How precisely align diy pcb drill press? - Page 1
Forum section: electronics / projects

author: zappedy
author_rank: Regular Contributor
timestamp: January 25, 2017, 06:09:10 pm
content: Edit: My question is how do you measure and improve accuracy of a drill sled/press without access to expensive measuring equipment, or is there a clever diy design for a drill press that makes this simple?Edit again: added a drawing, below.Since the solder pot was not economical, it's on to the next impractical diy project!I'd like to have a very precise drill press/jig, not just to use for pcb drilling but for drilling precise holes in wood, etc.I've readthis linkand it looks like a good idea to use ready made Hiwin clone linear rails.But how do you align the drill in along 4 axis? First there's the two axis of the "sled" for the Proxxon tool, but the Proxxon also has to be aligned within the sled.Perhaps one could cobble together a workable solution with a machinist's 1-2-3 block and two high resultion digital cameras to watch how the drill bit moves in three dimesions?It seems like I'm always reinventing the wheel, poorly, with these sort of things. Do you guys already have a better solution?

author: rstofer
author_rank: Super Contributor
timestamp: January 25, 2017, 08:29:22 pm
content: I think your link is hosed...I would put alignment marks in the four corners of the board. I would probably has a guide rail at the back of the table that is known to be parallel to the axis.I bought a Grizzly G0704 mill and converted it to CNC. That gets me accurate positioning but it does nothing for parallelism. I usually clamp come kind of rail to the back of the bed and indicate it to get parallelism.

author: zappedy
author_rank: Regular Contributor
timestamp: January 25, 2017, 08:48:12 pm
content: Thanks, fixed the link and updated the post to clarify. The real question is how to measure and adjust accuracy on a (zero) budget.

author: zappedy
author_rank: Regular Contributor
timestamp: January 25, 2017, 09:44:28 pm
content: (Edit: not a suggestion for an actual mechanism! Only to clarify what I meant by 4 axis of misalignment)In (1) the holes would be drilled at an angle. In (2), the bits would break off. In practical reality, any drill press mechanism would have a combination of the misalignments in (1) and (2), and in two dimensions each. How can you minimize these misalignments? Is there any design that minimizes them?(pardon the crappy drawing, I just switched to Linux)

author: kurt
author_rank: Contributor
timestamp: January 25, 2017, 11:01:41 pm
content: My solution to this was a camera guided PCB drill JIG:http://kavionic.com/blog/building_a_camera_guided_pcb_drill_jig/And I wrote an application to help detect the center holes for accurate positioning:http://kavionic.com/blog/pixmicro/The JIG is primarily designed for PCB drilling, but should work fine for anything that have one flat side with visible markers for where to drill.

author: zappedy
author_rank: Regular Contributor
timestamp: January 25, 2017, 11:30:38 pm
content: Quote from: kurt on January 25, 2017, 11:01:41 pmThanks, I saw that before and intend to build a similar jig.However, your "naïve" construction only works for very thin and somewhat soft sheets of material (ie pcb's), otherwise your bits would snap unless you were extraordinarily lucky to have the drill very well aligned "by accident".Imagine drilling a deep hole with a .75mm bit into a thick piece of aluminum. The drill would have to go very straight down. How do you adjust your drill press to do that?

author: Benta
author_rank: Super Contributor
timestamp: January 25, 2017, 11:48:38 pm
content: QuoteErm... a drill press would normally consist of a table, and a vertical column carrying the head and drill motor with spindle etc. How would this not be vertical. I'm at a loss to understand the problem here. If you want to do coordinate drilling, you mount an X/Y table on top of the normal table.Your "4 axis" have me lost...

author: Muttley Snickers
author_rank: Unknown
timestamp: January 26, 2017, 12:01:38 am
content: Quote from: zappedy on January 25, 2017, 11:30:38 pmRather than go around in circles it might be easier if you Googledspindle tramming, there is a ton of information out there and it is not that difficult to do, just get yourself a dial or dial test indicator as most inclinometers will not have the required resolution for accurate alignment.

author: zappedy
author_rank: Regular Contributor
timestamp: January 26, 2017, 12:20:48 am
content: Ok, I didn't know the term, why else would I refuse to use it?Anyway, I'll rephrase my question then. Does anybody know of a (relatively cheap and simple, ie not an epoxy granite mill) diy drill press or z-axis assembly that can be trammed to good precision, and how do you tram the spindle and assembly without access to professional tramming tooling?If you do not, does anybody have any suggestions on how to get the best possible precision out of the construction linked to in the first post, again without expensive equipment?

author: zappedy
author_rank: Regular Contributor
timestamp: January 26, 2017, 12:26:05 am
content: A good dial indicator seems quite expensive, and from I can gather you really want a good fixture, such as a mill, to go with it.For one thing, I'm wondering if the manufacturing precision of a CCD/CMOS camera would be good enough for anything with regards to squareness and pixel homogenity. Or if anybody has any other ideas.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 26, 2017, 12:38:49 am
content: You still aren't clear on the accuracy you require, what kind of drill depth you are aiming for or what you define as "expensive". The basic tools for tramming as you will find when you do the Google search, are a dial indicator and a tool stand. You can get an adequate (for basic use) one at Harbor Freight for about $20. Add a couple bucks for a piece of drill rod and you can measure to about a thousandth of an inch over a travel of a few inches. Whether you can achieve perpendicularity is dependent on your patience and whatever mechanism you are using for adjustment.There is no need for a granite reference for this measurement, but it technically only applies for one x-y position of the table. If your x-y system is not accurate to your standards you need further work. A piece of plate glass isn't a laboratory reference, but will get you close enough to drill some fairly deep holes (high depth to diameter ratio).As you demand more and more precision you can spend more and more on your instruments. But it still isn't necessarily earthshaking. You will find excellent dial indicators on Ebay for well under $100. Good brand names that can measure to 250 millionths of an inch.

author: Ian.M
author_rank: Super Contributor
timestamp: January 26, 2017, 01:23:07 am
content: You can cheap-skate it but its a total PITA compared to using a dial indicator in an offset arm chucked in the spindle.For $2 tramming: You need:* a bent steel wire with a sharp point on the end to sweep the table,* a feeler gauge for rough alignment,* a dry-wipe marker.Start off by eye to get the wire nearly scraping the table. Get it closer with the feeler gauge. Finally, use the marker to 'blue' the arc the wire point traces so you can see if it scrapes it evenly to get it 'dead nuts'. Beware of the wire flexing if there is significant down-force - you want it just skipping at a minimum of three points reasonably evenly distributed round the circle.You also have to check the column is square to the table.AfterBeforetramming, chuck a precision ground steel rod (you can probably salvage a 'good enough' one from a dead CD/DVD drive) in a collet, check it for runout, then move the head up and down while checking between the rod and a rigid object clamped to the table with a feeler gauge. Repeat after moving the rigid object 90 deg round the rod.If you need a cheap flatness reference, you should get THREE pieces of plate glass so you can check them against each other with engineer's blue - three surfaces can only match at all angles if they are actually flat. N.B the glass may be wedge shaped - slightly thicker at one end than the other so if you are using the glass on the table to get an even surface to tram against, once you get it down to scraping the marker off, test again after turning the glass 180 deg.

author: zappedy
author_rank: Regular Contributor
timestamp: January 26, 2017, 01:40:22 am
content: Quote from: CatalinaWOW on January 26, 2017, 12:38:49 amWell, I don't really know either.Let's say, at least 10 times better precision and accuracy than you would get if you just winged it. As in, a good design for a diy drill press for pcb's or shallow holes, but deeper than pcb holes, in wood. How about 1 mil accuracy and precision in half inch plywood? That should be usable to make jigs to achieve 10 mil accuracy and precision with.The various "webcam microscope mounted beneth drill press" looks like they can achieve both accuracy and precision down to 1 mil with some effort taken to tighten the rails, and assuming a decent spindle. Is it correct to say that this is because it more or less is limited to one plane, and that the source of this is the webcam's good manufacturing tolerances in the same plane?

author: zappedy
author_rank: Regular Contributor
timestamp: January 26, 2017, 02:09:26 am
content: Quote from: Ian.M on January 26, 2017, 01:23:07 amThanks, I like this as I have lots of time and patience but very few monies.However, I don't think it will work that well for a home-built drill press (or cnc mill for that matter).When tramming a real mill, you adjust the table to make it perpendicular to the drill bit throughout its' movement, right? So it all hinges on the table being flat and stiff (plate glass: check) and the tool being parallel to the z-axis movement (homebuilt stuff: not check!).That was what my (admittedly weird) drawing was trying to say, it is difficult to get the z-axis movement parallel with the tool.How can you fix that? Is there any good design, if starting from nothing rather than from having cnc machined parts? It looks to me like most diy designs (for diy cnc routers etc) don't really address this, and it is not a problem if only drilling pcbs or 3d printing.

author: Ian.M
author_rank: Super Contributor
timestamp: January 26, 2017, 02:23:12 am
content: If you can move the head up and down (Z axis) and the clearance (X and Y axes) between a precision ground rod in a collet chuck in the spindle (that you've checked for runout) and a fixture attached to the table doesn't change, you know the spindle is parallel to the Z axis. Then its just a matter of tramming the table to the spindle. Of course you *NEED* those precision rails to start with and a solid stable base.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: January 26, 2017, 03:29:56 am
content: I was a machinist for 10 years and I don't completely understand what you are asking. But, in order to get your machine tool system all aligned on the X-Y and Z axis, you use a dial indicator and get yourself a good dial caliper in order to accurately measure any test parts that you use. There will be math...Place the dial indicator in the chuck of the drill using the extensions that will allow the dial indicator to ride the surface like a flytool and lower the spindle until the indicator pin touches the surface and then go another mm lower in order to get good frictional contact with the surface. Slowly rotate the spindle by hand and observe the dial on the indicator moving. If the dial moves more than 0.03 mm in either direction, then you need to adjust your table surface. If your table surface is not flat then you can tell using this method as well. You need a flat surface in order to achieve a precise system.The X and Y axes are done by setting up the indicator onto the X or Y moving platen so that the pin contacts a desired stationary X or Y surface plane, then observe changes in the indicator when you move the slide. Your alignment methods may vary from tapping on the system to get proper alignment, or to cranking on adjustments built into the system. It is difficult to tell what your system is from your description.If you could get your hands on a used machinery's handbook for cheap (or borrow one from a friend or the library), I suggest that you do so. There is a treasure of information in it.PEACE===>T

author: jpanhalt
author_rank: Super Contributor
timestamp: January 26, 2017, 07:16:53 am
content: Zero budget is tough, if you do not already have decent measuring tools.If open to an alternative and considering only drilling holes in a PCB, I use EAGLE, and there is a user program called drill-aid.ulp. That effectively center punches wherever a hole is needed. You can adjust the diameter of the indent (etched area).With that done, I have no problem hand drilling using a non-precision drill press. Vertical alignment of the drill press was done simply with a machinists square.Wood is a bit different. I typically use a brad pointed drill for larger holes (picture attached). Again, that helps keeps things centered without rigid clamping.John

author: Ian.M
author_rank: Super Contributor
timestamp: January 26, 2017, 11:21:09 am
content: Some more thoughts - if you have access to the 'dead printers graveyard' (inkjet or dot matrix) so you can scavenge two precision ground rods that the head carriages run on + four head carriages (for the sliding bronze bearing) from the same model printer, then the rest of the Z axis mechanism would be within the capabilities of a village blacksmith without machine tools, and without buying the linear rails. You aren't going to get sufficient rigidity in the frame if you cant do metalwork - wood will move and warp with changing temperature and humidity causing the drilling head to bind on the rails.I wouldn't use a glass table - you want something you can drill or tap for fixtures + it would be a PITA drilling the clearance hole for the bits so you can through-drill boards directly on the table without wrecking the bit. Hand scraped (to get it flat), cast iron, or heavy steel plate would be the best options, as they let you use magnetic base indicators, clamps etc.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 27, 2017, 12:30:38 am
content: Quote from: Ian.M on January 26, 2017, 11:21:09 amI totally agree that a glass table is inappropriate for the operating base. I was merely suggesting plate glass as a poor mans granite table for referencing measurements in set up.If the op understands the concepts in aligning a machine a great deal can be done with low cost/scrap materials. After all that is effectively how we got from Watts steam engine specifications on clearances between piston and cylinder no greater than a farthing coin to todays ability to match diameters to a few millionths of an inch if necessary. It was a long process of bootstrapping better measurements from the previous cruder measurement. With the advantage that now the OP can look back and see what went before and how to get from there to here.