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Aluminium CNC build (TEP mill converted) by Craynerd

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raynerd: I`ve been wanting a little CNC machine for the last couple of years, not specifically for anything, just to learn more about it really. I feel I`m doing well with my manual machines and want to keep machining that way. I`m learning all the time and this cnc build is just to help me learn the basics of cnc, not to take over my manual work (slightly irrelevent, as this machine won`t be up to it anyway!). I just don`t dare start from scratch and anything more complete is too expensive, as is buying a bench mill and converting. So this is a cnc build based on confidence and available funds. I started with a TEP cnc mill. One went on ebay a while ago for about 200 and just the other day another went for £350!! I can assure you I paid only a fraction of that price for mine. These are a sturdy machine and quite well made...just a dreadful design and dreadful software which is locked onto the driver hardware!! I was lucky enough to get hold of the original TEP software (isn`t available from anywhere!!) and it was dreadful. Imagine MSWindows Paint, no numberical input (so no saying I want a 20mm line, 10mm from the origin!!, just simple drag and click stuff!!) Then from that, tell the machine to move. Here is the machine from purchased: Very very bizzare design and many machine limitations: Cons: In my opinion the x axis should be mounted so the slides are vertical parallel, not horizontal. No z axis, it is just a solanoid motor to raise and lower the spindle to a fixed level. All hardware is locked so commands can only be sent from the PC interfaced by the TEP software - it won`t talk to Mach or EMC Stepper motors are only about 50Ncm Both axis are fixed off centre to allow space at the back for the electronics Only 12v 5A supply. Pros: I had a working CNC machine as a basis If all else failed, I strip it down and the ally bar/plate is worth more than the price I`d payed for the machine ! :D In truth, there is little going for this other than having a solid working basis to start from.

raynerd: First job was to strip the electronics completely from it. I will be using a TB6560 3 axis driver. I`ve heard nothing but BAD things about these, but I have one anyway and it`ll certainly get me going if I can avoid blowing it up. I wanted to flip the X axis and although replacing the entire side piece would have been ideal, I couldn`t afford it and had some pieces suitable in stock. I raised the sides and used a plate to join them. It may need some supports bridging the sides later on. After flipping the X, I could then mount a Z axis. I made the Z axis from a small leadscrew someone kindly gave me and the slides are olite 8mm ID bushes on 8mm silver steel rod slides. The rest is just plate bolted together. There is a problem in that I`ve used a flexible coupling but I haven`t "trapped" the leadscrew. This means that the Z axis compresses on the flexible coupling and moves the relative position of the axis - not good!! This is easy to correct but I haven`t done it yet. Once i had the X flipped and raised and the Z built, I couldn`t help try it out... it is running of only 12v at the time and the noise from these small motors is horrific, I think the TB6560 is also to blame but since then I`ve jumped upto 24v and the noise is quieter. At this point, the mill went back to its owner while we negotiated price. Other than electronics that we both agreed wouldn`t be needed, it was all replaced to original, thankfully, if he had seen the work I`d put into it I expect the price would have gone up! Further updates to come: Now running on 24v from two ATX supplies in series, spindle connected, first door sign engraving done...all good fun! Issues: still not sorted the z axis flexible coupling issue. Is the Z axis height too big. Flex is the spindle.

raynerd: First door Sign. Actually, that is a lie, I did one for my daughter that didn`t work out quite as well and I stalled the spindle whilest pocketing it out. This was my second attempt for my niece, with a slower feed during the pocketing. I have an issue somewhere but I`ve noticed that when the spindle is turned on, the spindle drops a significant fraction of a mm! The sign is too deep as areas that should be a thinner line are deeper than desired.  I was pleased with my first results. Chris

HS93: that may be due to you energising the coils the magnets are pulled in to line moving the bell with them in down and the spindle with it. you need to find a way of getting rid of the end float, did you put a collapsible washer on the spindle ? you should not need it with the thrust bearing. peter

raynerd: Pete, thanks for that tip, you were right and I never posted a reply to say so...sorry! I removed the end float by applying pressure to the main shaft while locking down the bell and it got rid the float. An update and advice if anyone has any!... During the last week I`ve stripped the machine to do some mods and in the last few days got it back together. However, I just can`t get my head around the fact that the movement is well out of sync! Just a simple example, say I draw two ovals concentric to one another, they will end up overlapping and even with little flats on them instead of nice curves! The wierd thing is, I get the same results on both Mach3 and EMC2... so either I`ve got a setting wrong in the software on both or something is wrong with the TB6560 driver? I`m sure it was working OK just last week and so after nearly a full day trying to correct it today, any thoughts or suggestions would be helpful...I`m totally out of ideas! Chris

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