{"id":39,"date":"2015-09-30T18:11:00","date_gmt":"2015-09-30T17:11:00","guid":{"rendered":"https:\/\/blog.hslracing.com\/workshop\/2015\/09\/30\/dro-for-the-mill\/"},"modified":"2021-06-08T18:20:05","modified_gmt":"2021-06-08T17:20:05","slug":"dro-for-mill","status":"publish","type":"post","link":"https:\/\/blog.hslracing.com\/workshop\/2015\/09\/dro-for-mill.html","title":{"rendered":"DRO for the Mill"},"content":{"rendered":"

I was doing some work on my Mini Mill the other day and noticed that despite the fact that I had set a 0 position on the Z axis, the readout that came with my Chinese scales would randomly reset and as a result the 0 value was suddenly elsewhere.<\/p>\n

This was not a huge problem for the task being undertaken at the time, as it was not hugely critical dimension wise, I just needed to be more careful with regards the bottom of the hole I was boring.<\/p>\n

<\/div>\n
This re-piqued my interest in the\u00a0TouchDRO<\/a>\u00a0project and I finally built a board, the writeup can be seen here<\/a>.<\/div>\n
<\/a><\/div>\n

I bought some shielded USB cables from\u00a0ebay<\/a>\u00a0seller\u00a0cnredceo<\/a>\u00a0for $0.99 (\u00a30.63) each with free P&P.<\/p>\n

<\/a><\/div>\n

I needed to cut off the outer plastic cover from the mini USB end, I then wrapped it in electrical tape before substituting it for the original cable on each of the\u00a0igaging<\/a>\u00a0scales.<\/p>\n

For the tablet I bought an A33 Cortex A7 8GB 10.1″ 1024×600 from\u00a0ebay<\/a>\u00a0seller\u00a0adornsource<\/a>\u00a0for \u00a342.99 inc P&P.<\/p>\n

<\/a><\/div>\n
The default cpi (counts per inch) value in the\u00a0TouchDRO<\/a>\u00a0app is 10,000.00 for each axis, this is way too high for use with my\u00a0igaging<\/a>\u00a0scales.<\/div>\n
<\/div>\n
Yuiry talks about setting via measurement on his calibration<\/a> page, which is fine, however these scales are actually all the same and use a standard cpi.<\/div>\n
<\/div>\n
Calculating cpi based on a feed-back calculation similar to that on Josef Prusa’s<\/a> site can be very useful if you have already converted to CNC and can jog your axis a ‘known’ distance which you then compare with reality and update the software based on the output from the formula.<\/div>\n
<\/div>\n
The correct cpi value for these scales is 2560 as stated on the\u00a0Schumatech OpenDRO<\/a>\u00a0website for the 21bit Chinese protocol that they use.<\/div>\n
<\/div>\n
In actual use, the scales exhibit some backlash<\/a> due to the gauge ‘sticking’ on the slide, but this can be compensated for with some care.<\/div>\n
<\/div>\n","protected":false},"excerpt":{"rendered":"

I was doing some work on my Mini Mill the other day and noticed that despite the fact that I had set a 0 position on the Z axis, the readout that came with my Chinese scales would randomly reset and as a result the 0 value was suddenly elsewhere. This was not a huge…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[7],"class_list":["post-39","post","type-post","status-publish","format-standard","hentry","category-uncategorised","tag-mini-mill"],"_links":{"self":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts\/39","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/comments?post=39"}],"version-history":[{"count":1,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts\/39\/revisions"}],"predecessor-version":[{"id":243,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/posts\/39\/revisions\/243"}],"wp:attachment":[{"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/media?parent=39"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/categories?post=39"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.hslracing.com\/workshop\/wp-json\/wp\/v2\/tags?post=39"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}