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CNC Router.
Designed and built byRoger Hampson
This is a BIG movie download!!
A new project that will be built on line for you to copy
The minimum amount of engineering tooling is required for this project is listed below
mail to:info@foundry-fopars.co.uk
| Medium sized lathe . |
| Vertical milling machine. |
| surface table and height gauge. |
| good understanding of engineering know how. |
Latest update:-25 June 2007.
X Axis Y Axis Z Axis Wiring Control electronics
Please be aware that the photographs on this page are large and may well take some time to download
The building of the project requires that many of the parts are made from aluminium castings, and it is assumed that if you under take this project that you will have access to a reasonably well equipped workshop.
This is another BIG photo!!
Well i did say equipped not tidy!!!!
I have recently been making an increased number of moulds for various casing projects with the prospect that many more will be required, the realization that too many hours were being spent making patterns for the casting, and as the time was spent here the cost of the "project patterns" was increasing out of control as the majority of my projects require a “one off” pattern, then some method of quickly producing a pattern was urgently required.
I investigated using polystyrene as a lost foam casting method, this worked
and worked quite well, but the use of a friend and his CNC laser cutter was
being abused, and not wishing to stretch out friendship I put a stop to its
use.
This did however open my eyes to the benefits of such a machine and the almost limitless applications it could be put to.
It was not long before I decided that as I had the foundry, and the engineering capability, I would make my own CNC router.
But where to start, I saw a book on ebay entitled Build your own work bot, this book I found was excessively padded out with unnecessary and superfluous detail, and was more instrumental in making me decide how not to build it rather than how to, I was so disappointed that I BURNT the book and decided i would build my own design from scratch knowing absolutely nothing about it.The CNC plan
Design specifications.
To be home built. thus simple construction follow the KISS rule ( This rule has obviously not been followed )
To supply as many of the components from the foundry as possible
If the components could not be cast then i would source them form EBAY, at as lower cost as is possible
To be capable of full 3 axis movement full 3D routing will depend on what software i can get
To be repeatable
To be as accurate and as solid as practicable
To be a minimum of A3 size (210 x 420mm)
Accuracy
Both Feed rates of the X & Y axis is via 4mm pitch ballscrew, this is rotated with a 200 full step or 400 half step stepper motor, so the resolution of the machine is set to 4mm travel for 1 rotation of the lead screw which equates to 0.02mm per step or 0.01mm per half step which will give fine detail and good for accuracy but i am not sure what the fast travel rate will be.
Most gantry style CNC machines, or at least the ones that I have read about had high gantries, this will cause errors and excessive mechanical stresses that will cause instability, I have from the outset decided to have as lower working height as possible, to this end the Y axis bars are horizontal not vertical, the overall effect is that the frame work of the machine is far more rigid and less prone to mechanical instability.
I mentioned to a friend what I was about to do, and he immediately sold me some stepper drivers and one motor, for more money than I would have liked to have spent. but 4 stepper drivers and one good sized motor was what I needed so the deal went ahead not realizing how difficult it would be to “match” the one now obsolete existing motor. So I decided to resort to Ebay with the intent that i would sell a life times accumulation of "stuff" to fund and to source everything else.
After some hasty and on reflection unwise bidding i got the hang of the EBAY knack and learnt a deal of patience ready to pounce as soon as you see what you want.
I have thus sourced all 8 ball bushings to fit 1 inch diameter rod, two more identical stepper motors, and found a shop that sells linear products at a good price so visit Marchandice and ask for kevin, (Please mention where you found the information)this is where i bought the 1 inch steel rod, ballscrew 's and nuts the total spend so far is
| Stepper motor and 4 drives | £75.00 |
| Two matching motors | £73.00 |
| inch steel bar 4 off | £109.0 |
| ball screws and nuts x 2 | £233.0 |
| bearing seals 12 off | £60.00 |
| Total Spend | £550.0 |
| Stepper motor and 4 drives | Cash | £75.00 |
| Two matching motors | self financed from EBAY | £73.00 |
| inch steel bar 4 off | self financed from EBAY | £109.0 |
| ball screws and nuts x 2 | self financed from EBAY | £233.0 |
| bearing seals 12 off | cash | £60.00 |
| Total Spend | this now drops to | £135 |
This offset by sales through EBAY now significantly reduces the overall cost of the project to well within the realms of the average engineer, and i am sure that you all could do with a slightly shorter projects list and a bit more space, this has reduced my projects list by at least one life time...
I originally started out by buying 4 meters of Silver Steel or Drill Rod, but soon learnt the folly of my thinking, it is far too soft to use in its natural form, and is impossible to harden the lengths i required with out loosing all of the most desired properties, lineararity, surface finnish and overall diameter, thus the exercise was a total waste of cash that had to be recouped before the project could really restart, but gave valuable time for both formulating a plan and making patterns. It would be a wise decision not to repeat this mistake!!!
The Build Starts with The frame or table.
The main frame of the CNC Router is to be sat onto a substantial steel framed desk having first removed all of the wooden sections, then additional cross bracing was added to stop any side wise movement.
it was a little smaller that what i really wanted but as it turned out it was the right size for my workshop. The main Base of the CNC machine is built out of 50mm x 50mm x 5mm iron angle section, carefully cut to length and welded to be square and flat, it was then simply sat onto the desk with small sections of angle welded to the frame to locate it squarely on the desk.
For the work surface, it would be best to use as heavy as piece of steel sheet as you can find, bearing in mind that it should also be flat!!, or you can make up the thickness with sections of thinner sheet steel bolted together to form the work surface.
I used two sheets of 0.125 inch galvanized sheet steel bolted through from the center with counter sunk M6 hex head set screws, starting from the center and working out in concentric circles, to form a solid flat steel plate, then bolting this to the steel frame, while keeping an eye on flatness as the edges are tightened down, checking with a straight edge periodically as you proceed.
The Construction.
The first part to be cast are the four aluminium
support legs, placed at the corners of extent of travel of the X Axis, these
castings are of solid aluminium and are designed to take the full weight of
the machine, and to cope with what ever mechanical stresses are present when
cutting, they are all machined to be of identical size, height and be parallel. Careful machining of these parts is essential
as these will provide reference points and set the square running of the machine.
the method i used to machine is, First, the base is faced off and centered,
then machine the base square with a dividing head and fit into a four jaw chuck
or faceplate, center by referencing of of each of the four base faces, then
face off the top, and center, then turn to the required diameter, when this
is complete square off the top to height on the mill and cut the slot to take
the rod, if larger diameter bar is used then of course the corner supports will
need to be scaled up to suite. all mechanical attachments are secured to
the support corners and used to mount the X axis motor drive coupling and ballscrew
support bearing as well as providing a method of fixing down the X axis bars. Having constructed the
base and work surface, the corner supports can be fitted, the method i used
to locate the support legs was rest one X Axis bar into two support legs and
move them into position, mark the table through the four bolt holes drilled
into the base of the support leg and drill tapping holes into the table. Then fix one with four self threading M6
hex head setscrews, insuring it is square with the table corner, checking for
alignment by placing the bar in the grove with the far end simply resting in
a second support leg, mark the holes drill and fix the other support leg, the
remaining two legs are not fixed until all four X axis bearing blocks are cast
and machined, these are then slid together as shown in the first photo, with
the far side simply resting on top's of the support legs, temporarily fix the
"Y"axis bars and run them up and down to set the as yet unfixed legs
to parallel, this is a time consuming procedure but one that must be done with
care and precision when all four corners are secure recheck for square and adjust
by adding limit stops as necessary, this is done to prevent the Y Axis pulling
out of true and jamming should the Y axis strike an end stop un even the four X axis bearing
blocks both hold one linear ball bushing and two wiper seals, i have since discovered
that the best method to secure these bearings is by cutting a slot in the casting
and clamping both the bearing and the wiper seals in place with a single M6
bolt in each casting. The general design of these blocks is not as good
as it could be, and with hindsight i would keep these blocks square, as this
gives more room to secure additional bits as and when necessary. Stop!! A problem i found by this method was that the table
was just not flat!! infact it moved with temprature wich resulted with
a rise
on warm dayd and a dip on cold days even with the
"T" bars bolted down it was so far out it was impossible to use. To correct this error i invested in a 20mm thick
tooling plate which i bolted down onto the existing frame very carfully checking
for flat before, during and after bolting it down
The tops of these castings (support corners) were all machined with the same
machine set-up to ensure identical working height over the table, and were all
secured to the mill table by clamping at the base.
I cannot stress high enough how important it is that you lay out the foundations correctly for this part of the build it will save you like me having to strip it all down and do it again
X Axis Y Axis Z Axis Wiring Control electronics