc-v30-arduino-compatible-shield

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Mark

Did you add stepper motors to a manual machine or buy a CNC version straight off?

[MarkyD]

11 hours ago, Gina said:

Did you add stepper motors to a manual machine or buy a CNC version straight off?

I bought the CNC version straight off.  It has a marginally longer bed compared to the manual one.  I do have the manual version but I could be bothered to source and make the cnc bits - not sure whether to keep it for small quick jobs or sell it

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Mark

[NickK]

Are the steppers on the CNC version have encoders?

[MarkyD]

9 minutes ago, NickK said:

Are the steppers on the CNC version have encoders?

No - so if you move them manually or hard panic stop they don't know where they are so you have to run a homing cycle again

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Mark

[MarkyD]

Ok - I have just finished the first successful CNC Isolation PCB.  From design in Designspark to drill, routing and board cutout.  I'm not to sure whether I like the finish, it may be the way I set the milling bit up but the old method of making a mask on the inkjet to exposing and developing then etching gives a much "cleaner" product.  Drilling is still done by CNC but aligning the mask to the holes is reliant on the mask and Excellon files being accurate to match up.  Also with etching it gets rid of unwanted copper areas without having to go through and create another cnc gcode job to merge with the main files

Etched and CNC holes drilled - you can see the slight difference in hole positions.  On a lager board it would be worse

 

CNC produced from plain copper board

 

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Mark

[MarkyD]

Well I have come to a usable solution.  I wasn't that impressed by the isolation routing method.  Even after flattening the sacrificial bed and running an autolevel on the PCB it wasn't great - factors depend on the bit and how worn it is, which at this size is impossible to see.

After spending some time on calibrating the steppers by performing a couple of test squares and measuring actual distance to CNC values and then altering the steps/mm I have now got good alignment between the mask and the drill data.  I will probably have to re adjust as things start to wear but that will be hours of use.

The method I am going to work with is create the Excellon files from Designspark, Use FlatCAM to produce the G Code and then run this on bCNC.  After drilling it is a matter of aligning the mask to the holes, exposing for 90secs then develope and etch.  This produces a much cleaner PCB with good traces.  Final results are below for the Power/Filter daughter board for my Dew Controller which I am very happy with.  It's not yet complete as I am waiting for two more filters to arrive from RS

   

Being OCD about my resistors I've just noticed I have installed one 180deg out from the rest

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Mark

[NickK]

Very very interesting.. if only the manufacturer would make a hot extrusion accessory for the mill.. and I think S would be more impressed if there was a sowing attachment for CNSewing..

Oddly there is a way to solve the whole (pun intended) issue. Think of the holes as stars. It should be possible to create a transform map just in the way that star alignment (the holes) are done. Keep the drilling dimension and then 'star align' the etching over the top.